Newsletter

Volume 9, Number 5
September-October 1992

Director’s Note

Water is a renewable resource. Water vapor
from evaporation and plant transpiration enters
the atmosphere, condenses into clouds and
returns to Earth as precipitation. Some of this
water immediately cycles back into the
atmosphere, some is taken up by plants, and
the rest seeps into the soil or runs off into
streams, rivers, lakes and oceans.

Water resources can be degraded by human
activity: forestry and agricultural practices, for
example, can lead to excess amounts of
nutrients and pesticides. Eight of the Institute’s
scientific staff are doing research on aquatic
ecosystems — streams, rivers and lakes — to
learn more about what factors affect our
waters, and what the potential impacts might be
on these valuable resources. A major site for
long-term IBS research on aquatic eco.systems
is the Hubbard Brook Experimental Forest in
the White Mountains of New Hampshire (see
page 3 of this newsletter). The cover story
describes a recent project, in progress in
relatively pristine lakes in northern Michigan.

The lES 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, Admini.strator
Alan R. Berkowitz, Head of Education

Editor: Jill Cadwallader
Printing: Central Press

INSTITUTE OF ECOSYSTEM STUDIES
The New York Botanical Garden
Mary Flagler Cary Arboretum
Education Program
Box R

Millbrook, NY 12545
(914) 677-5359

Lakes as Laboratories

Studies Library

FEB. - ■ i- -'"

Ask someone, “Where do scientists do
experiments?”, and the likely answer will
be “laboratories”. If that individual knows
a scientist who studies the natural world,
he or she might add that field work — the
collection of data at an outdoor site — is
also an integral part of research. Few
would guess that scientists occasionally
have the opportunity, or the means, to
experiment with whole ecosystems. This,
however, is exactly what Institute ecolo-
gists Dr. Michael L. Pace and Dr. Jonathan
J. Cole are doing ...

People can affect lakes in at least two
ways. First, they cause fluctuations in fish
populations by fishing and by restocking.
Second, human activities often lead to the
input of nutrients' into lakes. These
nutrients are released in the surrounding
watershed from landscape destruction,
forestry, sewage, and lawn and agricultural
fertilizers, and carried to lakes through
seepage, runoff and stream flow. What is
the combined effect of these two types of
human impacts on lakes, especially on the
long-term dynamics of lake ecosystems?

In order to learn more about this, and to
make predictions about yet-unaffected
lakes, Drs. Pace and Cole are collaborating
with scientists from the University of
Wisconsin/Madison and the University of
Notre Dame, South Bend, Indiana on
whole-lake experiments.

' Nutrients are elements such as niwogen,
phosphorous, carbon and oxygen that are the
raw materials for the growth and development
of organisms.

The four lakes that are the “laboratories”
for this study are in a relatively remote area
in northern Michigan, at the University of
Notre Dame Environmental Research
Center. The lakes are small, approximately
10-20 hectares each (25 - 50 acres), and
relatively pristine, with no summer homes
and no fishing. When the University of
Wisconsin scientists conceived the project,
they sought the expertise in microbial
processes of Drs. Pace and Cole at lES.
Research, supported by a grant from the
National Science Foundation, began in
1991 and will continue through the 1995
field season, with the three research teams
carefully controlling the fish populations
and nutrient inputs on whole lakes in an
experimental fashion.

During the 1991 and 1992 field seasons,
the investigators set up experimental fish
communities. In a narrow body of water —
Long Lake — with basins at either end,
they installed neoprene rubber curtains
across the middle, thereby creating two
lakes with identical water conditions. The
other lakes in the study are Peter and Paul.
Each of the four lakes already had natural
populations of piscivorous (fish-eating)
fish, but, because Peter and East Long were
to represent lakes where over-fishing had
removed the top predators, all bass and
perch were relocated to other lakes. At the
same time, planktivorous (plankton-eating)
minnows were added to Peter and East
Long, where, in the absence of predatory
bass and perch, these smaller fish could be
expected to thrive.

continued on page 2

Dr. Jonathan Cole sampling one of the experimental lakes in northern Michigan.

Lakes, from page I

The next phase of the study will be done
during the field seasons of 1993-1995. The
nutrients nitrogen and phosphorus will be
added to Long Lake, whose two basins had
the different fish treatments. Peter and Paul
will not have nutrients added, and thus will
serve as controls for the effects of different
fish populations. When nutrient levels are
increased in the waters of Long Lake,
numbers of bacteria and algae are expected
to show a corresponding increase, and the
whole lake should turn green as a result.
Interestingly, the scientists predict that East
Long will turn green faster than will West
Long. Why would this happen?

The prediction is based on the idea of a
trophic cascade, “trophic” referring to
nutrition and “cascade” suggesting
movement from the top down. This term,
then, describes how feeding behavior that
begins at the top of a lakes’ food web
ultimately affects the organisms at its base.
In West Long, bass will eat minnows,
which will decline. The minnows’ diet,
zooplankton, consequently will thrive,
especially the largest species. Finally, since
larger forms of zooplankton graze most
effectively on algae, their large numbers in

this lake should hold in check the popula-
tion of algae despite its tendency to
explode after the addition of nutrients.

In East Long, the situation should be
reversed. Here, with no predatory fish to
limit their population, minnows will
flourish and eat large quantities of zoo-
plankton. Reduced numbers of these
microscopic animal grazers will mean
fewer controls on growth in algal popula-
tions, so East Long should turn green first.

Each of the three teams of scientists is
concentrating on a part of the overall
picture. Drs. Pace and Cole are focusing on
how microorganisms, specifically zoop-
lankton and bacteria, influence and are
influenced by the changes made in the
lakes’ animal populations and water
chemistry. In lakes with high amounts of
nutrients, for example, the larger species of
zooplankton have a tendency to stabilize
the ecosystem until nutrient levels get very
high. The Institute’s ecologists hope to
determine the “break point” at which lake
ecosystems become unstable, and to learn
more about what regulates microbial
processes in general.

Early data suggest that, of the two param-
eters that are being changed, the addition
of nutrients should have the greater impact
on the lake ecosystem due to its direct
effect on microbial growth. Changes in fish
populations should have a weaker but still
noticeable effect. When the study is
completed, the collaborators hope to have
answers to some of their questions: Can we
predict the conditions leading to instabil-
ity? What role is played by the food web in
determining the break point? What
regulates microbial activity in lake
ecosystems? Findings from this bold
whole-lake approach to answering
questions about the functioning of ecosys-
tems should provide ecologists and
environmental managers with the basic
knowledge needed for practical applica-
tions as well as for making predictions
about interactions within other ecosystems.

Note: When the whole-lake study is
finished, nutrients no longer will be added
to East and West Long, and bass and perch
will be restocked in Peter and East Long.
Soon, the four lakes will have returned to
their pre-study conditions.

Dr. Krischik Exchanges IPM Expertise

The importance of scientific findings is
maximized when results are shared. This
exchange of information can be through the
publication of scientific papers and the
presentation of research results at work-
shops and conferences, or it can be on a
more personal basis, as simple as a
conversation between two colleagues over
a cup of coffee. Another way in which
scientific information is shared is through
international exchange visits. The goal of
the Office of International Cooperation and
Development (OICD), a division of the
U.S. Department of Agriculture, is to
provide opportunities for scientists to
become involved internationally. With this
goal in mind, the agency reviews and funds
proposals that deal with scientific ex-
change, and it was to the OICD that Dr.
Vera A. Krischik, Dr. Wendell E.
Burkholder and Dr. Chen Shek Yu
submitted a proposal for a visit to the
People’s Republic of China.

Each of these three scientists is an expert in
different aspects of integrated pest
management (IPM) techniques. Dr.
Krischik, at the Institute under the auspices
of a two-year National Science Foundation
Visiting Professorship for Women, is an
ecologist who recently developed the first
how-to book for IPM, Management of

Grain, Bulk Commodities, and Bagged
Products. Dr. Burkholder, of the Depart-
ment of Entomology at the University of
Wisconsin, has worked on developing
synthetic pheromones' and pheromone
traps for 40 years. Dr. Shek Yu, a chemist
at The Chlorox Company, developed a
pheromone trap and IPM program for pests
in commercial stores.

Integrated pest management is a multi-
disciplinary approach to controlling pests
of plants or of stored grain and food
products. IPM, developed around a
knowledge of the ecology of the target
pests, uses insects or disease organisms in
conjunction with other management

' Many animals produce and secrete phero-
mones, chemicals that influence the behavior of
other animals of the same species. Insects
produce aggregation pheromones to attract
both males and females of the same species and
sex pheromones to attract a mate. When used in
specially designed traps, these chemicals lure
insects into an enclosure from which they
cannot escape. Common examples of pheromone
traps are the small yellow and green net
enclosures seen hanging in local lawns — we
cannot smell the natural chemicals that they
contain, but Japanese beetles can ...

techniques to reduce the likelihood of pest
outbreaks. Pests of field plants or stored
grain are monitored using pheromone traps
and controlled with biological control
agents, insect disease organisms (e.g..
Bacillus thuringiensis, which is commer-
cially available for control of garden pests),
natural desiccants and other means. An
advantage of IPM, especially with regard
to grain and food products, is that pests are
controlled without the use of pesticides
(except in the most severe infestations) so
harmful residues in foods are avoided. (For
more on IPM, see lES NEWSLETTERS
November-December 1991: The End of an
Era in the Greenhouse', and May-June,
July- August 1992: lES Notes.)

China is an ideal choice for scientific
exchange on natural methods to manage
insect pests. Stable ecosystems lead to
increased species richness, and, in the case
of rice that has been grown in the same
areas for 7,000 years, the increase has been
in the numbers of biological control agents.
The Chinese are long-time practitioners of
IPM: over two thousand years ago they
found that by keeping ants in citrus trees
they could control attacks by caterpillars
and boring beetles. Another of their early

continued on following page

Exchange, from preceding page

strategies involved the inundation of rice
paddies with water to reduce pest out-
breaks by drowning insects that pupate in
the soil. The American scientists’ goal in
participating in a scientific exchange
program with China was to learn more
about IPM methods in that nation as well
as to share their own knowledge and
experience. Dr. Krischik’s particular
interest was to learn more about the use of
predatory insects and of biological control
agents, such as parasitic wasps, for killing
fcain pests. Also, she hoped to learn more
Pbout the long tradition among Chinese
people of using native and medicinal plants
not only to treat human ailments but also to
kill insects.

The exchange visit was planned for the
period directly following the 19th Interna-
tional Congress of Entomology, where Dr.
Krischik chaired a session on the ecology
of grain pests. On July 4, Drs. Krischik,
Burkholder and Shek Yu were met in
Beijing by Chinese officials from the
Ministry of Commerce and started work
the same day with a visit to a grain storage
facility. Pheromone traps are the most
effective way to search for pests in stored
grain, and during visits to agricultural
colleges and grain storage facilities in six
cities the scientists demonstrated the use of
these traps and left them in place for
continued monitoring by warehouse
personnel. After data are collected on the
species composition and the size of the
pest populations, appropriate control
strategies can be implemented. The
scientists also searched for biological
control agents at the granaries, discovering
a large predatory bug, unknown in the
^nited States, in stored wheat, as well as a
Bmber of species of parasitic wasps. The
Chinese hosts were asked to investigate

experimentally how these insects attack
local grain pests.

Chinese grain storage specialists shared
their IPM experiences as well. Using
perforated copper tubes to construct grain-
probe traps modeled after traps given to
them previously by Dr. Burkholder, they
had experimented with the use of cracked
grain and crushed locust tree beans as bait.
(This use of locally available foods was a
practical solution to the problem posed by
a lack of the technology needed to
synthesize pheromones.) The bait was
placed at the bottom of the tube, and not
only attracted insect pests to the trap but
also helped keep them there.

The American scientists gave lectures
about integrated pest management and
participated in discussions with their
Chinese counterparts at each site they
visited. China places a high priority on
having at least three months of food in
storage, a necessary form of insurance in a
nation of 1.3 billion people, and the U.S.
team found that in general the grain storage
conditions were excellent. Because the
Chinese representatives are eager to learn
more about the latest methods for insect
detection and control, especially regarding
the use of pheromone traps, plans were
made for continued cooperation: a Chinese
team will come to the United States in
1994.

The American IPM experts hope to be able
to return to China, not only to take
advantage of an apparent greater diversity
of biological control agents there but also
to visit universities with programs investi-
gating the use of plant products for insect
control. Findings about new parasites and
predators and about plants and plant by-

products as natural insecticides could have
important applications to pest control
programs in this country.

One of the good guys, the warehouse pirate hug
(Xylocoris flavipes), is a predator of insect
pests in stored grain. While the number of
potential biological control agents, like this one,
is unknown, in the entire world there are only
ten major species of the beetles and moths that
are insect grain pests. Searching areas of the
world where grains have been grown or stored
for the longest periods of time should reap the
greatest rewards in the search for biological
control agents. Therefore, agricultural fields
dating hack thousands of years present the
greatest opportunities for evolution of both
pests and their predators and parasites.

lES Notes

The Hubbard Brook Ecosystem Study was
initiated in 1963 by Dr. Gene E. Likens
(then with Dartmouth College and now
director of lES) and colleagues. At the
Annual Cooperator’s Meeting on July 8-9,
1992, held at U.S. Forest Service Head-
quarters at Hubbard Brook, N.H., special
events honored the retirements of three of
the founding scientists: Dr. Robert S.

Pierce (U.S. Forest Service); Dr. F. Herbert
Bormann (Yale University) and Dr. Frank
Sturges (Shepherd’s College, W.Va.).
Though retired from their respective
institutions, they will continue to be active
in Hubbard Brook research.

/. to r.:

Dr. Likens, Dr. Pierce,
Dr. Bormann and
Dr. Sturges with
Dr. Richard T. Holmes,
a professor at
Dartmouth College
who has been studying
bird communities at
Hubbard Brook since
the mid-1960s.

Fall Calendar

CONTINUING EDUCATION PROGRAM
Winter and Spring Semesters

The winter semester begins in mid-January.
Catalogues describing classes, workshops and
ecological excursions offered during winter and
spring will be available early in December. Call
the number below for information.

SUNDAY ECOLOGY PROGRAMS
Free public programs are held on the first and
third Sunday of each month, except over holiday
weekends. Programs begin at 2 p.m. at the Gifford
House on Route 44A unless otherwise noted. Call
(914) 677-5359 to confirm the day’s topic.

Dec. 6: An Origami “Forest Ecosystem”,
an activity led by Jill Cadwallader
Jan. 17: A program for children led by Kass
Hogan

• For outdoor programs, dress for the weather
conditions, with sturdy waterproof shoes. In case
of inclement weather, call (9/4) 677-5358 after
/ p.m. to learn the status of the day's program.

lES SEMINARS

ART EXHIBIT

"Little Brother of the Sea" is one of the many
nicknames given the Atlantic puffin. It is also the
name of the collection of bird paintings and
drawings by artist Karen L. Allaben-Confer that is
now on exhibit at the Institute. This collection of
wildlife art has been on tour for the past year,
displayed at the Montshire Museum of Science, the
QLF/Atlantic Center for the Environment, and
ZooAmerica North American Wildlife Park. Works
include the title piece. Little Brother of the Sea,
paintings of other sea birds, sketches of owls, and
collages illustrating the steps in the development of
a finished work of art. The Institute is the final stop
of the tour, and the exhibit will be open to the
public through the end of December in the lobby of
the Plant Science Building.

Hours: 9 a.m. - 4 p.m. Closed weekends, and on
Nov. 26 & 27 and Dec. 25. Admission is by free
visitor permit.

Note: Posters of the title piece are sold weekdays at
the lES Education Program Office on the 2nd floor
of the Gifford House. The cost is $15.

GIFT SHOP

LITTLE BROTHER

OF THE SEA

The In.stitule’s program of scientific seminars
features presentations by visiting scientists. Free
seminars are held at the Plant Science Building on
Fridays at 3:30 p.m.

Dec. 4: Host Nutrition, Resource Competition
Between Host and Pathogen, and the Outcome
of Infectious Disease, by Dr. Val Smith, Univ. of
Montreal

Dec. 1 1 : Rodents As Seed Consumers and
Dispersers, by Mary V. Price, Univ. of Califomia-
Riverside

The scientific seminar series will resume early in
January 1993.

Senior Citizens Days: On Wednesdays, senior
citizens receive a 10% discount (except sale items).
Annual Pre-Holiday Sale: Friday, Saturday and
Sunday, December 4-6 — members receive 20%
off on gifts and plants, and 10% off on books.

ARBORETUM HOURS
(Winter hours: October 1 - April 30;
closed on public holidays)

Arboretum grounds are open Mon. - Sat.,

9 a.m. - 4 p.m.; Sun. 1 - 4 p.m. (Trails and internal
roads are closed during deer hunting season.)

The Gift and Plant Shop is open Tues. - Sat.,

1 1 a.m. - 4 p.m. and Sun. 1 - 4 p.m.

(Closed weekdays from 1-1:30 p.m.)

• All visitors must obtain a free permit at the
Gifford House Visitor and Education Center on
Route 44 A for access to the Arboretum. Permits are
available until 3:00 p.m. daily.

GREENHOUSE

The lES greenhouse is a year-round tropical plant
paradise as well as a site for controlled environmen-
tal research. The greenhouse is open during
Arboretum hours. Admission is by free permit from
the Gifford House.

MEMBERSHIP

Become a member of the Mary Flagler Cary
Arboretum. Benefits include a member's rate for
lES courses and excursions, a 10% discount on
purchases from the Gift Shop, a free subscription to
the lES NEWSLETTER, and parking privileges and
free admission to the Enid A. Haupt Conservatory
at The New York Botanical Garden in the Bronx.
Individual membership is $30; family membership
is $40. For information on memberships, contact
Janice Claiborne at (914) 677-5343.

For more information, call (914) 677-5359 weekdays from 8:30 - 4:30.

INSTITUTE OF
ECOSYSTEM STUDIES
The New York Botanical Garden
Mary Flagler Cary Arboretum
Education Program
Box R

Millbrook, New York 12545-0178

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U.S. Postage
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Newsletter

Volume 9, Number 5
September-October 1 992

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