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My lab’s approach to plant ecology and
evolution is based on the underlying assumption that
climate is a primary selective agent. Our
goal is to improve our understanding of the physiological responses of
plants to climate change, and to determine the ecological and biogeochemical
consequences of those responses. Climate change is defined broadly, as
we are interested in biotic-abiotic interactions from millennial scale
climate change down to the seasonal progression of weather fronts. Our
physical scale of study ranges from the subcellular to individuals, ecosystems
and landscapes up to the regional level where physical and physiological
processes modify the atmospheric boundary layer. The scope and scale
of our research interfaces biochemistry, physiology, ecology, evolution
and the earth sciences, and hence necessitates interdisciplinary collaboration
that often includes, apart from biologists, meteorologists and geochemists.
Our research both examines
natural processes and develops methods by which to measure
them. A primary tool for elucidation of these processes is
the analysis of natural abundance stable isotopes. Abiotic
processes (e.g. precipitation and biomass burning) and biotic
processes (e.g. photosynthesis and respiration) differentially
affect the stable isotope abundance of atmospheric CO2, O2
and water. Hence, stable isotopes provide a tracer for biological
activity from the scale of a chloroplast to the globe, and
allow us to address questions of plant physiological ecology
and climate on a variety of temporal and spatial scales.
The analysis of stable isotopes both in atmospheric air and
in plant material allows us to estimate plant and whole ecosystem
responses to environmental change, partition terrestrial
versus oceanic photosynthesis and assess changes in plant
distribution and productivity over daily to geological timescales. Here are some specific questions
that motivate our research:
1) How do changes in abiotic
inputs (e.g. CO2 concentration, precipitation, radiation)
and the processes of photosynthesis and respiration affect
the carbon and water cycles at ecosystem to regional scales?
2) What are/were the selective
forces behind the physiological and anatomical differences
between C3 and C4 plants (particularly grasses)? How are
these differences manifest in current and past distributions
of C3 and C4 plants? How do intra-annual and inter-annual
variations in C3 and C4 distribution affect carbon and water
cycles?
3) What are the mechanistic
explanations for observed differences in carbon and oxygen
isotope signatures in plants? Can we use these observations
and the underlying mechanisms to reconstruct plant and ecosystem
responses to past climatic change?
4) Can we use measurements
of CO2, H2O and their isotopes in the atmospheric boundary
layer to measure regional-scale (104-106 km2 ) photosynthetic,
respiratory and fossil fuel contributions to the global carbon
cycle?
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