Influence of Temperature and Moisture on Autotrophic and Heterotrophic Respiration in a Semi-Arid Highland Elm Sparse Forest

Little is known about the response of soil respiration components to environmental changes, especially in high-altitude forest ecosystems. To examine the different effects of temperature and moisture on separate soil respiration components, namely autotropic ( R a ) and heterotrophic ( R h ) respirations, the gap formation method was adopted in a semi-arid highland elm ( Ulmus pumila L.) sparse forest, Northwestern China. In 2021, a 9.33 m transect between two elm trees was built, forming a gap of elm sparse forest on the plateau. Soil respiration was measured along the transect between two elm trees. The results showed that the soil respiration under the canopy decreased with increasing distance from the base of the elm, and that the root had no effect on the soil respiration outside the canopy. Here we demonstrated that the mean value of R a contribution to the total respiration ( R t ) is 63%. Results of this study also showed that the temperature sensitivity of R h ( Q 10 = 4.29) was much higher than that of R a ( Q 10 = 1.40), and that soil moisture (SM) explained the variation of R a (64.4%) better than that of R h (49.9%). Our results suggested that the key driver of R h was soil temperature (ST), and that of R a was SM in the semi-arid highland elm sparse forest in Northwest China. The gap formation method is helpful to better understand the different responses of R a and R h to the variation of ST and SM in elm sparse forest in the semi-arid highland of Northwest China. We highlight that the different responses of R h and R a to the same environmental factors should be considered when predicting the future soil carbon cycle.