HR: 1400h
AN: B13A-01    [Abstracts]
TI: Examining the Physical Controls on Soil Organic Matter Decomposition Through Depth: Results of a Temperate Forest Soil Mesocosm Experiment
AU: * Gabriel, C
EM: cgabriel@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, Physical Sciences Complex, 1 West Street P.O. Box 5000, Antigonish, NS B2G 2W5, Canada
AU: Kellman, L
EM: lkellman@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, Physical Sciences Complex, 1 West Street P.O. Box 5000, Antigonish, NS B2G 2W5, Canada
AB: The physical environment in soils exerts a primary control upon rates of soil organic matter (SOM) decomposition, however quantifying the relationships between temperature, moisture and SOM decomposition is methodologically challenging. In situ it is difficult to separate the effects of temperature and moisture on decomposition, while in the lab, disturbance effects may inflate or alter apparent relationships. To overcome these methodological challenges, we investigate the depth dependence of SOM decomposition measured as soil surface carbon dioxide flux in a managed red spruce temperate forest soil by subjecting minimally disturbed shallow (0-25 cm) and deep (25-50 cm) soil cores to varying thermal and moisture conditions in a climate controlled phytotron facility. Parallel incubations with constant and diurnal temperature cycling were carried out upon soils representing a range of moisture contents. The CO₂ flux from shallow soils were up to 10 times greater than corresponding deep soils, with clear moisture driven changes in decomposition rates at fixed temperatures observed. The temperature sensitivity of decomposition decreased with increasing moisture for shallow soils, but displayed no clear trend in corresponding deep soils. The results allow insight into how the physical controls that govern SOM decomposition in shallow and deep layers differ, highlighting the critical role of moisture in determining the relationship between decomposition and temperature, and providing a model of soil moisture-decomposition relationships that can be extended to other similar forests within the region.
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)
SC: Biogeosciences [B]
MN: 2009 Joint Assembly