Thresholds of Soil Moisture on the Temperature Response of Soil Respiration in Semiarid High-Altitude Grassland in Northwestern China

Although soil temperature (T-s) is generally considered as the primarily factor influencing soil respiration (R-s), the correlation between soil respiration and soil temperature is often affected by soil moisture (M-s). In this study, we analyzed the correlation between R-s and T-s under different soil moisture condition in semiarid high-altitude grassland in northwestern China. The results showed that (1) when the values of M-s were higher than the field capacity (FC), R-s were mainly controlled by M-s. (2) FC was also an important threshold to affect the selection of R-s-T-s model and the determination of temperature sensitivity (Q(10)). Our findings highlight that R-s is significantly influenced by M-s in a threshold manner, and FC is an important moisture threshold for R-s and its temperature response in high altitude semiarid ecosystems.We suggested that the effect of M-s on R-s cannot be neglected in high altitude semiarid ecosystems.