Research in my lab focuses on forest ecology, terrestrial biogeochemistry and global change biology. As a forest ecologist I am interested in understanding how resource competition among individuals within a community affects the distribution and abundance of tree species across the landscape. In my studies I combine field experiments with modeling studies so that I can extrapolate measurements consistent with empirical inquiry over large spatial and temporal scales. My current research in this area includes a field and modeling study aimed at understanding how the availability of water, nitrogen and calcium affects tree seedling growth and survivorship along a soil resource gradient where one or more of these resources limits plant growth rates.
As a terrestrial biogeochemist, I am interested in the factors regulating the pool sizes and fluxes of carbon (C) and nitrogen (N) in terrestrial ecosystems. At one level, interspecific differences in resource uptake and loss affect the distribution of C and N in terrestrial ecosystems. Thus one can link changes in the distribution of species with variation in C and N cycling. Carbon and N fluxes in terrestrial ecosystems are also affected by the size, composition, and activity of soil microbial communities, physical disturbance, and time. Thus I am generally interested in understanding how the different components of an ecosystem (soils, microbes, plant species) interact with the physical environment to affect C and N cycling.
My interest in global change biology stems from the fact that human activity is transforming the basic function of the terrestrial biosphere at an accelerating rate. There are 3 transformations to which I pay particular attention. They are changes in the global C-cycle, changes in the global N-cycle, and changes in land-use. Fossil fuel combustion is increasing the concentration of carbon dioxide in the atmosphere and changing the earth's climate. Fixation of atmospheric N by humans now exceeds the rate of non-anthropogenic N fixation (e.g. lightening, symbiotic N fixation) and terrestrial ecosystems whose productivity has historically been N limited, are now receiving N in excess of biological demand. To what extent does excess N affect the basic functioning of terrestrial ecosystems? Finally, shifts in land-use practices (e.g. the conversion of forest land to agricultural land) affect C and N cycling by changing the species composition of plant communities, changing the distribution of biomass, and removing or leaching nutrients.
My current research in the area of terrestrial biogeochemistry and global change biology focuses on the effect of Free-Air CO2 Enrichment (FACE) on C-storage and nutrient cycling in a southern pine - hardwood forest. The core of my research asks the following question: Will the availability of nutrients (N or P) limit the C-storage potential of forest ecosystems? To answer this question I measure pool sizes and turnover times of N and P in this maturing ecosystem. I focus on primary production, decomposition, microbial ecology, and nutrient availability.