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r
e s e a r c h.. p r o g r a m .
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v e r v i e w
Much
of the research in this lab analyzes ecosystem metabolism. Energy
flow and chemical cycling are the fu ndamental
processes upon which life depends, whether at the level of an organelle
in a cell or the entire biosphere. Our research concentrates on
these processes and, particularly, the coupling between trophic
levels in ecosystems.
We are particularly interested in ecosystems where large mammals
are significant members of the food web, and how those mammals interact
with energy flow and nutrient cycling. The focus of field studies
is Serengeti
National Park, Tanzania, east Africa, a grazing ecosystem
with Earth's largest concentration of such mammals. Previous localities
of research have included Yellowstone National Park in the USA,
the Galapagos Islands - where the grazing giant tortoises were studied,
and southern Kenya.
Solar energy is captured as the energy of carbon-carbon bonds in
the leaves of plants and mineral nutrients are captured from the
soil by roots. Plant tissues can be consumed by herbivores, herbivores
eaten by carnivores, and at each step some of the carbon is retu rned
to the atmosphere and energy is lost from the web while mineral
nutrients are recycled to soil pools. Our interest is the organisms
that catalyze these reactions and, specifically, how the cycling
of different mineral nutrients (for example, N and P) are coupled
and are related to energy flow through the food web.
Important instrumentation in the lab used to assay nutrient cycling
include a gas chromatograph for measuring N and C, a continuous
flow autoanalyzer to measure NO3, NH4, and SO4, and an Inductively
Coupled Argon Plasma Spectrometer (ICP) which assays 20 elements
simultaneously from plant tissue, soil extracts, or animal wastes.
The ICP provides evidence on most minerals of interest in animal,
plant, and microbe metabolism. Those include micronutrients, for
example cobalt and sodium.
Our research has documented the patchy distribution of essential
minerals and the importance of "critical" habitats where
limiting minerals are in sufficient quantity in soils and plants
to meet the nutritional needs of growing young animals and pregnant
or lactating females. Current research is documenting the response
of vegetation, microbes, and animals to supplemental nitrogen, and
how the cycles of different minerals interact.
To
read a 1999 article by SU Magazine featuring my research work in
Africa, please
click here.
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