Precipitation is a key meteorological factor regulating plant water acquisition and utilization in arid desert environments. However, it remains unclear how the water use strategies of Tamarix ramosissima on coppice dunes at the southwestern edge of the Gurbantunggut Desert respond to precipitation changes, particularly regarding the coordinated relationship between soil water partitioning and leaf water physiological traits. We combined stable isotope analyses (δD, δ18O and δ13C) with key leaf water physiological measurements to examine the water sources and response strategies of T. ramosissima in the different developmental stages of coppice dunes. The results indicate that water use strategies of T. ramosissima are jointly regulated by shifts in water source partitioning and leaf water physiological responses. T. ramosissima in the initial and growth stages of coppice dunes mainly relied on 0–180 cm soil water in spring and autumn but shifted toward 180–500 cm soil water during drought, whereas plants in the stable and declining stages of coppice dunes showed persistent reliance on deep soil water. Notably, T. ramosissima in the declining stage of coppice dunes showed the highest reliance on 180–500 cm soil water under drought conditions (86.5%), accompanied by reduced leaf water status. Following the 7 mm precipitation pulse, T. ramosissima in all coppice dunes increased water uptake from the 0–60 cm soil layer. In particular, T. ramosissima in the growth stage of coppice dunes shifted its water uptake toward the 0–180 cm soil layer. Meanwhile, improved leaf water status enhanced water balance and supported the maintenance of photosynthetic function. By contrast, the 4.2 mm event produced only transient shallow water uptake. The capacity of T. ramosissima to modulate water source partitioning, optimize leaf hydraulic traits, and regulate stomatal conductance forms the basis for its differing water use strategies in all coppice dunes. Such adaptive adjustments allow the species to sustain carbon gain and water balance under variable precipitation regimes, thereby supporting plant growth and ecosystem stability in desert environments.
Xu et al. (Mon,) studied this question.