HR: 0800h
AN: B21C-01 INVITED    [Abstracts]
TI: Potential for Abrupt Changes in Soil Carbon
AU: * Trumbore, S
EM: setrumbo@uci.edu
AF: Department of Earth System Science, University of California, Irvine, CA 92697, United States
AB: Predictions of terrestrial feedbacks to climate warming differ dramatically in the magnitude and even the sign of soil C responses over the next century. These differences reflect uncertainties inherent in how models parameterize two key responses: the temperature dependence of decomposition rates and the rate of C accumulation given hypothesized increases in vegetation productivity due to CO2 fertilization. Abrupt changes in soil C (gains or losses of C at rates of 1MgC ha-1 yr-1 or more) are observed in early stages of soil formation, following vegetation change, or with changes in soil drainage, pH or nutrient status. Radiocarbon measurements provide a tool for determining the source and age of the C being stored or lost, and also provide a means of detecting processes destabilizing C that has previously been stable over decades to thousands of years. To be important for the global C cycle, abrupt changes need to occur over large land areas, which focuses attention on high latitude soils and vegetation change at low to mid-latitudes. This talk will provide examples and explore the observational constraints of the potential for soils to act as globally important C sources or sinks over the next century. It will underscore the need to understand the complex and interacting factors – physical and chemical as well as biological – that can allow organic matter to persist in and be lost from the soil environment on a range of timescales
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting