Research
Human activities such as fossil fuel combustion and fertilizer production have radically shifted the distribution of carbon (C) and nutrients throughout the biosphere. These disturbances have led to unprecedented rates of atmospheric warming over the past half-century and have widespread effects on global ecosystem function. The growth of terrestrial plants and stabilization of decaying plant tissue in soils currently slows the rate of carbon dioxide (CO2) accumulation in the atmosphere, but our mechanistic understanding of these processes and our ability to predict how they may shift under concurrent changes in environmental conditions (elevated atmospheric CO2 concentrations, warming temperatures, increased nutrient availability) is limited. The goal of my research program is to advance understanding of the mechanisms by which plants and microorganisms influence the movement of carbon and nutrients throughout terrestrial ecosystems in order to better predict how ecosystem processes may respond to global change. My approaches integrate long-term field studies, targeted laboratory experiments, and global-scale data syntheses and combine the approaches and theoretical frameworks of classical ecology with modern analytical tools and statistical techniques.
Global patterns in plant carbon allocation and plant resource use efficiency: Plants allocate fixed carbon to different biomass pools in order to access limiting resources and maximize growth. The fraction of photosynthate allocated belowground to acquire soil-derived resources represents a trade-off from competition for above ground resources, as well as an important linkage between ecosystem cycles of C, nitrogen (N), and other soil resources. As a component of my graduate work, I performed a global-scale analysis to assess how the proportion of plant C allocated to acquire soil-derived resources varies across space. The work shows that plants in high latitude ecosystems allocate >2-fold more photosynthate to roots and associated microorganisms in order to acquire soil resources than plants in low latitude systems . This variation reflects energetic constraints on enzyme efficiency in cold ecosystems, which increase the carbon “cost” of soil resource capture and drive a strong dependency on plant-associated fungi for nutrient uptake at high latitudes. The results provide a critical empirical validation for ecosystem models, which represent coupled soil C and nutrient cycle dynamics and are used to predict the behavior of terrestrial ecosystems under future climate regimes (Gill & Finzi 2016, Ecology Letters). Collaborators: Adrien Finzi, Boston University
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