Spatiotemporal differentiation and coupling mechanisms between vegetation and ecological water demand in a typical arid region of Xinjiang, China.

Introduction: Climate change and anthropogenic activities have jointly reshaped vegetation growth processes and water-consumption patterns in arid regions, complicating the relationship between vegetation restoration and water-resource constraints. Existing studies have mainly focused on individual ecological processes. A systematic understanding of how vegetation growth is coupled with ecological water demand (EWD), and of the mechanisms driving this relationship, remains limited. Methods: Xinjiang was selected as a representative arid region, and multi-source datasets from 2000 to 2024 were used. The vegetation growing season was divided into the start of season (SOS), peak of season (POS), and end of season (EOS). Trend analysis, the coupling coordination degree (CCD) model, quadrant analysis, GeoDetector, and PLS-SEM were applied to characterize the spatiotemporal patterns of the Normalized Difference Vegetation Index (NDVI) and EWD, identify their coupling types, and reveal the driving mechanisms of NDVI-EWD coupling. Results and discussion: The results show that: (1) The NDVI and EWD of Xinjiang showed fluctuating upward trends from 2000 to 2024. The improvement of vegetation was mainly concentrated in the northern and southern slopes of the Tianshan Mountains, the Ili River Valley, the southern margin of the Altai Mountains and the periphery of the Tarim Basin. The highest EWD occurred in the POS stage, reaching 139.90 mm. (2) The CCD between NDVI and EWD generally shifted from imbalance toward coordination. Areas characterized by low vegetation cover and limited EWD (LL) remained the dominant coupling type, but their extent continued to decrease. The main transition was toward areas with high vegetation cover and limited EWD (HL). The most active type conversion occurred during the POS stage. (3) Land-use intensity, topographic wetness index, evapotranspiration, temperature and soil organic carbon were identified as important driving factors, and climate, topography and anthropogenic activities affected the coupling intensity through the soil environment, water redistribution and land-use processes. The findings provide scientific support for the assessment of vegetation restoration, the optimization of ecological water-supplementation and the management of water resource carrying capacity in arid regions.