Soil properties drive multidimensional desert plant diversity in northwestern China’s inland river basins: a holistic biodiversity perspective

Understanding how soil properties shape plant diversity is essential for conserving fragile ecosystems in arid inland river basins. However, most previous studies have focused on single-dimensional diversity metrics. To address this gap, we developed a holistic biodiversity (HB) index that integrates taxonomic, functional, and phylogenetic diversity to comprehensively evaluate desert plant communities in three inland river basins of northwestern China. Using linear regression and partial least squares path modeling (PLS-PM), we assessed the effects of environmental variables—including soil physicochemical properties, nutrients, climate, and geography—on HB. HB varied slightly between basins but responded strongly to soil conditions. Higher levels of soil organic carbon and available nitrogen, along with near-neutral pH, enhanced HB, whereas high soil salinity significantly constrained it (p < 0.01). In contrast, climatic and geographic factors had weaker effects on HB. Dominant drivers differed by basin: annual precipitation in the Shiyang River, soil salinity in the Shule River, and a combination of soil and geographic factors in the Heihe River. The PLS-PM results confirmed that soil properties exerted the strongest direct influence on HB (p < 0.01), while climate and geography affected HB mainly through soil mediation. These findings underscore the central role of soil in maintaining plant diversity and suggest that improving soil quality—particularly by increasing organic matter and reducing salinity—should be a conservation priority in arid inland ecosystems.