The impact of different water–salt gradients on the health and growth of Populus euphratica in the oases of the Taklamakan Desert's interior

Populus euphratica is a crucial foundation species within desert riparian forests in Central Asia and an important component of desert carbon sinks. However, these forests currently face significant threats of widespread decline. To quantitatively investigate the relationship between environmental changes and the health of P. euphratica on a large scale, this study combined a UAV deep learning model with GF-2 satellite imagery to achieve high-precision extraction of P. euphratica , with an extraction accuracy of 91.5 %. Subsequently, spatial distributions of nine environmental factors, including soil moisture, salinity, and groundwater depth, were derived using random forest models, to quantify the importance of each factor. The results indicated that suitable habitats for P. euphratica were primarily concentrated where water availability was moderate and salinity was moderate. The growth of P. euphratica is constrained by the combined stresses of limited water availability and salinity. Groundwater depth, surface water distribution, and soil moisture collectively accounted for 66.4 % of the influencing factors while electrical conductivity and sodium ion concentrations accounted for an additional 20.4 %. Excessive salinity significantly increased branch mortality and cavity rates and reduced the crown width to diameter ratio, indicating potential structural damage and reduced vitality due to salinity stress. This study systematically quantified the comprehensive impact of water-salt gradients on multiple growth indicators of P. euphratica . The findings enhance our understanding of vegetation dynamics in the Taklamakan Desert, provide scientific evidence for the management of oasis vegetation and water resources in arid regions, and emphasize the importance of considering the water-salt balance during ecological water transfers.