Despite significant efforts to reduce rates of deforestation in the Brazilian Amazon region, land-use change and its interaction with climate change remain significant threats for the integrity of Amazonian ecosystems. Common land-use changes include conversion of mature forest to pasture using fire, both single and double-cropping agricultural systems, as well as low and high intensity beef production. This project seeks to identify the circumstances under which these land-use changes, fire, and their interactions affect the balance of N-P limitation and co-limitation as well as their impacts on C cycling.

More specifically, we are constructing a model of C, N, and P, to examine how:

• nutrient limitations can affect pasture productivity and the rate of regrowth of secondary forests, and how rates of regrowth, in turn, affect time to canopy closure and resistance to fire

• land use affects the linkages between nutrient cycling of terrestrial systems and nutrient losses through leaching to groundwater and surface water and through trace gas emissions to the atmosphere

• nutrient management affects the sustainability of agricultural practices, including ranching, small-holder agriculture, and large-scale cropping systems