干旱区生态环境知识资源中心

Soil respiration (R-s), conventionally considered as net soil CO2 flux, is an important link in the terrestrial carbon cycle. However, existing estimates of R-s in drylands may be erroneous, because of the abiotic soil CO2 flux. This may seriously hamper our understanding of the carbon cycle of desert ecosystems. In this study, we monitored CO2 flux of natural and sterilized soils, and obtained the net and abiotic soil CO2 flux in a desert ecosystem in Ningxia, China, and then computed R-s by using these data. Daily R-s was much larger than the net soil CO2 flux both in the growing and non-growing season. Further analysis indicated that R-s was controlled by soil temperature (T-s) over the annual cycle, and an exponential model could provide a good prediction of R-s. During the growing season, R-s increased significantly with rising soil water content (VWC) (P < 0.05). A bivariate (T-s and VWC) exponential-power model had a better performance for predicting R-s in the growing season than a T-s-only model. However, during the non-growing season, this model failed to simulate R-s. Our results suggest that R-s is greatly underestimated, and the exponential model is more applicable for annual R-s prediction.