Seasonal and episodic moisture controls on plant and microbial contributions to soil respiration |
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Authors: | Carbone Mariah S Still Christopher J Ambrose Anthony R Dawson Todd E Williams A Park Boot Claudia M Schaeffer Sean M Schimel Joshua P |
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Institution: | (1) Department of Geography, University of California, Santa Barbara, CA 93106-4060, USA;(2) Present address: National Center for Ecological Analysis and Synthesis, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA;(3) Department of Integrative Biology, University of California, Berkeley, CA 94720, USA;(4) Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA |
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Abstract: | Moisture inputs drive soil respiration (SR) dynamics in semi-arid and arid ecosystems. However, determining the contributions
of root and microbial respiration to SR, and their separate temporal responses to periodic drought and water pulses, remains
poorly understood. This study was conducted in a pine forest ecosystem with a Mediterranean-type climate that receives seasonally
varying precipitation inputs from both rainfall (in the winter) and fog-drip (primarily in the summer). We used automated
SR measurements, radiocarbon SR source partitioning, and a water addition experiment to understand how SR, and its separate
root and microbial sources, respond to seasonal and episodic changes in moisture. Seasonal changes in SR were driven by surface
soil water content and large changes in root respiration contributions. Superimposed on these seasonal patterns were episodic
pulses of precipitation that determined the short-term SR patterns. Warm season precipitation pulses derived from fog-drip,
and rainfall following extended dry periods, stimulated the largest SR responses. Microbial respiration dominated these SR
responses, increasing within hours, whereas root respiration responded more slowly over days. We conclude that root and microbial
respiration sources respond differently in timing and magnitude to both seasonal and episodic moisture inputs. These findings
have important implications for the mechanistic representation of SR in models and the response of dry ecosystems to changes
in precipitation patterns. |
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