Climate change significantly affects vegetation dynamics. Thus, understanding interactions between vegetation and climatic factors is essential for ecological management. This study used kernel Normalized Difference Vegetation Index (kNDVI) and climatic data (temperature, precipitation, humidity, and vapor pressure deficit (VPD)) of China from 2000 to 2022, integrating Geographic Convergent Cross Mapping (GCCM) causal modeling, Extreme Gradient Boosting-Shapley Additive Explanations (XGBoost-SHAP) nonlinear threshold identification, and Geographical Simulation and Optimization Systems-Future Land Use Simulation (GeoSOS-FLUS) spatial prediction modeling to investigate vegetation spatiotemporal characteristics, driving mechanisms, nonlinear thresholds, and future spatial patterns. Results indicated that from 2000 to 2022, China's kNDVI showed an overall increasing trend (annual average ranging from 0.29 to 0.33) with distinct spatial differentiation: 52.77% of areas locating in agricultural and ecological restoration regions in the central-eastern plain) experienced vegetation improvement, whereas 2.68% of areas locating in the southeastern coastal urbanized regions and the Yangtze River Delta experience vegetation degradation. The coefficient of variation (CV) of kNDVI at 0.30-0.40 (accounting for 10.61%) was significantly higher than that of NDVI (accounting for 1.80%). Climate-driven mechanisms exhibited notable library length (L) dependence. At short-term scales (L<50), vegetation-driven transpiration regulated local microclimate, with a causal strength from kNDVI to temperature of 0.04-0.15; at long-term scales (L>100), cumulative temperature effects dominated vegetation dynamics, with a causal strength from temperature to kNDVI of 0.33. Humidity and kNDVI formed bidirectional positive feedback at long-term scales (L=210, causal strength>0.70), whereas the long-term suppressive effect of VPD was particularly pronounced (causal strength=0.21) in arid areas. The optimal threshold intervals identified were temperature at -12.18°C-0.67°C, precipitation at 24.00-159.74 mm, humidity of lower than 22.00%, and VPD of <0.07, 0.17-0.24, and >0.30 kPa; notably, the lower precipitation threshold (24.00 mm) represented the minimum water requirements for vegetation recovery in arid areas. Future kNDVI spatial patterns are projected to continue the trend of "southeastern optimization and northwestern delay" from 2025 to 2040: the area proportion of high kNDVI value (>0.50) will rise from 40.43% to 41.85%, concentrated in the Sichuan Basin and the southern hills; meanwhile, the proportion of low-value areas of kNDVI (0.00-0.10) in the arid northwestern areas will decline by only 1.25%, constrained by sustained temperature and VPD stress. This study provides a scientific basis for vegetation dynamic regulation and sustainable development under climate change.

Drought is a natural disaster that significantly impacts the Earth's ecological environment, especially in arid and semi-arid areas. However, drought at a large watershed scale, which plays an important role in sustainable environmental development, has received limited attention. In this study, we analyzed the spatial and temporal variations in drought in the Yellow River Basin, China from 2002 to 2022 and its driving factors using a vegetation health index (VHI). Results showed that average VHI in the Yellow River Basin from 2002 to 2022 was 0.581, with the most severe drought occurring in summer and autumn. The basin showed a slow decreasing trend in drought during the study period. Regarding spatial distribution of monthly drought frequency and trend of VHI, the mean of the frequency was 13.00%, and 78.00% had a drought frequency of 10.00%-20.00%, with moderate drought generally prevailing. Regarding land use types, forest land, grassland, agricultural land, construction land, water body, and wasteland showed a descending order for the annual average VHI. VHI of each land use type was the lowest in summer and autumn, with pronounced seasonal characteristics. The uneven distribution of drought in the Yellow River Basin was primarily influenced by annual precipitation, solar-induced chlorophyll fluorescence, and relative humidity. VHI effectively quantified drought conditions at a regional scale and proved to be highly applicable in the Yellow River Basin. The results clarify the effectiveness of VHI for drought monitoring in the Yellow River Basin and can provide a reference for drought monitoring across the basin.

Accurately revealing the spatial heterogeneity in the trade-offs and synergies of land use functions (LUFs) and their driving factors is imperative for advancing sustainable land utilization and optimizing land use planning. This is especially critical for ecologically vulnerable inland river basins in arid regions. However, existing methods struggle to effectively capture complex nonlinear interactions among environmental factors and their multifaceted relationships with trade-offs and synergies of LUFs, especially for the inland river basins in arid regions. Consequently, this study focused on the middle reaches of the Heihe River Basin (MHRB), an arid inland river basin in northwestern China. Using land use, socioeconomic, meteorological, and hydrological data from 2000 to 2020, we analyzed the spatiotemporal patterns of LUFs and their trade-off and synergy relationships from the perspective of production, living, ecological functions. Additionally, we employed an integrated Extreme Gradient Boosting (XGBoost)-SHapley Additive exPlanations (SHAP) framework to investigate the environmental factors influencing the spatial heterogeneity in the trade-offs and synergies of LUFs. Our findings reveal that from 2000 to 2020, the production, living, and ecological functions of land use within the MHRB exhibited an increasing trend, demonstrating a distinct spatial pattern of ''high in the southwest and low in the northeast''. Significant spatial heterogeneity defined the trade-off and synergistic relationships, with trade-offs dominating human activity-intensive oasis areas, while synergies prevailed in other areas. During the study period, synergistic relationships between production and living functions and between production and ecological functions were relatively robust, whereas synergies in living-ecological functions remained weaker. Natural factors (digital elevation model (DEM), annual mean temperature, Normalized Difference Vegetation Index (NDVI), and annual precipitation) emerged as the primary factors driving the trade-offs and synergies of LUFs, followed by socioeconomic factors (population density, Gross Domestic Product (GDP), and land use intensity), while distance factors (distance to water bodies, distance to residential areas, and distance to roads) exerted minimal influence. Notably, the interactions among NDVI, annual mean temperature, DEM, and land use intensity exerted the most substantial impacts on the relationships among LUFs. This study provides novel perspectives and methodologies for unraveling the mechanisms underlying the spatial heterogeneity in the trade-offs and synergies of LUFs, offering scientific insights to inform regional land use planning and sustainable natural resource management in inland river basins in arid regions.

Territorial spatial ecological restoration is a crucial prerequisite for optimizing the territorial spatial patterns, enhancing the ecosystem functions, and achieving sustainable development at the regional scale. The Qaidam Basin, located in the alpine arid region of the Qinghai-Xizang Plateau, China, is experiencing desertification, biodiversity loss, soil erosion, and environmental pollution. Selecting the Qaidam Basin as the study area, we identified 9 ecological sources in the region using the Morphological Spatial Pattern Analysis (MSPA) method and the landscape connectivity assessment, and extracted 10 significant corridors and 26 general corridors using the Minimum Cumulative Resistance (MCR) and Gravity models. Then, we determined 114 ecological "pinch points" and 42 ecological barrier points by employing the Circuit Theory, thereby constructing the ecological security pattern of the area. Further, we evaluated the ecosystem health of the Qaidam Basin during 2003-2023 using the Vitality-Organization-Resilience-Service (VORS) model. Finally, we integrated ecosystem health assessment and ecological security pattern to comprehensively identify the key areas for ecological restoration in the Qaidam Basin. The results revealed that the ecosystem in the basin fluctuated toward a healthier state from 2003 to 2023. The average ecosystem health index (EHI) for the basin decreased from 0.34 in 2003 to 0.28 in 2013, followed by a substantial recovery to 0.36 in 2023. Higher EHI values were found in the northeastern, southeastern, and southwestern fringes and lower values were located in the basin interior and northwestern region. During 2003-2023, the areas that exhibited a decrease in EHI were primarily located in the interior and northwestern regions of the basin, while those that exhibited an increase in EHI were located in the northeastern, southeastern, and southwestern fringes, demonstrating expanded spatial differences. This may be attributed to the fact that once an eco-environment is damaged, the ecological recovery of the vulnerable areas within the eco-environment will be slow and difficult. This study identified four types of ecological restoration areas, including corridor connectivity, artificial restoration, ecological recovery, and ecological enhancement zones, covering a total area of 6034.7 km², and proposed targeted ecological restoration strategies according to these different categories. Our findings can serve as a valuable reference for optimizing the territorial spatial patterns, enhancing the ecosystem functions, and promoting sustainable development in the Qaidam Basin.

In recent years, many studies have focused on the effects of global climate warming and increased nitrogen deposition on the structure and function of grassland ecosystem. However, there are still significant uncertainties in the response mechanism of stability of plant community biomass in alpine meadows of the Qinghai-Xizang Plateau, China to these two major climate factors. Given this, based on field control experiments, this study systematically evaluated the effects of different levels of climate warming (W0 (no warming), W1 (air temperature increased by 0.47°C or soil temperature increased by 0.61°C), W2 (air temperature increased by 0.92°C or soil temperature increased by 1.09°C), W3 (air temperature increased by 1.44°C or soil temperature increased by 1.95°C)), nitrogen deposition ((N0 (0 kg N/(hm²•a), N16 (16 kg N/(hm²•a), and N32 (32 kg N/(hm²•a)), and their interactions on plant community biomass and its temporal stability, and explored its potential regulatory mechanisms. The results showed that the biomass of total community, Gramineae, and dominant species increased significantly with increasing temperature, but the biomass of common and rare species decreased significantly. Nitrogen deposition also significantly promoted the biomass accumulation of community and gramineous plants. Under the treatment of W3N32, the biomass of plant community, Gramineae, and dominant species reached the highest values, indicating that there was a synergistic effect under this treatment. Structural equation model showed that increasing temperature significantly decreased the stability of plant community biomass by reducing the stability of grass and dominant species biomass and weakening species asynchronism. Interaction of increased nitrogen deposition and temperature increased the biomass fluctuation of grass functional group, thus amplifying its negative influence on community stability. More attention should be paid to the response and regulatory mechanisms of dominant species and functional groups under global climate change. This study provides a theoretical basis for revealing the stability maintenance mechanism of alpine grassland and also provides scientific support for the development of future grassland ecosystem management and assessment.

Grassland shrub encroachment is a phenomenon that is prevalent in arid and semi-arid regions worldwide, impacting grassland ecosystems in several ways. In the context of escalating climate change and human activities, examining the nutrient and stoichiometric characteristics of Spiraea shrubs in grassland ecosystems, along with their relationships with environmental factors, can yield valuable insights into the nutrient utilization and survival strategies of these shrubs. This, in turn, offers a scientific foundation for developing future conservation measures. This study was conducted in July 2023 in the Altay Mountains, Northwest China, where Spiraea shrubs thrive across five grassland types: temperate steppe desert, temperate desert steppe, temperate steppe, temperate meadow steppe, and mountain meadow. Leaf and soil samples were collected from each grassland type to analyze the concentrations of carbon (C), nitrogen (N), and phosphorus (P), as well as the stoichiometric characteristics of both the leaves and soil. Subsequently, correlation analysis and redundancy analysis (RDA) were conducted to investigate the variations in leaf C, N, and P concentrations and leaf stoichiometry of Spiraea shrubs as well as their influencing factors. The results indicated the presence of significant or highly significant differences (P<0.050) in the leaf C, N, and P concentrations and leaf stoichiometry (C:N, C:P, and N:P ratios) of Spiraea shrubs across the five grassland types. The N:P ratios of Spiraea shrub leaves in the five grassland types ranged from 7.37 to 11.77, suggesting that N availability generally limits the growth of Spiraea shrubs. Results of RDA revealed that the most significant contributors to the C, N, and P concentrations and stoichiometric characteristics of Spiraea shrub leaves were in the following order: soil total N>mean annual precipitation>elevation>soil pH>soil organic C>mean annual temperature. These factors had contribution rates of 35.32%, 13.19%, 10.20%, 8.82%, 8.34%, and 6.48%, respectively. It was determined that soil nutrients have a greater impact on the growth and nutrient accumulation of Spiraea shrubs compared to climatic factors. This study makes an important contribution to the theoretical basis and data support, enabling a deeper understanding of the response mechanisms of shrub species in the grassland ecosystems of the Altay Mountains to climate change.

Continuous cropping can lead to soil environment deterioration, cause plant health problems, and reduce crop productivity. However, the response mechanisms of soil microbial co-occurrence patterns to the duration of continuous melon cropping remain poorly understood. Here, we employed the metagenomic techniques to comparatively investigate the bulk and rhizosphere soil microbial communities of major melon-producing regions (where the duration of continuous melon cropping ranges from 1 to 30 a) in the eastern and southern parts of Xinjiang Uygur Autonomous Region, China. The results showed that soil pH clearly decreased with increasing melon cropping duration, while soil electrical conductivity (EC) and the other soil nutrient indices increased with increasing melon cropping duration (with the exception of AN and TK in the southern melon-producing region). The most dominant bacterial phyla were Proteobacteria and Actinobacteria, and the most abundant fungal phyla were Ascomycota and Mucoromycota. Redundancy analysis (RDA) indicated that soil pH and EC had no significant effects on the bacterial communities. However, after many years of continuous melon cropping in the southern melon-producing region, fungal communities were significantly negatively correlated with soil pH and significantly positively correlated with soil EC (P<0.050). Co-occurrence network analysis showed that continuous melon cropping increased the complexity but decreased the connectivity of the cross-domain microbial networks. Moreover, the enrichment patterns of microorganisms in the main microbial network modules varied significantly with the duration of continuous melon cropping. Based on the analysis of keystone taxa, we found that continuous melon cropping increased some plant pathogens (e.g., Fusarium and Stagonospora) but decreased beneficial bacteria (e.g., Mesorhizobium and Pseudoxanthomonas). In conclusion, this study has greatly enhanced the understanding of the effects of continuous melon cropping on alterations in the microbial community structure and ecological networks in Xinjiang.

Soil organic carbon (SOC) and total nitrogen (TN) play an important role in the global carbon and nitrogen cycles. Soil aggregates are critical reservoir of SOC and TN. Therefore, in areas with severe wind erosion, the changes in the accumulation of SOC, TN, clay, silt, and sand contents within different dry aggregate size fractions can offer crucial insights into soil conservation by the control of wind erosion. In this study, surface soil samples (0-5 cm depth) were collected from farmland and grassland in the Bashang region of northern China in 2020. The bulk soil and aggregate size fractions were used to determine the concentrations of SOC, TN, clay, silt, and sand. The results showed that: (1) farmland had lower SOC and higher TN than grassland; (2) SOC in the aggregates of farmland decreased with increasing aggregate size (P<0.010), while SOC in the aggregates of grassland increased with increasing aggregate size (P<0.010), and nonsignificant variation of TN and clay was observed among different aggregate sizes; (3) the mean of aggregate silt significantly decreased with increasing aggregate size and the mean of aggregate sand increased with increasing aggregate size (P<0.001); (4) no correlations between sand or silt of aggregate and TN or texture of bulk soil was found; and (5) SOC in bulk soil was correlated with those in different aggregate sizes, and was also affected by the texture of bulk soil (P<0.010). This study highlights the role of dry soil aggregate size in the redistribution of SOC, TN, clay, silt, and sand contents under different land uses, thereby facilitating the understanding of the process of wind erosion induced SOC, TN, and mineral dust emission.