Vegetation Dynamics Along
Utility Rights-of-Way

Newsletter

Volume 5, Number 3
May - June 1988

At the Arboretum

We remind our visitors of the new loop
on the Cary Pines Trail and of the
portion of the Wappinger Creek Trail
that has been rerouted. Both these
paths lead through old hemlock stands
... cool, peaceful places to spend time
during warm summer weather.

The Acid Rain Study Ponds and
Pollution Garden are open to the public.
For information on these and other IES
research displays, see the calendar on
the last page of the Newsletter.

Sunday Ecology Programs will
continue throughout the summer.
Please see the calendar for dates and
titles.

The IES Newsletter is published by
the Institute of Ecosystem Studies
at the Mary Flagler Cary Arboretum.
Located in Millbrook, New York,
the Institute is a division of The
New York Botanical Garden. 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
Design and Printing: Central Press

INSTITUTE OF
ECOSYSTEM STUDIES
The New York Botanical Garden
Mary Flagler Cary Arboretum
Box AB

Millbrook, NY 12545
(914) 677-5343

You’ve seen the wide strips of cleared land
zippered with the utility poles and cables
that allow electric power to flow across the
landscape. How do these green belts
remain clear of woody plants? What
prevents rapidly growing trees from
reaching the high voltage lines? These are
questions faced by utility companies, who
must ensure that trees in rights-of-way
don’t grow into the power lines. These are
also questions currently being addressed
by IES scientists working to understand
the natural processes that might prevent
trees from becoming established in these
areas.

Utility companies currently use both
herbicides and mechanical cutting to
control tree growth along rights-of-way.
Concerns about the costs and
environmental effects of herbicides have
led them to seek alternatives. In ecological
terms, vegetation management along
rights-of-way in the northeastern United
States is largely an effort to halt or
successfully set back a natural process of
succession from communities dominated
by herbaceous plants and shrubs to
forests. Management techniques that
involve only repeated cutting of the
vegetation at a site can actually stimulate
rapid regrowth of the unwanted trees.

For many years, ecologists have been
proposing that there are ecological
alternatives to the cycle of intensive

management followed by rapid regrowth.
One of the strongest proponents of
alternative approaches has been Dr.
William Niering, of the Connecticut
Arboretum, who has documented the
persistence of native shrub thickets that
show little invasion by trees. The work of
Dr. Niering and others suggests that some
native communities of low growing plants
may act to inhibit the establishment and
growth of trees.

In April 1984 representatives from Central
Hudson Gas and Electric Corporation met
with IES scientists Charles Canham, John
Eaton, Gene Likens, Jay McAninch and
Mark McDonnell to discuss ecological
approaches to managing vegetation along
rights-of-way. IES scientists were
encouraged to submit a proposal
describing their ideas. After an extensive
review, the proposal and an addendum
were approved by Central Hudson. The
project, entitled “Vegetation Dynamics
Along Utility Rights-of-Way: Factors
Affecting the Ability of Shrub and
Herbaceous Communities to Resist the
Establishment and Growth of Tall Woody
Plants,’’ runs from May 1985 to December
1991. Dr. Canham, a plant ecologist at
IES, directs the overall project, with Dr.
Alan Berkowitz, Mr. McAninch and Dr.
McDonnell as co-investigators.

While Central Hudson serves as the direct
sponsor of the research, roughly three-

continued on page 2

Young trees are transplanted into a new nursery study. As a part of the IES investigation of plant growth
along rights-of-way, the effects of simulated herbivory (using clippers) will be observed. Left to right:
Summer project assistants Chris Fox, Andrea Kim and Michelle Beucler-Gorsira, with Dr. David Wood
in the background.

Rights-of- W ay, from, page 1

quarters of the funding conies from the
Empire State Electrical Energy Research
Corporation (ESEERCO). This funding
consortium manages research and
development money contributed by New
York State’s utility companies, and a
portion of the money is allocated for
environmental research.

Untold millions of seeds are produced by
trees bordering rights-of-way, but
relatively few germinate and survive to
emerge above the surrounding shrubs and
herbs. What fates do they meet along the
way, limiting their growth? To understand
better the process of emergence, IES
ecologists are looking at factors that affect
all stages in the life cycles of trees.

Seed dispersal is the first step in a plant’s
life cycle and also the first stage at which
limitation occurs. Under the direction of
Dr. Mark McDonnell and research
assistant Judi Koch, seed traps -- devices
for collecting wind-dispersed seeds - were
placed at random points along rights-of-
way. The ecologists are finding that even
the wind-dispersed seeds don’t travel long
distances and are thus most likely to land
near the forest edge. Seedling densities of
these trees are therefore lower at the
centers of rights-of-way.

What happens to seeds once they land at a
site? Ground-feeding birds and small
herbivorous mammals such as mice and
chipmunks can consume large numbers of
seeds. This seed predation may be a
significant cause of mortality, one that will
be investigated by the scientists. Those
seeds that don’t become lunch for local
herbivores may germinate, but others will
rot or die first, reducing the viable
population even further. Finally, whether
or not seedling establishment occurs
depends upon how well individual plants
compete with the intact vegetation for the
nutrients, water and light resources they
need for growth.

During the first three years of the study,
the scientists and their research assistants
worked at over 50 different sites along 966
kilometers (600 miles) of high voltage
transmission line rights-of-way in the area
served by Central Hudson. From fertile
lowlands in Dutchess County to rocky
highlands in the Catskills, they sampled
the shrub and herbaceous vegetation, the
physical environment and all tree seedlings
present. Fascinating and complex patterns
of seedling invasion were found. Some of
the patterns are related to the patchwork
of vegetation types found at a given site,
while environmental factors (soil moisture
and nutrients, light levels) and disturbance
history also appear to be important in
determining where seedlings occur.

One final study during the first phase of
the project addressed the problem of how
to control those trees that do emerge,
without using herbicides. Since cutting is a
likely technique, the scientists asked: What

is the best time of the year to cut trees
along power lines? The traditional time to
cut trees is winter. However, this is also
the time when energy for tree growth has
already been stored in the roots, and, since
most trees along rights-of-way are capable
of resprouting when cut, regrowth is rapid
in the spring when the energy is released.
Dr. Canham and co-workers experimented
with cutting trees at different times during
the growth season to determine when
those reserves had been depleted and new
energy not yet stored. Lower carbo-
hydrate levels in the roots should
lead to shorter shoots the following season
and regrowth should be minimized. Sprout
growth is being monitored for two years to
gauge the effectiveness of this technique.

Current studies by Dr. Canham and
colleagues focus on experiments designed
to test ideas and hypotheses generated
during the first phase of study. The role of
interactions with the intact vegetation, of
herbivory, and of physical disturbance in
reducing or increasing seedling growth
and survival are being assessed. The
breadth of these studies, with their focus
on many different plant communities and
environments, makes this investigation
unique in the study of tree seedling
establishment.

The importance of resource competition
has been difficult to judge in natural
communities, but Dr. Alan Berkowitz, an
agricultural ecologist with extensive
research experience in studying
competition among crop plants, and Dr.
Canham are directing competition studies
along rights-of-way. This summer, tree
seedlings will be transplanted into intact
communities to measure how the presence
of the natural vegetation affects seedling
growth. Results will be compared with
those from a “garden plot”, nearby, where
the seedlings are transplanted into areas
cleared of vegetation. To complement this
study, critical resources - the soil
nutrients, water and light - are being

Dr. Charles Canham uses an all-sky camera to
measure the amount of light a seedling receives.

measured by research assistant Vicky
Kelly to see if their availability is reduced
by other plants. Then, by artificially
providing nutrients, water or light to
transplanted seedlings in future studies,
the importance of resource competition
can be confirmed.

Jay McAninch, an IES wildlife ecologist,
will focus on the effects of herbivory on
seedling establishment and growth. This
summer, working with post-doctoral
associate Dr. David Wood, he will study
the effects of different timings and
intensities of biomass reduction (leaf or
branch removal) on tree seedlings under
different levels of environmental stress in
a test garden. The scientists will also
evaluate the impact of herbivory and
seedling predation on rights-of-way
vegetation by transplanting tree seedlings
into many different sites along rights-of-
way, and then monitoring the natural rates
and timing of herbivory. In addition,
important data will be collected on how
plant communities differ with regards to
species of herbivores present.

Seedling establishment often occurs after
some form of physical or human
disturbance to a site. Frost heaves or dirt
bike tracks, for example, might allow a
plant to become established where it
would otherwise be shaded and stunted; or
maybe a deer’s hoof scraping away the
layer of leaf litter would let a seedling
reach mineral-rich soil below. Predation
on a seedling can also be affected by a
disturbance: while small mammals may
avoid even the smallest gaps in vegetation
cover because of fear of predators, deer
might be more apt to notice an isolated
seedling growing in that same opening.
This summer, research assistant Jim Hill
(see article on page 3 of the Newsletter)
will survey the types of natural and
human-induced disturbances that occur
along rights-of-way. Then, next summer,
he and Dr. Canham will set up field
experiments to look at the effects of
different kinds of disturbances on
germination, establishment and growth of
tree seedlings.

Although sampling and observations go on
year-round, the most active time for data
collection on the rights-of-way project is
spring, summer and fall; the 1988 field
season began in the last week of March
and will extend to November. A large
group of dedicated people is required for
such an ambitious project to succeed.
Current full-time staff are Dr. David
Wood, Judi Koch, Vicky Kelly and Jim
Hill. The full-time research assistants
during earlier phases of the project were
Jon Kays, Karen Kays and Marty Burd.
This summer Dr. Canham and colleagues
are hiring up to 12 summer project
assistants to join this collaborative effort
to understand the ecology of utility rights-
of-way of the Hudson Valley.

Likens Elected to
Royal Swedish
Academy

Dr. Gene E. Likens, Director of the
Institute of Ecosystem Studies, was
recently elected a Foreign Member in the
class for Botany of the Royal Swedish
Academy of Sciences. Dr. Likens was
notified of this honor in March 1988 by
Academy Secretary General Professor
Tord Ganelius.

The Royal Swedish Academy of Sciences
is an independent, non-governmental
organization that was founded in 1739 to
promote mathematics and the natural
sciences. It achieves its aims through six
institutes, each with a different area of
focus, through international scientific
exchange programs, and through
publications and informational activities.
The Academy also awards research grants
and prizes; perhaps the most well known
of the latter are the annual Nobel Prizes.

The Academy has approximately 250
Swedish members and a quota of 134
foreign members. Of the foreign
members, approximately one fourth are
American. Being elected to an academy of
this sort is one of the highest honors a
scientist can achieve. Dr. Likens was
elected to the U.S. National Academy of
Sciences in 1981.

New Staff

JAMES DAVID HILL, research
assistant II, is working for Dr. Charles
Canham on the rights-of-way study (see
page 1). He is involved with three major
aspects of the project: doing an annual
census of tagged seedlings in the research
plots, selecting and preparing sites for a
competition experiment, and surveying
disturbances along rights-of-way. Mr. Hill
has a bachelor of arts degree, cum laude,
in biology from Hartwick College, and a
master of science degree in botany from
the University of New Hampshire.

Workshop: Air Pollution and
the Wilderness

One purpose of the Clean Air Act is to
prevent significant deterioration of air
quality. Federal land managers in charge
of wilderness areas need knowledge of
possible air pollution effects when they
review applications for construction of
major new emission sources or for
modification of existing sources, on
neighboring lands. To help land managers
knowledgeably screen the many requests
for permits that they receive annually, the
Institute of Ecosystem Studies and the
U.S. Forest Service co-sponsored a
workshop to achieve consensus on the
levels of air pollution likely to damage
sensitive ecosystems. The workshop,
“Effects of Air Pollution on the
Wilderness”, was held at the Institute
from May 2-5, 1988.

Planning for the workshop began when
managers from the U.S. Department of
Agriculture (USD A) Forest Service
contacted IES director Dr. Gene E. Likens
to ask for guidance on the question of
pollutant levels. Dr. Likens, James G.
Byrne and Douglas G. Fox of the Forest
Service, with a steering committee, co-
organized the workshop. Its goal was to
develop the best possible estimates as to
what levels of air pollution cause damage
to wilderness ecosystems. The workshop
brought together 40 specialists: scientists
from Canada, Norway, Sweden, the
United Kingdom and the United States,
and U.S. Forest Service managers. The
Institute was represented by Dr. Likens,
an ecologist, Dr. Gary M. Lovett, a plant
ecologist, and Dr. Michael L. Pace, an
aquatic ecologist. These three scientists
are actively involved in research on the
effects of atmospheric pollution on local as
well as global ecosystems.

On the first day of the workshop IES
scientists gave a primer for Forest Service
managers, covering basic concepts of
ecosystems, air pollution, and the effects
of air pollution on terrestrial and aquatic
ecosystems. The following day was
devoted to a discussion of the regulations
in the Clean Air Act and the Wilder-
ness Act, and on the third and
fourth days small working groups

determined critical loading values for
three pollutants - sulfur, nitrogen and
ozone - in nine representative Class I
wilderness areas (areas in which only very
small increments of air pollution are
allowed, under the Clean Air Act.)

The group proposed a framework for
classifying pollution levels for wilderness
areas. Pollutant levels that fall below a
“green line” - a defined range of values --
are acceptable, and permission can be
granted to go ahead with building plans.
Levels that rise above a “red line” will
cause definite damage to the wilderness
areas and permission for building will be
denied. For those operations whose
deposition levels lie within the “yellow
zone”, with values above green but below
red, permits will be delayed pending
additional monitoring and research on the
effects of the pollutants on the ecosystem.

Workshop participants applied these
guidelines to each of the nine wilderness
areas to examine the consequences of such
a scheme. The report will be published
this summer and the guidelines put into
operation by the Forest Service managers
of the various Class I wilderness areas. It
was informally agreed to meet again in ten
years to review the research and
reevaluate green line and red line values
based on new information.

Just one year ago, participants in the
second IES Cary Conference, “Long-
Term Studies in Ecology: Approaches and
Alternatives,” drafted a statement about
the critical need for sustained ecological
research. This statement read, in part:
Because they have common long-term
goals, we propose a new partnership
between scientists and resource
managers ... Sustained ecological
research supported by this new
partnership can contribute significantly
to the resolution of critical
environmental problems.

In the recent workshop on air pollution
and wilderness areas, scientists and
managers took an important step toward
achieving this critical and effective
partnership.

Local Weather

Data collected at the IES Weather Station provide background information for
ecological research at the Institute and serve as a standard against which long-term
trends in weather and air quality may be compared.

March and April, 1988

Highest temperature: 22.7°C (73°F) on March 24
Lowest temperature: -14.4°C (6°F) on March 22
Daily average temperature: 5.3°C (42°F) (Normal*: 4.9°C (41°F)

Precipitation: 8.45 cm (3.32 in.) (Normal: 17.10 cm (6.73 in.)

Average rainfall pH**: 4.17

Strongest wind gust: 56 km/hr (35 m.p.h.) from the West on March 27
Prevailing wind: Northwest (307°) Average wind speed: 10 km/hr (6 m.p.h.)

* “Normal” values are taken from data collected for a 30 year period at the Millbrook School

* ‘Degrees of acidity or alkalinity are indicated using a logarithmic pH scale. On the scale of 0-14, vinegar - an
acid - has a pH of approximately 3, and “neutral” is 7.0. The pH of “Normal” rain is 5.6 or higher.

Perennial Garden
Highlights: June -
July - August

Late June Oenothera missourensis (Evening Primrose)
Oenothera tetragona ‘Fireworks’

(Sundrops)

Achillea taygetea ‘Moonshine’ (Yarrow)
Ornamental grass garden

Early to Asclepias tuberosa (Butterfly Weed)

Mid-July Phlox paniculata ‘Star Fire’ and ‘Everest’
(Phlox)

Astilbe chinensis ‘Pumila’

Cut flower garden annuals

Mid-to Rudbeckia fulgida var. sullivantii
Late July ‘ Goldsturm ' (Black-eyed Susan)

Echinacea purpurea ‘Bright Star’
(Coneflower)

Liatrus spicata (Blazing Star)

Limonium ‘Robert Butler’ (Sea Lavender)

Early to Lobelia cardinalis (Cardinal Flower)

Mid- Lobelia siphilitica (Blue Cardinal Flower)

August Chrysanthemum parthenium (Feverfew)

Platy codon grandiflorus ‘Album’

(Balloon Flower)

Herb garden

Mid-to Kirengeshoma palmata

Late Hosta plantaginea var. grandiflora

August Phlox paniculata ' Fujiyama’

... and many more ...

For weekly listings, see the “Dutchess
Living” section of the Taconic Newspapers.

Library Note

The IES Circulating Collection, formerly
housed at the Gifford House, has been
moved to the Scientific Library in the
Plant Science Building. Arboretum
Members who wish to borrow books from
this collection may do so while the
Librarian, Annette Frank, is on duty.
Members are invited to call Mrs. Frank at
(914) 677-5343 ext. 311 to make
arrangements for a short introduction to
the new policies regarding use of the
Circulating Collection.

Books on reserve for IES adult education
courses are still kept at the Gifford House.
Call Marcia Davis at (914) 677-5358 for
information.

Summer Calendar

COURSES, WORKSHOPS AND
ECOLOGICAL EXCURSIONS

Adult Education Program catalogues with listings
for the fall semester will be mailed to Arboretum
Members by mid-July. Copies will also be available
at the Gifford House Visitor and Education Center,
or by mail if you call the number below.

SUNDAY ECOLOGY PROGRAMS

Free public programs are offered on the first and
third Sunday of each month. All programs are from
one to two hours long, and begin at 2:00 p.m. at the
Gifford House on Route 44A unless otherwise noted.

Tentative schedule (please call (914) 677-5358 to
confirm the day's topic):

July 3: Independence Day Weekend - no program
July 17: Seeing the Trees for the Forest: A
Beginner’s Introduction to Tree Identification
(Alan Berkowitz) - Walk

Aug. 7 Air Pollution and the Forest: Field Work on
High (Gary Lovett) - Walk
Aug. 21: Pond Ecology: Plants and Animals in a
Freshwater Soup (Michael Pace) - Walk
Sep. 4: Labor Day Weekend - no program

For ecology walks, wear long pants and sturdy,
waterproof footwear with socks; long-sleeved shirts
or jackets are also recommended. In case of
inclement weather, call (914) 677-5358 after 1 p.m.
to learn the status of the day’s program.

ECOLOGICAL RESEARCH
DISPLAYS

Demonstrations at the Arboretum introduce visitors
to the methods and results of ecological research.
The Acid Rain Study Ponds display behind the
Gifford House Visitor and Education Center is open
from early May through October. Here, a series of
tanks that serve as model ponds (complete with
aquatic animals and plants) are exposed to simulated
acid rain, and the results recorded twice a week. The
Pollution Garden, comparing some visible effects of
atmospheric ozone on ozone-sensitive and ozone-
tolerant flowering and crop plants, is adjacent to the
study ponds. The Meadow Management display, at
the Plant Science Building, contrasts the
effectiveness of mowing vs. burning in maintaining
an attractive little bluestem meadow.

ART EXHIBIT

“The Life Forms of Leonard Cole” is an exhibit of
oil paintings and charcoal sketches by Leonard Cole,
father of IES aquatic ecologist Dr. Jonathan Cole.
The exhibit is at the Plant Science Building and is
open to the public from 9 a.m. to 4 p.m. weekdays
through August 12th.

GREENHOUSE

The IES Greenhouse performs double duty: it is a
year-round tropical-plant paradise as well as a site
for controlled environmental research. The public is
invited to explore both aspects during Arboretum
hours. There is no admission fee, but visitors should
first stop at the Gifford House for a free permit.

ARBORETUM HOURS

May 1 - September 30: Monday through
Saturday, 9 a.m. to 6 p.m.; Sunday 1 p.m. to 6 p.m.
The Gift and Plant Shops are open Tuesday through
Saturday 11 a.m. to 5 p.m. and Sunday 1 - 5 p.m.
(The Greenhouse and Plant Science Building
continue to be closed to visitors at 4 p.m. during the
summer hours.)

October 1 - April 30: Monday through Saturday,
9 a.m. to 4 p.m.; Sunday 1 - 4 p.m. The Gift and
Plant Shops are open Tuesday through Saturday 11
a.m. to 4 p.m. and Sunday 1 - 4 p.m. Arboretum
closed on public holidays. (Also closed during the
deer hunting season and when roads are snow-
covered.)

All visitors must obtain a free permit at the Gifford
House for access to the Arboretum. Permits are
available up to one hour before closing time.

MEMBERSHIP

Become a member of the Mary Flagler Cary
Arboretum. Benefits include a special member’s rate
for IES courses and excursions, a 10% discount on
purchases from the Gift Shop, six issues of the IES
Newsletter each year, free subscription to Garden
(the beautifully illustrated magazine for the
enterprising and inquisitive gardener), and parking
privileges and free admission to the Enid A. Haupt
Conservatory at The New York Botanical Garden in
the Bronx. Individual membership is $25; family
membership is $35. For information on
memberships, contact Janice Claiborne at
(914) 677-5343.

For more information, call (914) 677-5358 weekdays from 8:30 - 4:30

INSTITUTE OF
ECOSYSTEM STUDIES
The New York Botanical Garden
Mary Flagler Carv Arboretum
Box AB, Millbrook, New York 12545

Newsletter

Volume 5, Number 3
May - June 1988

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