Effect of management on the environmental impact of agroecosystems

To determine the environmental impact of agroecosystems I am estimating ecosystem-level balances of nitrogen. For this end I am measuring pools and flows (fluxes) of nitrogen in ecosystems. I am also measuring nitrogen transformations in soils (N fixation, N mineralization, nitrification, and denitrification), emissions of gaseous N forms (ammonia, nitrous, and nitric oxides) from soils to the atmosphere, and leaching of nitrogen beneath plants root zone.

Impacts of environmental and land-use changes on linkages between C and N cycles in agroecosystems

Environmental change does not have just а gradual effect on mean environmental conditions but also affect the variability of weather such as frequency and intensity of extreme events, including droughts and heavy precipitation. In general, I am interested in pulse events and their effects on soil biogeochemistry as well as on whole ecosystem functioning. Specifically, I am interested in understanding what effects drought/rewetting cycles have on the biogeochemistry of soil greenhouse gas emissions in systems under different management. Some particular questions I am asking are: Are soils that experience repetitive drying/rewetting cycles developing biogeochemical responses differently from soils experiencing prolonged droughts and infrequent wetting? How will soil management affect soil and ecosystem N and C biogeochemistry under changing frequencies of drying/rewetting cycles? These questions are being answered by rain addition experiments where I measure soil greenhouse gas emissions and N transformations (e.g., mineralization, nitrification) in fields with different soil organic carbon contents and identical management but differing land-use histories and in mesacosm studies.

Controls on soil trace gases emissions

Land use change and management are the most common features of today's landscapes and both have large influences on the C cycle, which is tightly connected to the N cycle. In my research, I am exploring linkages between the two cycles by asking: How do soil C availability, dominant N forms (i.e. NH4+ or NO3-), and N availability interact to affect soil emissions of the N-oxides (N2O/NOx)? To answer this question, I am using ecosystem-level measurements of trace gas exchanges with eddy covariance towers, coupled with ground-based static flux chambers and detailed measurements of N cycling processes in soils. Often, I combine ground measurements with data-mining to assess the importance of different drivers to soil trace gas emissions.