Unifying soil respiration pulses, inhibition, and temperature hysteresis through dynamics of labile soil carbon and O2. Issue 4 (10th April 2014)

• Record Type: Journal Article
• Authors: Oikawa, P. Y.; Grantz, D. A.; Chatterjee, A.; Eberwein, J. E.; Allsman, L. A.; Jenerette, G. D.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 4(2014:Dec.)
• Page Start: 521
• Page End: 536
• Publication Date: 2014-04-10
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2013JG002434
• Languages: English
• ISSNs: 2169-8953

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Event‐driven and diel dynamics of soil respiration (R<sub>s</sub>) strongly influence terrestrial carbon (C) emissions and are difficult to predict. Wetting events may cause a large pulse or strong inhibition of R<sub>s</sub>. Complex diel dynamics include hysteresis in the relationship between R<sub>s</sub> and soil temperature. The mechanistic basis for these dynamics is not well understood, resulting in large discrepancies between predicted and observed R<sub>s</sub>. We present a unifying approach for interpreting these phenomena in a hot arid agricultural environment. We performed a whole ecosystem wetting experiment with continuous measurement of R<sub>s</sub> to study pulse responses to wetting in a heterotrophic system. We also investigated R<sub>s</sub> during cultivation of <italic>Sorghum bicolor</italic> to evaluate the role of photosynthetic C in the regulation of diel variation in R<sub>s</sub>. Finally, we adapted a R<sub>s</sub> model with sensitivity to soil O<sub>2</sub> and water content by incorporating two soil C pools differing in lability. We observed a large wetting‐induced pulse of R<sub>s</sub> from the fallow field and were able to accurately simulate the pulse via release of labile soil C. During the exponential phase of plant growth, R<sub>s</sub> was inhibited in response to wetting, which was accurately simulated through depletion of soil O<sub>2</sub>. Without plants, hysteresis was not observed; however, with growing plants, an increasingly significant counterclockwise hysteresis developed. Hysteresis was simulated via a dynamic photosynthetic C pool and was not likely controlled by physical processes. These results help characterize the complex regulation of R<sub>s</sub> and improve understanding of these phenomena under warmer and more variable conditions.</p> </abstract>