Isotopic differences in soil–plant–atmosphere continuum composition and control factors of different vegetation zones on the northern slope of the Qilian Mountains

Abstract

Abstract. Understanding the differences and control factors of stable water isotopes in the soil–plant–atmosphere continuum (SPAC) of different vegetation zones is of great significance in revealing hydrological processes and regional water cycle mechanisms. From April 2018 to October 2019, we collected 1281 samples to investigated the stable water isotopes' changes in the SPAC of three different vegetation zones (alpine meadows, forests, and arid foothills) in the Shiyang River basin. The results show the following: (1) precipitation plays a major control role in the SPAC. From alpine meadows to arid foothills, the temperature effect of precipitation isotopes increases as altitude decreases. (2) From the alpine meadow to the arid foothills, soil water isotopes are gradually enriched. (3) Alpine meadow plants are mainly supplied by precipitation in the rainy season, and forest plants mainly utilize soil water in the dry season and precipitation in the rainy season. The soil water in the arid foothills is primarily recharged by groundwater, and the evaporation of plant isotopes is strong. (4) Temperature and altitude are potential factors that control the isotopic composition of the SPAC. This research will help in understanding of the SPAC system's water cycle at different altitudes and climates in high mountains.