Difference of SPAC composition and control factors of different vegetation zones in north slope of Qilian Mountains

Abstract. Understanding the differences and controlling factors of stable water isotopes in the soil-plant-atmosphere continuum of different vegetation zones has important guiding significance for revealing the hydrological processes and regional water cycle mechanisms.This study selected three different vegetation zones (alpine meadows, forests, and arid piedmont zones) in the Shiyang River Basin for study. This paper’s analysis results show that: (1) In SPAC, precipitation isotope has the main controlling effect. From alpine meadows to arid foothills, as the altitude decreases, the temperature effect of precipitation isotopes increases. (2) From the alpine meadow to the arid foothills, the soil water isotope is gradually enriched, indicating that the evaporation is gradually increasing. (3) Alpine meadow plants are mainly supplied by precipitation in the rainy season; forest plants mainly utilize soil water in the dry season and precipitation in the rainy season. The soil water in the arid mountain foothills is mainly recharged by groundwater, and the evaporation and fractionation of plant isotopes are very strong.This research will help understand the SPAC system’s water cycle at different altitudes and climates on high mountains.