Stable Isotope Analysis of Plant Water and Soil Water in a Pair of Grassland and Shrub Sites on the Qinghai-Tibet Plateau

Studying the interrelation of soil water and plant water is essential for an in-depth understanding of eco-hydrological processes. However, water use relationships and comparative studies between shrubs and alpine grassland of the Qinghai-Tibet Plateau remain poorly understand. In this study, we compared δ 18 O and δ 2 H values of water from soil, plant, precipitation, and groundwater between shrub and grassland locations at two neighboring sites in order to better understand the interface between plant and surrounding soils of shrubs and grasslands. Our results showed that δ 18 O and δ 2 H of soil water, precipitation, and plant water varied significantly over time and water sources in grassland and shrub sites. Both soil evaporation and plant transpiration at the shrub site were relatively lower than they were at the grassland site . Grassland plant water had a stronger dynamic fractionation effect in the process of transportation and was more sensitive to environmental conditions. However, plants at the shrub site displayed more flexible water use patterns , and shifted their water sources between shallow soil water and deep soil water. The results of this study will help to better understand the interface between plant and surrounding soils of shrub and grassland sites, thereby providing guidance for meadow management from ecohydrological processes on the Qinghai-Tibet Plateau