Ecosystem Ecology
Sunday March 13:
10:00am-11:30am
Back to Concurrent Session
III
ABSTRACTS |
THE EFFECTS OF BURNING AND MOWING
ON DETRITUS AND SOIL FAUNA OF A TALLGRASS PRAIRIE
Larimer, A., Mitros, C., Wang, H.,
and Brown, J.
Grinnell College, Grinnell, Iowa
50112
Prescribed burning and mowing are commonly
applied management techniques in tallgrass prairie
restorations, as they are thought to mimic historical
impacts of wildfires and migratory grazers. These
practices alter biotic and abiotic conditions influencing
both the floral and faunal composition of the prairie,
although few studies have examined their impact on
the invertebrate community. We investigated the effects
of eight years of spring burning and five years of
mid-summer mowing on the plant and soil invertebrate
community in experimental plots within a 17 year-old
reconstructed tallgrass prairie in central Iowa. We
quantified the responses of three distinct invertebrate
groups: litter arthropods caught in pitfall traps,
soil microarthropods, and soil nematodes. These groups
exhibit important interactions with other biota as
well as sensitivity to changes in soil and environmental
conditions. The abundance of litter Collembola, specifically
Isotomidae, decreased as a result of burning, while
ant abundance increased. Burning also significantly
reduced nematode abundance in plots. Herbivorous nematodes
were found to be the most fire-resistant of the five
nematode feeding groups. In contrast, mowing explained
the greatest variation in the soil microarthropod
community, with a significantly higher number of individuals
found in unmowed plots. Mowed plots had significantly
lower ANPP and stem density of Asteraceae, while burned
plots had significantly higher stem density of the
dominant grass, Andropogon gerardii, and the legume
Lespedeza capitata. Therefore, this study reveals
the influences of these management practices on both
native prairie plants and invertebrates. The opposite
effects of burning on different aboveground taxa points
to the need for future studies seeking to understand
interspecific interactions within the detritus layer.
Along with the immediate physical responses of the
plots to burning and mowing, more gradual alterations
in the underground chemical composition, especially
the C:N ratio of soil and roots, may be accountable
for variation witnessed within soil invertebrates.
Keywords: prairie restoration, invertebrates,
nematodes
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BOREAL PEATLAND INITIATION IN WESTERN
CANADA
Bloise R.E.
Department of Plant Biology, Southern
Illinois University, Carbondale, IL 62901
Peatlands, wetlands that form peat,
the build up of poorly decayed organic material, cover
approximately 20% of the landscape in Canada. Peatlands
in boreal Western Canada began developing in the mid-Holocene
period, approximately 8000 to 4000 years Before Present,
after the Laurentide ice sheet retreated. Peatlands
then spread across boreal Canada by one of two methods:
paludification or terrestrialization. Peatland development
and spread are affected by external (allogenic) and
internal (autogenic) factors, including: climate,
precipitation/evapotranspiration, hydrology, substrate,
and vegetation development. Exhaustive studies have
been done on the vegetation and chemistry of Canada’s
boreal peatlands, but few studies have compared initial
substrate to peatland initiation.
Key Words: peatland, paludification,
terrestrialization, wetland
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VARIATION
AMONG FISH SPECIES IN THE STOICHIOMETRY OF NUTRIENT
EXCRETION
Torres, L.E. and Vanni, M.J.
Department of Zoology, Miami University,
Oxford, OH 45056
Ecological stoichiometry theory could
provide a conceptual framework for how species vary
in mediating ecosystem processes and therefore shed
new light on how the loss of biodiversity can affect
ecosystem functioning. This study investigates how nutrient
cycling rates and ratios vary among different fish species
and with body size, and how rates and ratios are related
to body nutrient contents. Nutrient excretion rates
and body nutrient contents of seven fish species in
four families were estimated in a eutrophic reservoir.
Per capita nitrogen and phosphorus excretion rates increased,
and mass-specific excretion rates decreased, with increasing
mass. Body phosphorus content varied among species and
was correlated with body mass, but this relationship
varied significantly among species. In accordance with
predictions of stoichiometry theory, species with low
body phosphorus content tended to have high phosphorus
excretion rates while those with high body phosphorus
tended to have low phosphorus excretion rates. These
results suggest that ecological stoichiometry can provide
a conceptual framework for variation among species in
nutrient cycling, and thus for evaluating the ecosystem
consequences of biodiversity loss.
Keywords: stoichiometry, nutrient cycling,
species identity, reservoir
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BENTHIC
FORAMINIFERAL ASSEMBLAGE DATA: TOWARD A PREDICTIVE MODEL
OF ECOSYSTEM CHANGE, BISCAYNE BAY, FLORIDA
(Honorable mention!)
Williams, C.P. and Ishman, S.E.
Department of Geology, Southern Illinois
University, Carbondale, IL 62901
Ecosystem restoration requires understanding of natural
variability within a system so that comparison to and
contrast with anthropogenic-induced change is possible.
Restoration must account for anthropogenic effects,
which are irreversible based upon current patterns of
land use for sustainability and cost-effectiveness of
any proposed transformation of land use. The goals of
the Comprehensive Everglades Restoration Program are
to restore natural conditions of freshwater input to
the Biscayne Bay and Florida Bay ecosystems. The goals
of the foraminiferal research are to identify assemblage
variability between modern environments related to salinity
and nutrient conditions, and in shallow (<2m) cores
from Biscayne Bay, to show temporal changes in these
conditions at particular sites. Changes in the assemblage
data are interpreted to reveal changes in Biscayne Bay.
Featherbed Bank core, central Biscayne Bay, was analyzed
for foraminiferal assemblages. The core assemblage data
compared to modern foraminiferal assemblage data from
Biscayne Bay is used to characterize down core environmental
changes. The site revealed an overall shift to more
marine salinities, as indicated by significant recent
influxes of Archaias and Articulina, and an inverse
decline in Cribroelphidium and Elphidium. Furthermore,
an increase in Bolivina is indicative of enriched nutrient
conditions in central Biscayne Bay. Interestingly, the
species diversity at this site has increased during
the period of increasing nutrients and salinity. This
is not surprising as foraminifera are only found in
marine environments, but the data reveal that it is
important to recognize that not all increases of species
diversity necessarily imply ecosystem health. Low salinity
environments are dominated by the presence of Ammonia
and Elphidium with several samples having nearly 100%
representation by these two genera alone. More marine
assemblages have increased diversities with the presence
of the genera Miliolinella, Quinqueloculina and Triloculina.
The application of non-parametric trend analyses to
the down core foraminiferal data is used to identify
trends in the data toward specific environmental conditions.
Successful results from these analyses provide a useful
technique in utilizing foraminiferal data as indicators
to monitor the success of restoration efforts, as well
as help to develop a predictive model of ecosystem change.
Keywords: Foraminifera, Ecosystem History, Biscayne
Bay, Ecosystem Restoration
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NATURAL
NITROGEN ABUNDANCE AND POTENTIAL IMPACTS OF INCREASING
N DEPOSITION ON BOREAL PEAT BOGS IN THE OIL SAND REGION
OF ALBERTA, CANADA
Xu, Bin
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III
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