ABSTRACT PROPOSAL # : DEB-9707296, DEB-9708376 INVESTIGATOR(S) : BURKE JOHNSON INSTITUTION: COLORADO STATE UNIVERSITY DESERT RESEARCH INSTITUTE, UNIVERSITY OF NEVADA Although much research has focused on the biotic mechanisms by which ecosystems retain N, there has been relatively little attention paid to nonbiological fixation (capture) of N in soils. The available evidence suggests that soils are capable of fixing N in chemical sinks such as humus and clay lattices but controls on this fixation are poorly understood and the processes of chemical fixation are not included in the leading biogeochemical models. It is important to fill this gap in our understanding if we are to be able to predict and understand effects on soils of global increases in both atmospheric N deposition and fertilizer use. The aims of this proposal are to investigate controls on the long-term accumulation of nitrogen in soils, particularly by nonbiological chemical fixation, and to determine the ecosystem consequences of increased nonbiological N retention in grassland soils in Colorado. The research design combines experimental addition of 15-N containing compounds, followed by sophisticated chemical analysis of chemical transformations. A second series of experiments involves addition of humus precursors to the soil.
