9-1 Environmental and Geological Controls on the Soil Carbon Cycle In a Changing World

See more from this Division: Overarching Sessions
See more from this Session: Pardee Keynote Symposia: Carbon Sequestration: Methods, Markets and Policy

Wednesday, 8 October 2008: 3:05 PM
George R. Brown Convention Center, General Assembly Theater Hall C

Ronald Amundson, Division of Ecosystem Sciences, University of California, Berkeley, Berkeley, CA, Jonathan Sanderman, Earth and Planetary Sciences, UC Santa Cruz, Albany, CA and Kyungsoo Yoo, Plant and Soil Sciences Dept. and Dept. of Geological Sciences, University of Delaware, Newark, DE
Abstract:
Soil C is the balance between plant inputs and biological and physical losses. Nearly 20% of anthropogenic CO2 emissions are from land use changes, but reducing this loss requires understanding the natural and management-specific impacts on soil C. The main control on the soil C cycle is climate. Radiocarbon measurements have shown that decomposition accelerates with increasing temperature and that under projected warming scenarios soils should release CO2 and provide a positive feedback to warming. Ecosystem-scale C fluxes also reveal a strong temperature effect on soil C residence times. Recently-assessed reductions in soil C storage in Great Britain provide support for the concern about positive feedbacks to warming. Recent research has refined the rates of C erosion and its fate in both cultivated and undisturbed upland ecosystems. Briefly, soil C on actively eroding hillslopes is in a perpetual non-steady state due to ongoing erosion and deposition. Additionally, vegetated upland watersheds act as filters for large annual fluxes of DOC, ultimately releasing small refractory C pools to aqueous systems. In cultivated soils, the changes in soil C are further impacted by climate. Comparative studies of cultivated and non-cultivated soils in the Great Plains and India show that fractional losses of soil C during cultivation are greater under humid climates. Recent 14C work shows that large-scale soil structure significantly controls soil C storage, and that disruption of this structure by tillage can rapidly release pools of C that have been stored for millennia. While improved and scientifically-informed management of agricultural ecosystems is an important tool in mitigating anthropogenic greenhouse gas emissions, the most significant impact on C emissions can be achieved by reducing the rates of global land conversion.

See more from this Division: Overarching Sessions
See more from this Session: Pardee Keynote Symposia: Carbon Sequestration: Methods, Markets and Policy

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