|Castellano, Michael j|
|Graham, Chris b|
Submitted to: Geoderma
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/27/2011
Publication Date: 5/15/2011
Citation: Castellano, M., Schmidt, J.P., Kaye, J.P., Walker, C., Graham, C., Lin, H., Dell, C.J. 2011. Hydrological controls on heterotrophic soil respiration across an agricultural landscape. Geoderma. 162:273-280. Interpretive Summary: Modeling the impacts of global climate change will depend on a better understanding of carbon dioxide emissions from soils. Our objective was to determine the most consistent indicator of carbon dioxide emission across different soil types of a Coastal Plain landscape and as groundwater levels fluctuate. Matric potential was the most consistent indicator of instantaneous maximum carbon dioxide flux, better than volumetric soil water content or water filled pore space. However, water content normalized to field capacity water content was a more consistent scalar throughout the observed range of carbon dioxide flux. These results suggest that matric potential and water content normalized to field capacity should be used to develop models for predicting carbon dioxide flux across varying soil types.
Technical Abstract: Water availability is an important determinant of variation in soil respiration, but a consistent relationship between soil water and the relative flux rate of carbon dioxide across different soil types remains elusive. Using large undisturbed soil columns (N = 12), we evaluated soil water controls on heterotrophic carbon dioxide flux across three soil types from an agricultural catena. To simulate water table fluctuations that were observed at the field site, we flooded columns from bottom to surface and then allowed the columns to drain while monitoring volumetric soil water content (VWC), water filled pore space (WFPS), water content normalized to field capacity, matric potential, and carbon dioxide flux. Mean cumulative carbon dioxide flux was 4649 mg carbon dioxide-C per m squared per 96 h. Regardless of soil type, carbon dioxide flux rates exhibited a single maximum below saturation near field capacity. Across soil types, matric potential was the most consistent predictor of instantaneous maximum carbon dioxide flux, which occurred between -0.15 and -4.89 kPa. Because instantaneous maximum carbon dioxide flux rates occurred near field capacity, water content normalized to field capacity was a relatively consistent predictor of carbon dioxide flux. Although matric potential was the best predictor of instantaneous maximum carbon dioxide flux rate, water content normalized to field capacity was a more consistent scalar throughout the range of carbon dioxide flux. In contrast, VWC and WFPS were not consistent predictors of instantaneous maximum carbon dioxide flux rate. These data suggest matric potential and water content normalized to field capacity should be used as water scalars in cross-soil analyses of carbon dioxide flux.