IES newsletter

Volume 13, Number 3
May - June 1996

lES invites you ...

... to the Perennial Garden, where
there is a new “Edible Annual Bed” in
the sunken garden, and where — later
in summer — a water garden and
xeriscape bed will join other educa-
tional displays.

... to the Fern Glen, where it is often
10" cooler than elsewhere. Over 20
kinds of ferns are hiding their reproduc-
tive spores on the undersides of their
leaves, so bring a magnifying glass;
each species of fern produces a different
shape spore. Also, a new sign details
the relationships of the “Shrub Swamp”.

... to the Greenhouse, to follow the
new, self-guided “Economic Botany
Trail” and learn about edible and
medicinal plants.

The lES Newsletter is published by the
Institute of Ecosystem Studies, located at
the Mary Flagler Cary Arboretum in
Millbrook, New York.

Director: Gene E. Likens

Administrator: Mr. Joseph S. Warner

Head of Education: Alan R. Berkowitz
Newsletter editor: Jill Cadwallader

Address newsletter correspondence to the
editor at:

Institute of Ecosystem Studies

Education Program, Box R

Millbrook NY 12545-0178

or e-mail to Jillcad@aol.com

Printing: Central Press, Millbrook, N.Y.

Why Are Cats kill Mountain Forests
Leaking Nitrate into Streams?

by Ann Botshon

Cold, sparkling Catskill Mountain streams
supply most of the drinking water in New
York City’s reservoirs. This precious
water is still of high quality, but it is
worrisome that nitrate concentrations in
the stream water have increased several-
fold over the past 20-plus years.

This troubling change in stream water
nitrate concentrations is behind the efforts
of lES ecologists Gary Lovett and
Kathleen Weathers, and Mary Arthur of
the University of Kentucky, to understand
the connections between the pattern of
nitrogen deposition, the tree composition
of the forest, and the chemistry of Catskill
Mountain stream water. Complicating the
puzzle is the fact that even though the
streams show that the forest has been
losing nitrate over time, there has not been
a corresponding increase in the amount of
nitrogen being deposited from the
atmosphere over the last 20 years. Where
is the nitrate coming from, then? Says Dr.
Weathers, “We think the forest itself
greatly influences the amount of nitrate
found in streams.”

Shedding Excess Nitrogen

Nitrate is a drinking water pollutant,
although nitrate concentrations in Catskill
streams are not yet high enough to warrant
direct health concerns. Nitrogen, as nitrate
as well as in other forms, reaches ecosys-

tems in rain, snow, and clouds, and even as
dry particles or gases. “The Catskill
Mountains experience some of the highest
rates of nitrogen deposition in the North-
east. These rates are influenced in part by
air pollution from the New York-New
Jersey urban corridor,” says Dr. Weathers.
“Some areas at the tops of mountains in the
Catskills — ‘hot spots’ — receive up to
four times more nitrogen than nearby low-
elevation sites.”

Nitrogen is, of course, a nutrient as well as
a pollutant, and historically researchers
have believed that the more nitrogen added
to a forest, the more the forest would grow
(much like adding nitrogen fertilizer to
your garden would cause a spurt in
growth). “If forests really acted like a
limitless sponge for nitrogen, we wouldn’t
expect increased nitrogen deposition
through air pollution to result in increased
nitrogen in stream water,” Dr. Weathers
points out, “because the plants and
microbes would simply continue taking in
all that was available and grow more.”

But in recent years a number of ecologists
have begun to think that as a result of
chronic pollution, more nitrogen is being
deposited on Catskill Mountain ecosystems
than the forests and microbes can use. This
suggests that any nitrogen in excess of what
the ecosystems need will leak out into
stream water. Quite simply, this theory
implies that now the forests are saturated
with nitrogen and dumping the excess. But
Dr. Weathers and colleagues think some-
thing else is going on as well.

What Role Do Forests Play?

In addition to, and perhaps in conjunction
with, air pollution, there is another
possibility, one proposed by the lES
ecologists, which draws on the fact that
forest types differ at taking up and process-
ing nitrogen — a model that implies that if
the forest composition has changed over
time, the nitrogen export patterns also may
have changed. For example, the lES
researchers have found that yellow birch
and sugar maple trees may make more
nitrate available for leaking into streams
than do beech or hemlock. Their theory
suggests that if there were an increase in
birch and maple trees in Catskill forests,
more nitrate would leach out from the soils
and into the water.

continued on page 2

Complex Forest Dynamics Link Acorns, Deer Ticks,

Gypsy Moths by Ann Botshon

A bumper year for acorns may result in a
bad season for Lyme disease two years
later. It may also mean a population
explosion of gypsy moths in some future
year.

Such intriguing links are among the
findings of a long-term lES study of
ecological relationships in oak forests of
the eastern United States. Institute of
Ecosystem Studies scientists Richard S.
Ostfeld and Clive G. Jones,
together with colleague Jerry O.

Wolff of Oregon State University,
described the interplay of a host of
characters in the oak forest drama in
the May 1996 issue of the journal
BioScience.

The lES ecologists are working now to
ascertain if bumper years for acorns are
followed two years later by unusually large
numbers of nymphal ticks or an unusually
high incidence of the Lyme disease
bacterium in the ticks, or both. The year
1 994 brought an extremely healthy acorn
crop; Dr. Jones and Dr. Ostfeld expect large
numbers of ticks this summer.

In those acorn-rich years when deer
gather in the oak forest to feed,
large numbers of adult deer ticks
drop from their hosts onto the forest
floor and lay their eggs in leaf litter
there. Thus, in the summer follow-
ing a heavy acorn crop, there is an
outbreak of larval ticks (the stage
that hatches from eggs) in oak
forests.

Meanwhile, an autumn’s abundance
of acorns also encourages growth of
populations of white-footed mice.

In a peak acorn year, mice get fat,
survive the winter well, and
actually breed in the dead of winter
(something that does not occur
when acorns are absent or only few
in number). The result is that mouse
populations get a head start and also
reach a peak the summer following
a peak acorn year.

Spirochetes

White-Footed
Mice

Acorns

/

Humans

Lyme

Disease

iMi

Hunting

Timber

jiUjf

Forest

Aesthetics

y

years in a row, it can kill trees. Such
outbreaks occur every ten years or so.

Speaking of the recent findings. Dr. Jones
observes, “It is often such indirect connec-
tions that can have a big influence on the
structure and function of ecological
communities.”

The surprisingly complex web of intercon-
nections revealed in these oak forest studies
indicates that particular species
cannot be managed in isolation
from other interacting species. For
example, one strategy for improv-
ing the timber harvest might be to
keep the number of gypsy moths
low by keeping the number of mice
high (e.g., by deliberately providing
food for mice in the year after a
peak acorn crop). But since mice
also carry deer ticks, such an
approach could have the unwanted
consequence of increasing the risk
of tick bites and the occurrence of
Lyme disease in people.

J

The relationships between humans and oak forests, and between them
and the organisms that affect Lyme disease and gypsy moth outbreaks.

Drawing by Sharon Machida Okada.

Acorns Now, Gypsy Moths Later

This study points to the compelling
need to explore the complex
ecological connections that affect
the health of both humans and
forests. “Typically, community
ecology has focused on understand-
ing the direct effects of one species
on one or a very few other species,”
says Dr. Ostfeld. “The new work
emphasizes the importance of
viewing such ‘pairwise’ interac-
tions within the context of the
overall ecosystem.”

“In other words,” says Dr. Ostfeld, “Just at
the time that legions of larval ticks are
hatching from eggs and crawling about in
the forest, they encounter enormous
numbers of the preferred host animal, the
white-footed mouse.” The larval ticks take
a blood meal from the mice, but it is not
until another spring arrives that the ticks —
now in the nymph stage — attach to
humans or other mammals. After a blood
meal on that host, the nymphs molt into
adult ticks.

It is the mice that are responsible for
infecting feeding larval ticks with the Lyme
disease bacterium, since, of all the animals
ticks may feed on, only mice carry large
populations of these microorganisms in
their blood. Without mice, the ticks would
be a nuisance but would not cause Lyme
disease.

White-footed mice also have a beneficial
effect on the oak forests, in an indirect
connection that involves the gypsy moth.
Mice are voracious consumers of gypsy
moth pupae (the insect’s cocoon stage). So,
when mice are abundant and gypsy moth
populations are low, the mice may prevent
gypsy moth outbreaks. (In contrast, most
other natural enemies of gypsy moths are
not abundant when gypsy moths are at low
density.)

But two to three years after a heavy acorn
crop, white-footed mouse populations
typically “crash”. That allows many gypsy
moth pupae to survive, so that the moth
population can start to escalate to outbreak
levels. The caterpillars strip the oak trees of
their leaves, often over thousands of acres
of forest. When this happens a number of

Catskill Mountain Forests, from page I

There is, in fact, historical evidence that
beech bark disease moved through the
Catskills between 1940 and 1960, leaving
many beech dead and dying, and perhaps
resulting in a forest species shift. Drs.

Lovett, Weathers and Arthur are working to
see if the increase in nitrate in Catskill
stream water over time can be linked to a
decline in the number of beech.

The researchers also are studying the
connection between forest type and the
concentration of nitrate in different places
in the Catskills. They have established that
there are large differences in nitrate
concentration among Catskill streams. Now
they are working to link that information to

Student Evolution at lES

Pamela Templer extracts pore water from a sampling device
called a peeper.

It has been only two years, and research
assistant Pamela Templer is about to move
on to her fourth incarnation as an lES
researcher: this fall, she will begin her
doctoral studies in a joint graduate program
between Cornell University and the
Institute of Ecosystem Studies.

Ms. Templer’ s lES story began in summer
1994, when, as a student at the University
of California at Santa Cruz, she was one of
10 students accepted to that year’s lES
Research Experiences for Undergraduates
(REU) program'. She spent three months at
the Institute, working with mentor scientist
Dr. Richard Pouyat on the lES Urban-to-
Rural-Gradient program and studying
nitrogen and ammonium uptake in red oak
(Quercus rubra) and Norway maple {Acer
platanoides) seedlings. The following
summer she returned to the Institute as a
Polgar Fellow^. This time, she studied the
biogeochemistry of marshes at Tivoli Bays,
a Hudson River marsh north of Red Hook,
with lES aquatic ecologists Drs. Stuart
Findlay and Cathleen Wigand. Her project
was a comparison of nutrient cycling (the
transfer of chemical elements such as
nitrogen and carbon between living and
non-living parts of the environment) in the
native wetland plants Phragmites and
cattail with that in non-native purple
loosestrife.

After Ms. Templer graduated from the
University of California with a bachelor’s
degree in biology and environmental
studies, she was hired as an lES research
assistant, working with Dr. Findlay and
post-doctoral associate Dr. Cathleen
Wigand. She is continuing her Polgar
Fellowship project, and also is doing
nutrient analyses in underwater plant stands
with Vallisneria (wild celery) and
Potamogeton (clasping pondweed) — two

differences in forest type in the watersheds’
ecosystems.

The Institute’s pursuit of the connection
between air quality, water quality, and
forest dynamics and health is no obscure
academic exercise, but a study that will be
of great interest to managers of Catskill
Mountain watersheds, to people interested
in clean air, and to Catskill residents whose
welfare depends on the functioning
ecosystem. “And, especially,” says Dr.
Weathers, “to those millions of people who
turn on their taps daily to receive a Catskill
Mountain gift: clean, forest-filtered water.”

species common in the Hudson
River.

During a typical day of field work,

Ms. Templer sets “peepers” to
collect pore water in the sediments
of Tivoli Bays. Peepers are small,
rectangular samplers that are sunk
to a depth of 20 centimeters (8
inches), which is the root zone of
the study plants. Holes in the
peepers’ sides are covered by very
fine membrane that allows
chemicals to pass through. After
they equilibrate in the sediments
for a week, Ms. Templer brings
them to the laboratory where she
extracts the water with a syringe
and injects it into a device called
an autoanalyzer, which measures
ammonium, nitrate and phosphate.

Results of Ms. Templer’s work last summer
showed a significant difference in the pore
water nutrient levels between native species
and purple loosestrife, with the lowest
nutrient levels in sediments where loose-
strife is growing. The ability to grow with
reduced nutrients could give this invasive
plant a competitive advantage. This
summer. Dr. Findlay is expanding his
research to include three more marshes in
the Hudson River — Piermont Marsh just
south of the Tappan Zee Bridge, Constitu-
tion Marsh in Cold Spring, and Stockport
Flats in Columbia County — as well as
some in the Connecticut River, so Ms.
Templer will be setting peepers in sedi-
ments at these sites as well.

With Dr. Wigand, she is doing similar pore
water nutrient analyses with submerged
plants. The aim here is to compare sedi-
ments from vegetated and non-vegetated
areas, as well as from different sites within
vegetated areas. While many aspects of the
Hudson River have been thoroughly
studied, no one has yet looked at nutrients
in the sediments. Data from this study will
help complete the picture of the whole
ecosystem.

The end of summer will bring the end of
Ms. Templer’s work as an lES research
assistant and the beginning of her five-year
career as a graduate student. She has been
accepted by Cornell University’s Section of
Ecology and Systematics as one of the first
students in a new program. Human
Accelerated Environmental Change,
developed by Cornell and lES and funded
by the National Science Foundation. After
two years of course work, she will do
doctoral research related to a human-
induced environmental change — one topic
she is considering is land-use effects on

plant communities and nutrient cycling.

The co-chairs of her doctoral committee are
Dr. Findlay, at lES, and Dr. Todd Dawson,
a Cornell University plant ecologist.

Pamela Templer’s evolution through the
Institute is not an exception. A recent
tracking of former lES REU students found
14 Ph.D. candidates, five masters degree
students and a number of others already
working in research and education related
to science and the environment. lES
laboratory assistants also frequently move
on to graduate programs; Ms. Erika Latty,
for example, a doctoral student whose work
was described in the story on Dr. Charles
Canham’s Adirondack Mountain project in
the March-April 1996 issue of the newslet-
ter, was a research assistant for three years
before entering the same Cornell/IES
program that Ms. Templer is beginning.

The nurturing and encouragement of young
scientists is one way in which the Institute
is accomplishing its educational mission.

1 . Developed by the National Science Founda-
tion (NSF), a federal agency, the REU
program 's purpose is to improve science
education in the US. and to help assure an
adequate supply of scientists, mathematicians
and engineers for the future. Many institutions
compete for annual NSF funds to support REU
students, and consistently lES has been among
the recipients. The 1996 REU program at the
Institute will be featured in the next issue of the
I ES NEWSLETTER.

2 . The Polgar Fellowship Program, sponsored
by the Hudson River Foundation and the
Hudson River National Estuarine Research
Reserve, enables students to do research related
to Hudson River ecosystems. The Institute
participates in the program, both by providing
advisors and facilities for research projects and
by serving as the site for the final symposium
where students present their results.

CONTINUING EDUCATION
For summer semester catalogues and program
information, call the Continuing Education office
at 914/677-9643. Upcoming programs are;
Landscape Design

Aug. 3: Landscape Design for the Small
Residential Site

Aug. 3; Perspective: A Crash Course
Aug. 10 & 11: Transit and Level Use for
Landscape Construction - Extended
Aug. 17: Quick Sketching for Landscape
Design

Gardening

July 6; Container Gardening
July 13: A Natural Way to Attractive Lawns
and Gardens: A Professional Horticulturist
Shares His Secrets

July 20: Color Relationships in Illustration and
the Garden

July 20; Pinching, Deadheading, Staking and
More - Extended

July 21 ; Summer Wild Plant Identification
July 27: Designing a Perennial Border for All
Seasons

Aug. 3 & 10: Fundamentals of Gardening
Aug. 10 &/or 17: Annuals on Slides and at The
New York Botanical Garden

Biology and Earth Science Courses
Aug. 3 & 4: Field Identification of Grasses
Aug. 4; The Spineless Inhabitants of Flowing
Water

Natural Craft Course
Aug. 24: Black Ash Splint Basket
Excursions and Tours

July 20: Duck Hill and the Hammond Museum
Japanese Stroll Garden
July 21 : Ecology and Behavior of Raptors
July 27; Noah’s Garden: An Ecological Model
for Transforming the Suburban Landscape
Aug. 1 1 : Wave Hill and The Cloisters

lES SEMINARS

From mid-September through mid-May,
scientific seminars are held each Friday at 3:30
p.m. at the lES Auditorium. Seminars are free,
and the public is invited to attend.

INSTITUTE OF
ECOSYSTEM STUDIES
Education Program
Box R

Millbrook, New York 12545-0178

Newsletter

Calendar

SUNDAY ECOLOGY PROGRAMS
Free public programs are held on the first and
third Sunday of the month, except over holiday
weekends. Call 914/677-5359 to confirm the day’s
topic or, in case of poor weather, to learn the status
of the day’s program. The following programs
begin at 2 p.m. at the Gifford House:

July 21 : Call to see if a program has been
scheduled for this date

Aug. 4; Deer Impacts on Forest Vegetation, a
walk led by Mr. Ray Winchcombe
Aug. 18: Weather Monitoring at lES, a program
led by Ms. Vicky Kelly

We strongly recommend that participants wear
long pants tucked into socks and sturdy waterproof
footwear for all outdoor programs.

VOLUNTEER OPPORTUNITIES
We’re hoping to find a few people who enjoy
gardening and would like to volunteer a few hours
a week in the lES display gardens ... it’s a great
learning experience! Volunteers also are needed for
visitor reception and for work in the Gift and Plant
Shop. For information on benefits and responsibili-
ties, call Ms. Su Marcy at 914/677-5359.

GREENHOUSE

The lES greenhouse, a year-round tropical plant
paradise and a site for controlled environmental
research, is open until 3:30 p.m. daily except
public holidays. Admission is by free permit (see
“HOURS”).

lES GIFT AND PLANT SHOP
New in the Shop ... bark birdhouses ... the latest
edition of 50 Hikes in the Hudson Valley ... for
children ... kaleidoscope-on-a-rope ... garbage
garden (a kit for using composted kitchen waste to
make a kid’s garden) ... and in the Plant Shop ...
“Toad Stools”: plant fertilizer garden ornaments
Senior Citizens Days: 10% off on Wednesdays

•• Gift Certificates are available ••

HOURS

Summer hours: May 1 - September 30
Closed on public holidays.

Public attractions are open Mon. - Sat. 9 a.m.-
6 p.m. & Sun. 1-6 p.m., with a free permit*.

(Note: The Greenhouse closes daily at 3:30 p.m.)
The lES Gift and Plant Shop is open Mon.- Fri.

1 1a.m. -5 p.m.. Sat. 9 a.m.-5 p.m. & Sun. 1-5 p.m.
(The shop is closed weekdays from 1-1:30 p.m.)

* Free permits are required for visitors and are
available at the Gift Shop daily until 5 p.m.

MEMBERSHIP

Join the Institute of Ecosystem Studies. Benefits
include a member’s rate for courses & excursions,
a 10% discount on Gift Shop purchases, a free
subscription to the newsletter and participation in
a reciprocal admissions program. Individual
membership: $30; family membership: $40. Call
Ms. Janice Claiborne at 914/677-5343.

The Institute’s Aldo Leopold Society
In addition to receiving the benefits listed above,
members of The Aldo Leopold Society are invited
guests at spring and fall lES science updates. Call
Ms. Jan Mittan at 914/677-5343.

TO CONTACT lES ...

... for research, graduate opportunities, library
and administration:

Institute of Ecosystem Studies
Box AB

Millbrook NY 12545-0129
Tel: 914/677-5343 • Fax: 914/677-5976
Street address: Plant Science Building,

Route 44A, Millbrook, N.Y.

... for education and general information:
Institute of Ecosystem Studies
Education Program, Box R
Millbrook NY 12545-0178
Tel: 914/677-5359 • Fax: 914/677-6455
Street address: Gifford House Visitor and
Education Center, Route 44A, Millbrook, N.Y.

lES e-mail: cacw@vm.marist.edu

lES home page: http://www.marist.edu/~ies

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Volume 13, Number 3
May - June 1996

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