title: Quantifying the timescales over which exogenous and endogenous conditions affect soil respiration.
abstract: Understanding how exogenous and endogenous factors and above-ground-below-ground linkages modulate carbon dynamics is difficult because of the influences of antecedent conditions. For example, there are variable lags between above-ground assimilation and below-ground efflux, and the duration of antecedent periods are often arbitrarily assigned. Nonetheless, developing models linking above- and below-ground 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 under bunchgrasses) in the Sonoran Desert. We evaluated timescales over which endogenous and exogenous factors control Rsoil by analyzing data in the context of a semimechanistic temperature-response model of Rsoil that incorporated effects of antecedent exogenous (soil water) and endogenous (Asat ) conditions. For both microhabitats, antecedent soil water and Asat significantly affected Rsoil , but Rsoil under shrubs was more sensitive to Asat than that under bunchgrasses. Photosynthetic rates 1 and 3 d before the Rsoil measurement were most important in determining current-day Rsoil under bunchgrasses and shrubs, respectively, indicating a significant lag effect. Endogenous and exogenous controls are critical drivers of Rsoil , but the relative importance and the timescale over which each factor affects Rsoil depends on above-ground vegetation and ecosystem structure characteristics.
authors.affiliation: School of Geography & Development, University of Arizona, Tucson, AZ, 85721, USA.|B2 Earthscience, Biosphere 2, University of Arizona, Tucson, AZ, 85721, USA.
authors.forename: Greg A
authors.initials: GA
authors.lastname: Barron-Gafford
authors.affiliation: International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Cable
authors.affiliation: Environmental Change Institute, University of Oxford, Oxford University Centre for the Environment, South Parks Road, Oxford, OX1 3QY, UK.
authors.forename: Lisa Patrick
authors.initials: LP
authors.lastname: Bentley
authors.affiliation: Southwest Watershed Research Center, USDA-ARS, Tucson, AZ, 85719, USA.
authors.forename: Russell L
authors.initials: RL
authors.lastname: Scott
authors.affiliation: Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA.|Center for Environmental Biology, University of California, Irvine, CA, 92697, USA.
authors.forename: Travis E
authors.initials: TE
authors.lastname: Huxman
authors.affiliation: Department of Botany and Plant Sciences, University of California Riverside, Riverside, CA, USA.
authors.forename: G Darrel
authors.initials: GD
authors.lastname: Jenerette
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors.forename: Kiona
authors.initials: K
authors.lastname: Ogle
mesh_terms: D002244:Carbon / Q000502:physiology*; D002245:Carbon Dioxide / Q000502:physiology*; D003889:Desert Climate; D017753:Ecosystem; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology*; D006109:Poaceae; D029862:Prosopis; D012987:Soil; D013696:Temperature; D014867:Water
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon
keywords: Bayesian modeling; Prosopis velutina; antecedent conditions; lag effects; mesquite; photosynthesis; soil respiration; woody plant encroachment