title: Antecedent moisture and temperature conditions modulate the response of ecosystem respiration to elevated CO2and warming.
abstract: Terrestrial plant and soil respiration, or ecosystem respiration (Reco), represents a major CO2flux in the global carbon cycle. However, there is disagreement in how Recowill respond to future global changes, such as elevated atmosphere CO2and warming. To address this, we synthesized six years (2007-2012) of Recodata from the Prairie Heating And CO2Enrichment (PHACE) experiment. We applied a semi-mechanistic temperature-response model to simultaneously evaluate the response of Recoto three treatment factors (elevated CO2, warming, and soil water manipulation) and their interactions with antecedent soil conditions [e.g., past soil water content (SWC) and temperature (SoilT)] and aboveground factors (e.g., vapor pressure deficit, photosynthetically active radiation, vegetation greenness). The model fits the observed Recowell (R2= 0.77). We applied the model to estimate annual (March-October) Reco, which was stimulated under elevated CO2in most years, likely due to the indirect effect of elevated CO2on SWC. When aggregated from 2007 to 2012, total six-year Recowas stimulated by elevated CO2singly (24%) or in combination with warming (28%). Warming had little effect on annual Recounder ambient CO2, but stimulated it under elevated CO2(32% across all years) when precipitation was high (e.g., 44% in 2009, a 'wet' year). Treatment-level differences in Recocan be partly attributed to the effects of antecedent SoilT and vegetation greenness on the apparent temperature sensitivity of Recoand to the effects of antecedent and current SWC and vegetation activity (greenness modulated by VPD) on Recobase rates. Thus, this study indicates that the incorporation of both antecedent environmental conditions and aboveground vegetation activity are critical to predicting Recoat multiple timescales (subdaily to annual) and under a future climate of elevated CO2and warming.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors.forename: Edmund M
authors.initials: EM
authors.lastname: Ryan
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors.forename: Kiona
authors.initials: K
authors.lastname: Ogle
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, USA.
authors.forename: Tamara J
authors.initials: TJ
authors.lastname: Zelikova
authors.affiliation: USDA-ARS, Fort Collins, CO, USA.
authors.forename: Dan R
authors.initials: DR
authors.lastname: LeCain
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Williams
authors.affiliation: USDA-ARS, Fort Collins, CO, USA.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Morgan
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, USA.|Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia.
authors.forename: Elise
authors.initials: E
authors.lastname: Pendall
keywords: antecedent effects; carbon cycle; elevated CO2; grasslands; soil respiration; temperature acclimation; warming