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} “A DS -A002 OS
Be ceun i Spartina sinters for

Substrate Stabilization and
Salt Marsh Development
by
W. W. Woodhouse, Jr., E. D. Seneca,
and S. W. Broome

~ TECHNICAL MEMORANDUM NO. 46
AUGUST 1974

Prepared for

U. S. ARMY, CORPS OF ENGINEERS

COASTAL ENGINEERING

(8 RESEARCH CENTER
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yo Te

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4. TITLE (and Subtitle) 5S. TYPE OF REPORT & PERIOD COVERED

PROPAGATION OF SPARTINA ALTERNIFLORA FOR
SUBSTRATE STABILIZATION AND SALT MARSH
DEVELOPMENT

7. AUTHOR(s)
W.W. Woodhouse, Jr.
E.D. Seneca

S.W. Broome
- PERFORMING ORGANIZATION NAME AND ADDRESS

Technical Memorandum

PERFORMING ORG. REPORT NUMBER

8. CONTRACT OR GRANT NUMBER(s

DACW72-70-C-0015
DACW72-72-C-0012

10. PROGRAM ELEMENT, PROJECT, TASK
AREA & WORK UNIT NUMBERS

North Carolina State University
Raleigh, North Carolina 27607

G31167
12. REPORT DATE

August 1974

13. NUMBER OF PAGES

155

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Department of the Army
Coastal Engineering Research Center

Kingman Building, Fort Belvoir, Virginia 22060
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Unclassified

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- SUPPLEMENTARY NOTES

- KEY WORDS (Continue on reverse side if necessary and identify by block number)

Cordgrass Fertilization Seeding
Dredge Spoil Marsh Transplanting
Erosion Primary Production

Estuaries Salinity

ABSTRACT (Continue on reverse side if necesaary and identify by block number)
Techniques were developed for propagation of Spartina alternitflora
Loisel., smooth cordgrass, in the intertidal zone on dredge spoil and eroding
shorelines. Both seeding and transplanting methods were successful. Trans-
plants proved to be more tolerant of rigorous conditions such as storm waves

and blowing sand, but seeding was more economical and was successful on
protected sites. Vegetative development of seeded and transplanted areas

was rapid with primary production equal to that of a long established marsh
by the second growing season. At the end of the first growing season,

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20. Abstract (Continued)

more plant cover was produced from seeding at the rate of 100 viable seeds per
square meter than from transplanting single-stem plants on a 0.9-meter spacing.

The relationship of mineral nutrition to productivity of S. alterntflora
was determined. Plants and soils in natural stands were sampled and analyzed
for productivity interrelationships using multiple regression techniques.
Salinity of the soil solution, plant and soil manganese concentrations, and
plant sulfur concentrations were negatively associated with aboveground produc-
tion. Variables positively associated with production included phosphorus
concentration in the plant tissue and in the soil. Fertilizer experiments
showed that the production of a natural stand of S. alterniflora growing on
sand was increased significantly by additions of nitrogen and increased three-
fold when both nitrogen and phosphorus were added. The production of natural
marsh growing on finer-textured sediments doubled when nitrogen was added,
but there was no response to phosphorus. Nitrogen and phosphorus fertilizers
also enhanced growth of transplants and seedlings on sandy dredge material.

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PREFACE

This is a report of research started in November 1969 with support
from the U.S. Army, Coastal Engineering Research Center (CERC) through
Contract DACW72-70-C-0015, and continued through Contract DACW72-72-C-0012.
This effort has also received support from the North Carolina Sea Grant
Program, Office of Sea Grant, National Oceanographic and Atmospheric
Administration, Department of Commerce, Grant No. GH-78, GH-103, 2-35178
and 04-3-158-40; North Carolina Coastal Research Program; and the North
Carolina Agricultural Experiment Station.

The authors are W.W. Woodhouse, Jr., Professor of Soil Science,
E.D. Seneca, Associate Professor of Botany and Soil Science, and
S.W. Broome, Research Associate in Soil Science, North Carolina State
University, Raleigh, North Carolina.

The authors express appreciation to personnel of the Cape Hatteras
and Cape Lookout National Seashores, National Park Service; the U.S. Army
Engineer District, Wilmington; and the North Carolina Highway Commission
for their cooperation; and to A.W. Cooper for his advice and encourage-
ment in the initiation of these studies. Special thanks are due D.M. Bryan,
€.L. Campbell, Jr.,.and U.O. Highfill for their assistance in all phases
of the field work; and to R.P. Savage, Chief, Research Division, CERC,
for his advice and encouragement throughout the course of these studies.

NOTE: Comments on this publication are invited.
Approved for publication in accordance-with Public Law 166, 79th

Congress, approved 31 July 1945, as supplemented by Public Law 172,
88th Congress, approved 7 November 1963.

JAMES L. TRAYER
Colonel, Corps Engineers
Commander and Director

an ian 40b
i tie a
“ ae Hey Ta n

Ey 3 af
tite t3 ota ‘

CONTENTS

Page

PN DRO DW GION) erie, vseercciee tevehewareuee nen tat det lsd! ev itellewaneeunes ier te. leelulew sie es ial
eee Generali sinc are Pave Aaey Veer etl co benmonn es ial

2. Biology of Spartina alterntflora mt eeee Be Rh setae 12

3. Characteristics of the North Carolina Goat ash RE ce 14

WIE A DNOLG IDOI Riss 50-5 y) toed i AG Siva Guia: Momrolatol oehOseaabow-biab eucuroulonsd 14

IIE PINORAGNITION o's woh oor eo od so 6 Joe Yoo" fa of bolo 6 6 IS)

Iho TSREINS LEI ETN SONS lout G omtic) omomuna oon di delows (oc 19
27, =» OCCA Wo. =. Go Oauo ota bl tomtom sara bo=Gh On OnsOaa Ona Ome 42
Sa Sues Requirements Oe O-oOMB ONG OO GO 2G 6. o O 6 7

IY AIRS SU DENA ILONAWIBINEL = GG 6 On Gud 1d 0 oO ow pio det oro oma “lo 6 76

Vi SHORE SPROTEGLIONPAND! SUBSTRATE STABIEIZATION® = 39s so 6. 90
Pa STNO WAUSEM GUCAarn | erate tenet Met nneot reer Mra Cant Soni Meat tee te watcha. ot 90
Di Cedar sESihAN Cites fs tteutis: Tiss ost het Cnet eee ee ere tien 99

VI THE RELATIONSHIP OF MINERAL NUTRIENTS TO PRODUCTIVITY
OF SPARTINA ALTERNIFLORA ... Meee goer aro erase emt a eeNG 102
1. Nutrient Status of Necunall Stands SMU They ou tosses 104
De Sere CES One Gautad llstz Creare tan earn cer men reat Semetl tl sin te esiere: sie 123

VII PLANTING SPECIFICATIONS - SPARTINA ALTERNIFLORA ...... 147
hg.) Wace lembalNe: Bo er tad oS 7606 emia Ao Waco eM eNaNIeNS co 147

ho, WilenESNG- DAKO or Si'te Ss OSS VES a CEN oS SNE! Ge oo. 148

Sane etal 2 atehOMi. wefan cm carinc sw tanger... Sua vsucle, tase aver 6) Zs 148

APES COOLING Wu ecto ca etc ian Waumrsie earaiete cnc um tl Nes: loko ay ie Nua) logeeh weno Ts 148

Wale lelseeOMEIE RGSS Pir CAE Sa tran a mstkceniciatcl aia onsen isch, vouuroMzeWe el Norge casa ou yuciult stamens) ove 149
Xa SO UMMARYAFAN DE CON GIEU STON S wars ares etolmu siren oti tcpurcilircn Comirstit circle) ome ils 150

LUA NOIRE CIM Soe 6 a MMO 6 66 lo loom Bho W8 6 Gg a 76) 6 152

TABLES
mse xXperimentalll (SaltCSaeu neck asus Eset 6 GM chases) ciieicniwe 3: toys 16

2 Comparison of Growth of Four Transplant Types
S. alternitflora Collected and Transplanted at
Drew GINLEE 6 gia Boo ol! eS %e bo a tela (6 dS, Mow ames Mele Matic 21

3 First-Year Aerial Yield of S. alterntflora Transplants
from Four Locations Grown in a Flooded Nursery,
Gay tonaNomth es Carolina 3 sie icpyirtcs pious) tse /</uler malo mrss) [i 26

Ital

I7/

CONTENTS - Continued
TABLES

Survival and Growth of Freshly Dug Transplants
and Heeled-In Transplants at Beaufort, 1973 .

Survival and Growth of Freshly Dug Transplants
and Heeled-In Transplants at Drum Inlet, 1973 .

First-Year Performance of S. alterntflora Plant
Sources at Snow's Cut .

Second-Year Performance of Plant Sources
che sens Gime, WIV 5 6 65S

List of Flowering Plants Invading the S. alterntflora
Planting During the Second and Third Years Following
Transplanting in 1971

First-Year Performance of S. alterntflora Plant
Sources at Drum Inlet .

First-Year Performance of Plant Sources at
One cone sa wten igs tari dene upe i saremexen ee urea rome nes

Mean Aboveground Biomass for Two Growing Seasons for
Four Geographic Population Groupings Grown on Dredge
Spoil at Snow's Cut, North Carolina .

Effect of Spacing on First-Year Growth of
S. alterntflora, Drum Inlet, 1972

Effect of Spacing on First Year Growth of
S. alterntflora, Drum Inlet, 1973

Mean Standing Crops Produced from S. alterntflora
Seediny Two! Growanign Season's; mits me nas ee ele

A Comparison of Growth Measurements of S. alterniflora
Seedlings from Two Seeding Methods ......

Mean Aboveground and Belowground Standing Crops
Produced from Two Seeding Dates at Beaufort,
Noth Car oleiniateimnysl C7 2e ato eon cai

Seed Harvest from Three Sample Areas at Oregon
Inlet in September 1972 .

Soil Solution and Sound Water Salinity Measurements
19) DALES) < NS NOES he Wovsi Sessewbes.4 1565 66.610 0 0

Page

oil

CONTENTS - Continued
TABLES
Soil Solution Salinity - Drum Inlet 1973...

Growth and Development of an S. alterniflora Planting
at Snow's Cut over Three Growing Seasons .

Distribution of Belowground Growth by eas
SMOWUS GUe UGTA so Siang G soe On Olsolh Ge Gabo

Rate of Spread (meters per year) of S. alterniflora
at Snow's Cut, 8 April 1971 to 27 November 1973 .

Development of Transplanted S. alterniflora
Ene. WWeAWHNs WMC So. SS a Gn ae she. Oh DladilO wo

Invertebrate Species Found at Drum Inlet and Snow's Cut
PLOMeMarchy tOwNOviemb ere UOe5) im con ci eeeeciicy ast aro mch names) me

Second-Year Development of S. alterniflora Plantings -
Cedanpilisiand salts) Septembe re lS Site vena cineycn ie! ae

Soil Texture and Percent Organic Matter of Tall and
Short Heights Forms of S. alterntflora for Seven
HO CACHONIS sn 4 rsjq cumio we mone seers cade Micah emis ect t vale subhepat oh boll elo

Variables Used in Model Building and Their Simple
Correlations with Dependent Variables Height and Yield

Means and Least Significant Differences for Yield,
Height and Number of Stems of S. alterntflora Samples
from the Tall and Short Height Zones of Seven Locations

Analysis of Variance Table, Regression Coefficient and
Statistics of Fit for Dependent Variable Log, NaeldiG

Analysis of Variance Table, Regression Coefficients, and

Statistics of Fit for Dependent Variable Log,, Height .

Selected Models’ for Predicting Log,, of Yield and Height .

Means and Least Significant Differences for Variables
which appear in Regression Equations for Yield and
Fleasohita estates lereht cl sas of yom ere |e otkie

Simple Statistics and Regression Equations for Standing
Crop of Mineral Nutrients in the Aboveground Shoots of
So: CHEBABE PUIG So Ee OB. OOO ee) OO. Or Oo

Page
75

102

106

108

iat

116

CONTENTS - Continued
TABLES

Apparent Recovery of Fertilizer Nitrogen in the Shoots
at Harvest

The Relationship of Nutrient Concentration in the
Plant Tissue to Nitrogen Rate .

Effect of Nitrogen and Phosphorus on Belowground
Standing Crop (1972)

Effect of Nitrogen and Phosphorus Aboveground Growth
ataOcracokea (MOA \e Aisa is ste, volte ncurep eh eit uses cunee es

Effect of Nitrogen and Phosphorus on Belowground
Standing Crop (1973)

The Effect of Nitrogen and Iron Applications on
S. alterniflora at Oak Island . his

Effect of Nitrogen and Phosphorus on Short and Tall
Height Forms of S. alternitflora at Oak Island, 1972

Effect of Nitrogen and Phosphorus Fertilizers on Short
S. alterniflora at Oak Island (1973)

The Standing Crop of Seedlings at Beaufort to which
Nitrogen and Phosphorus Fertilizers were Applied

Effect of Nitrogen and Phosphorus Fertilizers on
Growth of Seedlings on South Island near Drum Inlet

The Effect of Nitrogen and Phosphorus on Growth of

S. alterniflora at Drum Inlet when applied at the
Tine ofairansplant ingest. Paces. welmdve eta eahet

FIGURES

Experimental sites used in propagation studies

Natural invasion by vegetative means .......
Typical transplant, Oregon Inlet, 8 May 1970 .

Flooded nursery, Clayton, North Carolina .

Flooded nursery

Page

127

129

IOS

134

135

NOY

140

141

142

143

145

18
20
22
24

iil

1/7

IY)

CONTENTS - Continued
FIGURES
Lifting planting stock, Beaufort, 10 April 1972
Beaufort tall transplanted at Snow's Cut
Tiramspoleimiciine 6 vals oes oF 9) No, 16) Mar BF Oho

Effect of transplanting date on survival of
So CHC ARRE YL UOIRG, So 0 6 66 6 OhiGe OD) Gao oS 2

Effect of transplanting date on first-year growth
Ol Gs GLB LORE Go cog (S614 6 66 6 6 S608

Natcineall aimyASalOmy. DN S@GGIS. » av aay Glo. ver ler (ay) Gs ior oho
See dMmarviesiver=rpacpeeuestiin 1) del liee ke cat otis
MMGeISITAIMNS SSCS coe cay eeets eileret ves yay) ete Jey) veramice a

Seed in spikelets mixed with pieces of stems, and seed
heads scominic: strom thase sinensis. va) veuentsy werileul cio aiey aaomte

Seeds being separated from broken stems and unthreshed
seed heads using a motorized screening device .....

Threshed and cleaned seeds in plastic containers;
containers ready for filling with saltwater and
Seong sin eae) COlGh soos ei Gio a 6M oF 6 oo Go 5

Location of seed collections in North Carolina . .

Effect of storage treatments on germination of
SCLLern aECORGLES Cede rrOMetinicmlOCcatlOnsm cy) rile esl (ells

Effect of harvest date on germination of
S. alterniflora seed stored in estuarine water .....

Effect of afterripening of S. alterniflora seed
SeOwech scopy WeAeLOUS: Iemeelns Osean’ G6 4 Go foo 6 6

Comparison of germination of S. alterntflora stored
in estuarine water and distilled water

Farm tractor incorporating seed on dredge spoil near
Beewaronee..uNoneeloy Cebsolayovey Wi Gh 1s Ga by GelaxdoNo

Broadcasting seed after preparing a seedbed with
GLaACCOrmandeculieanjatcOrSmejersexem aie en ce seis one

Page
28

41
43
45

BS)

ay)

CONTENTS - Continued
FIGURES

Mixing dry sand with wet seed to improve
distribution when broadcasting

Broadcasting seed and sand mixture on a small experimental
plot on a dredge island near Snow's Cut, North Carolina .

Incorporating seed with a rototiller .

Garden tractor used in seeding at locations not
accessible to the farm tractor

S. alterntflora seeded 21 June 1972 yee ilblt Stacey 1972
(right) i ie. Ree nite ; 5

The first of three sand fences erected at Beaufort to
protect seedlings from blowing sand .

By 12 April 1973 the first fence was completely full
and a second fence had been erected . asc s

Seedlings (April 1973) among second year rhizome growth
in an area near Drum Inlet which was transplanted
15 April 1972 on 0.91-meter centers .

Transplanting S. alterniflora near Old House Channel,
Pernlsl oo). Soxbaaysl Om II Weay WOW sho § G6 bo Mo oo 6

The surrounding area was seeded after 26 months
(2S ARUN SG eho a Goro. Oo bo 0.8.00 40

Rhizome culms from a seeding on South Island .
Transplanted 8 April 1971; photo taken 2 June 1971 .
Five weeks later on 8 July 1971

Near end of first growing season, 14 September 1971
First-year growth from a single stem transplant
Starting the second growing season, 10 April 1972

Approaching full vegetative proguce vary, for this
Saieenl LeMay 9iSiar. SpE ceache peed GF oar Os IO, AC

Lateral spread of Ocracoke plants at Snow's Cut,
5 March 1973

Page

68
70
77
78
79
80

CONTENTS - Continued
FIGURES
Diagram showing location of transects at Snow's Cut

Planted transect, No. 1, Snow's Cut; 2 June 1971
to November 1973 6 ashes tures coma:

Planted transect, No. 3, Snow's Cut; 2 June 1971
to November 1973

Planted transect, No. 7, Snow's Cut; 2 June 1971
to 26 November 1973 .
Unplanted transect, No. 2, Snow's Cut; 25 April 1972
COmMZOMNOVEMDE TONGS 7. ley mreres cor Wel. rely cy bs) ce lee wee temu clubs
Unplanted transect, No. 4, Snow's Cut; 25 April 1972
COmZOmNOVeMb ers AOS) tat ueyerse sh to ele ete sl) ot Leatropine es
Unplanted transect, No. 5, Snow's Cut; 25 April 1972
OR COMNOVEMDEt sl Oesioet sicroui te eal isinsris) ven usu fe eh ve

Unplanted transect, No. 6, Snow's Cut, 25 April 1972
to 26 November 1973 . Si Asterey tek re Sea Nem eee chats

Side view of vegetated block showing sediment
accumulation

Shoreline at Cedar Island after transplanting,
11 May 1972 . waters

View of the Cedar Island shoreline in the fall of 1973 .

Cedar Island shoreline transplanted 11 ee IO7S8
photo taken September 1973 : 6° 620 SHO

Locations of sampling sites (indicated by arrows)

Relationship between height and ns of
S. alterntflora . saan euray ets Steet

Effect of nitrogen and phosphorus fertilizers on
yields during two successive growing seasons

A comparison of unfertilized and fertilized plots in

a natural marsh at Ocracoke Island, 11 September 1972 .

The relationship between nitrogen fertilizer applied
and nitrogen content of plant tissue at harvest .

Page
91

O7/

100

101

103

105

110

126

128

CONTENTS - Continued

FIGURES

Page

59 The relationship of nitrogen rate to total uptake of
nitrogen, potassium, and sodium . A eats ak ee 130

60 The relationship of nitrogen rate to total uptake of
phosphorus, calcium, sulfur, and magnesium ... . 131

61 The effect of nitrogen fertilization on the aboveground

136

and belowground standing crop of S. alterniflora

PROPAGATION OF SPARTINA ALTERNIFLORA FOR SUBSTRATE STABILIZATION
AND SALT MARSH DEVELOPMENT

W.W. Woodhouse, Jr., E.D. Seneca,
and S.W. Broome

I. INTRODUCTION
1. General.

Natural tidal marsh has become recognized as a valuable resource
(Gosselink, Odum, and Pope, 1974). Marshes serve as a nursery ground or
as a source of energy or both, for a large number of sports and commercial
fishery species (Odum, 1961; Teal, 1962; Odum and de la Cruz, 1967;
Cooper, 1969; Williams and Murdoch, 1969). Under suitable conditions,
dry-matter production in these marshes may exceed that of the major food
crops of the world grown under the best conditions (Odum, 1961). Tidal
marshes are also important in the storage and transfer of mineral nutri-
ents between sediments and surrounding estuarine waters (Pomeroy, et al.,
1969; Williams and Murdoch, 1969). Further, in many situations these
marshes stabilize shorelines and afford protection to developed areas
during storms by absorbing and dissipating wave energy, and by storage
of water.

In many parts of the world intertidal marshes have been prime targets
of reclamation for agricultural, industrial and commercial development
for a long time. Some Dutch polders are believed to have been reclaimed
from marshes over 1,000 years ago. Until recently, marshes along much of
the Atlantic coast of the United States have been viewed as wasteland
suitable for conversion to other land uses by dredge and fill operations
and as a place to dump waste materials. Consequently, the coastal marsh
areas have decreased markedly in many regions causing concern, particularly
along the Atlantic coast of the United States.

Although dredging for development and for navigation has destroyed
substantial amounts of marsh over the years, much of the marsh that has
developed in recent times arose on dredge spoil deposits in and around
estuaries. Dredging continues to be essential to the maintenance of navi-
gation, and it seems likely to increase in importance. The stabilization
of dredged materials will often be desirable. If this activity could be
successfully combined with marsh creation, substantial multiple benefits
should be possible. This is a report of a study started in the fall of
1969, to explore the possibility of stabilizing dredged material in the
intertidal zone and the concomitant establishment of estuarine marsh
plants under conditions existing along the North Carolina coast (Woodhouse,
Seneca, and Broome, 1972; Broome, 1973; Broome, Woodhouse, and Seneca,
WAN:

Efforts were concentrated primarily on the perennial salt marsh grass,
Spartina alterntflora Loisel. (smooth cordgrass). At the start of this

study, little was known about establishing new stands of this plant,
although natural stands had been investigated extensively for a long time.
Marsh planting of a closely related species, S. townsendii H. & J. Groves
(Ranwell, 1967) has been practiced in northern Europe primarily for the
purposes of land reclamation.

2. Biology of Spartina alterntflora.

Spartina alterntflora is the dominant flowering plant in regularly
flooded intertidal marshes along the Atlantic and Gulf coasts from
Newfoundland to Texas. These low marshes are almost pure stands of S.
alterntflora, and constitute what is generally considered the most valua-
ble type of estuarine marsh. Although the shoots of the grass are often
covered with algae that may be grazed by the salt marsh periwinkle,
Littortna trrorata (Say), only a small part of the annual production of
the grass itself is consumed by other organisms (mainly insects and birds)
while the plant is living. After the aboveground parts of the plant die
and fragment, small suspended particles called detritus with associated
decomposing microorganisms are exported into the estuary. The detritus
is utilized by fish and invertebrate animals which may be permanent or
temporary inhabitants of the estuary. In estuaries where high turbidity
reduces light penetration which lowers phytoplankton production, marsh
grasses account for most of the primary production by the system.

Primary production of marshes dominated by S. alterntflora varies
with latitude and also within any given marsh. An increasing annual
production trend from north to south has been described by the combined
work of Good (1965) and Durand and Nadeau (1972) in New Jersey, Keefe and
Boynton (1973) in Maryland-Virginia, Stroud and Cooper (1968) and Williams
and Murdoch (1969) in North Carolina, Smally (1959) in Georgia, and Kirby
(1971) in Louisiana. This production trend may be partially due to a
latitudinal gradient of increasing length of growing season from north to
south. Production also varies a great deal within a particular marsh due
to height of the grass which varies from about 0.5 to 3.0 meters. Three
distinct height forms described as short, medium, and tall are generally
recognized (Teal, 1962; Adams, 1963; Stroud and Cooper, 1968). Based on
their study in Brunswick County, North Carolina, Stroud and Cooper reported
differences in annual net production of the short, medium, and tall height
forms as 280, 471, and 1,563 grams per square meter per year, respectively.

There is some disagreement about whether the difference in growth
habit and production among the height forms is due to genetic differences
between the short and tall height forms or if the size difference is the
result of environmental factors. Chapman (1960) suggests that the stunted
S. alterniflora is actually a genetic variety which is inherently smaller
than the closely associated taller form. Data reported by Stalter and
Batson (1969) from a transplant experiment suggest that there are two forms
of S. alterniflora, one which is inherently dwarf and one which is
inherently tall. However, the period over which the transplants were
observed was too short to be conclusive. The most obvious environmental
factor to which zonation in salt marshes may be related is the relationship

between tide and elevation and the amount of inundation to which a parti-
cular area is subjected (Johnson and York, 1915; Hinde, 1954; Adams, 1963).
Reed (1947) pointed out that individual S. alterniflora plants reached
their best development halfway between the low and high tide levels and
decline in height and luxuriance both seaward and shoreward. Bourdeau

and Adams (1956) found that salinity increased markedly from the tall to
the short height zone. Results of a greenhouse study by Mooring, Cooper,
and Seneca (1971) conducted with North Carolina plants indicated no
differences in seedling response to various levels of substrate salinity
due to height form of the parent plant. Based on seedling biomass and
height response, these researchers postulated that differences in height
forms were not genetic and may result from exposure to environments
differing in salinity. Biochemical evidence based on total soluble proteins
and enzyme patterns, along with field transplant studies of tall and short
height forms from Connecticut, also led Shea, Warren, and Niering (1972)

to conclude that the two height forms were due to environmental conditions
at a given site and not to genetic differences.

In established stands, the primary means of reproduction is vegetative
by means of extensive belowground hollow cylinders of stem tissue called
rhizomes. Along intertidal creeks and in newly established stands of the
grass, sexual reproduction often occurs. In these areas, the aboveground
stems, which are often called culms in grasses, reach their tallest height.
Flowers emerge at the terminal end of culms to form elongate flowering
heads or inflorescences. Flowering (anthers available for pollination)
occurs earlier in more northern populations along the Atlantic coast, often
in July, and becomes progressively later in southern populations (Seneca,
in press). Pollen is usually transported by the wind, and following
fertilization, seed development proceeds. Seeds reach maturity from
September to November depending on latitude, and they shatter shortly
thereafter.

The plant can grow in a wide range of substrate textures, from coarse
sands to silty-clay sediments. The grass appears well-adapted to the
anaerobic substrates characteristic of most salt marshes, because of its
oxygen transport system. Large, hollow, air-filled tissue called
aerenchyma extend from openings (lacuna) in the leaves down the shoot to
the rhizomes and roots (Teal and Kanwisher, 1966; Anderson, 1974). Thus,
belowground tissues in the anaerobic substrate are able to receive necessary
supplies of oxygen.

Although S. alterntflora does not usually reach its maximum growth in
higher salinity (35 parts per thousand) areas, it is well-adapted to and
can outcompete most other flowering plants in these regularly flooded
saline habitats. The plant tolerates salinity by taking salt up through
its roots and excreting it through special structures in the leaves called
salt glands. Because the species can tolerate salt but is not restricted
to highly saline areas, it has been termed a facultative halophyte. In

some brackish to freshwater tidal marshes S. alterntflora and a related
species, S. cynosurotdes (L.) Roth (giant cordgrass), occur together but
can be distinguished by the occurrence of a prominant midrib on the leaf
of the latter species and its total absence on S. alterniflora.

3. Characteristics of the North Carolina Coast.

The North Carolina coast is about 530 kilometers (330 miles) long,
lying between about 33.5° and 36.5° N. latitude. The outer coast is made
up of a chain of low, sandy, barrier islands. These are separated from
the mainland by large bodies of water along the northern half of the coast
from Cape Lookout to the Virginia line -- Core, Pamlico, Albemarle and
Currituck Sounds. These sounds are generally shallow with sandy bottoms.
South of Cape Lookout, the sounds narrow as in Bogue Sound or disappear
altogether leaving only tidal creeks and marshes between the islands and
the mainland as from Southport southward.

The state is drained by four principal rivers that reach the sea
directly or indirectly within North Carolina. These are the Roanoke,
Pamlico, Neuse, and Cape Fear Rivers. Only the latter empties directly
into the Atlantic Ocean; the other three enter the sounds at distances of
50 to over 100 kilometers from the nearest inlet. The inlets, really
"outlets,'' between the barrier islands are shallow, narrow and unstable.

Tide range along the outer coast is lowest (mean about 1.1 meters)
near the Virginia-North Carolina border and increases to about 1.4 meters
near the North Carolina-South Carolina border. Due to the low water
exchange capacity of the inlets and the damping action of the sounds, astro-
nomical tide effects within the sounds are confined to the close proximity
of the inlets north of Cape Lookout. However, the long fetches and shallow-
ness of these bodies of water permit large wind setup effects. South of
Cape Lookout damping action is greatly reduced, and astronomical tides
dominate.

Salt and brackish marshes are distributed throughout the coastal zone
of North Carolina. These marshes can be divided roughly into low or
regularly flooded, and high or irregularly flooded marshes. There are
about 24,000 hectares of the low marshes, primarily S. alterntflora, and
41,000 hectares of the high marshes dominated largely by Juncus romertanus
Scheele (black needlerush) .

The amount of silt and clay brought into the lower reaches of the
estuaries is low except for the Cape Fear River. Consequently, most sub-
strate materials near the inlets are sandy and during this study there has
been little opportunity to work with any other materials, except for one
location, The Straits.

II. PROCEDURE

Primary emphasis was placed on field experimentation with support as
necessary from laboratory, phytotron (growth chambers), greenhouse, or
nursery experiments. Field techniques developed as the work progressed
and tended to be a blend and adaptation of agronomic and botanical
approaches. Where feasible, variables were tested in replicated trials.
Exploratory trials and field-scale plantings generally have been unrepli-
cated, but did extend whenever possible to two or more experimental

Sicesm Gabe diwand Falck 1h) vsate) duplication spreads ithe xask, so,that jaf
one site is destroyed not all the information is lost.

Special measures of plant growth response are described for certain
experiments, but the following measures generally have been used to obtain
estimates of vegetative growth and development in the field:

1. Aerial dry weight - oven dry weight of aboveground
growth per transplant (hill) or per unit area.

2. Belowground dry weight (yield of rhizomes and roots) -
oven dry weight of belowground plant material (rhizomes and
roots) for entire transplant (hill) for first-year transplants;
for older plantings usually two cores were taken from each
quadrat harvested for aboveground growth. Samples were taken
to a depth of 30 centimeters with a stainless-steel coring tube
with an inside diameter of 8.5 centimeters. Samples were washed
and plant parts separated, weighed, and expressed as belowground
growth per transplant (hill) or per unit area.

3. Number of flowers - flowering culms per transplant (hill)
or per unit area, gives some measure of vigor.

4. Number of center culms - number of culms (stems)
clustered around the original transplant (hill), recorded on
first-year transplants only.

5. Number of rhizome culms - number of culms (stems) arising
from rhizomes, away from the original transplant (hill), gives
some measure of spread, recorded on first-year transplants only.

6. Height - distance from base to tip of culm in centimeters,
usually the average of five culms per sample.

7. Basal area - area covered by culms (stems) at ground
level as determined by harvesting culms, holding them tightly
bunched and measuring their cross sectional diameter, then
determining cross sectional area; recorded per transplant (hill)
or per unit area.

The exposed locations and unstable conditions of many study sites
rendered them more vulnerable to damage or total loss than is typical of
upland studies; hence, higher experimental errors are obtained from coastal
studies. Compensation for this problem was attempted through duplication
of field tests. Major hazards inflicting damage and loss were: storm
associated wave action, shifting of channels causing undermining, and
burial by windblown sand.

III. PROPAGATION

Spartina alterntflora invades new sites by both vegetative means and
by seeds. Pieces of marsh dislodged by water or ice may be deposited on

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bare areas, take root and spread (Fig. 2); or seeds may drift onto such
sites at optimum times, germinate and establish new stands (in Sec.

III, see Fig. 11). It has not been unusual to see both means of coloni-
zation taking place at the same site. These observations indicate that
the species lends itself to propagation by three general methods:
transplanting of established plants obtained by digging and dividing mature
plants from natural stands or from "nursery" plantings, direct seeding
with seeds that have been suitably processed and stored, and transplanting
of seedlings produced in the greenhouse or under other controlled or semi-
controlled environments (E.W. Garbisch, Jr., personal communication).
Attention was devoted to the first two methods, since they seem to have
wider application under North Carolina conditions. The third method is
technically feasible, but we have not pursued it on a field scale.

Initial emphasis was determined largely by availability of plant
material and flexibility in use of this material. Use of field-collected
or -produced planting stock has several advantages. Seeds do not have to
be collected in advance, and planting stock can be obtained from sites
producing few or no seeds. Planting material can be carried over from
year to year, or can be held in reserve for unforeseen needs. Further,
it requires less initial investment, and seems likely to be more economical
than producing plants in the greenhouse. Direct seeding, where feasible,
appears to be a rapid and very economical approach. It requires prior
planning to ensure adequate quantities of seeds. Greenhouse-grown seedlings
may have advantages (as less transplanting shock) under rigorous condi-
tions, but their requirements for prior planning and investment, depend-
ence on suitable seed supplies, and unsuitability for carryover without
additional handling may limit their use.

1. Transplanting.

a. Plants. Choice transplants consist of a large, single stem (culm)
with small shoots or pieces of rhizomes left attached, or discarded
(Fig. 3). Plants were obtained initially by hand digging in natural
stands, usually those of recent origin growing on sandy substrates.
Planting stock is more difficult to dig and process from older marsh
because of the dense root mat. Plants from older marshes are usually
smaller, of poorer quality, and tend to be subjected to considerable wear
and tear during the digging process.

A substantial amount of size variability will be encountered among
plants from any given site. Thus, in 1972, a test was conducted at Drum
Inlet to determine the effect of height and stem robustness of plants on
their value for transplanting purposes. Plants dug from a natural stand
near Drum Inlet were graded into four groups, transplanted, and later
compared (Tab. 2). Both the thin- and large-stemmed tall plants were
growing along the open water's edge, but the thin-stemmed plants occurred
in more dense stands. The short, large-stemmed plants were from new plants
originating from rhizomes invading open areas. The short, thin-stemmed
plants came from thick stands 1 to 2 meters behind the tall plants. For
most measures of first-year growth (aerial dry weight, number of flowers,

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number of center culms, height and basal area) the short, thin-stemmed
plants were inferior to the other three types of plants. There was some-
what less difference in survival. It appears from this test that the
larger, plumper stems, which probably contain the most food reserves, are
preferable for transplanting purposes. However, even the very small plants
are not worthless and may be used if limited sources are available.

It is advantageous to establish nursery plantings at locations within
the intertidal zone accessible by tractor-mounted equipment which facili-
tates digging. These plantings can be established by either seeding or
transplanting in 1 year, and planting stock can be dug from them the next
spring. Plants grown in this manner are more uniform and generally of
better quality than those obtained from natural marshes. Certainly, this
method offers substantial savings in time spent in searching and moving
between different patches of desirable natural stands. Marsh recovery
following digging is rapid, making it feasible to take plants from the
same site year after year as long as the growth does not become so dense
that the stand loses vigor.

Nursery production has also been tested on upland sites under irriga-
tion. This type of production was done first on the North Carolina State
University (NCSU) Clayton Research Farm in 1971. Transplants were grown
under sprinkler irrigation on a very sandy substrate. First-year growth
was roughly comparable with that on sites of intermediate productivity
on the coast. Weed control was the most difficult problem. Frequent
irrigation coupled with the very sandy soil tends to nullify the effect
of herbicides while encouraging rapid germination of weedy annuals
following cultivation. Consequently, frequent cultivation was required,
which discouraged the lateral spread of the S. alterniflora.

Another approach, under flood irrigation, was undertaken in 1972 on
a nearby field with a less pervious subsoil. A low dike was constructed
around the area, transplants from several locations were introduced on a
0.61-meter spacing, and several hundred viable seeds per square meter
from one source were broadcast. The area was flooded intermittently by
supplementing rainfall with water pumped from an irrigation pond. This
effort was more successful than the planting under sprinkler irrigation
(Figs. 4, 5). The weed problem was greatly reduced, but not eliminated,
as there was still some invasion by freshwater marsh species (Typha sp.,
cattail) and other plants tolerant of flooded conditions. Survival and
production by large and medium transplants from Drum Inlet, the large
transplants from Snow's Cut, and both transplants and seedlings from
Oregon Inlet were good (Tab. 3). Aerial yields were considerably lower
for short and medium transplants from Snow's Cut and short and tall ones
from Beaufort, as was the case in the field trial in the Core Sound
estuary at Drum Inlet. Since the flooding periods on this field were days
to weeks in length rather than hours and, thus, vaguely simulated wind
setup (referred locally as wind tide), it might be expected that trans-
plants and seeds from wind setup areas, in this case Oregon Inlet and Drum
Inlet, would do relatively well. The yield from seedlings was greater
than from transplants because the heavy application rate of seeds resulted

Transplanted 5 May 1972 on 0.61-meter centers;

Flooded nursery, Clayton, North Carolina.

photo taken 8 August 1972.

Figure 4.

Flooded nursery. Seeded 4 May 1972; photo taken 8 August 1972.

Figure 5.

Table 3. First-Year Aerial Yield of S. alterniflora
Transplants from Four Locations Grown in a
Flooded Nursery, Clayton, North Carolina.*

Source Propagule Aerial
of Plants Description Yieldst
(kg/ha)

Oregon Inlet¢ Plants 2,314

Seedlings$ 5,786
Drum Inlet ¢ Small 1,776
Medium 3,310
Large 3,014
Snow's Cut ¢ Small 619
Medium 807
Large 2,018

Short
Tall

Beaufort |

*Single stems transplanted on 61-centimeter
centers, May 1972; harvested October 1972.

+Comparable yield under sprinkler irrigation in
1971 was 1,695 kg/ha. Means of three samples
(individual plants for transplants and 0.25 m?
areas for seedlings).

tPlants harvested from one location and graded
into large, medium and small size culms.

§Seed broadcast

l|Tall and short height forms

in a denser stand than those produced from transplanting on a 0.6l-meter
spacing.

Using an upland nursery is a technically feasible method, but certainly
not as easy or economical as nursery plantings in the intertidal zone.
It does offer a practicable alternative when intertidal sites are not
available. Also, mechanical digging might be easier since the field
could be drained beforehand.

b. Digging and Processing. Plants can be dug from natural stands
manually with shovels or mechanically with a small back-hoe. Nursery
plantings can be loosened by tractor-drawn tillage and lifted by hand
(Fig. 6). The uprooted material should be separated into single stem
(culm) propagules or ''plants.'' Small shoots or short pieces of rhizome
may be left attached or discarded if damaged or broken. Small single stems
are not usually satisfactory transplants (Tab. 3). Survival of rhizomes
solely, i.e. not attached to culms, that were planted at 10- to 15-centi-
meter depths was unsatisfactory. Pruning of shoots to facilitate machine
planting may be necessary, but experience suggests that severe defoliation
should be avoided. The leaves may be necessary for satisfactory rate of
survival, possibly for supplying oxygen to the roots.

Plants to be transported to planting sites may be stacked roots down
in tubs, baskets or boxes if moisture loss is prevented. Storage in this
manner is satisfactory for a few days. For longer period of storage,
plants should be heeled-in in trenches within the intertidal zone.

Two plant storage trials were conducted in 1973. One test site was
adjacent to the nursery area at Beaufort. There was little difference in
growth or survival between the freshly dug and the heeled-in plants for
all five planting dates (Tab. 4). As might be anticipated, the later
plantings of both types of transplants produced markedly less first-year
growth than those plantings made earlier in the season.

Table 4. Survival and Growth of Freshly Dug Transplants
and Heeled-In Transplants at Beaufort, 1973.*

Aboveground Dry Wt. (g/m“)+ Survival (percent)
Freshly Dug Heeled-In¢ Freshly Dug Heeled-Inz

Planting
Date

7 May 62 72 86
14 May 75 69
28 May 76 ES
11 June 65 59
10 July 59 59

*Harvested 10 September 1973
tMeans of three samples (individual plants)
tDug and heeled-in 26 April 1973

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The other trial, at Drum Inlet, covered only three planting dates,
but used plants from both Beaufort and Drum Inlet. Growth and survival
were lower and more erratic at Drum Inlet than at Beaufort (Tab. 5).
This differential response is believed due to the occurrence of salt
buildup several times during the growing season at Drum Inlet. However,
the relative performance of freshly dug versus heeled-in transplants in
the two trials was similar, which suggests that it is feasible to dig
and store planting stock of S. alterntflora for at least several months.

Survival figures of heeled-in plants for the later planting dates may
be somewhat misleading. Some selection probably occurs as they are
removed from the trench. Plants that initially appeared as acceptable
transplants may have withered during the storage period and would be
rejected at this time as nonusable transplanting material. Consequently,
there can be some decrease in transplant numbers during storage.

ce. Sources. The growth habit and vigor of S. alterntflora varies
widely along the North Carolina coast. Whether this variability is genetic
or environmental or both is still in doubt. Thus, a question arises about
the range of adaptation of the transplant material as it is moved from
one site to another. This question was examined in several experiments.
The first and most comprehensive trial was started at Snow's Cut, 7 April
1971. This trial included plants from five locations ranging from regu-
lar tides to mostly wind setup and with salinities ranging from about
10 parts per thousand to nearly sea strength (Tabs. 1 and 6). The
material from nearby, labeled ''Snow's Cut,'' most closely resembled an
intermediate height form. The Beaufort tall was definitely a tall height
form from a tidal creek bank in the Beaufort marshes. Plants from Oregon
and Ocracoke Inlets were intermediate in height and were growing on sites
exposed to substantial wind setup. The Beaufort short came from the short
height zone well away from the creeks, under a regular tide regime and
salinities near sea strength.

All five sources grew well the first year (Fig. 7). Some morphologi-
cal differences were still apparent at the end of the growing season, as
well as the characteristic north to south flowering sequence. In addition,
there were differences in aerial dry weight, height, number of flowers,
number of rhizome culms (an indication of the rate of spread), and total
number of culms (Tab. 6).

While growth of transplants from all five sources was satisfactory,
the local type, Snow's Cut, appeared to be superior. This source had
more aboveground production and a greater rate of spread (rhizome culms)
than transplants from other sources, and was intermediate in number of
center culms and height. The following spring (1972), new shoots popu-
lated the entire area of all plots so that individual hills and rows were
indistinguishable (discussed later in Sec. IV, Fig. 39). Vegetative
cover and yield increased several fold over that of the first year
(Tabs. 6 and 7). Some differences between transplants from different
sources were still distinct with Beaufort short definitely shorter than
the other sources, and Beaufort tall having produced fewer flowers and

Table 5. Survival and Growth of Freshly Dug Transplants
and Heeled-In Transplants at Drum Inlet, 1973.*

Aboveground Dry Wt. (g/m?)+

Drum Inlet
Hee ed ine ae Heeled-Ins

fe aan eS) ame | 9
SiS Dod 18.
Syere Boll

Planting Date

29 May
11 June

10.3

Survival (percent)

29 May
11 June
10 July

*Harvested 12 September 1973
tMeans of three samples

tDug and heeled-in 26 April 1973
§Dug and heeled-in 10 May 1973

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Table 6. First-Year Performance of S. alternitflora Plant Sources
at ySnowlsm Cut, 4

Number of Rhizome
Flowers/ Culms/
Hill Hill

Source

Oregon Inlet

Ocracoke
Beaufort short
Beaufort tall
Snow's Cut

LSDt 0.05
0.01

CV (percent)

Go NO WA OF fF WU

*Harvested 14 September 1971. Three row plots, 9l-centimeter
spacing, randomized complete block design with three blocks.
Three samples (individual plants) taken from each plot in
the elevation zone of maximum growth.

tLeast significant difference

ECoefficient of variation

culms than the other sources. Material from Ocracoke and from Snow's Cut
was the most productive (in dry weight), but differences in production
during the second year were less marked than differences recorded the
first year. The north to south flowering sequence (characteristic of the
original sites) was still apparent. Adequate sampling of root and rhizome
production is difficult (Coefficient of Variation = 57 percent) and
differences would have to be quite large to be detectable. However, data
on this variable give an indication of the belowground biomass and related
soil-binding capability of this vegetation (Tab. 7).

This trial was followed through the third growing season, but compari-
sons made for the 1971 and 1972 data do not appear valid for the 1973
season. By 1973, the higher elevations of the plots were extensively
invaded by fresh and brackish water marsh species plus some common inland
weeds (Tab. 8). Furthermore, there were visual indications of some mixing
by the plant material from the five sources. Therefore, while data are
presented elsewhere on stand maturation, sediment accumulation, and
colonization by other organisms, the individual plots were not distinct
after the second growing season.

It seems reasonable to conclude, from the first 2 years of this trial,
that plants from any of the five sources tested would be satisfactory for
initial stabilization of this site. However, this site with its regular
tide (1.15 meters) and low salinity (8 to 10 parts per thousand) does not

represent the most rigorous test of the range of adaptability of the plant
material.

Table 7. Second-Year Performance of Plant Sources
at Snow's Gut, 1972 .*

Root and
Rhizome
Yield
(kg/ha)

Aerial
Dry Wt.

Number of
Flowers/

Source

(kg/ha)

Oregon Inlet 9,281.0 14 ,461.0 ars) Poll
Ocracoke 12 ,626.0 I soOsil 50 Drop UE 62
Beaufort short | 9,233.0 20,9730 PASSE 89.9
Beaufort tall ORAZ S AO 22 aS 250 16.9 50.9
Snow's Cut 12535640 BST, 5 {0 25.6 68.7
LESDiiie 40/105 2,967.0 O50) 12S

0.01 t 8.0 16.7
CVS (percent) 33.9 30.4 TDD

*Data collected and plants harvested 19 September 1972. Means
of four 0.25 m* samples per plot taken from four elevation
zones.

+Least significant difference
ENot significant

§Coefficient of variation

A similar trial was conducted in 1972 at Drum Inlet (Tab. 9). Growth
was slow and erratic, due presumably to the salt buildup on this site which
occurs periodically during the summer. Differences between sources were
small except for the low survival of the Snow's Cut plants. This response
would appear reasonable in view of the low salinity at Snow's Cut if it
were not for the fact that the Clayton plants were also plants from Snow's
Cut which were grown under freshwater irrigation before being transplanted
to Drum Inlet.

A small test comparing Snow's Cut plants with Oregon Inlet plants was
conducted in 1971 at Oregon Inlet (Tab. 10). In this case Snow's Cut
material performed poorly when moved to a location with high salinity
and significant wind setup.

The above results suggest that within a latitudinal region such as the
North Carolina coast there are naturally occurring populations of
S. alterniflora that are distinctly different in several respects,
including adaptation to specific sites, vigor, morphology, and flowering
dates.

Extending beyond this immediate region, seeds of this species were
collected from populations from New England to Texas (Seneca, in press).
Germination response of these populations was examined in 1972, and some
of the seedlings produced were transplanted at the Snow's Cut field site

Table 8. List of Flowering Plants Invading the S. alterniflora
Planting During the Second and Third Years Following

Transplanting in 1971

Scientific Name

Aeschynomene tndtca L.

Alternanthera phtloxerotdes (Mart.) Griseb.
Amaranthus cannabinus (L.) J.D. Sauer
Aster subulatus Michx.

Aster tenutfoltus L.

Atriplex patula L.

Borrtchta frutesecens (L.) DC.

Cyperus polystachyos var. texensts (Torr.) Fern.
Cyperus strigosus L.

Daubentonta puntcea (Cav.) DC.
Echinochloa waltert (Pursh) Heller
Ertanthus gtganteus (Walt.) Muhl.
Fimbrtstylts spadicea (L.) Vahl.

Iva frutescens lL.

Juncus roemertanus Scheele

Panteum dtehotomiflorum Michx.
Panteum virgatum L.

Phragmites communts Trin.

Pluchea purpurascens (Sw.) DC.
Polygonum pensylvanteum L.

Sabatta stellarts Pursh

Setrpus amertcanus Pers.

Setrpus robustus Pursh

Setrpus validus Vahl.

Spartina patens (Ait.) Muhl.

Suaeda linearis (E1l.) Moq.

Vigna luteola (Jacq.) Benth.

Year Recorded

1973

(al tx tal

Table 9. First-Year Performance of S. alterntflora Plant Sources
at Drum Inlet.*

Rhizome
Culms/
Hill

Aerial
Dry Wt.
(kg/ha)

Survival

Transplant
Source

(percent)

Oregon Inlet

Clayton 8.6
Ocracoke LBe6
Drum Inlet olf
Snow's Cut Or
LSD+ 0.05 .0

0.01

*Transplanted 30 May 1972; harvested 3 October 1972.
Three row plots, randomized complete block design
with three blocks; three samples per plot (indi-
vidual plants).

tLeast significant difference

<Not significant

Table 10. First-Year Performance of Plant Sources at Oregon Inlet.*

Number
Flowers/
Plant

Transplant
Source

Snow's Cut

Oregon Inlet

*Transplanted 31 March 1971, samples 31 August 1971.
Means of three samples (individual plants).

on 19 May. Aerial dry matter production data for 1972 and 1973 suggest
that there are major differences in adaptation within populations of this
species (Tab.-11). The latitudinal population grouping nearest North
Carolina grew best the first year but the South Atlantic and Gulf coast
population groupings forged ahead the second year. Production by the

New England material was definitely less both years. These results imply
that there may be serious risks in producing seeds or transplants from
any single population for planting far away from the site of origin with-
out first testing for adaptation. However, within an area such as the
North Carolina coast, it appears that populations may generally be moved
with no great difficulty except for extremes, such as from Snow's Cut to
Oregon Inlet. Further, it appears that populations having broad adapta-
tion within a region might be found, as in the case of the Oregon Inlet
and Ocracoke populations in North Carolina. Propagation of such popula-
tions could have real practical application in nursery production of
material that might be used for stabilization purposes on a variety of
sites. This is one area of study that warrants additional attention.

Table 11. Mean Aboveground Biomass for Two Growing Seasons for
Four Geographic Population Groupings Grown on Dredge
Spoil at Snow's Cut, North Carolina.*

Population Grouping Aerial Dry Wt. (kg/ha)
1972 WS
New England 150 1,140

(Massachusetts, Rhode Island, and
Connecticut populations)

Mid-Atlantic 560 3,430
(New York, Virginia, and North
Carolina populations)

South Atlantic 350 14,190
(Georgia and Florida populations)

Gult 160 11,340
(Mississippi and Texas populations)

*Transplanted 19 May 1971; harvested in September of 1972
and 1973.

d. Transplanting Method. Hand planting is more appropriate on small,
irregularly shaped areas where access for equipment is difficult. Planting
is done by opening a planting hole with a dibble or shovel, inserting a
plant to a depth of 10 to 15 centimeters, and firming the soil around it.
The team approach is best with men working in pairs; one opening holes and
the other planting. This can be done while the soil surface is under
water, if the soil is pressed firmly around the plant before it floats out
of the hole. However, due to the tendency of plants to float free, trans-
planting while the surface is exposed is preferred.

Planting depth was not investigated due to the impracticality of
keeping holes open long enough for insertion of plants to depths greater
than 13 to 15 centimeters. Further, planting depth appears unimportant
under these conditions, provided that the plant is anchored until it takes
root and becomes established. Drying of roots near the surface is not a
problem as it is in dune grass establishment.

Machine planting is feasible on many sites and is preferable on larger
areas. It can be done with any of several commercial transplanters
designed to transplant cultivated plants such as peppers, tomatoes, and
tobacco. A standard farm tractor can be used through the addition of dual
wheels and high flotation tires (Fig. 8). With care, this equipment can
be operated on surfaces that barely support hand planting.

For machine transplanting, the surface must be exposed and not under
water. With the equipment presently available, it is not feasible to time
the closing of the furrow precisely after the release of the plant to
prevent its floating out.

e. Spacing. Early in the study, it became apparent that with plants
on 0.91l-meter (3 feet) centers, cover was nearly complete by the following
spring. It did appear likely that closer spacing would be helpful on some
of the more exposed sites during the first growing season, and spacing
tests were established, at Drum Inlet in 1972 and again in 1973 (Tabs. 12
and 13). Unfortunately, second year observations were not possible on the
1972 test due to excessive deposition of sand by the ''February blizzard"
in early February 1973. Although the data from both experiments are
variable, the cover produced by the end of the first growing season was
roughly proportional to the spacing. Mean aboveground dry weights for
the two trials are 25.2 grams per square meter for 0.46-meter (1.5 feet)
spacing, 15.0 grams per square meter for 0.6l-meter (2 feet) spacing,
and 7.5 grams per square meter for 0.9l-meter (3 feet) spacing. There
was no test in either year of the value of this from the standpoint of
stabilization. It seems reasonable to expect that under some circumstances
the higher density planting would be helpful, but this would depend a
great deal on the timing and the nature of the disturbance to which the
planting is exposed. The denser spacings should have some advantage in
the case of erosive action on the substrate occurring after the initial
establishment period. Dense spacing appears to offer little protection
during the first 60 days after transplanting or against heavy sand
deposition such as occurred on the 1972 experiment.

Spacing of transplants is important and needs further clarification
since it greatly affects planting costs. It is difficult to evaluate
under field conditions due to the unpredictability of storm events and
their effects on a specific site. If a spacing trial is placed on a
fairly stable site, the trial probably will not be subjected to enough
stress to provide any measure of effectiveness. On the other hand,
locating a test on a more exposed site will likely result in severe damage
and little or no usable data. In the meantime, we are inclined to continue
with spacing of about 0.9 by 0.9 meters for most purposes.

‘Sur ue Tdsuesy

°g omns Ty

Table 12. Effect of Spacing on First-Year Growth of
: S. alterniflora, Drum Inlet, 1972.*

Spacing | Aerial
Dry Wt.
(ft. ) (g/m?)

*Transplanted 31 May 1972; harvested 3 October 1972.
Means of three samples (individual plants).

Table 13. Effect of Spacing on First Year Growth of
S. alterntflora, Drum Inlet, 1973.*

Spacing Number
Flowers/
(Gte,))

*Transplanted 8 May 1973; harvested 12 September
1973. Means of six samples (individual plants).

f. Date. Time of transplanting can be critical for many plant species,
and particularly for perennials. Consequently, planting date was one of
the first points examined in our study. Planting date experiments were
started in early November 1969, and some observations have been obtained
each year from then on. The data on survival and first-year aboveground
dry matter production are plotted in Figures 9 and 10. Although these
data are not all strictly comparable, particularly for yield, since some
sites tend to be more productive than others, these illustrations seem to
be the most useful way to examine the information.

In general, these results indicate survival to be good from midwinter
to early summer (Fig. 9). The very poor survival of December and January
plantings in 1970-71 is believed due to excessive wave action on an exposed
Site. Aboveground growth has been satisfactory from about December
through May, dropping off sharply in the summer months, due presumably,
to the shortness of the growing season remaining at that time (Fig. 10).
Both survival and growth have been poor from November plantings; this
probably can be attributed to the difficulty in identifying suitable
planting stock at that season and the long period of exposure to winter
weather before more favorable conditions for growth.

S. alterntflora can be transplanted with considerable success almost
the year round. The desirable planting season depends greatly on the
particular situation. The late fall and winter period is likely to be
risky for exposed sites due to the probability of rough weather. The
April-May period seems ideal, coming after the period of high storm fre-
quency, but early enough to take full advantage of the length of the
growing season. Summer plantings produce little cover to go into the
first winter. However, if they survive the winter, these late plantings
can provide full cover early in the next growing season, and there are
circumstances in which they would be warranted. For these reasons, it
appears unwise to state any rigid rules, but rather to suggest that
planting date should be adjusted to each particular set of circumstances,
keeping in mind the limitations described above.

g. Costs. The following are mean production figures taken from
several short periods of digging, processing, and transplanting over the
last 2 years. No allowance is made for travel time, machinery movement,
weather, and tides, or for management and overhead.

Harvesting and processing plants

By hand 180 to 200 plants per man
per hour

Backhoe (natural stands) 300 plants per man per hour

Lifted by plow 400 plants per man per hour

(nursery planting)

Aboveground dry wt (g/plant)

100 e

e @ i A
e S A

— A A
oe 80
S r a :
ee a
= 00: ° |
a a oo
we ° Year
5 40 . °e@ Oregon Inlet 69-70 O
a. = © Oregon Inlet 70-71
S A Ocracoke 70-7
- 20 B Beaufort Ue)

O Drum Inlet 73
A Drum Inlet 72

Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct
Planting date (month)

Figure 9. Effect of transplanting date on survival of
S. alterntflora.

80 Year

Oregon Inlet 69-70

Oregon Inlet 70-71

Ocracoke Otel .
Beaufort (2

Drum Inlet 73

Drum Inlet 72

> oO B Pe OO @

Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct
Planting date (month)

Figure 10. Effect of transplanting date on first-year growth
of S. alterntflora.

Transplanting
By hand - men working in pairs 180 hills per man per hour

Machine - tractor; two-row 360 hills per man per hour
planter with six-man crew
(one on tractor, four on
planter, and one supplying
plants)

Requirements on hectare basis

For 0.91 by 0.9l-meter spacing 12,000 hills per hectare or
approximately 111 hills
pee L OOO Sel ste

Hand digging and planting 134 man-hours per hectare
Machine digging from 63 man-hours per hectare
nursery area and machine
planting

These estimates may reflect higher productivity per man-hour than
would be realistic for large-scale operations. On the other hand, we feel
the digging operation could be speeded up appreciably with experience in
handling larger volumes, and by further development of harvesting
equipment.

2. seeding.

There are reports in the literature that S. alterniflora produces
very few viable seed (Chapman, 1960; Larimer, 1968), and that seeds are
not aS important as rhizomes in spreading this grass. However, early in
the studies, seedlings appeared to be the primary means of natural colo-
nization of S. alterntflora on freshly deposited sediments in the inter-
tidal zone in North Carolina estuaries (Fig. 11). Seed germinate in
March and seedlings grow rapidly through the summer, producing flowers
and seed by the end of the growing season (October). Seedlings are often
numerous in the debris of drift lines at high water and may also be present
at lower elevations, particularly in protected areas.

If natural seeding is an important means of spreading S. alterniflora,
it seems logical that direct seeding would be a suitable method for
artificial propagation. This method would have substantial economic and
labor-saving advantages over transplanting. To use direct seeding, effi-
cient techniques for harvesting, processing, storing and planting seed
had to be developed.

a. Seed Production. The amount and quality of seed available for
harvest varies from location to location and from year to year. As would
be expected, the most vigorous plants produce the best seed supply. Such
plants are generally found in areas recently colonized by S. alterntflora,

‘yooTq queTdsuer} 1evak-Z

0} JUS De pe

SSUT[pse9s JO pueys

asuog

*¢L61 ABW IT ‘43ND S,mMoUuSs
*spoos Aq UOTSBAULT [einjeN

II oan3ty

and seed production is rather uniform over the entire area. In older
marshes, there is little flowering and seed production in thick stands

of the short-height zone, but some seed are produced by the tall form
along creek banks. In such places, harvesting seed is inefficient because
the total area is small.

Since the quality and quantity of seed is variable, inspection of
potential harvest sites is necessary each year. Variations in rainfall
and other climatic conditions apparently affect seed production. Infes-
tation by flower beetles (family Moredellidae) may also reduce the seed
crop in some areas.

b. Harvesting and Processing. An adequate supply of seed for small-
scale experiments can be obtained by simply cutting the seed heads by

hand. For large field plantings, a more efficient means of harvesting
large quantities is desirable. To accomplish this task, a mechanical
harvester was developed which consists of a sickle bar blade, a reel,

and a canvas bag or tray for catching the seed heads. The apparatus was
mounted on a two-wheel garden tractor (Fig. 12). The machine works best
in- large areas of seed heads of uniform height. After cutting, seed
heads were wrapped in burlap sheets and returned to the laboratory where
they were stored temporarily in a cold room (2° to 3° Centigrade) until
they could be threshed. A threshing machine, previously used for small-
grain plot work, was used to separate the spikelets from the straw. This
leaves nearly all seeds still in the spikelets (glumes, lemma, and palea).
The threshing procedure reduced the storage space required for keeping
the seed over winter (Figs. 13 through 16). Germination studies indicate
that seed should be harvested as near maturity as possible, but it is
often necessary to compromise on complete maturity since many seed may be
lost due to natural shattering if harvesting is delayed too long.

c. Storage and Laboratory Testing. A study by Mooring, Cooper and
Seneca (1971) showed that 52 percent of S. alterntflora seed germinated

when subjected to a 18° to 35° Centigrade diurnal thermoperiod after
storage in sea water at 6° Centigrade for 8 months. Seed stored dry
during the same period did not remain viable. In the beginning of our
studies, we tested the effect of several storage treatments on germination.
Seed of S. alterntflora were collected from five locations along the North
Carolina coast (Fig. 17) and samples from each location were subjected to
the following storage treatments: (1) submerged in estuarine water at

2° to 3° Centigrade, (2) submerged in distilled water at 2° to 3° Centi-
grade, (3) suspended over water on screen wire at 2° to 3° Centigrade,

(4) frozen dry, (5) frozen in estuarine water, and (6) freeze-dried.
Salinity of the estuarine water was between 20 and 25 parts per thousand.

Germination was tested in February 1970 by placing 50 seeds, which
were disinfected by soaking in a 25 percent Clorox solution for 15 minutes,
on moist filter paper in a petri dish. Three replicates of seed from each
treatment and location were prepared with a replicate consisting of a
petri dish of 50 seeds. Careful selection was made to be reasonably sure
a seed was present within each spikelet. The petri dishes containing the

Cutter bar, reel, tray and motor mounted on two-wheel tractor.

Seed harvester.

Figure 12.

Figure 13. Threshing seed. Thresher in
center foreground; seed heads
in burlap sheets at left fore-
ground and right background.

Figure 14. Seed in spikelets mixed with
pieces of stems, and seed heads
coming from thresher.

Figure 16.

Seeds being separated from
broken stems and unthreshed
seed heads using a motorized
screening device.

Threshed and cleaned seeds in

plastic containers; containers
ready for filling with salt-
water and storing in the cold
room.

EASTERN NORTH CAROLINA

36° N. Lat.

a BEE NOTE

By
) 5
aia co N. Lat.

A § i BEAUFORT

SURF CITY

34° N. Lat.

g
OAK ISLAND

Figure 17. Location of seed collections in North Carolina.

seeds were placed in canisters to exclude light, and were subjected to an
alternating thermoperiod of 7 hours at 35° Centigrade and 17 hours at 18°
Centigrade in a growth chamber. Germinating seed, indicated by the emer-
gence of the epicotyl, were counted after 5, 7, 9, 21 and 30 days. Since
none of the seeds subjected to freeze-drying germinated, the results of
this treatment were deleted from the statistical analysis. Germination
failure of freeze-dried seed is consistent with the findings of Mooring,
Cooper, and Seneca (1971), and showed S. alterntflora seed must remain
moist to retain viability.

Results of the effect of storage treatment on germination indicate
that freezing, either dry or in estuarine water, was clearly detrimental
to germination of seeds from all locations (Fig. 18). Freezing was
particularly harmful to seed from Surf City and Oak Island. Germination
of seed from Oregon Inlet, Ocracoke and Beaufort, which were stored frozen
was fair; however, germination was delayed. This indicates that the after-
ripening or development process of the seed was retarded while the seed
were frozen.

@Estucrine water Distilled water
Over woter O Frozen dry
10! Oregon Inlet 4 Frozerin estuarine water

LSD .05-7.5

($0.05-12.2

LSD 05-148

Germination (x)

Surf City

LSD.05-14.9

804 Ook Island

LSD .05-173

5 ‘ 10, 5 20 25 30
Germination period (days)

Figure 18. Effect of storage treatments
on germination of S. alterni-
flora seed from five locations.

The effects of storage of seed in estuarine water, distilled water
or over water on germination were more variable between locations. Seed
from Oregon Inlet showed no statistical difference in percent germination
of seed among these three treatments at the end of 30 days. Germination
of seed stored over water did lag for the first 10 days of the germination
period. Storage over water produced the best germination percentages for
seed from Ocracoke and Oak Island, while storage in estuarine water was
Significantly better than any other treatment for seed from Beaufort and
Suita Grits.

The explanation for the variable response to storage treatment of
seeds collected from different locations is probably due to the degree
of maturity of seed at the time of harvest. Spartina alterniflora seed
apparently are never dormant but continue development during an after-
ripening period. The degree of seed development at the time of harvest,
as well as the environment in which the afterripening proceeds, probably
influences viability of the seed. Although there is variation in seed
maturity even within a particular stand, flowering and seed maturity
occur earlier along the northern coast of North Carolina with about a
3-week span from north to south.

The seed collections from the different locations used in the experi-
ment were made within 3 days; therefore, seed from the northern coast,
e.g., Oregon Inlet, were more mature than those from the southern coast,
e.g., Oak Island. Consequently, the difference in the effect of storage
in estuarine water, distilled water or over water on germination was
least in the seed collected from Oregon Inlet. Storage over water was
advantageous for seed collected at Ocracoke and Oak Island. Apparently
these seed were less mature at harvest and storage in a saturated atmos-
phere, but not submerged, was more conducive to the afterripening process.

This study of germination indicates that seed should be harvested as
near maturity as possible and that storage in estuarine water or possibly
freshwater at 2° to 3° Centigrade is an acceptable and relatively easy
way to maintain viability over winter. However, it is often necessary
to compromise on complete maturity, since many seed may be lost due to
natural shattering if harvesting is delayed too long. At Oregon Inlet
the best harvest period has been from about 20 September to 20 October.
The best harvest date is later farther south.

The effects of date of harvest, length of afterripening period, and
storage in distilled or estuarine water were evaluated with seed collected
in 1971. Seed harvested on 28 September 1971 at Oregon Inlet had a
Significantly higher germination percentage than those harvested 1 week
earlier (Fig. 19). However, seed harvested on 21 September were threshed
and stored in estuarine water within a few days of harvesting, while those
harvested on 28 September were stored in burlap sheets in a cooler for
3 weeks before threshing and storing in estuarine water. Subsequent
experience indicates that storing the seed at 2° to 3° Centigrade for
several weeks before submerging in water enhances the germination
percentage.

Germination (%)

100
80

40 GHarvested 28 Sept 1971

OHarvested 21 Sept 1971

20 LSD.05-12.5

0 4 8 2 16 20 24 28
Germination period (days)

Effect of harvest date on germination of S. alterni-
flora seed stored in estuarine water. Seeds were

harvested at Oregon Inlet; the germination period
began 17 February 1972.

Results of a study on the effect of length of storage on germination
indicate that immediately after harvest, seed were slow to germinate,
requiring about 24 days to reach 50 percent germination (Fig. 20). By
February, 50 percent of the seed sample germinated within 4 days. The
results suggest that an afterripening process occurs that speeds germi-
nation and increases the germination percentage as the length of storage
increases. Similar results were obtained by Van Shreven (1958) in a
study of S. townsenditt seed. It is difficult to evaluate the effects of
length of storage on germination beyond 6 or 7 months since the epicotyl
of a large percentage of seed emerges even though stored in salt water
at 2° to 3° Centigrade. Experience has indicated that seed stored longer
than 1 year do not retain their viability. A study to develop techniques
to increase longevity of storage could prove beneficial.

Samples of seed harvested 21 September 1971 at Oregon Inlet were used
to compare storage in estuarine water with distilled water. After
2 months storage, there was no difference in germination between the
storage treatments (Fig. 21). However, after 5 months, when the after-
ripening process was apparently complete, seed stored in estuarine water
had a significantly higher germination percentage than those stored in
distilled water. At least in some cases, storage in salt water enhances
seed germination.

d. Planting Methods for Field Experiments. Several methods of

planting and incorporating seed have been used. In the first field
experiment with seed (1970), the plots consisted of three rows of seed
planted in furrows 1.0 meter apart and 15.2 meters long. Since the
seedlings were confined to narrow rows, little growth per unit area was
produced during the first growing season (Tab. 14). The results of this
initial experiment indicated that seed could be successfully used to
establish S. alterniflora and that seed should be distributed evenly over
an area to give a better plant cover during the first growing season.

In 1971, comparisons were made between the performance of seed applied
to the surface in a clay slurry (attapulgite) and seed broadcast by hand
and incorporated 1 to 4 centimeters into the substrate. At Oregon Inlet,
seed applied to the surface in the clay slurry produced a greater amount
of aboveground growth than those which were covered (Tab. 15). The seed
in the clay slurry germinated earlier and got off to a faster start since
temperatures on the surface were probably higher and the seedlings did
not have to emerge through a layer of sand. However, at Snow's Cut, seed
planted in the clay slurry produced almost no seedlings. There is a
greater tide range at Snow's Cut, and due to the regular flooding the clay
slurry containing the seed did not remain in place long enough for germi-
nation and rooting to occur. In adjacent plots, where seed were
thoroughly mixed with the substrate by raking to a depth of 1 to 4 centi-
meters, there was a good stand of seedlings which produced very good
growth (Tab. 15). It appears that broadcasting the seed and covering to
a depth of 1 to 4 centimeters is the best method to ensure a good stand
of S. alterntflora seedlings over a wide range of conditions.

100

Germination (%)

Figure 20.

cr A 21 Jan 1972
~ 17 Feb 1972
19 Dec 1971

0 17 Nov 1971

20 Oct 1971
LSD .05-9.8
4 8 12 16 20 24 28 32 36

Germination period (days)

Effect of afterripening of S. alterniflora seed stored for
various lengths of time. Seed harvested 28 September 1971
at Oregon Inlet and stored in estuarine water until germi-
nation was begun on the dates indicated.

Table 14. Mean Standing Crops Produced from
S. alterniflora seed in Two
Growing Seasons.*

Dry Weight (g/m*)+

22 Sept. 70 B Genes 7

Mo®
7.0
WS

Plant Component

Shoots

Rhizomes

*Planted in rows 1 meter apart at
Oregon Inlet, 21 April 1970.

+Means of three samples
No data taken

Table 15. A Comparison of Growth Measurements of S. alterntflora
Seedlings from Two Seeding Methods.

Number
Flowers/m

Clay slurry
Raked

Snow's Cut (seeded 24 Mar., harvested 15 Sept. 1971)

Raked (Plot 1) 1,236.8 260.0 480.0 116.0
Raked (Plot 2) 685.6 120.0 388.0 116.0

*Means of three replications

100

DO Estuarine water

80 © Distilled water
se
6 60 17 Feb 1972
3
£
E 40 17 Nov 1971
S

)

O 4 8 12 16 20 24 28 Si
Germination period (days)

Figure 21. Comparison of germination of S. alterntflora stored
in estuarine water and distilled water.

Several methods of incorporating seed were used to replace raking for
larger scale plantings. Where access is available, a farm tractor may be
used. We have used a standard farm tractor equipped with dual wheels for
added flotation and traction. Seed were broadcast by hand on the surface
and covered by six narrow sweeps mounted on the tool bar of the tractor,
followed by a spiked-tooth harrow (Fig. 22). Seed were also incorporated
without the spiked-tooth harrow by going over the area with the sweeps,
broadcasting the seed (Fig. 23) and plowing again with the sweeps.

Mechanization of distribution of the wet seed would be difficult.
However, spreading by hand works very well. Seeds placed in tubs or
buckets should be drained of excess water and sufficient dry sand mixed

with them to cause the individual seeds to separate (Fig. 24). They are
then ready to be broadcast.

Many areas are not accessible to a full-sized tractor. Two portable
mechanical methods have been utilized in these areas. For small areas,

seed may be broadcast (Fig. 25) and incorporated with a rototiller (Fig. 26),

AM: RP ALLEN DREAD

Figure 22. farm tractor incorporating
seed on dredge spoil near
Beaufort, North Carolina.

Figure 23. Broadcasting seed after
preparing a seedbed with
tractor and cultivators.

Figure 24. Mixing dry sand with wet seed
to improve distribution when
broadcasting.

Figure 25. Broadcasting seed and sand
mixture on a small experimental
plot on a dredge island near
Snow's Cut, North Carolina.

*LOT[1IIOJOL & YIM poss Butzerodso0duy

"97 o1nsTy

but this technique is too slow for larger plantings. A faster method was
developed which utilized the same two-wheel garden tractor, equipped with
dual wheels, which was used for harvesting seed to pull a cultivator that
consisted of. six small sweeps about 25 centimeters apart (Fig. 27).
Furrows were opened with the sweeps, seed were broadcast and covered by

a second trip over the seeded area.

e. Seeding Date. Seed germination under natural conditions begins
as early as March on the North Carolina coast. However, when seeding
S. alterntflora, delaying the planting date until mid-April lessens the
chance of damage due to weather. The probability of storms which produce
damaging wave action decreases later in the spring. Earlier plantings
produce more growth by the end of the growing season, but a compromise
must be made between early planting and increasing the risk of being
washed out or buried by wave action.

A comparison of two planting dates was made at Beaufort in 1972.
About 0.5 hectare was seeded 11 April, but part of the seedlings were
washed out by a storm in May. A second seeding was made 21 June. Samples
of aboveground and belowground standing crops harvested 5 October 1972
from an area about in the middle of the tide range, indicate that the
April seeding was more productive the first growing season (Tab. 16 and
Fig. 28). After the second growing season, differences were less
striking.

Table 16. Mean Aboveground and Belowground Standing Crops Produced from
Two Seeding Dates at Beaufort, North Carolina in 1972

Seeding Date

Aboveground Standing Belowground Standing
Crop (g/m*) by Year Crop (g/m?) by Year

5 Octeelo72 dle Septem lO Simeon Oct. 1972 ia Sept.. 1973
354 644 541 1,077
56 527 176
Three seeding dates were compared in the spring of 1972 at Snow's Cut.
Seed were planted on 16 March, 10 April, and 10 May; yields of shoots
were 388, 304 and 116 grams per square meter, respectively. These results
indicate that there is very little difference in growth between the March
and April seeding; therefore, risk of weather damage can be reduced by

delaying planting until April without sacrificing growth potential.
Delaying until May reduced first season growth greatly.

11 April 1972
21 June 1972

f. Seeding Rate. Since the number of viable seed produced varies
from year to year and between locations, it is desirable to estimate the
number of viable seed per unit volume for each lot of seed that is avail-
able for planting. This can be done by simply measuring a small volume
of seed, germinating them, and counting the number of seedlings produced.

t accessible to the farm tractor.

ions no

t locat

ing a

in see

Garden tractor used

Figure 27.

Photo taken

Bala Noweats OVD (Gealgalme)).6

S. alterntflora seeded 21 June 1972 (left)
Compare with Figure 22.

11 November 1972.

Figure 28.

Experience has shown the number of viable seed per liter varies from as
low as 500 to as high as 27,000. A rule-of-thumb estimate generally used
is 10,000 viable seed per liter (10 per milliliter). When planting, the
volume of seed applied per unit area can be adjusted according to the
results of the germination studies. The rate used as standard is 100
viable seed per square meter. This rate can be adjusted up or down,
depending on amount of seed available and the exposure of the site.

Fewer seed are necessary in a protected area; heavy seeding rates increase
the chances of successfully establishing seedlings in areas exposed to
wave action.

g. Elevation. The elevation range over which seeding is an effec-
tive means of establishing new stands of S. alterntflora is less than the
elevation range of transplants. Seedlings are not as hardy as transplants
and are not as able to tolerate the rigorous conditions of inundation and
wave action characteristic of the lower elevations of the intertidal zone.
Observations at Beaufort and Snow's Cut illustrate this point in a quan-
titative manner.

At Beaufort, an average elevation of several points along the edge of
a natural marsh near the seeding experiment, indicated the lower limit of
growth to be 0.43 meter above MLW (mean low water). However, seedlings
produced by planting 11 April survived only as low as 1.02 meters above
MLW. The elevation of the upper edge of the natural marsh was 1.15 meters
above MLW. Therefore, the part of the elevation range normally occupied
by S. alterntflora which was effectively colonized by seeding was between
1.02 meters and 1.15 meters or a range of 0.13 meter. This amounts to
about 19 percent of the 0.72 meter elevation range of the grass at Beaufort.
Tide tables list the mean tide range at Beaufort as 0.76 meter. Seedlings
produced from seed planted 21 June had an average lower limit of survival
of 0.93 meter above MLW. The area colonized represents about 31 percent
of the elevation range of S. alterntflora. Apparently the late-planted
grass was able to survive at the lower elevation because it was not
subjected to storm-induced wave action as was the earlier planting.

Seedlings were successfully established over a larger part of the
elevation range on a dredge island in the Cape Fear River near Snow's Cut,
tide range 1.2 meters. Transplants survived from 0.25 to 1.41 meters
above MLW or a range of 1.16 meters. Seedlings survived down to 0.79 meter
above MLW which is a range of 0.62 meter or about 54 percent of the
elevation range at this location.

h. Protection from Blowing Sand. Covering of seedlings by windblown
sand appears to be a primary cause of failure of natural S. alterntflora
on sandy dredged material. If there is sandy material above the inter-
tidal zone, sand can be blown from these higher elevations until it
becomes armored with shell or covered with vegetation. When establishing
S. alterniflora on these sites by seeding, it is necessary to protect the
area with a sand fence, a vegetation strip such as Ammophila breviligulata
Fern. (American beachgrass), S. patens (Ait.) Muhl. (saltmeadow cordgrass),
Panicum sp., or preferably a combination of fencing and vegetation.

The experimental planting site at Beaufort was on the northeast side of
a large sandy dredged pile. Consequently, southwest winds periodically
moved large amounts of sand onto the planting site. Sand fences were
erected to prevent the planting from being smothered (Fig. 29). After
the first fence (1.2 meters high) was completely filled, it was necessary
to erect a second (Fig. 30) and finally a third fence. A strip of
Panicum amarulum Hitchc. §& Chase (silver bunchgrass) was also seeded to
intercept the blowing sand. (Seed were provided by the U.S. Department
of Agriculture, Soil Conservation Service, Cape May Plant Materials
Center, Cape May Court House, New Jersey.)

A similar seeding on the southwest side of a large dredged pile on
the Ocracoke side of Hatteras Inlet was completely destroyed by drifting
sand. This was seeded 13 and 14 April 1972 in the same manner as the
Beaufort planting; by mid-May, the seedling stand appeared comparable to
that at Beaufort. However, no sand fence was installed on this site
before the storm of 24 to 27 May, and the entire seeding was smothered by
the deposition of 15 centimeters of sand. Failure to protect seedings
from drifting sand can be critical under circumstances such as described
for these two sites. This experience emphasizes the potential of wind
erosion in transporting sand from dredge material back into the estuary.
By stabilizing the dredge material above the tidal zone with vegetation,
a Significant amount of refilling of the estuary may be prevented.

Sand deposition or erosion by waves or currents are also major threats
to seedling survival on exposed sites. If suitable structures could be
devised to protect such sites from wave action during the establishment
period, seeding might be feasible in many more locations than it is now.

i. Introducing Natural Seed Sources. The encouragement of natural

invasion of new areas through establishment of small ''seed patches" might
be the most economical approach in some situations. Both seedlings and
transplants of S. alterniflora almost invariably produce seeds the first
year and large numbers of seedlings have been observed among transplants
during the spring of the second growing season (Fig. 31).

Small plantings were made for this purpose at several locations. The
most successful was on a large (2 or 3 hectares) dredge island near Old
House Channel. A small area was transplanted in May 1971 on the shore-
ward edge of a flat on the southeast shore of the island (Fig. 32). There
were no other plants of this species evident on this or the adjoining
islands at that time. About 26 months later, S. alterntflora occupied an
area of about 0.5 hectare, on each side of and shoreward from the original
planting (Fig. 33), which could no longer be identified. This method of
colonization may be appropriate where resources are limited or where rapid
coverage is not required.

j. Large-Scale Seeding. An island, (which we call South Island),
comprising in excess of 10 hectares, has been developing for the last 18
months just south of Drum Inlet and several hundred meters west of the
barrier island. This island appears to result from sand coming in the

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inlet and accumulating around a small (1 hectare or less) spoil island
deposited during the course of opening the original channel. An island

in this vicinity was seeded in early May 1972, and the resulting seedlings
destroyed in the storm of 24 to 27 May of that year.

By early April 1973, an estimated 6 to 7 hectares of South Island
lay within the upper half of the tide range, the elevation zone in which
we have found seeding of S. alterniflora to be feasible. This situation
presented a unique opportunity to: (1) undertake field-scale seeding
using our portable equipment under the type of conditions for which it
was designed, and (2) test the feasibility of seeding a very exposed area
where little opportunity for natural invasion by marsh species seemed
likely in the immediate future. - The low elevation and closeness to the
inlet subjects the area to frequent flooding and strong turbulence. The
orobability of seeds drifting onto this site at the appropriate time for
germination and subsequent seedling establishment seems rather remote.

Seeding was delayed until the week of 16 April to reduce storm hazards.
About 4 hectares were seeded on 17 and 18 April using the two-wheel
tractor with cultivator. The area to be seeded was cultivated before
seeding and again immediately after seeding. Seed were broadcast by hand
aS previously described. On 2 May, a second area of about 1 hectare was
seeded in the same manner. Germination and emergence were excellent over
most of the area; by late May, an adequate stand of seedlings had survived
over an area of 3 to 4 hectares. However, the island continued to grow
and many seedlings were smothered by sand that moved over the island
during the summer. By the end of the growing season a 2-hectare block
lying roughly across the westerly one-fourth of the island still retained
an adequate stand with scattered plants remaining over another 1 or 2
hectares.

Rainfall was below normal for much of the summer in this region which
when coupled with the low, flat nature of the island, made the seeded area
vulnerable to salt injury (see discussion in Section 3c on Salt Damage).
Salt damage was believed to be the cause of both the stand thinning and
the slow rate of top growth of this planting. An area near the center of
the 2-hectare block (Fig. 34), devoted to a fertilizer test, was sampled
8 November 1973 and the data are presented and discussed later in Section
VI and Table 43. Top growth was quite restricted, much less than that of
the seeding of 21 June 1972 at Beaufort (Tab. 16). However, root and
rhizome production was equal to or better than the Beaufort planting.
These results suggest that the periodic salt-induced dieback observed
aboveground is not necessarily matched by losses in underground growth.
This does not seem too surprising since the large mass of succulent roots
and rhizomes underneath established stands probably plays a significant
role in their tolerance to salt buildup.

This planting was in good condition on 8 March 1974. The island

is still growing to the south and east with some erosion along the north-
west side. Additional sand has been deposited over most of the seedlings,

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but many of them are already sending new shoots through it. Unless
drastic shifts in erosion or deposition rates occur within the next 2 or
3 months, an adequate stand of well established vegetation is expected
over the area this spring. This is interpreted to be moderately success-
ful and to indicate that seeding under such conditions offers promise of
rapid and economical stabilization in some cases.

k. Cost. The cost of propagating S. alterntflora from seed is
reasonable and not unlike that of agricultural crops, except for diffi-
culties in gathering seed, and for access of equipment to some planting
sites. The time required to harvest a known amount of seed was determined
at Oregon Inlet in September 1972. One man operated the harvester, while
two others removed the cut seed heads from it at the end of each round.
Three sample areas were harvested (Tab. 17) to quantify yield of seed per
unit area and time required for harvesting. The variability of yield is
demonstrated by comparing the first sample area to the other two sample
areas. The volume of seed per unit area was about five times greater on
the first sample area than on the others, even though it was much smaller.
Variability of this magnitude in the seed crop of S. alterntflora is
common. Consequently, it is difficult to predict the resources necessary
to harvest seed at different locations or years or even different areas
within the same stand. In the sample, about 5 man-hours were needed to
harvest enough seed to plant 1 hectare.

The harvested seed were threshed to reduce the space necessary for
storage. Threshing required about one-half as many man-hours as harvesting.
The cost of storage was negligible, since refrigeration facilities were
available.

The amount of time required for planting depends on the equipment
available. Using a two-wheel garden tractor for preparing the seedbed
and covering the seed after they were broadcast by hand, 4 hectares were
seeded by 3 men-in about 10 hours. This amounts to 7.5 man-hours per
hectare.

In addition to the times listed there are other variable costs for
transportation to the sites, fuel, etc., which are difficult to estimate.
Fixed costs (equipment) are also difficult to estimate. In this case,
most of the equipment used was modified from that already owned by the
Soil Science Department, North Carolina State University.

3. Site Requirements.

a. Elevation and Tide Range. For propagation of salt marshes by
either seeding or transplanting, care must be taken in selecting or
preparing sites which meet the requirements of the species used. The
interactions of such factors as tide range, elevation, slope and
salinity determine the species of plants present and influence their
vertical zonation in marshes. The vertical range of S. alterntflora is
generally stated to occur from about mean sea level to mean high tide.
There are many exceptions to this generalization. Variations in vertical

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range occur in North Carolina estuaries where tidal fluctuations are
dominated by wind direction and velocity and where salinities are low.

At our Snow's Cut experimental site the salinity ranges from 7 to 10 parts
per thousand. Under this low salinity, freshwater plants have become
mixed with the S. alterniflora from about half way in the intertidal zone
upward. In completely freshwater, plant species adapted to freshwater
would probably become dominant.

In several North Carolina estuaries the range of periodic tides is
quite low because of few, narrow inlets and the large area of the estua-
ries. In such estuaries, surface fluctuations are greatly affected by
wind direction and velocity, and consequently, changes in surface levels
occur irregularly. This complicates the relationship between tide range
and the elevation zone occupied by S. atterntflora. In many locations,
S. alternitflora occurs as a narrow fringe at the water's edge. When
planning marsh restoration, it is best to take elevation readings of the
upper and lower limits of nearby natural marshes and plan to plant within
this zone. In preparing a site, the area available for planting can be
increased by making the slope as gentle as practicable without ponding
of water. The more gentle the slope the larger the area which will be
alternately flooded and drained.

b. Substrate Texture. Several substrate-related factors affect
propagation of S. alterntflora. Texture of the substrate as it affects
bearing capacity is an important practical consideration. Substrates
with high proportions of silt and clay are not suitable for conventional
planting equipment. The Straits test site is the only place where this
problem was found. Most of the dredged material in North Carolina
estuaries is composed mostly of sand, and consequently has excellent
physical properties. Additional opportunities to experiment with propa-
gation methods on finer textured materials will be welcome.

Sandy substrates are not without limitations. Sandy materials are
inherently less fertile than silt and clay since fewer mineral nutrients
are adsorbed. Experiments with fertilizers have produced increased
growth through applications of nitrogen and phosphorus at locations where
the substrate is sandy, such as Drum Inlet and Ocracoke Island. An
exception is the Snow's Cut location where the substrate is sand, but
nutrients are apparently supplied by the large amount of silt and clay
sediments carried by the Cape Fear River and deposited in the marsh on each
tidal cycle. At Ocracoke and Drum Inlet little deposition of fine materials
has been observed.

c. Salt Damage. Another substrate-related factor is salinity.
Although S. alterntflora is exceptionally well adapted to growth and sur-
vival under saline conditions, it can suffer serious salt damage. This
damage we observed in several instances during the field studies. All
observations were in the Pamlico and Core Sound region on sites subject
to wind setup. Salt damage may occur in such areas any time that extended
periods of low water coincide with periods of warm, clear weather. Under
these conditions surface salinities build up rapidly and can be particularly

severe on seedlings and young transplants. Established plants seem to be
able to tolerate much higher salinities at least for short periods of
time.

Core Sound and the southern part of Pamlico are particularly vulner-
able to this phenomena since the southwesterly winds normally prevailing
here during the warm part of the year result in low water levels. It
occurs also in northern Pamlico where low water results from northeasterly
winds. Heavy salt concentrations, even to the extent of a white crust on
the soil surface, have been observed. This condition develops at Oregon
Inlet, particularly in April and early May when northeasters of several
days duration are not uncommon. At such times the effect on young seed-
lings is quite severe.

While seedling stands are occasionally killed completely by salt
damage, the more frequent effect is a temporary dieback, thinning and
stunting. The less severe effect may be due to an intermediate salt
concentration or to shortening or interruption of the buildup period by
rain showers or wind shifts. This probably happened at the field-scale
seeding on South Island (Drum Inlet) during the 1973 growing season.
Early seedling emergence on most of this site was good, and by early May
a very dense stand seemed ensured. However, by early July many seedlings
had died and the remaining plants were stunted and exhibited the general
appearance we associate with salt damage -- dead leaves and varying degrees
of tip burn of living leaves. Spot checks of salinity were made on about
every site visit throughout the summer. All readings were approximately
sea strength, although plant appearances suggested that some additional
salt damage had occurred, probably on more than one occasion. When the
planting was sampled 5 November for estimates of aboveground and below-
ground production, salinity determinations were made at each sample site.
The mean for the 48 samples was 40 parts per thousand (sound water = 35
parts per thousand in this vicinity).

Stand losses that appear to be related to salt buildup have also been
observed in well established plantings, occurring as small irregular spots.
These have been identified at The Straits on recently dredged material,
highly variable in texture, and at Drum Inlet on recently dredged material
containing a high proportion of sand.

The damage always appeared the year after transplanting, and was first
observed at The Straits in the summer of 1971. Five sampling stations
were established and these were sampled three times (Tab. 18).

Wherever salinities of the soil solution exceeded 45 parts per thou-
sand, dieback of S. alterniflora leaves was observed; in more severe cases,
entire plants were dead.

A similar pattern appeared at Drum Inlet in the spring of 1973 on plots
transplanted to S. alterntflora in May 1972. Eight sampling stations were
established in May and followed through August (Tab. 19).

Table 18. Soil Solution and Sound Water Salinity
Measurements* in Dieback Spots at
The Straits

Date Salinityt
Soil Solution?

28 July 1971 28 32 to 58
OSepte. 971 35 to 80
BQ) Oees: UUs 5), 160), DS)

*Salinity determined in field
with hand-held refractometer.

+Parts per thousand
tRange among five stations

§Immediately after period of heavy rains

Table 19. Soil Solution Salinity - Drum Inlet, 1973

Station

Salinity* Vegetation

Condition

16 Aug.
Dead, soil bare
Normal
Dead, soil bare
Normal

Dead, soil bare

Normal

Sj. fon Cn SS Ss) TS)

Normal

*Parts per thousand
+Mean low water

At The Straits, it was theorized that the high salinity spots were
related to the interlayering of very fine and coarse sediments that
occurred at that site. This theory was abandoned when similar phenomenon
appeared at Drum Inlet, a site containing almost no fine material. At
Drum Inlet, the toxic areas were confined to the higher intertidal ele-
vation within these plantings. This would be the zone left exposed most
often, and it was exposed for days at a time during the summer. This does
not account for the localized nature of the high salinity spots within
this zone.

Station 8 at Drum Inlet is in the "high" elevation zone, but appears
very much out-of-place with salinities well below all other stations
(Tab. 19). This station is immediately adjacent to a part of the island
lying 1 meter or more above the intertidal zone. It is sandy and big
enough to develop a freshwater bubble, such as occurs under dunes
(Berenyi, 1966), and seepage from this elevated area into the vicinity of
Station 8 continually dilutes the soil solution at this location.

Freshwater seepage from sandy spoil piles can significantly reduce
soil solution salinities in the intertidal zone. This could be important
for plant establishment and survival in this zone in regions having
substantial wind setup. On South Island the absence of any area high
enough to permit the retention of freshwater was a handicap to the
initial establishment of a seedling stand.

IV. MARSH DEVELOPMENT

The ultimate objective of planting S. alterniflora will usually be
the initiation of a marsh, which has as one of its functions stabilization
of the substrate material. Consequently, the rate at which a planting
is able to achieve this objective is of interest. An area at Snow's Cut
has been followed since planting 7 April 1971. Planting was by hand, one
stem (culm) per hill, 0.91-by 0.91-meter spacing, using transplants dug
from nearby natural stands. Their development has been monitored by
sampling, counts, and measurements made annually in September, near the
end of the period of major aboveground growth. A photographic record has
been maintained, and elevation cross sections have been surveyed.

The developmental pattern of such a planting can probably be best seen,
through the early stages, in the pictorial record. The developmental
sequence over the first 12 months for this planting is shown in Figures
35 through 39.

Following spring transplanting, there were a few weeks during which
the transplants developed new roots and new shoots emerged from the base
(Fig. 35). This stage was followed by a period of rapid aboveground growth,
as seen by the proliferation of new stems (center culms) around the origi-
nal transplant, extension of rhizomes, and emergence of new stems from
rhizomes (rhizome culms) at various distances from the transplant (Fig.
36). This stage lasted a little past midsummer after which flowering
began and the season's aboveground growth approached maturity (Fig. 37).

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By late September, seeds were mature and aerial growth had decreased.

At this point, the stand consisted of large clumps of stems, 20 to 50 or
more, centered around the original transplant with rhizomes of various
lengths radiating from them and sending up new stems (rhizome culms)
(Fig. 38). At this stage, the substrate was partially stabilized by
roots and rhizomes but the cover was still quite open, leaving much of
the surface bare.

Seeds shattered rapidly following maturation in late September through
mid-October, and aerial growth took on the color of straw and became
susceptible to being broken and exported to the estuary by winter storms.
Belowground growth continued as evidenced by new rhizome shoots emerging
at the surface through the fall. Although not studied, it is evident
from observations that a substantial amount of root and rhizome expansion
goes on under these stands during the winter.

By March of the second growing season, new shoots so populated the
surface that the original hills and rows were no longer identifiable
(Fig. 39). Following the flush of spring growth, the site appeared to be
fully stabilized, or very close to it, as far as vegetative cover could

go.

Developmental data of this planting at Snow's Cut over the 3-year
period are presented in Table 20.

In September 1971, three fairly distinct zones of growth consisting
of about the upper 25 percent of the vegetated slope, the center 50 per-
cent, and the lower 25 percent were visible. Growth was best in the
center of the slope and much poorer at both extremes. Consequently, the
planting was divided into these three zones for sampling purposes for
1971. However, at the end of the next growing season, it appeared that
four zones would be preferable and sampling afterward was done accordingly.
It became evident, after 2 years, that for most measures the two center
zones could be combined with little loss of information. Visually there
is some difference, but this is primarily in the number of invading plants,
and these are numerous enough to sample only in the original upper zone.

A large increase in plant cover developed between the end of the
first growing season and the end of the second. This is reflected par-
ticularly in number of culms and in both aboveground and belowground
dry-matter production, with increases ranging from 3- to 10-fold. These
results probably indicate a concomitant increase in substrate stabiliza-
tion and resistance to wave action of the planted area.

By the end of the third growing season, some additional aboveground
development was recorded (Fig. 40), but the real change was belowground
(Tab. 20). While top growth increased noticeably at the higher elevations,
root and rhizome production increased dramatically throughout. Such
increase in root and rhizome mass should substantially increase the
stability of the area. Although the belowground plant material was not
separated by species, it was nearly all S. alterntflora except in the

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upper zone. Based on the first 3 years of stand development on this site,
it is evident from the standpoint of vegetative cover, substrate stabili-
zation, and primary productivity, that marsh development following trans-
planting can be quite rapid. Productivity was 7,000 kilograms per hectare
the second year and reached 10,000 kilograms per hectare in the third

year which compares with 5,100 and 16,000 for the short and tall height
forms in the long established natural marshes of Oak Island (discussed
later in Section VI, Tab. 40). Cover, as reflected in number and size

of stems, and production increased between the second and third year, but
the rate of increase slowed. Belowground growth expanded much more than
did top growth during the third year. However, these data may be decep-
tive, since this may mean an accumulation of another season's growth

added to that of the first 2 years. If this is the correct interpreta-
tion, the annual rate of production belowground appears to be slowing also.
There may be further increases in vegetative material in the root zone,
but it is difficult to comprehend how it can continue to expand at the
present rate without much deeper penetration into the substrate. We have
seen no evidence of change in this respect from the first year.

Distribution of roots and rhizomes by depths was examined at Snow's
Cut in 1972. It was feasible to take cores to a depth of about 30 centi-
meters, but only at low tide. There was little penetration of roots and
rhizomes below this depth, and no adequate method of sampling below 30
centimeters was found. Cores almost invariably broke off at the point of
sharp decrease in belowground growth which occurred around 25 to 30
centimeters below surface.

Cores collected in 1972 were divided into the 0 to 10- and 10 to
30-centimeter depth segments, and the roots separated from rhizomes.
The depth division was selected because belowground plant material was
more dense in the upper 10 centimeters. About two-thirds of the roots
collected are distributed in the upper 10 centimeters; the remainder
occurring in the 10-to 30-centimeter zone (Tab. 21). Rhizomes were more
evenly distributed between the two zones. There was a distinct tendency
toward less total belowground growth as the period of inundation increased.

Sampling variation is high with coefficients of variability of 37.5
to 84.3 percent. Consequently, differences would have to be quite large
to be detectable.

Estimates of rate of spread were obtained at Snow's Cut at the end of
the third growing season. The lateral rate of spread was from 0.9 to 1.5
meters per year (Tab. 22; Fig. 41). Data on downslope spread were avail-
able from only one plant source (Ocracoke) at one elevation. Since
lateral spread for all plantings at this location was uniform across the
four zones of inundation and of the same general magnitude as the single
downslope expansion determination, we assume that the latter would be
very similar to the lateral spread at all elevations within this range
(2 to 12 hours inundation).

Table 21. Distribution of Belowground Growth* by Depths,
Snow's Cut 1972

Inundation Zones | Dry Weight (kg/ha) Roots|Dry Weight (kg/ha) Rhizomes
(hr/day) (cm)

*Samples were four core samples (8.5 cm in diameter
and 30 cm deep) from each elevation zone. One core
was taken from each 0.25 m2 sample area.

tLeast significant difference
ENot significant

§Coefficient of variation

Table 22. Rate of Spread (meters per year) of S. alterntflora at
Snow's Cut, 8 April 1971 to 27 November 1973

Downslope Spread

Lateral Spread

Snow's Cut Planting Stock

From Single | Along Edge } Planted on
Isolated of Large | Old, Very
Row Compact

Ocracoke Plants

in 12 hr/day
Inundation Zone

Ocracoke Plants

Along Edge of
Large Block

SLOT YIteW S

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yn) s

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mous 3e sjzuetd ayoder199 Fo peords [es92e7]

Rate of spread of such plantings is useful in estimating the time
required for stands, established by seeds in the upper part of the tide
range, to advance downslope to the lower limit of growth for this species.
For example, direct seeding was successful at Snow's Cut down to 0.79
meters above MLW (inundated 5.7 hours daily); transplants survived down-
slope to 0.25 meters above MLW (inundated 16.6 hours daily). The hori-
zontal distance between these two points on this site was 39 meters.
Assuming an annual rate of spread downslope (1.31 meters) equal to that
measured for the transplanted area, 30 years would be required for the
seeded stand to spread to the lower limit. This is one of the strong
justifications for transplanting where early stabilization of the entire
slope is desired.

Development of a transplanted stand at Drum Inlet has been followed
over a 2-year period (Tab. 23). This stand was one that escaped serious
damage from the February 1973 storm and from salt buildup during the
summer. Second-year development was equal or somewhat superior to that
at Snow's Cut in terms of plant cover, primary production, and belowground
growth (Tab. 20). This growth response took place under conditions that
varied substantially from those at Snow's Cut. Salinity was much higher
(close to sea strength); tide range was lower and erratic due to wind
effect, and there appeared to be much less movement of fine grained sedi-
ments. The rapid development of S. alterntflora on this site is further
evidence of its ability to perform well under a wide range of conditions
and suggests the Snow's Cut data may be representative of the development
process.

Table 23. Development of Transplanted S. alterniflora at Drum Inlet

Culms /m2 Height Flowers/m? Basal Area Yield kg/ha
| fom) | Come/m?) m?)

Center|Rhizome Below-
aa
Oe ae

ee ae Sea 18,038

SAO T2 a were seven individual plants (means are
expressed in the table) for aboveground growth.

197.2%

TNot sampled

£1973 samples were six, 0.25 m* plots. Belowground
samples were two cores from each of the aboveground
sampling areas.

Another aspect of marsh development has been followed at the Drum
Inlet and Snow's Cut sites. Invertebrate species were sampled by taking

core samples of the substrate material, screening, and identifying those
present (Tab. 24).

Table 24. Invertebrate Species Found at Drum Inlet and Snow's Cut
from March to November 1973

Natural Marsh Dredged Material
Drum Inlet

Annelida
Heteromastus filtiformis
Laeonerets culvert
Eteone heteropoda
Seoloplos fragilis
Streblospto benedtett
Glycera sp.
Nereis succinea
Paranais litoralts
Henlea ventrtculosa
Tubificidae (Ltmnodrilotdes medtoporus?)

Annelida
Paraonts fulgens
Magelona papillicornis

Arthropoda
Ueca pugtlator
Acathohaustortus mtllst

Nemertea
Tubulanus pelluctdus

Arthropoda
Dolichopodidae
Ephydridae
Stratiomyidae
Insect adult A
Insect adult B
Neomysts amertcana
Uca pugtlator
Ocypode quadrata

Mollusca
Gemma gemma
Mya arenarta
Tagelus plebtus
Areuatula (= Modtolus) demissa

Snow's Cut

' Annelida Mollusca
Heteromastus filtformts . Telltna sp.
Laeonerets culvert Arcuatula (= Modiolus)
Seolocolepides vtridens demissa
Nerets succinea
Enchytraeus albidus — Nemertea
Unidentified

Arthropoda
Dolichopodidae
Ephydridae
Leptdactylus dyttscus
Cyathura polita

Uea pugilator

The invading species, in general, appeared to be the most widely
adapted of the typical salt marsh species. Common at both Drum Inlet
and Snow's Cut were the polychaetes Laeonerets and Heteromastus in the
creeks, and Dipteran larvae and Uca pugilator, the fiddler crab, in the
marsh itself. The polychaetes are deposit feeders; the others feed
mainly on the growth of algae and diatoms at the marsh surface. In time,
it is expected that these species will become less important as other less
common species invade, but that they will still be among the dominant
invertebrate fauna.

V. SHORE PROTECTION AND SUBSTRATE STABILIZATION

Stabilization was a major objective of the study, but one for which
we were unable to develop satisfactory evaluation procedures. The prob-
lem is the lack of unaffected or unbiased controls. For example, at the
Snow's Cut site, the original experimental plantings were divided into
three blocks, 45 to 60 meters wide, that extended roughly from the high
spring tide line, downslope to about MLW. These blocks were spaced 30 to
60 meters apart, leaving the intervening strips unplanted and undisturbed.
Dominant tidal currents are across the slope (parallel slope contours).
Erosion and deposition were monitored in two ways: (1) by cross-sectional
surveys started in 1971 through the planted blocks (Figs. 42 through 45)
and (2) by cross sections established in early 1972 through the unplanted
strips (Figs. 42 and 46 through 49). The latter might seem preferable
as controls, compared to following elevation changes of the planted blocks
over time. However, the protection afforded these unplanted areas by the
adjoining vegetated blocks affects the erosion, the deposition and the
revegetation occurring on them. Natural revegetation is gradually elimi-
nating these areas as "unvegetated controls."

Even the provision of unplanted blocks or strips appears inadvisable
on eroding shorelines such as at Cedar Island since they would likely
promote erosion of adjacent areas.

There appears to be no meaningful way to test stabilization effects
directly in small-plot field experiments. However, relative values between -
variables based on vegetative growth may be sufficient at this stage.

Beyond that, wave tank tests might be the best approach.

1. Snow's Cut.

As indicated, certain cross sections were monitored at this site from
June 1971 (Figs. 43, 44, and 45) and others (Figs. 46 through 49) from
April 1972. All three planted blocks have shown a steady gain in elevation
over the 30-month period. The northernmost block (Figs. 42 and 43) has
trapped the most sediment, averaging close to 30 centimeters over the
entire slope with largest gains in about the upper half of the normal
tide range (Fig. 50). It appears that more sediment may be coming from
the northern or upstream side and this planting may be intercepting
material and reducing the amount available to the areas downstream to it.

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= 1.0 Lower edge of
= S. alterniflora
Cc
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i)
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2
w 0.5
0
6) 20 40 60 80
Slope distance (m )
Figure 43. Planted transect, No. 1, Snow's Cut;
2 June 1971 to November 1973.

1.5
£10
Ss
= Lower edge of
Es S. alterniflora
2 igen, Seueetb aT)
=
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ZS |
WW

26 Nov 1973
e 2 Jun I971

6) 20 40 60
Slope distance (m)

Figure 44. Planted transect, No. 3, Snow's Cut;
2 June 1971 to November 1973.

e!0

3 926 Nov 1973 loveriedsetat

20.5 © 5 Mar 1973 8. alterniflora
423 Oct 1972
@25 Apr 1972
e2 Jun 1971

0 20 40 60
Slope distance (m)

Figure 45. Planted transect, No. 7, Snow's Cut;
2 June 1971 to 26 November 1973.

Elevation MLW (m)

Natural invasion

of S. alterniflora
Ke Mar Nov
1973 1973
051 026 Nov 1973

#25 Apr 1972

@) 20 40 60 80
Slope distance (m)

Figure 46. Unplanted transect, No. 2, Snow's Cut;
25 April 1972 to 26 November 1973.

Oct 1972 visual i :
Mar 1973 Natural. invasion

Nov 1973 Of > alterniflora

ro)

Elevation MLW (m)

0226 Nov 1973
825 Apr 1972

0) 20 40 60
Slope distance (m)

Figure 47. Unplanted transect, No. 4, Snow's Cut;
25 April 1972 to 26 November 1973.

rae ere Natural invasion

Nov 1973 Of © alterniflora

ro)

oS
on

Elevation MLW (m)

9 26 Nov 1973
@ 25 Apr 1973

0) 20 40 60
Slope distance (m)

Figure 48. Unplanted transect, No. 5, Snow's Cut;
25 April 1972 to 26 November 1973.

Natural invasion
of S. alterniflora
Oct Nov
1972 1973

ERIEO
=

ay
=

Cc
2

rs)

>
210!5
WW

2 26 Nov 1973
@25 Apr 1972

O 20 40 60
Slope distance (m)

Figure 49. Unplanted transect, No. 6, Snow's Cut,
25 April 1972 to 26 November 1973.

There was little difference in elevation gain between the other two
planted blocks; the change on these averaged around 15 centimeters.
Sediment accumulation definitely decreased in the zone immediately down-
slope of the vegetation.

Records on the four cross sections through the unplanted strips indi-
cate little change in elevation during the period of record (Figs. 46
through 49). Section 2 (Fig. 46) upstream from the others, exhibited the
most accumulation. The effect of volunteer seedlings is clearly visible
in the most recent survey on all of these unplanted areas. A minor amount
of erosion has occurred along these cross sections, largely at the bottom
of the slope.

There was no way to predict what elevations would exist along the
unplanted cross sections if no S. alterniflora were planted in the vicinity.
The planted blocks did trap substantial amounts of sediment, and the inter-
pretation is that this, along with the behavior of the unplanted strips is
reasonable evidence of a strong stabilizing effect of this vegetation.

Also, the slowness with which S. alterniflora invaded the unplanted strips
appears to indicate that natural colonization of the area would have been
extremely slow in the absence of such plantings. No seedlings appeared

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on the unplanted strips until the second year following the heavy first-
year crop of seed on the planted blocks. It seems, therefore, that these
areas were both seeded and protected by the planted blocks. It is
possible that without this protection, seeds could not remain in place

at this location long enough for germination and establishment, and that
revegetation would have to come from gradual expansion of vegetation from
a more protected part of the island.

2. Cedar Island.

The experimental area is on the former Lola Naval facility situated
on a promontory near the southern tip of Cedar Island. It is exposed to
a fetch of several miles across Pamlico Sound to the east and northeast
and across Core Sound to the south. It appears to be representative of
many eroding shorelines in much of the Core and Pamlico Sound region.

This area is believed to have a long history of erosion. On more
protected shores nearby, Juncus marsh is growing on a thick (0.6 to 1.2
meters) layer of peat well above normal water levels, with the perpendi-
cular face of the peat exposed along the water's edge. Apparently the
marsh has grown upward on the surface of the accumulating peat and has
long since lost contact with the intertidal zone along this edge. Conse-
quently, the exposed face is quite vulnerable to erosion. This was
probably true in front (east) of the Lola facility some years ago, but if
so, the thick peat layer has eroded away. This shoreline is steep (10 to
25 percent slope), and is presently composed of coarse sand interlayered
with thin lenses of peat. With only wind setup, a narrow area is available,
2 to 4 meters wide, on which-S. alterniflora could be expected to grow.
Before planting in May 1972 there were three or four small eroding patches
of S. alterntflora along this shore. About 1,900 S. alterniflora plants,
dug near Drum Inlet, were transplanted by hand on about 0.6-by 0.6-meter
spacing along a 0.2-kilometer stretch of shoreline south of the Radar
Tower (Fig. 51). Following this planting, the area was subjected to
strong northeast winds by a subtropical cyclonic disturbance from 24 to
27 May. A few weeks later, 60 percent of the transplants were washed out
and the appearance of the 40 percent remaining was not encouraging.
Consequently, this trial was written off as a failure and was not checked
again until late in the season. At that time, the surviving plants had
made a surprising recovery. When growth emerged the following spring
(1973), these plantings were well established, and by fall a high propor-
tion of this stretch of shoreline was effectively stabilized (Fig. 52).

Samples were taken from this area in the fall of 1973 to estimate
productivity (Tab. 25). Growth on this site was unusually dense and
vigorous. Number of culms and flowers per unit area was quite high, and
dry matter production was unusually high. When rechecked in January 1974,
the only noticeable change in these plantings was some sporadic sand
deposition by storm tides and waves. There was no evidence of stand loss

from erosion.

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101

Table 25. Second-Year Development of S. alterniflora Plantings* -
Cedar Island, 13 September 1973

Aerial
Dry Weight
(kg/ha)

Number Basal Area

Stems /m2

Number
Flowers/m2
(cm?/m*)

*0.25 m* samples

Another planting of 1,900 transplants was made on five small areas
north of the Radar Tower on 11 and 17 May 1973. This shoreline is more
exposed to the northeast and is eroding more rapidly than the area used
for planting in 1972. Plants were closely spaced, about 0.3 by 0.3 meters.
The total frontage covered was about 90 meters long. Erosion has con-
tinued on this area with little net recession of the shoreline, but sub-
stantial movement of material back and forth so that only about 20 percent
of the plants could be identified as surviving in September 1973 (Fig. 53).
Fewer were in evidence in January 1974, but some of these had grown quite
well, some were buried beneath sand and rubble, and the amount of new
growth that would appear in the spring was not predictable. Obviously
this planting will not be as successful as the 1972 planting nearby, but
it could be better than at present.

Experience in shoreline stabilization suggests that such plantings do
have potential for reducing sound-side shoreline erosion in this region.
Many eroding sound shorelines are similar to those in the study area at
Cedar Island. Any marsh vegetation remaining on them has lost contact
with the sound bottom,separated from it by a scarp. The plants can no
longer spread back into the bare zone by rhizomes. Further, since turbu-
lence along the shoreline is excessive for seedling establishment, there
is little possibility for natural revegetation. It is known from work
elsewhere that S. alterntflora can be established by transplanting under
conditions that are much too rigorous for natural invasion. If vegetation
is to be reestablished on these shores, transplanting is the only possi-
bility.

VI. THE RELATIONSHIP OF MINERAL NUTRIENTS TO PRODUCTIVITY
OF SPARTINA ALTERNIFLORA

The mineral nutrition of S. alterniflora was studied to obtain know-
ledge of the relationship of fertility of the substrate material to

102

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103

productivity of the grass. The role of fertility of the substrate
material as it affected starting new marshes by artificial propagation
had not previously been investigated.

The productivity of natural marshes varies greatly from one location
to another (Cooper, 1969). There is also variation within a given loca-
tion with three distinct height zones (tall, medium, and short) generally
recognized (Teal, 1962; Adams, 1963: Cooper, 1969). In the past, attempts
were made to relate differences in productivity to such factors as genetic
differences, time of inundation, and salinity. The efforts to relate
productivity to nutrients in this study were divided into two phases.

The nutrient status of plants and soils was sampled in natural stands from
seven locations along the North Carolina coast, and related to yields
using regression analysis. The second phase measured growth response to
fertilizer applications. Plants in natural stands, transplants, and
seedlings were included.

1. Nutrient Status of Natural Stands.

a. Methods. Stands of S. alterniflora at seven locations along the
North Carolina coast were selected for sampling during the summer of
1970 (Fig. 54). These stands are representative of variations in latitude,
in tidal range, and in type of substrate occurring along the North Carolina
coast. The Oregon Inlet, Hatteras Village and Ocracoke sites are similar
in their location on the sound side of barrier islands where the tide
range is 30 centimeters or less. Two important damper effects cause the
narrow tide range in estuaries north of Cape Lookout: (1) few inlets
through the barrier islands, and (2) a large expanse of water behind the
islands. Winds greatly influence the surface levels causing a greater
but irregular fluctuation. The Oregon Inlet and Ocracoke marshes are
young stands on sandy substrate low in organic matter. The Hatteras
Village marsh grows on a substrate containing 10 percent organic matter.
The North River marsh is also in a location of low tide, growing on sandy
substrate, and consists of a narrow fringe (about 20 meters wide) along
the shore.

The Beaufort, Swansboro and Oak Island marshes are in areas of wide
tidal range and are more typical of the regularly flooded southeastern
tidal marshes described by Cooper (1969). South of Cape Lookout, inlets
are numerous and the estuaries are narrow allowing a greater tide range.
Texture of the substrate is quite variable between the locations (Tab. 26).

Plant samples were taken from each location and each height zone
17 to 23 June, 5 to 17 August, and 30 September to 2 October. The dis-
tinctness of the height zones varied among the locations. The medium
height zone was a narrow transition zone which was barely discernable in
several locations. Consequently, only samples from the tall and short
height zones were included in the statistical analyses. The plant samples,
consisting of 0.25-square meter plots, were clipped at ground level from
each height zone. The sample plots were selected by establishing a
transect across and perpendicular to the height zones. From this line,

104

; ape
pee Ky r \ ) Hatteras
‘y atteras
\ sogltts Village
eo Ocracoke
iy
“North River
Cape Lookout

Beaufort

Swansboro

Oak Island

Figure 54. Locations of sampling sites (indicated by arrows).

105

three points for sampling were randomly selected within each height zone.
Sampling was done at low tide when possible. Soil solution salinity was
field-determined with a handheld refractometer.

Table 26. Soil Texture and Percent Organic Matter of Tall and Short
Height Forms of S. LA SLA for Seven Locations

Leeseate Sane | Seite || Ponce She | Percent [Boweete he | Percent OM:

Location

Oregon Inlet] 97.3

Hatteras 10.8
Village

Ocracoke OKs

North River 2.4

Beaufort 6.0

Swansboro 0.5

Oak Island
LSD 0.05+
x ht. zone 10.0

Loc. Mod

*Height zone

tLeast significant difference
(Main effects are not presented because of significant
location by height zone interaction)

Measurements on the grass included dry weight (dried at 70° Centigrade
in a forced-air oven), number of stems and their height (the average of
five randomly selected stems in each 0.25-square meter plot). The dried
samples were chopped with a silage chopper, and subsamples were ground in a
Wiley mill in preparation for nutrient analyses of the plant tissue.
Determinations of the concentrations of nitrogen, phosphorus, potassium,
sodium, calcium, magnesium, sulfur, iron, zinc, manganese and copper were
made by the Department of Soil Science, Analytical Service Laboratory at
North Carolina State University. Soil samples of the upper 15 centimeters
were taken in each height zone at the time of the first plant sampling.
These samples were air dried, and screened, and the following determina-
tions were made by the Soil Testing Division of the North Carolina
Department of Agriculture using their routine methods: organic matter,
calcium, magnesium, phosphorus, potassium, sodium, CEC (cation exchange
capacity) and soluble salts. Soil texture was determined by the hydro-
meter method (Day, 1956).

Regression analysis was the statistical technique used to detect
relationships between nutrient levels in the soil, plant tissue, and

106

productivity. After an attempt to use the raw data, yield and height
were transformed to their logarithm (base 10) to provide a better fit for
the curves, decrease random variation, and normalize the mean square
error. There are 48 independent variables in the original data which
consisted of the concentration of 11 different mineral nutrients in the
plant tissue at each of 3 sampling times, the salinity of the soil
solution at each sampling time, and 12 soil chemical and physical proper-
ties. The ''best'' regression model was selected using a combination of
the maximum R* (multiple correlation coefficient) improvement procedure
(Service, 1972), the stepwise regression procedure (Draper and Smith,
1966), and critical examination of the independent variables from an
agronomic view. In the stepwise procedure, the single variable model
which produces the highest R* is selected; then variables are added one
by one to the model according to their significance measured by the
F-test (0.1 level of significance for entry). At every stage of regres-
sion, the variables incorporated in the previous stages are reexamined
for significance. A variable entered at an early stage may lose its
Significance because of its relationship to other variables entering the
regression. The maximum R* improvement technique developed by J. H.
Goodnight (Department of Statistics, North Carolina State University,
Raleigh, North Carolina) selects the ''best'' one-variable model, the "best"
two-variable model, etc. according to R?%.

b. Selecting the Dependent Variable. The independent variables were

measurements of soil chemical and physical properties and nutrient con-
centrations in the plant tissue at three sampling dates (Tab. 27).
Multiple regression procedures were used as variable screening devices to
determine which of these independent variables were related to yield and
height of S. alterniflora. _It was necessary to select two models (one

for logy yield and one for log,g height), because the relationship

between height and yield was not as close as might be expected (Fig. 55).
esto nertign the relationship between yield and height is highly significant,
the R* is only 0.26. The R* was not greatly improved by transforma-
tion to logarithms. Stands are thinnest where the tallest grass occurs;
consequently, shorter grass may produce higher yields where stands are
thicker. An example is seen by comparing the data for yield and height
from the tall height zones at Oregon Inlet and Beaufort (Tab. 28). The
average height at Beaufort is much greater than at Oregon Inlet, but the
yield at Oregon Inlet is greater. This is attributed to there being
nearly twice as many stems per unit area at Oregon Inlet to produce the
total biomass. This difference in growth habit may be related to tide
range or possibly to genetic difference between the grass from different
locations. Shorter grass and thick stands occur at Oregon Inlet, Hatteras
Village and Ocracoke where the regular tide range is less than 30 centi-
meters. At Beaufort, Swansboro; and Oak Island where the tide range is
about 1 meter, the grass is taller but the stands are sparse.

There is also a significant difference in the number of stems per unit

area between the tall and short height zones. The stands are more dense
in the short height zones, but the yields are much less than in the tall

107

Table 27. Variables Used in Model Building and Their Simple
Correlations with Dependent Variables Height and Yield

Variables Abbreviations

Simple Correlation
Coefficient (r)

Organic matter

Cation exchange capacity
(meq/100 g)

Soluble salts (MMho) 0.22
Phosphorus (ppm) -0.09
Potassium (ppm) 0.38*
Calcium (ppm) -0.17
Magnesium OR22
Manganese (ppm) -0.08
Sodium 0.29
Sand (%) -0.36*
Silt (%)

Clay (%)

17 to 23 June
5 to 17 August
30 September to 2 October

17 to 23 June
Nitrogen (%)
Phosphorus (%)
Potassium (%)
Sodium (%)
Calcium (%)
Magnesium (%)
Sulfur (%)
Iron (ppm)
Zinc (ppm)
Manganese (ppm)
Copper (ppm)

~ *0.01 r > |0.30|
+0.05 r > |0.39|

108

Table 27. Variables Used in Model Building and Their Simple
Correlations with Dependent Variables Height and Yield-
Continued

Variables Abbreviations

Simple Correlation
Coéfficient (r)

5 to 17 August

Nitrogen (%) -0.18
Phosphorus (%) 0.09
Potassium (%) -0.33*
Sodium (%) -0.08
Calcium (%) 0.09
Magnesium (%) 0.02
Sulfur (%) -0.59T
Iron (ppm) 0.43t
Zinc (ppm) 0.01
Manganese (ppm) 0.24
Copper (ppm) 0.16
30 September to 2 October
Nitrogen (%) -0.27
Phosphorus (%) -0.04
Potassium (%) -0.38*
Sodium (%) -0.20
Calcium (%) 0.05
Magnesium (%) -0.05
Sulfur (%) -0.50+
Iron (ppm) 0.40+
Zinc (ppm) -0.02
Manganese (ppm) 0.16

Copper (ppm)
<OMOM >| 05 50)|
+0.05 r > |0.39|

109

height zones. Height and yield are more closely related within a given
marsh or type of marsh (Williams and Murdoch, 1969). That is, at a
particular location the taller grass produces higher yields. In this
study, the correlation between height and yield was low enough that it
seemed appropriate to create separate models for height and yield.

16
= (2 wee
2 R7= 0.26
@he
=
4
& e
ew?’ C.V. 56.8
=i Y=1298+58.5(X)
O
O 40 80 120 160
Height (cm)

Figure 55. Relationship between height and yield
of S. alterntflora.

110

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111

c. The Model Building Process. There were 47 independent variables
in the original model. Silt was omitted since the pefcent sand, silt
and clay always sums to 100 percent. This causes any two of these varia-
bles to correlate perfectly with the third; therefore, only two of the
variables can be used in a regression equation. The number of variables
in the original model was reduced with the stepwise regression procedure
and the maximum R* improvement procedure. By regression techniques,
two sets of variables most likely to be related to yield (Tab. 29) and
height (Tab. 30) were selected. Each model contains 11 variables with an
R2 of 0.90. Thus, about 90 percent of the variation in yield and height
is explained by the independent variables in each regression equation.
The variables in these models represent a subset of variables which can
be used to explain differences in yield and height; however, they may not
be the most important variables affecting plant growth in the salt marsh
system. Other subsets may produce similar R2 values, but the two pre-
sented were considered the most agronomically feasible. Some models with
fewer variables also produced satisfactory R2 values (fabs Si).
Regression equations with more independent variables produced higher R*
values, but beyond 11 variables there was very little increase in the
regression sum of squares or reduction in the error mean square and the
coefficient of variation.

d. Interpretation of the Yield Model. As would be expected in a

natural ecological system, an examination of the correlation matrix for
the 11 variables in the model revealed that there was some intercorrela-
tion of variables. When there is a correlation between independent
variables in a model, the regression coefficients (b's) may not be
reliable (Draper and Smith, 1966). However, by considering the regres-
sion model in combination with the simple correlations of each independent
variable with yield (Tab. 27) and the means and Least Significant
Differences obtained by analysis of variance, some insight as to the effect
of each variable on yield variation may be obtained. The partial sum of
squares are a measure of the relative importance of the variables in a
regression equation and the variables may be ranked on this basis (Tab.
29) (Draper and Smith, 1966).

The potassium content of the plant tissue at the fall sampling data
(CK) is the variable which accounts for the highest amount of yield
variation in the regression equation. At five of the seven locations,
potassium concentrations were greater in plants taken from the short
height zone (Tab. 32). The trend of lower potassium concentrations in
higher yielding plants is probably an indication of a greater dilution of
potassium in the plant tissue where higher yields occur.

Sodium concentration of the plant tissue at the first sampling date
(ANa) is positively related to yield. Significant differences in sodium
concentrations occur between height zones and locations (Tab. 32).

Plants from the tall height zones had higher concentrations than those
from the short height zones. The explanation for this is not apparent,
particularly since higher salinities of the soil solution (AS-SAL) were
clearly related to decreased yields (Tab. 27). High salinity of the soil

Mable 29%

Source

Regression
Deviations

Total

Source

Intercept
CK
ANat
CCat
AS-SAL
BMnt
S-Mn

. Analysis of Variance Table,
Statistics of Fit for Dependent Variable oe Yield

Regression Coefficient and

Sum of Squares F-Value GoW

(%)

pasts tl Bi eeeRi sooo Dian [eee Sel
30 0.3876 | ----- ==-

3.7428
-0.9873
OGIO
Ike SOS
-0.0161
-0.0095
-0.0046
3.4720
-0.0116
3.2208
0.0005
-0.3368

0.
0.
On
OF
0.
OF
0.
0.
0.
0.
0.

*0.01 level of significance
+Variables which also appear in the height equation
0.10 level of significance

Table 30. Analysis of Variance Table, Regression Coefficients, and
Statistics of Fit for Dependent Variable oe Height

Source Sum of Squares F-Value GoW.
(%)

Regression Pia =| ite = aa | (tesa | 54* 3.8
Deviations 0.1420 ---- ---

Total histiaar crop! 4722
Coefficient (b) of Squares
Intercept ----
BS 0. S28
ANat 0. DS oS
BMg 0. Bilea
AFe 0. US) 5 7
AMg 0. Wo Abs
CN 0. 1WA0F
AN 0. 10.2*
CCat 0. 8.4*
BPt 0. 6.54
BMnt 0. 4.0%
ASt 0. Seis

*0.01 level of significance
tVariables which also appear in the yield equation
£0.05 level of significance
§0.10 level of significance

114

Table 31. Selected Models for Predicting Log,,
of Yield and Height

No. in Model R2 Gave
Model (%)

Yield

BS
BS, BMn
BS, BMn, AS-SAL

AS-SAL, BMn, BS,
ANa, S-Mn

Coins CAs IS ak
o wo nN N

7 BMn, BS, AS-SAL, : 4
ANa, BCa, S-Mn,
ACu

11 CKwANaaiCGar ; “ll
AS-SAL, BMn,
S-Mn, AP, AMn,
BP, SP, AS

Height

BS
BS, ANa
BS, ANa, CCa

BS, CCa, ANa,
BFe, AS-SAL

7 BS, CCa, ANa,
BFe, BMn, S-Ca

11 BS, ANa, BMg,
AFe, AMg, CN,
AN, CCa, BP,
BMn, AS

Cn A AS)

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118

solution has often been suggested as a cause for reduced growth of 5S.
alterntflora (Mooring, Cooper, and Seneca, 1971).

The reason for the appearance of calcium concentration in the plant
tissue at the fall sampling date (CCa) in the regression equation cannot
be readily explained. The means (Tab. 32) and the simple correlations
(Tab. 27) show no obvious relationships between yield and calcium con-
centrations in the plant. It probably enters the regression equation
because of its relationship to other variables.

Manganese concentration in the plant tissue at the first sampling
date (AMn) and the second sampling date (BMn) and soil manganese (S-Mn)
are all negatively related to yield. The solubility of soil manganese is
increased under conditions of poor aeration. The importance of manganese
in the regression equation may be an indication that the more reduced
soils produce lower yields of S. alterntflora. The chemical environment
produced by waterlogging of soils produces several toxicity problems which
have been studied in relation to reduction of rice yields. Common problems
are iron, manganese and sulfide toxicity and toxicity from soluble organic
products (Black, 1968). However, manganese toxicity is unlikely because
of the concentration in the plant tissue (Tab. 32). Concentrations of
10 times this amount were found with no apparent ill effects to plants in
growth chamber studies with S. alterniflora in which the nutrient source
was modified Hoagland's solution (Hoagland and Arnon, 1950).

Phosphorus concentrations in the plant tissue at the first sampling
date (AP) and the second sampling date (BP) and soil phosphorus (S-P) are
positively related to yield. The need for adequate supplies of phosphorus
for plant growth is well known, and phosphorus is often a limiting factor
in the growth of plants.

Sulfur at the first sampling date (AS) is negatively correlated with
yield. The means in Table 32 clearly show that concentration of sulfur
is much less in plants from the tall height zones. It is impossible to
determine from the data if this is a dilution effect or if more sulfur is
available in the short-height zone.

e. Interpretation of the Height Model. Since some variables in this

model are also correlated, caution must be observed in interpreting regres-
sion coefficients.

The sulfur concentration in the plant tissue at the second sampling
date (BS) accounts for the highest amount of variation in height in the
regression equation. Sulfur concentration at the first sampling date (AS)
also appears in the equation. The sulfur concentration at the second
sampling time is the single variable with the highest R2 in both the
height and yield equations (Tab. 32). There is a clear relationship
between increased sulfur concentration and decreased growth, but it is
impossible to determine from the data if it is a cause and effect relation-
ship.

IIS)

Sodium concentration in the plants at the first sampling date (ANa)
is positively related to height as it was to yield. The concentration is
significantly higher in samples from the tall-height zone (Tab. 32).

Magnesium concentration in the plant tissue at the first (AMg) and
second (BMg) sampling dates are in the regression equation. However,
there is no relationship of magnesium with height apparent from the sim-
ple correlations (Tab. 27) or the means (Tab. 32). This variable may
have entered the regression equation due to its relationship with other
variables.

The iron concentration in the plant tissue at the first sampling date
(AFe) is positively correlated with height. The difference is greater
between locations than between height zones. This difference is probably
because finer sediments occur at the locations where taller plants are
found, and these sites would be expected to contain more iron (associated
with clay) than the sandy sites.

Nitrogen concentration at the first sampling date (AN) was positively
correlated with height, while nitrogen concentration at the third sampling
date (CN) was negatively correlated with height. A probable explanation
for this is that plant-available nitrogen is scarce in the marsh environ-
ment. At the first sampling date, high nitrogen concentrations in the
plant are indicative of a high potential for growth. At maturity, the
nitrogen concentration is lowest in plants which have achieved maximum
growth due to dilution in the greater amount of plant tissue.

Calcium concentration at the third sampling date (CCa) probably enters
the regression equation because of its relationship to other variables
since no relationship with height is apparent from the means (Tab. 32) or
the simple correlation with height (Tab. 27).

Phosphorus concentration at the second sampling time (BP) was posi-
tively correlated with plant height. This indicates that where greater
amounts of phosphorus are available for growth, greater heights are
attained.

The concentration of manganese at the second sampling time (BMn)
appears to be negatively related to height according to the regression
coefficient (Tab. 30). However, the simple correlation shows a positive
relationship of BMn to height. This is an example of sign reversal of
b-values when there is correlation between variables in the model. This
positive relationship of manganese concentration to height is opposite of
the relationship with yield.

f. Predicting Standing Crop of Mineral Nutrients from Dry Weight.

It is of interest to know the quantities of nutrients conveyed to estu-
arine food chains by S. alterntflora (Williams and Murdoch, 1969). From
the data in this study, standing crop of nutrients contained in the
aboveground part of mature S. alterniflora stands can be calculated
(Tab. 33). The data used were three 0.25-square meter samples clipped

120

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121

from the tall- and the short-height zones of seven locations when the grass
was mature. Since the total amount of nutrients incorporated in the plant
tissue is highly dependent on yields, the dry weight is a good predictor
for standing crops of the mineral nutrients. The R2 values for standing
crop of nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, and
sodium are quite high (Tab. 33), and these equations should be reliable

and useful for estimating the amount of nutrients contained in the mature
shoots of S. alterniflora salt marshes. However, the fate of the nutrients
as the plants decompose is more difficult to determine. Because of greater
variation, the predictions for iron, zinc, manganese and copper standing
crops would be less accurate.

g. Summary. The results indicate that tissue concentrations of
several nutrients and several soil properties were significantly associated
with variations in yield and height of S. alterntflora. It is important
to keep in mind the purpose of multiple regression analyses. Predictive
models are not necessarily functional, but can lead to insight into a
problem. According to Draper and Smith (1966), construction of this type
of model from problems where much intercorrelation of data exists is where
regression techniques can make their greatest contribution. It provides
guidelines for further investigation, pinpoints important variables, and
is useful in screening variables.

Several variables selected by the multiple regression procedure in
this study seem to warrant further investigation to determine their
relationship to productivity of S. alterniflora. Such variables negatively
associated with yield include salinity of the soil solution, manganese
concentration in the plants and soil, and sulfur concentrations in the
plants. Important variables positively associated with yield include
phosphorus concentration in the plant tissue and in the soil.

The reduction of yield of S. alterntflora with increasing soil salinity
has long been recognized. This study reconfirms this, but there was not
a striking difference in salinity between height zones. This is indicated
by the fact that the simple correlation of height with soil salinity is
near Ooi@habe 027)

The importance of manganese and sulfur in both the yield and height
equations and iron in the height equation suggests investigation into the
influence of the chemical effects of waterlogging of the marsh soil on
S. alterntflora growth. Undoubtedly there are different degrees of
aeration both within and between Spartina marshes which affect soil chemi-
cal properties. There is an extensive literature on waterlogged soils in
connection with rice culture (Redman and Patrick, 1965; Black, 1968).
Useful reviews on the chemistry of phosphorus and nitrogen in sediment-
water systems are presented by Syers, Harris, and Armstrong (1973) and
Keeney (1973).

The positive influence of phosphorus concentration in the plant tissue

would be expected, since in most natural plant-soil systems phosphorus is
second only to nitrogen as a limiting factor in plant growth. Nitrogen

2/2

concentration in the plant tissue was a part of the regression equation
for height but not for yield. Perhaps nitrogen does not show up in the
equation because it is the limiting factor in growth. If the availability
of nitrogen was limiting growth, then growth would proceed whenever nitro-
gen became available. Consequently, the concentration of nitrogen in the
plant tissue would remain relatively constant due to the increase in
biomass. It is possible that if samples had been taken earlier in the
growing season, the nitrogen concentration in the plant tissue would have
been a better indicator of yield potential.

It is interesting to note that there was no significant correlation
of yield with the soil properties measured (Tab. 27). There are two
factors which contribute to this: (1), the waterlogged conditions of these
soils tend to equalize chemical differences, and (2), the methods by which
these determinations were made. Standard soil testing procedures were
used which probably are not suitable for these soils. An important limita-
tion is that North Carolina soil test procedures and extracting solutions
are designed for acid soils. The pH (hydrogen-ion concentration) of the
soils in this study were between 7 and 8. Developing suitable techniques
for studying properties of marsh soils would be an extensive project.

In conclusion, it is not within the scope of this study to explain
each observed effect, but several relationships were shown to exist between
variables which were measured and yield and height of S. alterniflora.
Several of these effects may warrant further investigation.

2. Effects of Fertilizer.

In the natural marshes, fertilizer was used as an experimental tool to
determine if nutrients were limiting factors in growth. Marshes at
Ocracoke and Oak Island were selected because of differences in substrate,
tide range, and age. On seedlings and transplants, the objective of the
fertilizer studies was to determine if adding nutrients would enhance
growth to produce cover more rapidly.

a. Fertilizer Experiments in Natural Stands.

(1) Ocracoke Island. Fertilizer, plots were located on the north
end of the island near Hatteras Inlet. This is a relatively young 5S.
alterntflora marsh on a sandy substrate with little development of tidal
creeks. There is some difference in growth between the different areas
within the marsh, which is apparently due to environmental factors.

However, zonation of height forms is not as obvious as in many older marshes.
The regular lunar tide range at this location is about 30 centimeters, but
the added wind effect may extend the range to 1 meter.

A fertilizer experiment of factorial design with two rates of phosphorus
and four rates of nitrogen was started in 1971. It consisted of three ran-
domized complete blocks with 1.22- by 7.62-meter plots and 1.22-meter borders
between plots. Phosphorus was supplied by concentrated superphosphate at

123

rates of 0 and 74 kilograms per hectare of phosphorus. Nitrogen rates
were 0, 168, 336, and 672 kilograms per hectare of nitrogen supplied by
ammonium sulfate. An ammonium form of nitrogen was thought to be more
suitable to the marsh environment since it is the form of inorganic nitro-
gen found in greatest quantities in reduced soils. Application of nitrate-
nitrogen to poorly drained soils is undesirable since it is subject to
denitrification and loss to the atmosphere in gaseous forms (Keeney, 1973).
The ammonium form has the advantage of being adsorbed by the exchange
complex of the soil. It is also possible (considering the flooded condi-
tion in which it grows) that S. alterntflora is adapted to utilization of
the ammonium form of nitrogen as has been reported for some other plants
(Townsend, 1966; Van Den Driessche, 1971).

The fertilizer materials were applied in split applications with equal
amounts on 12 May, 22 June, and 27 July 1971 by broadcasting evenly over
the substrate surface. Samples were harvested 1 September 1971 by cutting
a 0.61- by 1.52-meter swath from each plot with a Jari sicklebar mower.
Saltecornia spp., dead stems of S. alterniflora from the previous year's
growth and other foreign matter, were separated from S. alterntflora
plants. The plants were dried at 70° Centigrade and weighed, subsamples
were ground in a Wiley mill, and analyzed for nutrient content by the
Department of Soil Science, Analytical Service Laboratory of North Carolina
State University.

The experiment was continued in 1972 with the same rates of nitrogen
and phosphorus fertilizers applied in split applications on 13 April,
20 June, and 19 July 1972. The plots were clipped and raked in early
spring in 1972 to facilitate harvesting and ensure that all plant material
harvested in the fall was produced-in that growing season. Samples were
‘harvested 11 September by clipping a 0.61- by 3.96-meter swath from each
plot. The plant samples were dried and processed in the manner previously
described. Roots and rhizomes were also sampled in 1972 by taking five
cores 8.5 centimeters in diameter and 30 centimeters deep from each plot.
In the laboratory the cores were divided into 0 to 10- and 10 to 30-centi-
meter layers and washed with tap water to remove the soil material. Ten
core samples were selected at random and roots were separated from rhizomes
to determine the relative proportions of each. The root and rhizome
samples were dried at 70° Centigrade. Combined root and rhizome samples
were processed and analyzed in the same manner as the shoots.

The experiment was continued in 1973 in the same manner as in 1972,
except roots and rhizomes were not separated.

The results of the nitrogen-phosphorus factorial experiment at Ocracoke
indicate that, although additions of nitrogen alone can increase yields
significantly, the availability of phosphorus quickly becomes limiting when
nitrogen rates are increased (Fig. 56). Yields at the end of the first
growing season were increased only slightly by the addition of nitrogen
without phosphorus. The only statistically significant (0.05 level)
difference was between the yield of the check plots and those receiving
672 kilograms per hectare of nitrogen. However, when phosphorus was

124

applied at the rate of 74 kilograms per hectare, yield was markedly
increased by additions of nitrogen up to 336 kilograms per hectare. The
yield produced by 672 kilograms per hectare of nitrogen was not signifi-
cantly greater than that where 336 kilograms per hectare were applied
during the first growing season.

Y=6169.1+17.7X

16
oO
< c ,
a2 Y= 2978.8 + 28.7X-0.024X
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coves 197]
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)

O 168 336 672
Nitrogen (kg/ha/yr)

Figure 56. Effect of nitrogen and phosphorus fertilizers on
yields during two successive growing seasons.

During the second growing season, higher yields and a greater response
to fertilization was attained (Figs. 56 and 57). When phosphorus was
supplied, the rate of yield increase did not level off beyond 336 kilograms
per hectare of nitrogen as in the first year, but was linear over the range
of nitrogen rates applied. There was also an increase in the difference
between yields of no phosphorus and phosphorus treatments, indicating
phosphorus became severely limiting during the second year as yields
increased.

125

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126

Nitrogen content of the plant tissue was closely related to the rate
of nitrogen applied as fertilizer (Fig. 58). During both growing seasons
the R* (multiple correlation coefficient, a measure of the percentage
variation in the dependent variable which is explained by independent
variables in the equation), values were higher where no phosphorus was
applied, indicating that a greater proportion of the variation in nitrogen
content is accounted for by nitrogen rate when nitrogen alone is applied.
Where phosphorus was applied, both the R2 and the actual concentration
of nitrogen in the tissue decreased. This decrease was probably due to
dilution of nitrogen in a greater amount of dry matter as yield increased
when the phosphorus became adequate.

The apparent recovery of fertilizer-nitrogen by the aboveground part
of the grass and the roots and rhizomes may be calculated by subtracting
the uptake of the check plots from that of the treated plots. The calcu-
lations reveal a surprisingly high recovery of nitrogen considering the
flooding which occurs (Tab. 34).

Table 34. Apparent Recovery of Fertilizer Nitrogen in the Shoots
at Harvest

| Shoots

*Rate of P (kg/ha)

Concentration of phosphorus in the plant tissue was not significantly
affected by nitrogen rate; however, the increase in phosphorus concentra-
tion due to phosphorus fertilization was highly significant (0.01 level).
In 1971 the mean concentration of phosphorus in the shoots was increased
from 0.084 to 0.150 percent, where 74 kilograms per hectare of phosphorus
were applied. In 1972 there was a similar increase due to phosphorus
fertilization from 0.087 to 0.147 percent in the shoots, and concentration
in the roots increased from 0.052 to 0.091 percent. The amount of
fertilizer-phosphorus recovered by the shoots for treatments receiving the
maximum rate of nitrogen was 15.0 and 26.1 percent of that applied during
1971 and 1972, respectively. Apparent recovery of phosphorus by the roots
in 1972 was 12.4 percent. The calculations of recovery of both nitrogen
and phosphorus in 1972 may include some carryover from 1971 through storage
in the roots and rhizomes or residual in the soil. It is more likely that
phosphorus would be retained by the soil than nitrogen.

WAT

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(Xx) 4000' +Z8° =A gd ON Over

cL6\ 1161

128

Analyses for other mineral nutrients included potassium, calcium,
magnesium, sulfur, iron, and sodium in both 1971 and 1972. An analysis
for manganese was included in 1972. Regression analysis was used to
determine if there were significant linear or quadratic relationships
between the nutrient concentrations in plant tissue and the nitrogen rate.
Of the nutrients checked in 1971, only potassium was found to be signifi-
cantly related to nitrogen rate (Tab. 35) and this was true only when
phosphorus was applied. In 1972, when no phosphorus was applied, phos-
phorus, calcium, and manganese concentrations were significantly affected
by nitrogen rate. Calcium and manganese concentrations increased as
nitrogen rate increased, while phosphorus concentration decreased as
nitrogen rate increased. The decrease in phosphorus concentration indi-
cates that there is a limited amount of phosphorus available and the
amount in the plant tissue is diluted as growth is increased due to nitro-
gen fertilization. Where phosphorus was applied, only iron and manganese
concentration was significantly affect by nitrogen rate. Manganese
increased and iron decreased as nitrogen rate was increased.

Table 35. The Relationship of Nutrient Concentration in the Plant
Tissue to Nitrogen Rate*

Year | P Rate R2
(kg/ha)
74 SOT

Nutrient Regression Equation

Vo =) J0n987 + 10500330)

P 0 Y= 0.09 - 0.00007(X) + 0.00000007 (Xx) 2
CA O.85 8 0.00036(X) - 0.00000039 (xX) 4%
Y= 15.75 + 10.0092(X)
¥i=) 32000 2808219109
Y 0.117(X)

*X = Rate of nitrogen fertilizer (kg/ha)
+Significant at the 0.05 level
tSignificant at the 0.01 level

Total uptake of mineral nutrients increased as nitrogen rate was
increased (Figs. 59 and 60). This was due mainly to an increase in yield
in response to nitrogen and phosphorus fertilization, producing more plant
material in which nutrients in adequate supply are incorporated. The
standing crop of these nutrients is controlled by yield which is in turn
limited by availability of nitrogen and phosphorus to the marsh plants.
The amount of nitrogen and phosphorus available is the limiting factor in
the total amount of nutrients exported from the marsh in the dead plant
material which contribute to the nutrient cycle of the adjacent estuary.

An obvious feature of the data for uptake of mineral nutrients is the
large difference in sodium uptake between 1971 and 1972. This was probably
due to periods of high salt concentration in the substrate in 1972. The
level of sodium in the substrate varies with rainfall and frequency of
flooding. At Ocracoke, southwest winds during summer often prevent

129

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131

regular flooding of the marsh for a week or more causing an increase in
the salinity of the soil solution as evaporation proceeds. Measurements
of salinity of the soil solution were made only at harvest time each year.
The salinity was 36 parts per thousand on 2 September 1971 and 30 to 34
parts per thousand on 11 September 1972. Although no data are available,
it was suspected that there were periods of salt buildup earlier in the
1972 growing season.

The standing crop of roots and rhizomes in the upper 30 centimeters
was increased significantly by nitrogen fertilization in 1972 (Tab. 36).
There was no response to nitrogen rates above 168 kilograms per hectare,
indicating that this rate of nitrogen was adequate for maximum growth of
roots and rhizomes. When root and rhizome weights are broken down from
0 to 10- and 10 to 30-centimeter layers, a variable response to fertili-
zation is noted... In the 0 to 10-centimeter layer there was a significant
response to nitrogen and no response to phosphorus similar to the case
when the total weight of the upper 30 centimeters is considered. However,
in the 10-to 30-centimeter layer there was a significant response to
phosphorus but not to nitrogen. The overall means of 120 core samples
show that 75 percent of the roots and rhizomes are in the 0-to 10-centi-
meter layer and only 25 percent in the 10 to 30-centimeter layer. From
field observations, almost all the roots and rhizomes were contained in
the upper 30 centimeters and any below this depth would be an insignifi-
cant part of the total weight. Results of separating roots and rhizomes
from 10 randomly selected core samples indicated that in the 0 to 10-centi-
meter layer, the percentages by weight were 49.6 percent roots and 50.4
percent rhizomes. In the 10 to 30-centimeter layer, only 34.6 percent
of the dry weight was roots with rhizomes accounting for 65.4 percent.
Since there was a higher proportion of rhizomes in the 10 to 30-centimeter
layer, it is possible that the response to phosphorus in this layer is due
to an increase in rhizome growth -- that is, the response to phosphorus is
relatively greater for rhizomes than for roots. The increase in dry weight
of the 0 to 10-centimeter layer was probably due to an increase of root
growth in response to nitrogen fertilization.

The total dry weight of roots and rhizomes in the upper 30 centimeters
exceeds the dry weight of shoots (Fig. 61). Since the response of roots
and rhizomes to fertilization is less than the response of shoots, the
ratio of shoots to roots and rhizomes increases with nitrogen rate from
0.29 for the check to 0.75 at the highest rate of nitrogen.

The same fertilization treatments were continued on the plots during
the 1973 growing season. The yield of aboveground growth (Tab. 37) was
increased significantly by nitrogen applications in combination with phos-
phorus; however, yields were not as great as in 1972. Other factors such
as rainfall and wind direction (which controls tidal flooding at this
location) cause year-to-year variations in shoot yields.

Underground growth also showed a significant increase due to fertili-
zation, particularly to phosphorus (Tab. 38).

132

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(ZZ61) doij B8utpueiS punorsmoTeg uo snzoydsoyg pue uas0I}IN FO 399FFY “9S OTQeL

133

Table 37. Effect of Nitrogen and Phosphorus
Aboveground Growth at Ocracoke (1973)

Aerial Dry Weight (kg/ha)

N Rate
(kg/ha)

*X = main effects
tLeast significant difference
tCoefficient of variation

134

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135

24 [| Roets and rhizomes

33] Shoots

Dry weight (metric tons /ha)
~

168 336
N rate (kg/ha/yr)

Figure 61. The effect of nitrogen fertilization on the aboveground
and belowground standing crop of S. alterntflora.

(2) Oak Island. In 1971 at Oak Island an experiment was begun to
test the theory of Adams (1963) that iron deficiency may be the cause of
the chlorotic condition often observed in stands of S. alterntflora and
to evaluate the effect of nitrogen fertilization. The experiment consisted
of three randomized complete blocks with plots that were 1.22 by 15.2
meters with 1.22-meter borders between plots lying perpendicular to a tidal
creek so that each plot contained the tall and short forms of S. alternt-
flora. Iron and nitrogen fertilizers were applied in split applications
18 May, 30 June and 3 August 1971 (Tab. 39). Ammonium sulphate was the
nitrogen source. The iron sources were: (1) a commercial iron chelate
applied as a spray to the plants, (2) iron chelate applied in the dry form
to the sediment surface and (3) ferrous sulphate applied as a spray.
Samples were harvested 4 October 1971 by clipping a 0.25-square meter area
from the short S. alterniflora and a 0.25-square meter area from the tall
S. alterniflora in each plot. The samples were washed in tap water and
distilled water to remove mud from the leaves and stalks, dried at 70°
Centigrade, weighed and ground in preparation for nutrient analyses of the
plant tissue.

136

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In 1972, an experiment was established adjacent to another tidal
creek in the same marsh to evaluate the effect of phosphorus fertiliza-
tion. The experiment was a factorial design with two levels of phosphorus
and four levels of nitrogen identical to the factorial experiment previous-
ly described for Ocracoke. Three randomized complete blocks were esta-
blished with the individual plots perpendicular to a creek so that each
plot contained the tall and short forms of grass. Plots were 1.22 by
15.2 meters with a 1.22-meters border between each plot. The fertilizer
was applied in split applications with equal amounts applied on 1 May,
22 June and 26 July 1972. Samples were harvested 20 September 1972 by
clipping a l-square meter sample from the short height zone of each plot
and a 0.25-square meter sample from the tall height zone of each plot.
The samples were dried in a forced-air oven at 70° Centigrade and weighed.

The marsh at Oak Island differs from that at Ocracoke in several ways
which would cause the response to fertilizer applications to be different.
The most important difference is that the sediments which form the sub-
Strate of the marshes are different. At Ocracoke the substrate is almost
pure sand, while at Oak Island it is much finer-textured (silt loam with
10 percent organic matter) and would be expected to be inherently more
fertile. Another difference is that the Oak Island marsh is older with
well-developed tidal creeks and distinct zonation of height forms. A
third difference is the greater tide range at Oak Island (1.3 meters)
which floods the marsh twice a day and is seldom affected appreciably by
the wind.

The experimental fertilizer plots at Oak Island contained the tall
and short forms of S. alterniflora. Neither growth, chemical composition
of the plant tissue or general appearance of the tall form, was signifi-
cantly affected by additions of iron or nitrogen (Tab. 39). This is
probably because the creek bank area is adequately supplied with nutrients
from fresh sediments deposited by the overflowing creeks at floodtide.
Levees which form are evidence of greater deposition along creek banks.
The meandering of creeks may expose fresh sediments which have not been
exploited by plant roots. If nutrients are taken up directly from the
tidal waters, then the tall height zone area is in a favorable position
for more frequent and longer inundation. However, it is also possible
that fertilizer applied to the sediments in the tall zone of S. alternt-
flora is dissolved in the estuarine water on floodtide rather than being
taken up by the plants. Fewer fine roots are near the sediment surface
in the tall S. alterntflora than in the short; consequently, uptake of
nutrients applied to the surface might be less. Calculation of the apparent
recovery of fertilizer-nitrogen for plants from the tall height zone which
received 336 kilograms per hectare of nitrogen indicates that only 3.2
percent of that applied was recovered in the grass shoots.

Growth in the zone of short S. alterntflora was enhanced by the addi-
tion of nitrogen but was not affected by the iron treatments (Tab. 39).
The characteristic chlorotic appearance of short S. alterniflora was
unaffected by iron, but nitrogen produced a greener appearance. Plots
which received applications of nitrogen fertilizer yielded about twice as

138

much dry matter as the check plots. The nitrogen content of the plant
tissue also increased as the amount of nitrogen fertilizer was increased,
indicating that uptake was more efficient than in the tall height zone.
The average recovery of nitrogen by the grass shoots in plots receiving
336 kilograms per hectare of nitrogen was 13 percent. This more efficient
recovery of fertilizer nitrogen is probably due to the greater amount of
roots at the soil surface in the short height zone and that loss due to
flooding is probably less than in the tall height zone. Another possible
difference is that the nitrogen supply in the tall height zone is adequate
and less of the fertilizer-nitrogen is used, while nitrogen is in short
supply in the short height zone. The efficiency of uptake of nitrogen is
less than at Ocracoke even in the short height zone. The less frequent
flooding at Ocracoke may allow the fertilizer to remain in place and
available for uptake for a longer period of time.

A fertilizer experiment was begun at Oak Island in 1972 to determine
if phosphorus was a limiting factor in productivity at this location as
for Ocracoke. At the end of the first growing season there was no signif-
icant yield increase due to phosphorus fertilization (Tab. 40). The
highest rate of nitrogen nearly doubled the yield of short S. alterntflora
compared to the check, and plots which received nitrogen were much greener,
but again the tall did not respond to fertilization. The lack of response
to phosphorus was expected due to the nature of the substrate at Oak Island.
The fine-textured reduced sediments have a greater potential for supplying
phosphorus than the sand at Ocracoke. However, the experiment was continued
during the 1973 growing season and the response to phosphorus and nitrogen
was significant (Tab. 41). Apparently, as yields increase due to fertili-
zation the supply of phosphorus in the soil becomes limiting.

b. The Effect of Fertilizer on Seedlings and Transplants. To deter-

mine if the addition of fertilizer would enhance propagation of S. alternt-
flora, fertilizer plots were established on seedlings growing on dredged
material at Beaufort. Seeds were planted on 4 Aprii 1972 in the inter-
tidal zone of a pile of sandy dredge spoil, which had been in place for
about 1 year. The seed were hand broadcast and covered by six sweeps
mounted on the tool bar of a tractor, followed by a section harrow (Fig.
22). After the seedlings were established, a randomized complete block
fertilizer experiment with three treatments (nitrogen, nitrogen-phosphorus,
check) and three replications was superimposed. Rates were 224 kilograms
per hectare of nitrogen (ammonium sulphate) and 49 kilograms per hectare
of phosphorus (concentrated superphosphate) with half applied 26 June and
half 26 July 1972. Plots were 1.22 meters by 7.62 meters with 1.22-meter
borders. Samples were harvested 5 October 1972 by cutting a swath 0.6-
meter wide by 6-meters long from each plot at ground level with a Jari
mower. The samples were dried at 70° Centigrade and weighed.

The dry weight of seedlings at the end of one growing season was
increased from 3,470 kilograms per hectare to 9,340 kilograms per hectare
by the addition of nitrogen. Where nitrogen and phosphorus were applied,
the dry weight was increased to 10,800 kilograms per hectare (Tab. 42).
These results indicate that at this location fertilizer was beneficial in

139

Table 40. Effect of Nitrogen and Phosphorus on Short and Tall Height
Forms of S. alterntflora at Oak Island, 1972

Aerial Dry Weight (kg/ha)

P Rate
(kg/ha)

N Rate
(kg/ha)

16,713.0

16 ,913.0

NA LS 30)

168 8,153.0 | 15,547.0] 18,623.0 | 17.085.0
336 T535550 1) AS59500 22 37/7 7/6 |) ZA doo)
672 11,053.0 10,353.0 | 18,967.0] 16,840.0 | 17,903.0

7,794.0 60) |) sRececas LOE MOS ON PSS Som OM Ra

*Height zone

+X = main effects

tLeast significant difference
§Not significant

|Coefficient of variation

140

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141

producing increases in growth; consequently there was an increase in the
cover produced by seedlings on dredged material during the first growing
season.

Table 42. The Standing Crop of Seedlings at
Beaufort to which Nitrogen and
PhoSpnorus Fertilizers were Applied*

Replicate Aerial Dry Weight (kg/ha)

Fertilizer Treatmentt

*Plots seeded 4 April 1972; harvested
5 October 1972.

+N rate = 224 kg/ha N; P rate - 49 kg/ha P;
half the fertilizer was applied on 26 June 1972
and half on 26 July 1972.

+X = main effects

A fertilizer experiment on seedlings was begun on an island near Drum
Inlet in 1973. The fertilizer was applied in a randomized complete block
design with three blocks and was superimposed on a part of the large-scale
seeding experiment planted 18 April 1973. The fertilizer treatments were
two rates of phosphorus as concentrated superphosphate (0 and 49 kilograms
per hectare of phosphorus) and four rates of nitrogen as ammonium sulfate
(0, 112, 224, 448 kilograms per hectare of nitrogen) in a factorial
arrangement. Fertilizer was applied in split applications 11 July and
16 August. Plots were 1.22 meters by 7.62 meters with 1.22-meter borders
between plots. Samples were harvested 8 November by ciipping 1 square
meter from each plot. Roots were also sampled by taking two cores 8.5
centimeters in diameter and 30-centimeters deep from each square meter
which was clipped.

Growth measurements indicate significant responses to both nitrogen
and phosphorus fertilization (Tab. 43). Unlike fertilizer experiments in
the natural marsh at Ocracoke, the nitrogen-phosphorus interaction was
not statistically significant. The dry weights of shoots and roots were
doubled by both additions of nitrogen and additions of phosphorus.

In another experiment, fertilizer was applied before planting at Drum
Inlet. The fertilizer treatments were a 2 by 4 factorial design
(nitrogen = 0, 56, 112, 224 kilograms per hectare and phosphorus = 0 and
25 kilograms per hectare). Plots consisted of three rows 0.91 meters

142

Table 43. Effect of Nitrogen and Phosphorus Fertilizers on Growth of
Seedlings on South Island near Drum Inlet*

N Rate P Rate
(kg/ha) (kg/ha)

Or ca

No. Flowers/m2 No. Culms/m2

0
LID
224
448
Xt
LSD: =
N 0.01 § §
0.05 § 67.0
P 0.01 Vell §
0.05 Saal 47.0
CV% |l 52.1 320
Basal Area Aerial Dry Wt.
(cm2/m2) (kg/ha)
0
LD
224
448
Gh
LSD: =
N 0.01 § §
0.05 § 69.0
P 0.01 § 68.0
0.05 § 49.9

*Seeded 18 April 1973; sampled 8 November 1973
+X = main effects

tLeast significant difference
(There were no significant N x P interactions)

§Not significant

|Coefficient of variation

143

Height (cm)

24.0
(0)
30.0
23.0
25.0
8
§
8
SiO
Ze

26.0
27.0
33.0
27.0

Belowground Dry Wt.

(kg/ha)

1,615.0

1,072.0

apart and approximately 18 meters long in a randomized complete block
design with three replications. The rows were perpendicular to a
drainage creek and extended over the elevational range of S. alterniflora
at this location. The fertilizer was applied in furrows under each row
which was opened by sweeps on a tractor the day before transplanting.

The transplanter closed the furrows and covered the fertilizer. The
dredge spoil, which is almost pure sand, was deposited during November
1971. However, transplanting was delayed until 28 June 1972 (later than
ideal) because extensive grading was necessary to prepare a suitable

area for the experiment within the elevational range of S. alterniflora
which is only about 30 centimeters at this location (the elevational
range of the grass is approximately equal to the tide range at this
location). Plant samples were taken 4 October 1972 by clipping one plant
from each row. Data recorded included dry weight, number of flowers,
number of center culms and number of rhizome culms per plant.

Fertilization enhanced first-year growth considerably (Tab. 44).
There were significant (0.05 level) increases in dry weight and number
of flowers and a highly significant (0.01 level) increase in the number
of center culms due to nitrogen fertilization. The number of rhizome
culms was not affected by nitrogen. There were highly significant
increases in dry weight, number of flowers and number of center culms due
to phosphorus fertilization. There was a significant increase in number
of rhizome culms due to phosphorus. Unlike results from experiments in
the natural marsh, there was no nitrogen-phosphorus interaction. The
Drum Inlet site was freshly deposited dredged material of almost pure
sand. The response of the transplants to fertilizer is evidence of the
low nitrogen and phosphorus content of this material. It is likely that
dredged material higher in silt, clay and organic matter would provide
adequate nitrogen and phosphorus for maximum growth of transplants during
the first growing season.

c. Summary. Increased growth of S. alterniflora in response to
applications of fertilizer indicates that the productivity of some salt
marshes is limited by the supply of nutrients. The standing crop of
aboveground shoots of salt marsh growing on a substrate of sand was
increased significantly by additions of nitrogen alone and increased about
threefold when phosphorus was also supplied. In a marsh developed on
finer-textured sediments, nitrogen fertilizer doubled the standing crop
of short Spartina, but there was no response to phosphorus. There was no
growth response from applications of iron to support previous speculation
that iron nutrition might be a particularly important factor causing the
chlorotic appearance of short Spartina and reducing its productivity.

The chlorotic condition was remedied by additions of nitrogen.

The response of short Spartina to nitrogen implies that a part of the
difference in productivity between the tall and short forms is due to the
amount of nitrogen available to the plants. Many other environmental or
possibly genetic factors or combinations of factors may be responsible
for producing the short form of S. alterntflora. The factor most often
implicated is that of salinity. High salinities will stunt Spartina and

144

Table 44. The Effect of Nitrogen and Phosphorus on Growth of
S. alterntflora at Drum Inlet when applied at the
Time of Transplanting*

N Rate (kg/ha) P Rate (kg/ha) P Rate (kg/ha)

[ass Eas ss

Dry Wt. (g/plant) No. of Flowers/Plant

0
56
Isl
224
XG
LSDE 0.05:

56
dale?
224

LSDt 0.05:
N
P

IN xen?
CVI (%)

*Transplanted 28 June 1972; harvested 4 October 1972
+X = main effects

tLeast significant difference

8Not significant

llCoefficient of variation

145

areas with high salinity and short Spartina can be found. However, we
have found short Spartina growing where the salinity was found to be only
about 10 parts per thousand at several different times during a growing
season. If the stunted form is produced by environmental factors, then
the factor or interaction of factors may vary from one location to
another. That is -- at a particular location, high salinity may limit
growth, while at another an unfavorable water regime or a shortage of
nitrogen or phosphorus or both might be limiting growth.

An explanation for nitrogen deficiency in the short height zone may be
in the development of a thick mat of roots which creates a sod-bound
condition. When sediments are deposited and later colonized by Spartina,
most substrates contain adequate nitrogen for plant growth except where
it is mostly sand, such as the Drum Inlet site. As the fibrous mat of
roots develops over the years, all the available nitrogen is absorbed and
either exported in the shoot growth, carried over in living root tissue
or bound up in dead root tissue. The dead root material is decomposed
and mineralized slowly (evidenced by accumulation of organic matter) due
to the anaerobic condition of the marsh sediments. Nutrients added from
natural sources apparently are not adequate for maximum plant growth.
The addition of nitrogen to the marsh probably includes small amounts
from rainfall, asymbiotic nitrogen fixation, directly from flooding tidal
waters, deposition of feces from filter feeders in the marsh and deposi-
tion of inorganic and organic sediments.

The amount of sediments deposited is probably the chief difference
between the nutrients available to the tall and short forms of Spartina.
Sediments are deposited regularly along creek banks providing a fresh
medium for plant roots to exploit. Unexploited sediments are also
exposed by meandering of creeks. The amount of nitrogen supplied would
depend on the nature of the sediments.

It is more certain that the sediment is the dominant factor in the
supply of phosphorus to S. alterntflora (Pomeroy, et al., 1969). This
is borne out in the results of our fertilizer experiments which showed a
response to phosphorus on sandy substrate but not on finer-textured
material. The texture of the sediments is quite important in the phos-
phorus-supplying capacity. In eroded soils of humid climates, phosphates
are associated with hydrated oxides of iron and aluminum which occur as
films on clay particles. When sediments are deposited in a marsh, the
reducing conditions cause the solubility of iron and aluminum phosphate
to increase. At the high pH (hydrogen-ion concentration) of marsh soils
(7.0 to 8.0) calcium phosphates probably become an important form of
phosphorus. The amount of phosphorus available to plants in a salt marsh
is related to the amount of clay in the substrate. Pomeroy, et al. (1969)
concluded that the subsurface-reduced sediments are the source of phos-
phorus for Spartina; however, the response to surface-applied fertilizer-
phosphorus in this experiment seems to contradict this. Uptake of
fertilizer-phosphorus apparently occurred at or very near the sediment
surface, indicating that nutrients in freshly deposited sediment would
be readily used.

146

The fact that nitrogen and phosphorus are the limiting factors in
growth of S. alterntflora in some salt marshes has several ecological
implications. It is possible that the marsh may act as a buffer for the
estuarine system providing a sink for excess nutrients which may stem
from municipal wastes and land runoff. In the marsh, excess nutrients
would produce increased growth of S. alterntflora which would provide
an increased supply of food energy and nutrients to the detritus food
chain of the estuary rather than altering energy pathways as often happens
when the phytoplankton system receives excess nutrients. This ability
of the salt marsh to use more nitrogen and phosphorus may be important
in managing estuarine systems. Disposal of wastes high in nutrients
(such as sewage effluent) may be less disruptive to the estuarine ecosys-
tem if dumped in the salt marsh rather than in open water. With proper
management such disposal might actually enhance estuarine productivity.
Further research is needed to determine the exact nature of the nutrient
cycle in the marsh-estuarine system and the capacity of the marsh to
receive excess nutrients.

Nitrogen and phosphorus fertilizers were shown to enhance growth of
seedlings and transplants artificially established on dredged material.
Since establishing a substantial vegetative cover rapidly may be critical
in stabilizing an area, application of fertilizer may be of some practi-
cal benefit. However, the dredge spoil was sandy at both locations;
hence, the nutrient-supplying capacity was low. Response to fertilizer
would be expected to vary with the inherent fertility of the substrate
material.

VII. PLANTING SPECIFICATIONS - S. ALTERNVIFLORA

1. Transplanting.

a. Plants. Healthy, single stems from uncrowded stands should be
used, keeping as much of the root system intact as possible. Rhizomes,
small shoots, and flowering stalks from the previous year may be removed
or trimmed so as to not interfere with transplanting. Plants from the
immediate area are preferable. If they are brought from any great dis-
tance, trial plantings should be made to test adaptation. Plants may be
stored indefinitely by heeling-in in the intertidal zone.

b. Planting. Hand- or machine-plant 10 to 15 centimeters (4 to 6
inches) deep, taking care that soil is firmed around plant immediately
to prevent the plant from "floating out" of hole or furrow.

c. Spacing. Under average conditions, plants set on l-meter center
will provide complete cover early in the second growing season. Closer
spacings, 0.5 and 0.3 meters (19 and 12 inches), may be warranted on
critical sites, keeping in mind that planting costs are in almost direct

proportion to the number of plants planted.

147

Spacing Plants per 1,000 square feet

inches meters
2 0.30 1,000
18 0.45 445
24 0.60 250
36 0.90 111

2. Planting Dates.

March, April and early May constitute the ideal planting season at
the latitude of North Carolina, late enough to avoid the worst weather,
and early enough to allow a long growing season. S. alterniflora can be
transplanted successfully the year round, but not with equal success.
Planting in winter subjects transplants to more severe weather, stronger
wave action, and greater erosion or deposition hazards. Summer planting
reduces the time for establishment before winter. Circumstances will
often warrant consideration of planting times which are less than optimum.

Elevation. S. alterntflora will usually grow in any area, roughly
between MHW and MLW for locations with low tide ranges and from MHW to
MSL for higher tide ranges. Since there will be variations where wind
setups are large, upper and lower limits of growth of natural stands in
the vicinity should be checked.

3. Fertilization.

Plantings may respond to the addition of nutrients in nutrient-poor
situations -- very sandy substrate, little or no clay or silt moving into
the area, and low concentration of nitrogen and phosphorus in the
surrounding water. Nitrogen and phosphorus are the most likely limiting
nutrients. Chemical assays are useful only to identify extremes. Conven-
tional tests for available phosphorus were developed for uplands and are
not reliable. for coastal conditions. There are no convenient chemical
methods that will satisfactorily forecast available nitrogen supplies.

4. 2SCCCIN Pe
a. Seeds. Harvest seed as near maturity as possible (late September

and early October in North Carolina) and store in estuarine water at 2°
to 3° Centigrade over winter.

b. Method. Broadcast at low tide and cover 1 to 3 centimeters by
tillage. Tillage is better before and after broadcasting.

c. Rate. Seeding rate should be based on viable seeds since quality
varies widely. Optimum rate appears to be around 100 viable seeds per
square meter. Adequate stands are possible under favorable conditions

with half this rate.

148

d. Planting Date. The best time is probably immediately after
natural seedlings appear (in March along the North Carolina coast).
Earlier seeding is susceptible to weather risks. S. alternitflora can be
seeded as late as the end of June in North Carolina. This produces
greatly reduced first-year growth, but if the stand survives the winter,
growth equals that of earlier seedings by the end of the second growing
season.

e. Elevation. Seeding should usually be confined to about the upper
half of the tide range.

f. Fertilization. Seedlings are usually more responsive to fertili-
zer than transplants and first-year growth can be increased substantially
by fertilization in nutrient-poor environments. Top dressings of about
100 kilograms per hectare of nitrogen (90 pounds per acre) and 25 kilo-
grams per hectare of phosphorus (50 pounds per acre P_0_), applied in
late June and again in late July, are suggested where nutrient deficien-
cies are suspected. Nitrogen should be from ammonium sulfate and
phosphorus from a soluble source such as treble superphosphate.

VIII. OTHER SPECIES

Although this study concentrated on the intertidal zone, stability
of bare areas lying immediately above this zone could not be ignored.
Patens (Ait.) Muhl. (saltmeadow cordgrass) frequently inhabits the zone
immediately above the upper limit of S. alterntflora in undisturbed
intertidal marshes. It is expected that this grass would be suitable for
propagation at elevations higher than the S. alterntflora zone. No formal
planting experiments were conducted with 5. patens but enough plantings
have been made during the last three growing seasons to provide some
useful observations.

Where we have compared S. patens with S. alterntflora over an eleva-
tion gradient in transplant experiments, there is some overlap in survival
at the end of the first growing season. After several years, competition
between the two will probably limit them to their respective elevation
zones as observed in nature. At Snow's Cut, the transplanted S. patens
survived the first growing season down to 1.05 meters above MLW, but the
lower limit of vigorous growth was about 1.25 meters. The upper limit of
this species is not well-defined, but its growth is depressed on higher
and drier sites. Patens was planted over an elevation gradient
at Snow's Cut on 27 April 1971; six samples were harvested from below
and six from above the mean high water spring tide line on 15 September
1971. The yield of aboveground growth of the plants at the higher ele-
vation averaged 26.6 grams per plant while those at the lower elevation
zone averaged 141.8 grams per plant. Survival of the transplants was
very good (93 percent) over the entire elevation gradient. Careful
plant selection is important for good survival and growth. The plants
should be from a sparse stand; preferably a sandy area where growth is
spreading, and divided into clumps of 6 to 12 culms per hill.

149

The growth of S. patens transplants is enhanced by the application
of nitrogen fertilizer. At Drum Inlet S. patens was transplanted 28 June
1972 and one part of the planting received 89 kilograms per hectare of
nitrogen on 1 August 1972. The averages of plants harvested 4 October
1972 were 4.6 grams per plant for the unfertilized and 10.4 grams per
plant for the fertilized.

We assumed that findings from our dune research program are applica-
ble to areas above the S. patens zone elevation. However, since Pantcum
amarulum can be established by direct seeding and dredged material sites
may be less exposed than some foredunes, this species was seeded on
dredged material to protect S. alterniflora plantings from blowing sand
on both the Beaufort and Drum Inlet sites. It was of little value for
this purpose during the first growing season because seedling growth was
not sufficient to materially affect sand movement. However, by the end
of the second growing season a good stand, capable of trapping sand, was
established.

Growth of this grass can be enhanced substantially by fertilization.
In an experiment at Drum Inlet, first-year seedling dry weight was
increased by a factor of 5 when nitrogen at the rate of 89 kilograms per
hectare was applied. Fertilizer response, if any, was obscured by blowing
sand on the Beaufort site.

IX. SUMMARY AND CONCLUSIONS

Techniques were developed for propagating Spartina alterntflora by
seeding and transplanting. Transplants are more vigorous than seedlings
and are better able to survive on exposed sites and at lower elevations.
Plants can be dug from natural marshes. The most vigorous and most
easily obtained plants are found in recently colonized areas where the
root mat has not fully developed. A sandy substrate also facilitates
digging and separating the plants. A nursery area may be established
on sandy dredge spoil by seeding or transplanting and used the following
growing season. Plants produced in such a manner provide a source of easy
to obtain vigorous plants. Transplanting should usually be done with
single stems spaced about 0.9 meters apart. Closer spacing increases
the chances of success on exposed sites. Machine transplanting is
feasible where there is access to the planting site and the substrate
will support equipment. The best months for transplanting in North
Carolina are April and May, although it may be done at any time. Although
survival is good for summer planting, growth is limited for that growing
season. Risk of storm damage is great when transplanting is done in
winter.

Seeding is an economical and effective method of establishing S.
alterniflora. Seed and seedlings are less tolerant of rigorous conditions
(such as storm waves and blowing sand) than transplants and are usually
effective only in about the upper one-half of the elevation range of 3.
alterniflora in a given location. Seed should be collected as near
maturity as possible (late September in North Carolina) and stored in

150

saltwater at 2° to 3° Centigrade over winter. Seeding should be done in
April (in North Carolina) at the rate of 100 viable seed per square meter
by incorporating the seed in the upper 1 to 3 centimeters of the substrate.
Seedlings grow rapidly during the first growing season and under favorable
conditions usually produce a better cover than transplants during the same
period.

Selecting a site within the proper elevation zone for growth of S.
alterniflora is critical. The vertical zonation of the grass is deter-
mined by interaction of environmental factors (the most important being
tide range) peculiar to each location. The upper and lower limits of
growth for a potential planting site can usually be found by determining
the upper and lower limits of growth of nearby natural stands. Stands
will resist competition from invading plants in areas of higher salinity
(>25 parts per thousand) and longer periods of inundation (>8 hours).
The substrate of a planting site is important in its ability to support
equipment, its nutrient supplying capacity, and its effect on salt
buildup.

Development of transplanted or seeded areas is rapid. After two
growing seasons there is little difference in appearance and primary
productivity of the vegetation between artificially propagated marshes
and long-established natural marshes. The length of time required for
a new marsh to achieve a fully functional biological role is unknown.

The relationship of mineral nutrition to growth of S. alterntflora
was determined by sampling plants and soils in natural stands and by
applying fertilizers to natural stands, transplants, and seedlings.
Results of the natural marsh sampling and subsequent regression analysis,
indicated that tissue concentrations of several nutrients and several
soil properties were related to productivity of S. alterniflora. Variables
negatively associated with yield were salinity of the soil solution,
manganese concentrations in the plants and soil and sulfur concentrations
in the plants. Variables positively associated with yield include
phosphorus concentrations in the plant tissue and in the soil.

Results of fertilizer experiments in natural stands indicate that the
productivity of some salt marshes is limited by the supply of nutrients.
The standing crop of aboveground growth of S. alterntflora growing on a
sandy substrate was increased significantly by additions of nitrogen
alone and increased about threefold when phosphorus was also applied.

In a marsh developed on finer-textured sediments, nitrogen fertilizer
doubled the standing crop of short S. alterniflora, but there was no
response to phosphorus. Tall S. alterniflora did not respond to either
nitrogen or phosphorus. Nitrogen and phosphorus fertilizers enhance
growth of transplants and seedlings artificially established on dredge
spoil. These findings suggest that salt marshes may be important in the
recycling of nutrients that may otherwise occur as pollutants in the
estuary.

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155

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