4.2. Comparisons between P. fruticosa shrub and alpine grassland
The δ18O in soil water and plant water showed significant differences between shrub and grassland sites (p < 0.05) in contrast to non-significant differences in δ2H, resulting in different slopes and intercepts for the water line equations of soil water and plant water. Isotope-fractionated differences were probably associated with local microenvironment and heterogeneity differences of surroundings between the grassland and shrub sites despite the same general conditions (Ellsworth&Williams, 2007).
The water line equations between δ18O and δ2H were established. Soil and plant water samples were well described by linear regressions, resulting of laying at an angle to the LMWL, this is consistent with previous studies (Goldsmith et al., 2012; Che, et al., 2019). Their slopes and intercepts from soil water at the grassland site were slightly than those at the shrub site, suggesting soil evaporation was slightly greater at the grassland site than at the shrub site. This was probably because the shrub site had a denser coverage shading the soil surface compared with the grassland site, as daily evaporation rates were slightly lower than grassland (Crawford et al., 2014; Schwärzel et al., 2020). Nevertheless, the slopes and intercepts in plant water lines at the grassland site were higher than the slope and intercept at the shrub site. The differences resulted from substantial variabilities for plant water at shrub and grassland sites, evaporative distinctions of2H/1H and18O/17O on the primary of leaf water (Farquhar et al., 2007) , and the transpiration from an area of grassland is greater than the transpiration from a similar area of shrubs.