Can Physical Protection Attenuate Temperature Sensitivity of Soil Organic Matter Dynamics?.
Alain F. Plante1, Alexandra Kougentakis1, Aslihan Sen1, Charles Slominski1, Johan Six2, and Richard Conant3. (1) University of Pennsylvania, Dept Earth & Environmental Science, 240 South 33rd Street, Philadelphia, PA 19104-6316, (2) University of California-Davis, Davis, CA 95616, (3) NREL, Colorado State University, Fort Collins, CO 80523-1499
Global climate change may induce an acceleration of soil organic matter (SOM) decomposition through increased soil temperature, and thus significantly impact the C balance in soils. The SOM protective capacity of a soil governed by biochemical recalcitrance may logically be subject to temperature sensitivities. However, the temperature sensitivity of physical protection provided by soil structure is less obvious, and the temperature sensitivity of SOM decomposition in tandem with variations in physical protective capacity has not previously been investigated. The hypothesis we proposed was that increased resistance to decomposition afforded by physical protection would decrease SOM sensitivity to temperature. Two experiments were undertaken to test this hypothesis. The first involved the incubation of intact soil cores, disrupted cores sieved to 1mm, and soil crushed to <50um. The second experiment involved comparing the decomposition of substrate added within or outside of reconstituted aggregates. Physical protection is known to reduce the decomposability of otherwise labile material by occlusion in aggregates; a process not expected to be temperature sensitive. However, preliminary results suggest that the hypothesized attenuation of temperature sensitivity provided by physical protection may be minor compared to the sensitivity imparted by basic thermodynamics as expressed by the Arrhenius equation.