Assessing vegetation changes in alpine arid and fragile ecosystems is imperative for informed ecological restoration initiatives and adaptive ecosystem management. Previous studies primarily employed the Normalized Difference Vegetation Index (NDVI) to reveal vegetation dynamics, ignoring the spatial heterogeneity alterations caused by bare soil. In this study, we used a comprehensive analysis of NDVI and its spatial heterogeneity to examine the vegetation changes across the Three-River Headwaters Region (TRHR) over the past two decades. A random forest model was used to elucidate the underlying causes of these changes. We found that between 2000 and 2022, 9.4% of the regions exhibited significant changes in both NDVI and its spatial heterogeneity. These regions were categorized into six distinct types of vegetation change: improving conditions (62.1%), regrowing conditions (11.0%), slight degradation (16.2%), medium degradation (8.4%), severe degradation (2.0%), and desertification (0.3%). In comparison with steppe regions, meadows showed a greater proportion of improved conditions and medium degradation, whereas steppes had more instances of regrowth and slight degradation. Climate variables are the dominant factors that caused vegetation changes, with contributions to NDVI and spatial heterogeneity reaching 68.9% and 73.2%, respectively. Temperature is the primary driver of vegetation dynamics across the different types of change, with a more pronounced impact in meadows. In severely degraded steppe and meadow regions, grazing intensity emerged as the predominant driver of NDVI change, with an importance value exceeding 0.50. Notably, as degradation progressed from slight to severe, the significance of this factor correspondingly increased. Our findings can provide effective information for guiding the implementation of ecological restoration projects and the sustainable management of alpine arid ecosystems.

Understanding the drying mechanism is critical for formulating targeted mitigation strategies to combat drought impacts. This study aimed to reveal divergent drying mechanisms in humid and non-humid regions across China from the multidimensional perspectives of climate, vegetation, and energy balance. During the period 1982–2012, the Standardized Precipitation Evapotranspiration Index (SPEI) revealed non-significant drying trends across China. Simultaneously, temperature and precipitation indicated a warming and drying pattern in the humid regions, contrasted with a warming and moistening pattern in the non-humid areas. The coupling effects of declined precipitation, increased vegetation coverage, and elevated temperature exacerbated dryness in the humid regions, while pronounced warming dominantly caused dryness in the non-humid regions. The inverse correlations between the actual evapotranspiration (ET) with precipitation and potential ET (PET) highlighted the principal role of moisture availability in divergent drying mechanisms over humid and non-humid regions. Random Forest models recognized precipitation and PET as the primary factors influencing SPEI in the humid and non-humid regions, respectively. Ongoing warming from 2013 to 2022 mitigated dryness in the humid regions due to the increased latent heat at the expense of sensible heat. Conversely, warming, amplified by the heightened sensible heat, exacerbated drought in the non-humid regions. By identifying the contrasting responses of humid and non-humid regions to warming and moisture availability, this study provides crucial insights for policymakers to mitigate drought impacts and enhance resilience in vulnerable non-humid areas.

The resilience of urban agglomerations (UAs) is recognized because of their ability to withstand, adapt to, and recover from natural disasters and social threats. However, limited information on the resilience of specific urban agglomerations may hinder their sustainable development. The emerging concept of Social–Ecological–Technological system (SETS) resilience presents a novel framework for understanding and evaluating the resilience of UAs. Taking the Beijing–Tianjin–Hebei urban agglomeration (BTHUA) as a case study, we constructed a comprehensive resilience assessment framework. By incorporating the coupling coordination degree (CCD) model, modified gravity model, standard deviation ellipse, and obstacle degree model, we systematically evaluated the BTHUA’s SETS resilience. The results show that from 2010 to 2022, both the SETS resilience and its CCD in the BTHUA improved significantly. All the cities reached the coordination stage, with CCD values exceeding 0.6. The key cities enhanced their influence on the surrounding cities, resulting in a more robust and interconnected intercity resilience network. However, the BTHUA still confronts challenges in resource endowment, technological innovation, and public services, which warrant a more integrated and systematic approach to enhance regional SETS resilience.

Increasing precipitation variability has been tightly coupled to livestock grazing through direct impacts on vegetation productivity in rangeland ecosystems. However, where and to what extent such impacts occur has not been quantified systematically at the regional scale; thus, adaptive grazing management is plagued by this knowledge gap. Hence, using 20 years of precipitation, rangeland productivity, and livestock density data across Tibet, we assessed long-term precipitation variability impacts on alpine rangeland grazing, specifically highlighting variations in intra- and inter-annual precipitation variability. We showed that the precipitation concentration index (PCI) and coefficient of variation in precipitation (CVP) both increased significantly across Tibet over the past two decades, especially in the western region. On the contrary, grazing intensity (GI) in most rangeland areas markedly declined over the same period. Moreover, we found that GI is highly responsive to PCI and CVP for the alpine steppe, but interestingly, only PCI is significantly associated with GI for the alpine meadow. Furthermore, the Granger causality test indicates an extremely significant causality between GI and PCI, further highlighting that PCI was a remarkable determinant of rangeland grazing over the last two decades. Notably, we statistically identified rangelands with higher precipitation variability that experienced intensive livestock grazing, specifically, GI responded positively to CVP and PCI. In conclusion, our findings provide novel support for the increasing precipitation variability impacts on rangeland grazing over time across Tibet, especially the intra-annual variation. Thus, we advocate the implementation of adaptive grazing management, such as excluding and minimizing grazing for the alpine rangeland ecosystem under higher precipitation variability.

Cover crops have been recognized as a sustainable practice to improve soil structure and fertility in intensive agroecosystems, yet quantitative evidence on their effects and underlying mechanisms remains limited in high-altitude cereal cropping systems. This study investigated the effects of diverse cover crops on soil physicochemical properties during fallow in southern Tibetan cereal cropping systems, quantified their effect sizes relative to bare fallow, and explored the associations among key soil properties. Results showed significant variations in 0–20 cm soil physicochemical properties among cover crop species. Specifically, the oat (Avena sativa)–common vetch (Vicia sativa) mixture significantly reduced soil pH and increased water-stable aggregate rate (WSAR), total carbon (TC), and C/N ratio compared with turnip (Brassica rapa var. L.) and common vetch monocultures, whereas bulk density, total nitrogen, and soil organic matter (SOM) did not differ among cover crop treatments. Effect size analysis indicated that cover crops significantly reduced soil pH by 3.39% and increased WSAR by 32.85%. Principal component analysis and the piecewise structural equation model revealed that soil pH, WSAR, TC, and SOM collectively explained 86.18% of the observed variation in soil physicochemical properties, with pH significantly and positively affecting TC but negatively influencing WSAR, which in turn strongly promoted TC and thereby greatly enhanced SOM. These findings demonstrate that cover crops substantially improve selected soil physicochemical properties, providing critical evidence for their integration into bare fallow to enhance soil health in high-altitude cereal cropping systems.