Location: Southwest Watershed ResearchTitle: Quantifying the time scales over which exogenous and endogenous conditions affect soil respiration ) Author
|Scott, Russell - Russ|
Submitted to: New Phytologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/30/2013
Publication Date: 4/4/2014
Citation: Barron-Gafford, G., Cable, J., Bentley, L., Scott, R.L., Huxman, T., Jenerette, G., Ogle, K. 2014. Quantifying the time scales over which exogenous and endogenous conditions affect soil respiration. New Phytologist. 202:442-454. DOI: 74310.1111/nph.12675. Interpretive Summary: Soil respiration is a significant contributor to atmospheric carbon dioxide concentrations. In order to accurately predict how much carbon dioxide will be respired in the future, critical information about how soil respiration responds to environmental conditions is needed. We carried out measurements of soil respiration and potential environmental drivers in a grassland habitat in southern Arizona and found that rates of soil respiration responded both to moisture in the soil and photosynthesis rates in nearby plants. But, this response differed depending on whether the nearby plant was a bunchgrass or a tree. Thus, improvement in our predictions of the carbon cycle may warrant the inclusion of plant-type specific responses that we found.
Technical Abstract: Understanding how exogenous and endogenous factors and aboveground-belowground linkages modulate carbon dynamics is difficult because of influences of antecedent conditions. For example, there are variable lags between aboveground assimilation and belowground efflux, and the duration of antecedent periods are often arbitrarily assigned. Nonetheless, developing models linking above- and belowground processes is crucial for estimating current and future carbon dynamics. We collected data on leaf-level photosynthesis (Asat) and soil respiration (Rsoil) in different microhabitats (under shrubs vs. bunchgrasses) in the Sonoran Desert. We evaluated time-scales over which endogenous and exogenous factors control Rsoil by analyzing our data in the context of a semi-mechanistic temperature-response model of Rsoil that incorporated effects of antecedent exogenous (soil water) and endogenous (Asat) conditions. Across both microhabitats, antecedent soil water and Asat significantly affected Rsoil, but Rsoil under shrubs was more sensitive to Asat compared to under bunchgrasses. Photosynthetic rates one and three days prior to the Rsoil measurement were most important in determining current-day Rsoil under bunchgrasses and shrubs, respectively, indicating a significantly lag effect. Endogenous and exogenous controls are critical drivers of Rsoil, but the relative importance and the time-scale over which each factor affects Rsoil depends on aboveground vegetation and ecosystem structure characteristics.