A systematic understanding of the spatial and temporal changes of grassland fractional vegetation cover (FVC) in Xinjiang and its drivers provide scientific reference for regional ecological restoration. In this study, we used MODIS EVI data from 2000 to 2023 and the Pixel binary model to estimate the grassland FVC value of Xinjiang; analyze its spatiotemporal dynamics with combination of trend and persistence detection methods; and explore its driving factors with ridge regression and residual analysis. The results show the following: (1) From 2000 to 2020, the grassland FVC in Xinjiang experienced an upward trend on the whole, yet a significant decrease after 2020. Spatially, the distribution characteristics are high in the northwest and low in the southeast, decreasing from mountains to basins. (2) Precipitation and soil moisture affected FVC positively, with contributions of 18.6% and 38.3%, respectively, while air temperature and solar radiation affected it negatively, with contributions of 22.9% and 20.2%, respectively. (3) The change in the grassland FVC in Xinjiang resulted from a combination of climatic factors and human activity, whose relative contribution rates were 57.2% and 42.8%, respectively; furthermore, the areas with positive effects on the FVC were smaller than those with negative effects. (4) While the FVCs of most grassland types in Xinjiang were dominantly influenced by both climatic factors and human activity, climatic conditions were the dominant drivers of the FVCs of temperate typical grasslands and temperate desert grasslands, whereas human activities had more influence on the FVC of temperate meadow grasslands. This study provides a scientific basis and guidance for optimizing the ecological barrier function and regulating vegetation coverage in arid areas by analyzing the spatiotemporal dynamics of grassland coverage in Xinjiang and quantifying the impact of different environmental factors on it.

Comprehending the role of stand density in soil properties and microbial communities is crucial for optimizing forest ecosystem functions. However, the relationship between them and how they respond to key environmental drivers at different planting densities remains unclear. In this study, we investigated the growth indices, soil properties, as well as soil microbial community composition and diversity of two Xanthoceras sorbifolium provenances (YC and KL) under three planting densities (low, medium, and high). Results indicated: (1) soil nutrient levels decreased with increasing stand density, while microbial community diversity was highest at medium density, followed by low and high density. Low planting density was more favorable for X. sorbifolium growth. (2) Microbial co-occurrence network stability was highest under medium and low densities. The assembly of bacterial communities was primarily governed by deterministic processes, whereas fungal community assembly was predominantly stochastic. (3) Soil total phosphorus (TP) and available potassium (AK) were the main drivers affecting microbial communities and their structures. (4) Compared with high-density soil, there were more abundant functional communities of bacteria and fungi in low- and medium-density soils, showing better adaptability to environmental changes and disturbances. These results will provide a scientific basis for the management optimization of X. sorbifolium plantations and are of great significance for the sustainable development of forest ecosystems.

A systematic understanding of spatiotemporal changes in fractional vegetation cover (FVC) of the Xinjiang grassland and its drivers serve as a scientific reference for regional ecological restoration and sustainable development. Based on the MODIS EVI data from 2000 to 2023, this study estimated Xinjiang grassland FVC by using the dimidiate pixel model, analyzed its spatiotemporal dynamics with the Theil-Sen trend analysis, Mann-Kendall test and Hurst index method, and explored the driving factors by ridge regression and residual analysis. The results showed that: (1) From 2000 to 2020, Xinjiang grassland FVC experienced an upward trend on the whole, yet a significant decrease after 2020. Spatially, it was distributed as high in the northwest and low in the southeast, and decreasing from mountains to basins. (2) Precipitation and soil moisture affected FVC positively, with contributions of 18.6% and 38.3%, respectively; while air temperature and solar radiation affected negatively, with contributions of 22.9% and 20.2%, respectively. (3) Climate change and human activities contributed 57.2% and 42.8% respectively to Xinjiang grassland FVC with 60.8% of grassland FVC dominated by climate change and 39.2% by human activities. (4) While most grassland types in Xinjiang have FVCs driven by joint actions of climate change and human activities, climatic conditions were dominant drivers of FVC in temperate typical grasslands and temperate desert grasslands, whereas human activities had more influence on FVC in temperate meadow grasslands. This study quantified the dual driving mechanisms of climate change and human activities together with their respective contributions by analyzing the spatiotemporal evolution characteristics of Xinjiang grassland FVC, thus providing scientific support and guidance for optimizing the ecological barrier functions and regulating the vegetation cover in arid zones.