Submitted to: Ecological Society of America Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2003
Publication Date: 7/22/2003
Citation: BURKE, I., LAUENROTH, W., MORGAN, J.A., MOSIER, A.R., PIELKE, R. CARBON MANAGEMENT, LAND USE AND GLOBAL CHANGE: FEEDBACKS AMONG CARBON, NUTRIENT AND WATER CYCLES. ECOLOGICAL SOCIETY OF AMERICA PROCEEDINGS. 2003.
Technical Abstract: The central grassland region of the U.S. is intensively managed for livestock and grain production, resulting in a matrix of rangelands, dryland cropping, and irrigated cropping. Each of these general classes of management has a different impact on carbon, nutrient, and water cycles, and the distribution of the practices in time and space integrates to influence the regional cycles. We have collected long term data on carbon, water, and nitrogen fluxes in the shortgrass steppe portion of the central grasslands, across multiple landuse types, using a variety of techniques including inventories of C and N stocks, estimates of trace gas fluxes, and Bowen ratio measurements of carbon dioxide and water exchange. In general, water is the main limitation over carbon inputs, and carbon and water availability are the main controls over nutrient retention. In rangelands, carbon and nitrogen cycling are enhanced by livestock grazing. Dryland cropping also enhances carbon and nitrogen cycling, and alters the seasonality and partitioning of evaporation and evapotranspiration vs. soil water storage. Carbon losses are significantly increased by cultivation management, and nitrogen trace gas losses are also stimulated by N fertilization. Irrigated land use management has the largest impacts on the relative magnitude of carbon, water, and nitrogen fluxes. Interestingly, although water and nitrogen are substantially increased by human additions, and net primary production increases in response, there is no apparent net change in carbon and nitrogen balance of the ecosystem. Biomass exports, increased volatile losses, and enhanced evaporation all balance the increased inputs. The current regional impact of all three landuse types is a substantial increase in nitrogen trace gas production, nitrogen leaching, and evaporation, and a decrease in methane uptake. There is strong evidence that these changes, as well as surface albedo, have a major impact on regional mesoscale climate.