Newsletter

Volume 12, Number 5
September - October 1995

Editor’s Note

During the colder months ofthe year, the
Institute’s greenhouse is considered by many of
our visitors to be atropical getaway ... an island
of flowers, greenery and warmth inacoldseaof
snow and ice.

In addition to cycads— the ‘living fossils’
introduced on page 3 — plant enthusiasts
encounter scented geraniums (rub the leaves to
learn how they got their name), a herb
col lection complete with herbal fact and folk-
lore, and carnivorous plants. (Do you know
why they trap insects? Signs in the greenhouse
explain.) January and February bring out the
best in the begonia collection, and some of the
orchids are blooming. Ponderosa lemon trees
are laden with grapefruit-sized fruit, and other
citrus trees are doingtheir bestto compete.

Beneficial insects and their relatives help
contribute to the health and well-being ofthe
greenhouse ecosystem . . . there has not been a
general pesticide spraying in the facility for four
years .During your visit, keep an eye out for the
green lacewing, whose larvae eat aphids, white
flies and mealybugs.

The IBS Newsletter is publ ished by the
Institute of Ecosystem Studies, located at the
Mary FlaglerCary Arboretum inMillbrook,
New York. All newsletter correspondence
should be addressed to the editor.

Gene E. Likens, Director
Joseph S. Warner, Administrator
Alan R. Berkowitz, Head of Education

Editor: Jill Cadwallader
Writer: Ann Botshon
Printing: Central Press

INSTITUTE OF ECOSYSTEM STUDIES
Education Program
Box R (Route 44 A)

MilIbrook,NY 12545-0178
(914) 677-5359

Small Creatures Make Big Impact on Soil

lES postdoctoral associate Dr. Patrick
Bohlen is intrigued by a worm-filled soil
patch. “Wormy soil is like a plow layer,” he
says, “with mineral soil completely mixed
with the organic matter.” Among his
reasons for valuing these living earth
mixers are that they are a key food source
for larger animals and can be biological
indicators of pollution.

Dr. Bohlen has yet another reason for
holding earthworms in high regard: their
important influence on retention or loss of
nutrients in the soil system. Indeed, his
years of experience observing worm-filled
soil stem from his dissertation work on this
topic, completed at Ohio State University.

Dr. Bohlen, who is coauthor of the third
edition of the book Earthworm Biology and
Ecology (now in press), says the explosion
of interest in earthworms over the past
decade is testimony to their importance.
Still, much remains to be discovered about
the factors that influence earthworm
abundance and diversity in agricultural
soils. Also largely unknown are the ways in
which earthworms, in their complex
communities, affect soil processes, and the
ways they will be affected by new agricul-
tural practices such as no-till agriculture.
“Soil is a three-dimensional living system;
a lot is going on,” Dr. Bohlen says.
Experimental evidence suggests that
earthworms and microbes are synergistic —
there are even microbes in the earthworm
gut that provide nutrition.

One of Dr. Bohlen’s pursuits at lES is a
study of denitrification as it relates to
earthworm activity. Denitrification is the
process by which nitrate is converted to
other nitrogen forms, such as the gases
nitrous oxide — a greenhouse gas that
contributes to global warming — and
elemental nitrogen (nitrogen gas). Denitrifi-
cation is important because it is one of the
pathways by which nitrogen moves out of
terrestrial ecosystems into the
atmosphere, and there is
evidence that earthworms are
influential in increasing this
process.

Dr. Bohlen, with the collabora-
tion of his supervisor, micro-
bial ecologist Dr. Peter
Groffrnan, is taking advantage
of the fact that nightcrawler

In an lES laboratory, Dr. Bohlen
uses a gas chromatograph with
autosampler to determine nitrous
oxide concentrations in gas
samples from soil incubations.

worms dig fairly permanent vertical
burrows, about 10 millimeters (0.4 inches)
in diameter and one to two meters (3 to 6
feet) deep. The scientists are taking samples
of soil from the burrows of nightcrawlers to
provide insight into whether the burrows
are local ‘hot spots’ of denitrification. Since
there are 80 to 90 nightcrawlers in a square
meter of soil, these hot spots could add up
to a lot of denitrification.

Another thrust of the nitrogen work is to see
whether the amount of free inorganic
nitrogen in the soil depends on the numbers
of earthworms. To determine that. Dr.
Bohlen is measuring the nitrogen in test
plots whose earthworm populations have
been experimentally increased or decreased.

Exotic Asian Earthworms in Forest Soils

Dr. Bohlen is supervising another earth-
worm-related study being done by a
Rutgers University student, Amy Burtelow,
who participated in the 1995 Research
Experiences for Undergraduates Program at
lES (see lES Newsletter 12:4). The point of
departure for her research was the recent
observation that exotic (that is, non-native)
earthworm species are colonizing previ-
ously worm-free forest soils, and in
particular, glaciated soils.

In many soils in the northeastern U.S. once
covered by glaciers, there were no earth-
worms before Europeans arrived, and these
soils still are not likely to have native
worms. What are often found are ‘per-
egrine’ species, which are worms with
fairly wide distributions, not native to the
Northeast. Working at lES, Ms. Burtelow
searched along stream corridors and near
wetlands for an Asian worm that, preferring
wet soils, is expanding its range. She is
looking at the earthworm’s influence on
denitrification and the cycling of nutrients
using techniques similar to those used by
Dr. Bohlen.

continued on page 3

Nitrate: A Hidden Cost of Increased Farm Yields

In our industrialized world, with its high
chemical-input agriculture, farmers apply a
great deal of nitrogen-containing fertilizer, a
practice that has increased crop yields but
also has elevated the levels of nitrate in soil
and groundwater. Unfortunately, high
nitrate levels are toxic to humans —
prolonged drinking of water with high
nitrate concentrations can lead to
methemoglobinemia (oxygen deficit in the
blood), especially in infants. This is where
Dr. Pierre-Andre Jacinthe, a new IBS post-
doctoral associate working with Dr. Peter
Groffman, comes in. His work — using
microbes to convert nitrate to other
substances — could give a boost to the
critical effort to find a way to limit nitrate in
groundwater.

In his doctoral research at Ohio State
University, Dr. Jacinthe had studied ways
to manipulate natural systems to encourage
them to remove nitrate from the soil by
converting it to nitrous oxide and elemental
nitrogen (nitrogen gas). Dr. Jacinthe says,
“At the end of the growing season much of
the nitrogen is left in the soil and remains in
the frozen soil through the winter. As the
soil warms up in the spring, soil microbes
become active, producing more nitrate. In
some years the soil nitrate level in March is
two to five times what it was in November.
With abundant precipitation in the spring,
the nitrate percolates down into the
groundwater. The result is a spring pulse of
nitrate in groundwater.”

Dr. Jacinthe knew that microbes (mainly
denitrifying bacteria) in waterlogged,
oxygen-poor soil would efficiently convert
nitrate to other (gaseous) forms. Because
many Ohio fields have drainage systems in
place, the researcher’s idea was to close the
drains in spring in order to bring the water
table up and get more microbial conversion
of nitrate to the other forms.

To test this idea. Dr. Jacinthe did a simu-
lation using big soil columns, 90 centime-
ters (3 feet) long and 30 centimeters (1 foot)
in diameter. In the laboratory he devised an
apparatus that would bring water up from
the bottom of the column to a desired
distance from the top surface of the column.
This simulates the water table in the
agricultural fields. Dr. Jacinthe explains,
“Since the soil bacteria are in the top 5-15
centimeters (2-6 inches) of the soil, if the
water table does not reach that zone, there
will be no significant effect. Bringing the
water to that height, I was able to remove
40 percent of the nitrate over 130 days. I
also found that the longer the water table
remains near the surface (hence the longer
the soil is oxygen-deprived) the more
nitrogen ends up in the elemental form.”

Dr. Jacinthe’s solution was not perfect:
nitrous oxide, one of the products of nitrate
conversion, is an ozone-depleting and
greenhouse gas. “Much less nitrous oxide
would be produced if we could keep the
water table high for long periods, in order to
encourage formation of elemental nitrogen.
But the limitation is time: farmers
need to use their fields! Usually the
spring thaw is in March and plowing
begins in late April. So there is a 30-
to 45-day window to use this
technique,” says Dr. Jacinthe.

At the Institute Dr. Jacinthe is
continuing nitrate conversion studies,
but in a riparian wetland. These
wetlands are the transition zone
between uplands and surface water;
they are dry but have a high water
table. Dr. Jacinthe’s work addresses
an earlier observation by Dr.
Groffman, that nitrate added to the
shallow groundwater of riparian
wetlands disappears at rates much
higher than one would predict from
laboratory experiments.

Field research also reveals that a
disproportionate amount of the nitrate
disappears in March. Clearly, higher
plants are not responsible since they
are not active in March, which
suggests that microbes are primarily
responsible for the nitrate disappear-
ance. Dr. Jacinthe is testing the idea
that patches of organic material

below the soil surface, rather than the soil at
large, may harbor high concentrations of
denitrifying microbes. He is looking for
such patches by digging pits to take soil-
core samples below the mean elevation of
the water table. He will pump nitrate
through the cores to see how much nitrogen
is removed and how much nitrous oxide
and nitrogen gas are produced. And he will
also measure the overall metabolic activity
of the core samples by measuring oxygen
consumption. In other core samples he will
add both nitrate and organic carbon
(prepared by extracting soluble organic
material from forest-floor litter) to see if the
addition of carbon affects the denitrification
process.

Dr. Jacinthe thinks his biggest headache
will be making sure his experimental
systems remain at specific oxygen levels.
“The key to this,” he says, “is to be patient
at the beginning to make sure it is all
working right.”

The nitrate problems that plague the
industrialized world are generally absent
from traditional agricultural societies. “At
home in Haiti and in many other underde-
veloped countries,” says Dr. Jacinthe,
“inorganic nitrogen fertilizers are too
expensive and not widely used.” ‘Home’ for
Dr. Jacinthe is Arcahaie, about 50 kilome-
ters north of Port-au-Prince. In Haiti,
commercial fertilizer is used mostly with
rice and with specialty crops. “In Arcahaie
we grow plantains, which we plant in May
or June. For nitrogen we intercrop a variety
of black-eyed peas (a legume and nitrogen
fixer) in summer, leave the pea plants
standing after pea harvest, and in December
plant a bean (another legume). The
plantains are finished in two to three years,
and we plant sugar cane to break the cycle.”
Nitrate in groundwater, then, is one of the
many hidden costs of chemical fertilizer
use.

Dr. Pierre-Andre Jacinthe, who says he
has known since his second year in college
that he was going to be a soil scientist,
received an undergraduate degree in
agronomy from the Faculte d ’Agronomic et
de Medecine Veterinaire, in Port-au-
Prince, Haiti. He received a masters
degree from Ball State University in
Muncie, Indiana, and this past June a
doctorate from Ohio State University. Dr.
Jacinthe arrived at lES in August. His
work at the Institute is being funded
through a National Research Initiative
grant of the US. Department of Agricul-
ture Water Resources Assessment and
Protection Program.

Dr. Jacinthe uses a dissolved oxygen meter to measure
oxygen levels in streamwater samples.

“Living Fossils” Nurtured in Greenhouse

Sidle past the luscious citrus and the
imposing staghorn ferns. Across the aisle
from the succulents, cheek-by-jowl with the
bird of paradise plant, are the greenhouse’s
very own cycads, ‘living fossils’ that more
than manage to hold their own against the
other spectacular denizens of the Institute’s
greenhouse.

Mr. David Bulkeley, IBS greenhouse
manager, has become an enthusiast of these
handsome dark green plants and the
greenhouse displays several different
cycads. One, Cycas taiwaniana, native to
an area reaching from Madagascar to
Japan, was raised from seed brought from
Hawaii some 19 years ago. So successful
was the germination that Mr. Bulkeley was
able to donate some of the plants to the U.S.
Botanical Garden in Washington and to The
New York Botanical Garden in the Bronx.

A second species, Cycas revoluta, came in
a small pot from the Franklin D. Roosevelt
Home in nearby Hyde Park, (“that makes it
historically as well as botanically interest-
ing,” Mr. Bulkeley says). Another gift was
Cycas circinalis, native to an area extend-
ing from India to New Guinea. Both of
these cycads are grown extensively as
ornamentals, reaching nearly tree size
outdoors in the tropics. C. revoluta is also
widely used for bonsai in Japan.

Looking much like palms, cycads are
entirely unrelated to them and in fact are an
ancient and primitive group of plants. Their
requirement for warm climates and the fact
that they are gymnosperms (from the Greek
gymnos, naked, and sperma, seed, with the
unprotected seed lying on the scales of the
female cone), testify to their origin in the
Mesozoic era, some 100-200 million years
ago. They were witness to giant reptiles
roaming a warm Earth and a landscape
dominated by spore-bearing ferns. For tens
of millions of years the cycads ranged
widely over the Earth, and with their dying
they made an important contribution to the
formation of coal.

female cone matures — a single, large,
fuzzy structure growing from the center of
the plant — and, as it disintegrates, ripe
seeds are released. (Unfertilized cones
develop in a similar way and regularly
appear on the lES greenhouse cycads, but
their seeds are not viable.)

Of these tenacious survivors of an earlier
time, a number of species are teetering on
the brink of extinction and the group as a
whole is probably the most endangered
group of plants in the world. A few are
imperiled due to destruction of their special
habitats — as, for example, in Florida and
South Africa, where land is being cleared
for development or agriculture. Probably the
main cause of their decline, however, is
overcollection for the horticultural trade.
These graceful plants had been traded for
more than two centuries with little impact,
but since the 1970s, when they began to be
regarded as collector’s items and traders
began to command steep prices for certain
rare species, the number of cycads in illegal
trade has climbed sharply. They are
protected by the U.S. Endangered Species
Act and the international treaty on endan-
gered species, but smuggling schemes
abound — for example, some are deliber-
ately mislabeled as palms or ferns, in order
to slip them past inspectors at the Mexican-
U.S. border.

Fortunately, as Mr. Bulkeley points out, a
considerable number of cycad species are
being commercially propagated to meet the
horticultural demand and thwart the
collectors of wild-grown stock. Home-
greenhouse enthusiasts interested in
growing cycads of their own should make
sure their supplier is offering only nursery-
grown stock.

But cycads are slow-growing, and private
growers will have to wait years before their
specimens look showy. Fortunately, here at
the lES greenhouse, the cycad specimens
are all thriving, and visitors are welcome to
stop by and make their acquaintance.

Small Creatures jfrom page /

Studying Forest-Floor Microbial
Processes

Though a big part of Dr. Bohlen’s work,
earthworms are just one facet of his
overriding interest in soil ecology, the
relations and interactions among inverte-
brates, microbes and nutrient cycling. At
the Hubbard Brook Experimental Forest in
New Hampshire (see lES Newsletter 12:4).
Dr. Bohlen is studying the factors control-
ling the microbial processes of the forest
floor. “Some (but not all) carbon and
nitrogen ‘pools’ of the forest floor are taken
up, metabolized, and turned over very
rapidly,” he explains. “These pools provide
information on what resources the microbial
populations have to work with. We’d like to
trace the movement of nutrients through
these pools: from the leaf, through the leaf
litter on the forest floor, to the soil. And in
particular, we’d like to relate that move-
ment to litter fall, litter type, and the flow of
nutrients.”

In one experimental approach Dr. Bohlen
fed a solution containing a naturally-
occurring nitrogen isotope into a tree by
puncturing the bark and attaching a
solution-filled collar that directed the fluid
into the transpiration flow of the tree. In this
way, he created beech and maple leaf litters
that are ‘labeled’ with the nitrogen isotope,
enabling him to track the nitrogen flow. He
hopes to relate the information he obtains
about leaf litter to information on what
nutrients are going into the soil.

Dr. Bohlen received his undergraduate
degree from the University of Michigan.
Before obtaining a masters degree from
Miami University in Ohio and a doctorate
from Ohio State, he spent a year at Wes
Jackson ’s Land Institute, the well-known
‘alternative ’ agricultural research center
in Salina, Kansas. He arrived at lES in
May 1994.

Over time, changes in the Earth’s weather
and increasing competition from flowering
plants gradually reduced cycad habitat;
today, some 168 species of cycads — 10
genera in three families — survive. All
tropical and subtropical, cycads differ from
such familiar gymnosperms as pines and
spruces in the internal structure of the stems
and roots and details of the reproductive
structures. Cycad plants are either entirely
male or entirely female, so seed production
is only possible when plants of both sexes
grow together and mature at the same time;
in cultivation, artificial pollination is
necessary. Months after pollination, the

Here, Mr. Bulkeley has selected
one of the six cycad plants in the
lES greenhouse to point out a
seed in a well-developed cone.

Calendar

CONTINUING EDUCATION
Winter/Spring semester catalogues are available
at the Gifford House or by calling the Continuing
Education Program office number below. Following
are justsome ofthe upcoming classes, workshops
and excursions:

Landscape Design

Feb. 8: Marketing and Estimating Landscape
and Gardening Services
Feb. 24: Residential Design Sketch Exercises
Gardening

Feb. 3: HowsofHouseplants
Feb. 3 : Developing Ecologically-Sound Nursery
and Landscape Practices
Feb. 5 (6 sessions): FundamentalsofGardening
Feb. 10: Gardens for Dry Sites and Dry Years
Feb. 24: Topiaries, Standards and Beyond
Workshops

Feb. 4: The Landscape with Perennials in the
Mixed Border

Mar. 3: Wildflower Celebration

Other Courses

Feb. 24 & Mar. 2: Introduction to Flower
Arranging

Excursions and Tours
Feb. 26: Philadelphia Flower Show

Cal I the Continuing Education Program office at
914/677-9643 forinformation.

SUNDAY ECOLOGY PROGRAMS
Free public programs are held on the first and
third Sunday ofthe month, except over hoi iday
weekends. Last-minute changes are sometimes
unavoidable, so call 9 14/677-5359 to confi mi the
day’s topic. In case of poor weather, call 677-5358
after 1 p.m. to learn the status of the day’s program.
The following programs begin at 2 p.m. at the
GiflFord House, except as otherwise noted’" :

Feb. 4: Echoes of the Ancient Skies, a program for
children and their families (’" to be held at the lES
auditorium)

Sunday Ecology Programs, continued
Feb. 1 8 : Holiday weekend (no program)

Mar. 3 : Human Accelerated Environmental
Change, aslide presentation by Dr. Gene E. Likens
(’" to be held at the lES Auditorium)

Mar. 1 7: A Catskill Conundrum, a slide presenta-
tion by Dr. Kathleen Weathers

lES SEMINARS

The Institute’s program of free scientific seminars
features presentations by visiting scientists each
Friday at 3 :30 p.m. at the lES Auditorium:

Jan. 19: Indeterminacy (?) of ecological reactions
in an oldfield food web as revealed by perturba-
tion experiments. Speaker: Dr. Oswald Schmitz,
School ofForestry and Environmental Studies, Yale
Univ.

Jan. 26: Adaptive sampling strategies.

Speaker: Dr. Steven K. Thompson, Penn State Univ.
Feb. 2: Experimental studies of avian frugivory.
Speaker: Dr. Kathy Winnet-Murray, Hope College
Feb. 9: Community-level consequences of
competition. Speaker: Dr. Deborah Goldberg, Univ.
ofMichigan

VOLUNTEER OPPORTUNITIES
The lES Volunteer Program is looking for enthusias-
tic women and men interested in working with
Institute staff for a few hours (or more) each week at
the Gifford House Visitor and Education Center. For
information on responsibilities and benefits, call Su
Marcy,IES volunteer coordinator, at914/677-5359.

GREENHOUSE

The lES greenhouse, a year-round tropical plant
paradise and a site for control led environmental
research, is open until 4:00 p.m. daily except public
holidays. Admission is by free permit(see “Hours”).

lES HOME PAGE

The Institute is on the World Wide Web. Visit the
lES home page at: http://www.marist.edu/'ies/

HOURS

Winter hours: October I - April 30
Closed on public holidays.

Roadways are closed when snow-covered.
Public attractions are open Mon. - Sat., 9 a.m. -
4 p.m. & Sun. 1 - 4 p.m., with a free permit.

The lES Gift and Plant Shop is open Mon.- Sat.,
11a.m. -4 p.m. & Sun. 1 -4 p.m. (The shop is closed
weekdays from 1 - 1 :30 p.m.)

•All visitors must pick up a free permit at the
Gifford House Visitor and Education Center on
Route 44 A for access to lES public attractions.
Permits are available until 4 p.m. daily.

lES GIFT AND PLANT SHOP
January Sale: Discounts all month!!

New in the Shop ... bluebird, chickadee and wren
birdhouse kits ... bat house kits ... bird feeders . . . brass
bookmarks ... and in the PlantShop ... scented
geraniums ... staghorn ferns ... FELCO pruners and
sheaths... gardener’s soap
Senior Citizens Days: 1 0% off on Wednesdays

MEMBERSHIP

Become a member of the Institute of Ecosystem
Studies. Benefits include amember's rate for lES
courses and excursions, a 1 0% discount on Gift Shop
purchases, a free subscription to the lES Newsletter
and participation in a reciprocal admissions program,
with benefits at over 1 00 nature centers, forest
preserves, gardens and conservatories in the U.S. and
Canada. Individual membership is $30; family
membership is $40. Forinformation, call Ms. Janice
Claiborne at914/677-5343.

The Institute’s Aldo Leopold Society: In addition
to receiving the benefits I isted above, members of The
Aldo Leopold Society are invited guests at spring and
fall lES science updates. Call Ms. Jan Mittan at
9 1 4/677-5343 for information.

For general information, call the IBS Education Program Office at the Gifford House Visitor and Education Center:

914/677-5359 weekdays from 8:30 a.m. - 4:30 p.m.

INSTITUTE OF
ECOSYSTEM STUDIES
Education Program
Box R

Millbrook, New York 12545-0178

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Newsletter

Volume 12, Number 5
September - October 1995

100% Recycled
Paper