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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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