Abstract:Soil enzymes are a class of proteins with catalytic functions in the soil ecosystem. They are secreted into the soil by plant roots, microorganisms, and the decomposition of plant and animal residues, and participate in all biochemical processes in the soil, and their activity levels can sensitively reflect the direction and intensity of biochemical reactions. Due to its high altitude and cold climate, Qinghai-Tibet Plateau is regarded as a sensitive and fragile area to climate change. Global climate change significantly affects soil enzyme activities, and these impacts can potentially modify soil quality, thus affect vegetation productivity in the alpine grasslands of the Qinghai-Tibet Plateau. Soil enzymes play a critical role in the material cycle and energy flow of ecosystems. Their patterns, functions, and conversion processes have been widely studied. Nevertheless, the altitude pattern of soil enzyme activities in alpine grassland ecosystems still needs to be further explored. Therefore, we obtained soil enzymes in the alpine grasslands across the Qinghai-Tibet Plateau, and extended the study on the elevation gradient of soil enzyme activity from the site scale to the transect scale. We analyzed the altitude pattern of soil β-Glucosidase (βG) enzymes closely related to the soil C cycle, soil β-Nacetylglucosaminidase (NAG) enzymes, and soil leucine aminopeptidase (LAP) enzymes closely associated with soil N cycle, soil alkaline phosphatase (ALP) enzymes greatly related to soil P cycle, and further explored their main drivers. The results showed that:(1) the activity of ALP and βG showed significant differences along the altitude gradient, and their thresholds presented at 3546 m and 3364 m, respectively. And the enzyme activity of ALP and βG at low altitudes was significantly higher than that at high altitudes (P<0.01). However, there were no significant relationships between NAG and LAP activities and altitude. (2) The ALP activity was significantly linked to mean annual precipitation (P<0.01), but was not affected by mean annual temperature. At high altitudes, the βG activity was affected by precipitation, but the climate had no significant effect on the βG activity at low altitudes. In conclusion, the change of temperature and precipitation caused by altitude can directly or indirectly affect soil enzyme activities. Precipitation is one of the key factors governing soil enzyme activities in the alpine grassland across the Qinghai-Tibet Plateau. This adaptive change enables soil enzymes to adapt and play their functions under different environmental conditions, thus affecting the material cycle and energy conversion processes of the soil ecosystem. The results can be used to evaluate the ecosystem functions of soil nutrient transformation, organic matter decomposition and circulation at different elevations, and provide a scientific basis for ecosystem management and protection, which is of great significance for understanding the biogeochemical cycle processes and mechanisms in alpine grasslands.