11/2/2014 1 Community Ecology I Stability, Resilience WFC 10 – D. A. Kelt A biological community is defined by the species that occupy a particular locality and the interactions among those species. A Primer of Conservation Biology, 3rd ed. R. B. Primack 2004 Community Ecology is the study of biological communities. In what ways are communities organized, structured, predictable? In what ways are they not? Note the difference between “habitat” and “community.” The former refers to a physical location, whereas the latter refers to constituent species. Many communities may appear very similar. Coniferous Forest near Mt. Rainier central Oregon King’s Canyon National Park Sandy Desert Sahara Desert Simpson Desert (Australia) Death Valley, California Thus, there may be great variation from point to point in these communities One major way in which they differ is in composition – the particular species that occur at a site. Example: Burrowing mammals N. Amer. - Gopher Asia - Zokor Australia – Marsupial mole S. Amer. – Tuco tuco Africa – Mole rat Ecologically similar species in different regions with different evolutionary origins. N. Amer. - Gopher Asia - Zokor Australia – Marsupial mole S. Amer. – Tuco tuco Africa – Mole rat 11/2/2014 2 Often true at smaller spatial scales as well . . . Geomys Eastern Pocket Gophers Cratogeomys Yellow-faced Pocket Gophers Pappogeomys Southern Pocket Gophers Thomomys Western Pocket Gophers 4 genera of North American pocket gophers From a conservation perspective we are interested in how stable a community is in the face of anthropogenic abuses. Stability – often portrayed in simple cartoon fashion as follows: So, given all this variation, how are communities structured, and how do they respond to disturbance? Global Stability Local Stability Stability may be measured by a community’s fluctuation over time. Communities often remain stable over time. However, they may be perturbed by some external force. What happens then? The American chestnut (Castanea dentata) made up >40% of trees in mature eastern deciduous forest. Chestnut blight – introduced to New York City in ca. 1900 By 1950 only 1 remaining large tree in North America What impact did this enormous loss have on the biota of eastern North America? Perhaps surprisingly, essentially no impact. Eastern deciduous forests are very diverse – maples, oaks, hickories, catalpa, etc. Loss of American chestnut led to NO major changes in animal or plant communities. Black bears may have suffered from loss of mast. Thus, this was a relatively minor perturbation from the perspective of the community – it evidently shifted to a different local stable point. Seven butterfly/moth species were specialists on American chestnut, and have gone extinct. Another 49 Lepidopterans simply shifted their hosts. 11/2/2014 3 Pollution – another perturbation that can result in ecological deteriorat.

1. 11/2/2014
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Community Ecology I
Stability, Resilience
WFC 10 – D. A. Kelt
A biological community is defined by the species that occupy a
particular locality and the interactions among those species.
A Primer of Conservation Biology, 3rd ed. R. B. Primack 2004
Community Ecology is the study of biological communities.
In what ways are communities organized, structured,
predictable?
In what ways are they not?
Note the difference between “habitat” and “community.”
The former refers to a physical location,
whereas the latter refers to constituent species.
Many communities may appear very similar.
Coniferous Forest
near Mt. Rainier
central Oregon
King’s Canyon National Park

2. Sandy Desert
Sahara Desert
Simpson Desert (Australia)
Death Valley, California
Thus, there may be great variation
from point to point in these
communities
One major way in which they differ is
in composition – the particular species
that occur at a site.
Example: Burrowing
mammals
N. Amer. - Gopher
Asia - Zokor
Australia – Marsupial mole
S. Amer. – Tuco tuco
Africa – Mole rat
Ecologically similar species in different
regions with different evolutionary origins.
N. Amer. - Gopher
Asia - Zokor
Australia – Marsupial mole

3. S. Amer. – Tuco tuco
Africa – Mole rat
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Often true at smaller spatial scales as well . . .
Geomys
Eastern Pocket Gophers
Cratogeomys
Yellow-faced Pocket Gophers
Pappogeomys
Southern Pocket Gophers
Thomomys
Western Pocket Gophers
4 genera of North American
pocket gophers
From a conservation perspective we are interested in how
stable a community is in the face of anthropogenic abuses.
Stability – often portrayed in simple cartoon fashion as follows:
So, given all this variation, how are communities structured,
and how do they respond to disturbance?
Global Stability Local Stability

4. Stability may be measured by a community’s fluctuation over
time.
Communities often remain stable over time.
However, they may be perturbed by some external force.
What happens then?
The American chestnut (Castanea dentata)
made up >40% of trees in mature eastern
deciduous forest.
Chestnut blight – introduced to New York City in ca. 1900
By 1950 only 1 remaining large tree in North America
What impact did this enormous loss have on
the biota of eastern North America?
Perhaps surprisingly, essentially no impact.
Eastern deciduous forests are very diverse – maples, oaks,
hickories, catalpa, etc. Loss of American chestnut led to NO
major changes in animal or plant communities.
Black bears may have suffered from loss of mast.
Thus, this was a relatively minor perturbation
from the perspective of the community – it
evidently shifted to a different local stable point.
Seven butterfly/moth species were specialists on
American chestnut, and have gone extinct.

5. Another 49 Lepidopterans simply shifted their hosts.
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Pollution – another
perturbation that can
result in ecological
deterioration on large
scales.
Are such trends
reversible?
Not always, but
sometimes yes.
Puget
Sound
Lake
Washington
Lake Washington – ca. 18 mi long, 3 mi wide;
requires about 2.3 yr to flush.
Greater
Seattle
Region
Portage Bay
UW (Go Huskies)

6. I-5
Lake
Washington
Lake Washington – ca. 18 mi long, 3 mi wide;
requires about 2.3 yr to flush
In early phases of urban development,
Lake Washington was used for disposal
of raw sewage.
This stopped between 1926-1936 when
treatment plants were built.
However, as the population grew, more
sewage treatment plants were built
between 1941-1959, and released
more sewage to Lake Washington.
What is the problem? What is in sewage?
Ecologically speaking – nitrogen and especially phosphorus.
Consequences of this
“perturbation”?
Phosphorus input over time
(mostly in effluent)
Phosphorus in lake water
Response of algae
Transparency of water

7. By 1955, problems were becoming obvious
Citizens began diverting sewage (to Puget Sound!)
By 1967, most sewage being diverted
Effects of diversion?
With sewage addition to lake,
sedimentation tripled!
Phosphorus input
(metric tons/yr)
Phosphorus content
(micrograms/liter)
Algal density
(mm3/yr)
Water transparency
Daphnia populations
rebounded in ca. 1975.
Small crustaceans, eat algae,
keeping water clear.
During “polluted phase”,
however, a dominant alga
(Oscillatoria) fouled the
feeding apparatus of Daphnia.
Since 1976, water has remained
clear because Daphnia keep
algal levels low

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Take home message from this?
1. Ecological systems can
bounce back from perturbation.
2. Certain elements – in this
case phosphorus – can have
strong influences on ecosystems
(especially aquatic ones!)
Where do we find much P?
Laundry detergents – led to
strong push in 1960s for
phosphate-free detergents.
View from above Lake 226 in August 1973.
The two basins of this lake were separated by
a plastic curtain. The lower basin received
additions of carbon, nitrogen and phosphorus;
the upper basin received carbon and nitrogen
only. The bright green color results from
bluegreen algae (Cyanobacteria), which are
growing on phosphorus added to the near side
of the curtain.
Aerial view of Lake 227 (foreground) in 1994.
Note the bright green color caused by algae
stimulated by the experimental addition of
phosphorus for the 26th consecutive year.

9. Lake 305 in the background is unfertilized.
(photo by Karen Scott)
http://www.umanitoba.ca/institutes/fisheries/eutro.html
+C
+N
+C
+N
+P
+P
Some communities require perturbation
Chaparral
Monterrey pine
Cones open only after fire
Chamise re-sprouting
Consider the Scottish moors . . .
Might a system shift to an alternative
stable state or configuration?
What if the perturbation is extreme?
Calluna vulgaris (heather)
Today, heather dominates the moors. Originally found
principally
in open parts of pine, birch, and oak woodlands on acid soils.

10. Calluna vulgaris (heather)
• Periodic fires set to maintain habitat for sheep.
• Combination of grazing and burning reduced survival of
tree seedlings . . .
• Now, after many hundreds of years of this, there are
virtually no seeds left.
• Even if grazing were to stop, no trees would grow here.
Heather required disturbance that provided clear areas.
• Significant forest destruction began in Scotland about
3000 B.C. (human needs for fire, housing, agriculture).
• Simultaneously, climate cooled and moistened.
• Grazing animals (esp. sheep) introduced to open areas
– sheep stocks increased greatly b/t 1700s-1800s.
A new stable state
Another example – kangaroos
Numbers of larger kangaroo species have increased since British
colonization.
In spite of intensive hunting as pests and for food and leather.
Evidently, ranchers have improved habitat of kangaroos, in 3
ways:
1. Increased water for sheep (‘roos drink too).
2. Clearing of timber, production of grasslands.

11. 3. Removal of a major predator – the dingo.
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3. Removal of a major predator – the dingo
SOUTH AUSTRALIA
WESTERN
AUSTRALIA
NORTHERN
TERRITORY
QUEENSLAND
VICTORIA
NEW SOUTH WALES
The dingo fence
One way to evaluate the impact of grazing is to
remove grazers, and follow the response of the
plant community.
Grazing animals can have substantial impacts on ecosystems
European rabbits – in Britain for >1000 yrs,
agricultural pests for >100 yrs.

12. In 1954, a virus (myxomatosis)
decimated rabbit populations.
By 1960, rabbits began developing resistance
(natural selection), and populations increased.
In response to low rabbit numbers:
• Grasses increased in height.
• A spectacular increase in flowers – even
orchids previously known from only a few
leaves!
• Woody plants also increased – brambles,
heather, tree seedlings.
A rabbit’s-eye view of the world:
Preferred edible
• decline under grazing.
Not-preferred but edible
• likely decline under grazing.
Inedible
• increase under grazing.
Another example of the impact of rabbits
is provided by a fenced rabbit exclosure,
put in place in 1946, and censused for
plant diversity through 1960.
European rabbit
H = Hieracium
= Festuca

13. Fencing
installed
Hieracium pilosella
Festuca ovina
In the absence of grazing, 2 plants are
especially competitive.
Sheep’s fescue grass (Festuca ovina)
Hawkweed (Hieracium pilosella)
Fescue dominated under grazing
pressure.
Hawkweed increased upon rabbit removal.
Note that this plant became senescent and
was beginning to be replaced again by the
grass in 1960.
Is this a long term cyclic relationship?
A final example of how
perturbations alter communities
- Lake Erie -
Detroit
Buffalo
Cleveland
Historically (1800) bordered

14. by large stands of forest and
extensive marshes.
Chicago
Limited soil erosion,
clean runoff water,
healthy aquatic vegetation.
By 1870 this was an agricultural region.
By 1910, nearly all marshes and swamps
had been drained.
Woodlands cleared,
swamplands drained.
Silt runoff covered spawning beds.
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Photo: Rutherford B. Hayes Presidential
Center (Fremont, Ohio)
Back to 1800 – Lake Erie hosted a great variety of fish.
By shore’s edge:
Largemouth Bass
Smallmouth bass
Muskellunge
Northern pike
Channel catfish

15. In open lake:
Lake herring
Blue pike
Lake whitefish
Lake sturgeon
Walleye
Sauger
Freshwater drum
White bass
At eastern end of lake,
Lake trout
Back to 1800 – Lake Erie hosted a great variety of fish.
By shore’s edge:
Largemouth bass
Smallmouth bass
Muskellunge
Northern pike
Channel catfish
Back to 1800 – Lake Erie hosted a great variety of fish.
In open lake:
Lake herring
Blue pike
Lake whitefish
Lake sturgeon
Walleye
Sauger
Freshwater drum
White bass
Back to 1800 – Lake Erie hosted a great variety of fish.

16. At eastern end of lake,
Lake trout
Today, Blue pike,
Sauger,
Lake trout . . .
. . . are gone
Greatly reduced populations of sturgeon, lake herring,
whitefish, muskellunge
Present fish community dominated by: yellow
perch
white bass
channel cat
freshwater
drum
carp
goldfish
rainbow
smelt
As a general pattern, commercially
valuable species have been
replaced by less valuable species
Introduced
Introduced

17. Introduced
Introduced
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The commercial catch from Lake
Erie over past 150 yr has exceeded
that of other four Great Lakes
combined!
However, the fishery has been a
major stress on the community.
Commercial catch began after the
War of 1812 and developed rapidly.
Through 1850 the catch grew by
about 20% per year.
First casualty:
Lake sturgeon
• large (to over 80 kg (=170lb))
• covered with heavy scales
• tore nets
• fishermen got heavier nets,
caught sturgeon in large numbers,
stacked them like cordwood,
and burned them with oil

18. In 1860s an immigrant arrived with
knowledge of how to smoke sturgeon
and make caviar from its eggs.
By 1870 it was rare from over-fishing.
Fishermen turned to Lake trout in
1880s . . .
Fishermen turned to Lake trout in
1880s . . .
and then Lake whitefish in 1890s.
In late 1800s, concern about
dwindling stocks grew.
Two solutions advocated.
1. regulate stringently
2. use a new technique from
France – fish hatcheries
Between 1867-1920 about 18
hatcheries were constructed.
All but one have been closed now;
virtually no fry survived.
When all else fails . . .
3. Stock new species.
Most introductions failed;
a few succeeded.

19. Rainbow smelt – 1931
Smelt live in open waters and
are eaten by lake trout,
whitefish, blue pike, sauger.
Initially great, but . . .
Over-fishing of these species
allowed increased numbers and
greater survival of smelt.
Older smelt feed upon young fry of
lake trout, whitefish, blue pike, and
sauger.
Thus, desirable species have thus
been driven even further down.
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Another factor in Lake Erie is pollution.
Sewage and industrial wastes feed blue-green algae
now dominate the plankton.
decompose.
The western basin is shallow
and has very valuable
spawning grounds

20. Detroit
and Toledo
It also has . . .
Central and eastern basins are deeper, cooler.
-water
fishes – herring, whitefish, blue pike.
Increased pollution means that even these basins are
becoming more “productive,” and less oxygenated.
Prognosis? -- partial recovery is possible if we
drastically reduce our discharges to the lake.
However, the presence of smelt will preclude recovery of some
species, and further
introductions – Pacific salmon (to please sport fishermen) –
further complicate issues.
Recovery rests directly on the need for continuous oxygen-rich
bottom waters in the
central basin.
Prognosis? -- partial recovery is possible if
we drastically reduce discharges to the lake.
However, the presence of smelt will preclude recovery of
some species, and further introductions – Pacific salmon
(to please sport fishermen) – further complicate issues.
Recovery rests directly on the need for continuous
oxygen-rich bottom waters in the central basin.

21. Current status?
In fact, partial recovery has occurred.
US and Canada have invested >$7.2 billion
since 1972 to treat wastewater.
Reduced P discharge from 15,260 tons (1972)
to 2449 tons (1985).
Reintroductions of native predatory fishes
has also helped.
Total phosphorus discharge
from Detroit Wastewater Trt.
Plant (1966-2003).
A 2010 report by Healing Our Waters – Great
Lakes Coalition* refers to a “sewage crisis” in the
Great Lakes. Five cities dumped 41 billion gallons
of untreated sewage and dirty storm water into the
Lakes in 2009.
Estimate that the Buffalo Sewage Authority, as one
example, will need to spend up to $500M to
eliminate sewage overflows.
Heart of the problem – an old system that
combines sewage and storm runoff in common
pipes; high storm runoff leads to overflows.
Is this reparable? Heck yes – it just takes resolve!
*
http://www.buffalonews.com/incoming/article96926.ece/BINAR
Y/sewagereport.pdf

22. Are there any attributes of
communities that allow them
to resist such perturbations?
Complexity begets Stability
Resilience – a measure of the
ability of a system to persist in
the presence of perturbations
(e.g., weather, physical and
chemical factors, other
organisms, human activities).
Data slowly accumulating . . .
Study sites with more species
were more resistant to drought
(measured as biomass after vs.
before a major drought).
Recent work shows that plots with MORE
SPECIES not only had MORE BIOMASS,
but that the effect of more species greatly
exceed the effect of water or fertilization!