Soil Rewetting Respiration Dynamics Across a Lithologic Gradient
Abstract
Rewetting of dry soil is followed by a large pulse of respiration, which has been attributed to both microbial stress physiology and physical mechanisms. From a physical perspective, rewetting may liberate and redistribute carbon protected by diffusional barriers or sorption on mineral surfaces. We explored the importance of these physical mechanisms by comparing rewetting dynamics across a lithologic gradient of Californian oak-woodland soils. In surface soil (0-10 cm) rewetting dynamics followed a nearly identical negative-exponential response across all rock types, but rewetting dynamics varied at depth (40-50 cm). In sandstone derived subsoils, respiration rates in the first 24 hours after rewetting matched and then exceeded respiration potentials achieved by adding bioavailable substrate. In contrast, in clay-rich subsoils derived from shale, basalt, or ultramafic rocks, respiration rates in the first 24 hours after rewetting were a small fraction of respiration potential, and declined exponentially with time. These patterns indicate that soil physical properties control release of bioavailable carbon during rewetting in subsoils. In contrast, conserved rewetting dynamics in shallow soil across all rock types is more consistent with control by physiological mechanisms.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B23E0632S
- Keywords:
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- 0404 Anoxic and hypoxic environments;
- BIOGEOSCIENCESDE: 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0463 Microbe/mineral interactions;
- BIOGEOSCIENCESDE: 0490 Trace gases;
- BIOGEOSCIENCES