Soil carbon release responses to long-term versus short-term climatic warming in an arid ecosystem

Abstract. Climate change severely impacts grassland carbon cycling, especially in arid ecosystems, such as desert steppes. However, little is known about the responses of soil respiration ( R s ) to different warming magnitudes and watering pulses in situ in desert steppes. To examine their effects on R s , we conducted long-term moderate warming, short-term acute warming and watering field experiments in a desert grassland of Northern China. While experimental warming significantly reduced R s by 32.5 % and 40.8 % under long-term and moderate and short-term and acute warming regimes, respectively, watering pulses stimulated it substantially. Warming did not change the exponential relationship between R s and soil temperature, whereas the relationship of R s with soil water content (SWC) was well fitted to the Gompertz function. The soil features were not significantly affected by either long-term or short-term warming regimes, respectively; however, soil organic carbon content tended to decrease with long-term climatic warming. This indicates that soil carbon release responses strongly depend on the duration and magnitude of climatic warming, which may be driven by SWC and soil temperature. The results of this study highlight the great dependence of soil carbon emission on warming regimes of different durations and the important role of precipitation pulse during growing season in assessing the terrestrial ecosystem carbon balance and cycle.