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

概要

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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 (R_<eco>) on the environmental variables of soil water and plant biomass in a semiarid grassland ecosystem. We determined R_<eco> 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 R_<eco> were fitted to an exponential temperature function, and the standardized rate of R_<eco> at 20℃ (R_<20>) and temperature sensitivity (Q_<10>) of R_<eco> were calculated for each measurement plot and period. The results indicate that aboveground biomass significantly affected the variation in R_<20>, and the relationship was expressed with a linear model. The R_<20> residuals of the linear biomass model were highly correlated with soil water content by a quadratic function. The Q_<10> values showed a weak positive relationship with soil water content. Temporal and spatial variations in R_<eco> were well predicted by the exponential temperature model with R_<20>, which relates to aboveground biomass and soil water content, and with Q_<10>, which relates to soil water content.