the National Natural Science Foundation of China,
Soil extracellular enzymes play a key role in the degradation and turnover of soil organic matter since they depolymerize large organic matter into low molecular compounds assimilated by microbes. Enzymatic reactions are the rate-limiting steps in soil organic matter decomposition and have profound impacts on biogeochemical cycle in terrestrial ecosystems. However, we know little about the spatial distribution of soil enzyme activities and the underlying mechanisms. To explore the spatial distribution and the driving factors of soil extracellular enzymes along the altitude and aspect, we selected six sites along the altitude gradients on the windward and leeward slopes of the Tanggula Mountains in the Qinghai-Tibet Plateau, respectively. We measured six types soil extracellular enzymes activities which involved in carbon, nitrogen and phosphorus cycles of soil, soil moisture (SM), soil carbon content (TC), and soil nitrogen content (TN). We investigated plant root biomass (RB), obtained normalized difference vegetation index (NDVI) as aboveground biomass index, mean annual temperature (MAT), mean annual precipitation (MAP), and ultraviolet radiation (UV) as climate factors. The results showed that MAT, and C:N decreased, whereas MAP, UV, NDVI, TC, TN increased along the increasing altitude. MAP, UV, NDVI, TC, and TN were significantly higher, while C:N were lower on the windward slope than those on the leeward slope. The specific extracellular enzymes differed in their activity responses to altitudes and aspects. Specifically, the activities of C-acquiring exoenzymes α-glucosidase (AG), β-glucosidase (BG), β-xylosidase (BX), and N-acquiring exoenzyme N-acetyl-glucosaminidase (NAG) all increased along increasing altitude gradient. In addition, the activities of AG, BG, BX, and NAG were significantly higher on the windward slope than on the leeward slope. However, neither altitude nor aspect had significant effects on P-acquiring exoenzymes acid phosphatase (AP) and N-acquiring exoenzymes leucine aminopeptidase (LAP). Our further analysis of model average and relative importance suggested that the NDVI, RB and TC were the main factors driving the changes in activities of C-acquiring exoenzymes (AG, BG, BX) along altitude gradient and aspect. However, the changes in activities of N-acquiring exoenzymes (NAG) was predominantly only driven by NDVI. Overall, this finding indicate that climate and soil characteristics drive the spatial distribution of various extracellular enzyme activity in soils at different altitudes and aspects, regulating carbon and nitrogen cycling. This study provides justification for the prediction of the spatial patterns of soil extracellular enzyme activities.