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Response of ecosystem respiration to soil water and plant biomass in a semiarid grassland

Abstract The Mongolian steppe zone constitutes a major part of East Asian grasslands. The objective of this study was to evaluate the quantitative dependence of ecosystem respiration (Reco) on the environmental variables of soil water and plant biomass in a semiarid grassland ecosystem. We determined Reco using opaque, closed chambers in a Mongolian grassland dominated by graminaceous perennial grasses during six periods: July 2004, May 2005, July 2005, September 2005, June 2006, and August 2009. Using the data collected when soil water content and aboveground biomass were relatively constant, values of Reco were fitted to an exponential temperature function, and the standardized rate of Reco at 20°C (R20) and temperature sensitivity (Q10) of Reco were calculated for each measurement plot and period. The results indicate that aboveground biomass significantly affected the variation in R20, and the relationship was expressed with a linear model. The R20 residuals of the linear biomass model were highly correlated with soil water content by a quadratic function. The Q10 values showed a weak positive relationship with soil water content. Temporal and spatial variations in Reco were well predicted by the exponential temperature model with R20, which relates to aboveground biomass and soil water content, and with Q10, which relates to soil water content.