Water Use Strategies of Dominant Species (Caragana korshinskiiandReaumuria soongorica) in Natural Shrubs Based on Stable Isotopes in the Loess Hill, China

Water is a key and limiting factor for ecosystem processes (carbon dioxide fixation, vegetation growth, respiration, etc.) and functions (NPP, Net Primary Productivity) in arid and semi-arid areas. As the main regulator, knowledge of plant water use patterns is essential in understanding the SPAC (Soil-Plant-Atmosphere-Continuum) cycle. The tree-planting project in the southern and northern mountains of Lanzhou city aims to improve the ecological environment and promote urban construction. In this study, we analyzed the water use strategies of the dominant plantsC. korshinskiiandR. soongoricain natural shrubs of southern and northern mountains of Lanzhou city using oxygen stable isotope techniques. The result showed that the flexible water uptake pattern ofC. korshinskiiand its faster response to precipitation pulse, compared withR. soongorica, might help it to make full use of water and nutrients and adapt to the dry environment. However,R. soongoricaprogressively switched to suck up deeper soil water and increased the water use proportion from 0.5% to 84.4% as the seasons changed, indicating a greater degree of ecological plasticity. The flexible water use strategies ofC. korshinskiiandR. soongoricain the same habitat reduced competition for water and nutrients and enhanced adaptability to arid environments. The work presented here provides insights into vegetation restoration and ecological management for the southern and northern mountains of Lanzhou city.