Difference of water source of two communities in Ulan Buh Desert, China.

To understand the adaptation of water use strategy of plant community to habitat heterogeneity, we measured the δD and δO values of xylem water of shrubs and potential water sources (soil water in different layers or groundwater) of communities on sand dune and Gobi from April to September in 2021 in the Ulan Buh Desert. Employing the MixSIAR model, we examined the seasonal dynamics of water source of each shrub by quantifying the contribution of different potential water sources. The results showed that and on sand dune mainly used soil water of 10-25 cm in April and May after heavy rain in early spring, whereas mainly used soil water of 10-200 cm. During the drought event within summer from June to August, increasingly used soil water of 100-200 cm and groundwater, but and increased the usage of 50-200 cm soil water. After the moderate rain in September, evenly used soil water in all layers and groundwater, whereas two shrubs preferred soil water of 10-50 cm. On Gobi, and evenly used soil water in all layers in April and May, mainly used 50-150 cm soil water from June to August and used 10-50 cm soil water in September. mainly used soil water of 10-50 cm (from April to May), 25-150 cm (from June to August), and 10-25 cm (in September), separately. There were seasonal differences in water use of three shrubs on sand dune and Gobi communities. During drought, on sand dune could use deep soil water and groundwater, and that on Gobi relied only on deep soil water, which was more sensitive to rainfall.