Understanding the spatiotemporal evolution patterns of Populus euphratica Oliv. (P. euphratica) forests in the Tarim Basin (TB) and their influencing factors is crucial for regional ecological security and high-quality development. However, there is currently a lack of large-area, long-term systematic monitoring. This study utilized multi-source medium and high-resolution remote sensing images from the Landsat series and Sentinel-2, applying a Random Forest classification model to obtain distribution data of P. euphratica forests and shrublands in 14 areas of the TB from 1990 to 2020. We analyzed the effects of river distance, water transfer, and farmland on their distribution. Results indicated that both P. euphratica forests and shrublands decreased during the first 20 years and increased during the last 10 years. Within 1.5 km of river water transfer zones, P. euphratica forests more frequently converted to shrublands, while both forests and shrublands showed recovery in low-frequency water transfer areas. Farmland encroachment was most significant beyond 3 km from rivers. To effectively protect P. euphratica forests, we recommend intermittent low-frequency water transfers within 3 km of rivers and stricter management of agricultural expansion beyond 3 km. These measures will help maintain a balanced ecosystem and promote the long-term sustainability of P. euphratica forests.

Land use and land cover change (LULCC), along with the conversion of natural ecosystem cover into farmland, poses significant ecological challenges for desert riparian ecosystems. The Tarim River Basin (TRB), home to the world’s largest and most densely distributed and well-preserved desert riparian ecosystem, remains exceptionally susceptible to climate change. However, our understanding of the role of climatic factors (mean annual temperature (MAT); mean temperature during the warmest month (MWMT); relative humidity in September, October, and November (RH_SON); and the annual heat–moisture index (AHM)) in driving pattern changes in these ecosystems remains limited. To address this gap, we employed a transfer matrix approach coupled with geographically weighted regression models to conduct an extensive analysis of LULCC trends and their driving factors within the TRB from 1990 to 2020. The 30-year dataset on LULCC provided invaluable insights, revealing that the proliferation of farmland and shrubberies has precipitated the decline of arbor forests and grassland expanses. Furthermore, this expansion of farmland and shrubberies has resulted in heightened ecosystem fragmentation, particularly notable between 2005 and 2010. Our assessment indicates that artificial ecosystems are gradually transitioning back into natural states, encompassing 8.24% of the total area, chiefly attributed to the expanding shrubbery regions. Additionally, in-depth scrutiny of the impacts of climatic factors on ecosystem structure unveiled that moisture exerts the most pronounced influence on ecosystem patterns, followed by air moisture content during the growing season, while temperature exerts a relatively lesser impact. Overall, this study contributes to the realization of SDG 13 (Climate Action) and SDG 15 (Life on Land) by informing conservation efforts and sustainable land management practices in dryland desert riparian ecosystems.

To study the genetic diversity of phenotypic traits of natural Populus euphratica populations, we investigated the leaf, fruit and seed traits of the populations. The results of the phenotypic traits all showed that the variation among populations was larger than the variation within populations. The differentiation coefficients of phenotypic traits indicated that the variation among populations was the main source of population variation. The coefficient of variation of the phenotypic traits indicated that the leaf phenotypic traits directly exposed to the environment for a long time had the largest variation in the population. Correlation analysis between the phenotypic traits and environmental factors showed that geographical factors had a greater influence than climatic factors on phenotypic traits, and environmental factors had a certain degree of plasticity for phenotypic variation.

While regional hydro-climate theoretically dictates ecosystem multifunctionality (EMF) in arid riparian forests, local soil-moisture conditions often act as the final arbiter. In this study, we investigated a hierarchical mechanism where soil moisture modulates the effects of regional hydro-climatic stress, thereby shaping biodiversity, community traits, and EMF across spatial and functional thresholds. We focused our research on the desert riparian Populus euphratica forests in Northwestern China, quantifying EMF through both averaging and multi-threshold metrics (20% to 80%) across eight key ecological functions.Our results reveal that EMF increases with latitude but declines with elevation. We observed that the negative impact of hydro-thermal stress (Climate-PC1) intensifies significantly as distance from the river exceeds 1,500 m. Notably, soil moisture levels covaried with EMF and declined as riparian distance increased. Crucially, the regulatory drivers of EMF shift as functional demands rise: biodiversity and soil moisture jointly govern EMF at low to moderate thresholds (20%–40%), but direct hydro-climatic limitations take over at higher thresholds (60%–80%). Path analysis confirms that this transition—from biodiversity-mediated regulation to direct climatic control—is most pronounced where soil-moisture buffering is weak. We conclude that a hierarchical filtering mechanism dictates EMF in these riparian systems. To sustain high-threshold ecosystem services, conservation efforts must prioritize maintaining soil-moisture buffering near rivers while alleviating hydro-climatic stress in more distant, water-limited zones.