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Title: Antecedent conditions influence soil respiration differences in shrub and grass patches

Author
item CABLE, J.M. - University Of Alaska
item OGLE, K. - Arizona State University
item BARRON-GAFFORD, G.A. - University Of Arizona
item BENTLEY, L.P. - University Of Arizona
item CABLE, W.L. - University Of Alaska
item Scott, Russell - Russ
item WILLIAMS, D.G. - University Of Wyoming
item HUXMAN, T.E. - University Of Arizona

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2013
Publication Date: 6/18/2013
Citation: Cable, J., Ogle, K., Barron-Gafford, G., Bentley, L., Cable, W., Scott, R.L., Williams, D., Huxman, T. 2013. Antecedent conditions influence soil respiration differences in shrub and grass patches. Ecosystems. 16:1230-1247. DOI: 10.1007/s10021-013-9679-7.

Interpretive Summary: The response of ecosystem processes to variation in environmental conditions is important to understand in light of recent and future changes in vegetation and climate. This study explored how changes in vegetation associated with recent shrub expansion in grasslands potentially impact soil respiration and its relationship with antecedent environmental conditions. Continuous measurements of soil respiration, soil temperature, and soil moisture were made over an entire growing season under shrubs, grasses and bare soil in S. Arizona. Data were analyzed within a statistical framework to understand how antecedent conditions influenced soil respiration over time. We found that the antecedent conditions and their effects are more complex than previously understood. Also, the simultaneous estimation of how current and past conditions influence current ecosystem processes will improve our predictive understanding these processes such as soil respiration.

Technical Abstract: Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of this study was to characterize the effect of antecedent moisture and temperature conditions on soil respiration in a grassland now dominated by shrubs. Continuous measurements of soil respiration, soil temperature, and soil moisture were made over the entire summer of 2005 within distinct vegetation microsites in this shrubland community – under grasses, shrubs, and in open spaces. We analyzed these data within a Bayesian framework that allowed us to evaluate the time-scale over which antecedent conditions influence soil respiration. High soil moisture during the preceding month increased respiration rates in both the grass and shrub microsites. However, the time period over which antecedent soil moisture influenced the temperature sensitivity of soil respiration was shorter in the shrub compared to the grass microsites (1 vs. 2 weeks, respectively). The depth of moisture was important; for example, for respiration under shrubs, near-surface moisture was more influential on the day of the respiration measurement but subsurface moisture was more influential on the antecedent time scale. Although more mechanistic studies are required, this study is the first to reveal that shrub encroachment changes the time scales over which soil moisture and temperature affect soil respiration.