Introduction: The Daxing'anling forest-grassland ecotone is a critical ecological barrier in northern China and plays an essential role in maintaining regional ecological security. In recent decades, intensified regional development has increased human–environment conflicts; however, the spatiotemporal feedback mechanisms between ecosystem health (EHI) and human activity intensity (HAI) remain insufficiently understood. Methods: This study proposes a multi-scale Assessment–Coupling–Driving framework. Ecosystem health was quantified using the Vitality–Organization–Resilience–Service (VORS) model, while HAI was constructed by integrating multi-source socioeconomic and environmental datasets. Spatial statistical analyses and XGBoost-SHAP machine learning were applied to investigate spatiotemporal interactions and driving mechanisms of the human–environment system from 2000 to 2023. Results: From 2000 to 2023, EHI increased by 25.1%, yet strong spatial heterogeneity persisted. Higher EHI was observed in northern primary forest areas, whereas ecological degradation hotspots were concentrated in the southern agro-pastoral ecotone, largely driven by urbanization and agricultural expansion. HAI increased by 16.3%, exhibiting a high-in-plains and low-in-mountainous-areas spatial pattern, indicating strong topographic constraints on human activities. A significant negative spatial correlation was detected between HAI and EHI (Moran’s I = −0.62). Coupling coordination degree analysis revealed a 6.9% expansion of ecological protection zones with low coordination levels, identifying the region as a major conflict zone requiring urgent governance. Potential conservation areas accounted for 48.7% of the total area, highlighting their importance in maintaining regional ecological security. XGBoost-SHAP results demonstrated nonlinear threshold effects of key drivers. Potential evapotranspiration (PET) and low temperatures suppressed EHI, whereas plant available water enhanced ecological stability. Temperatures above 0°C promoted EHI and, together with high GDP, intensified HAI, while PET exceeding 850 mm inhibited HAI. Temperature and precipitation erosive forces dominated coupling coordination, and GDP exhibited a weak positive effect that became negative after exceeding a critical threshold. Discussion: The findings reveal clear spatial trade-offs and nonlinear threshold effects governing the coupled evolution of ecosystem health and human activities in the Daxing'anling ecotone. The proposed framework provides a scientific basis for coordinated optimization of ecological protection and regional development through process analysis, threshold identification, and zoning-based regulation.

Morus mongolica holds significant value in medicinal applications, livestock fodder production, and ecological restoration. Although polyploidization is we

Objectives: Grassland net primary productivity (NPP) in the Ili River Basin Grasslands, as Earth's largest terrestrial ecosystem, are crucial for global carbon cycling and ecological stability. Clarifying the spatiotemporal patterns and driving factors of grassland NPP is key to optimizing conservation strategies and enhancing productivity. Methods: Using MODIS data (2000–2022) and the CASA model, this study estimated grassland NPP in the Ili River Basin, and explored its dynamic characteristics and responses to climate and human activities through trend analysis, correlation analysis, and the Hurst index. Results: (1) NPP increased annually by 0.14% from 2000 to 2020, but decreased by 15.4% from 2020 to 2022, with an overall 12.95% decline over 23 years; extreme climates in 2008, 2014, and 2021 caused NPP to drop by 27.24%, 28.01%, and 21.31%, respectively, compared to the previous years. (2) High-NPP areas were concentrated in eastern mountainous regions (Nileke, Zhaosu, Tekes, etc.), while low-NPP areas were distributed in central urban zones and high-altitude regions, showing an “east-high-west-low” pattern. (3) Temperature was the main climatic driver (affecting 91,253 km²); human activities led to NPP decline in 55.94% of the area (far exceeding the 2.81% where NPP increased). (4) The Hurst index projected that 79.5% of the area would shift from decline to increase, 8% would continue to decline, and 9.81% would reverse from increase to decline. Conclusions: NPP showed a downward trend from 2000 to 2022 but is expected to rise significantly in the future, providing references for conservation efforts.

Permafrost wetlands are important components of the global carbon cycle, functioning as carbon stores while also releasing methane (CH₄). Although biochar amendment has been proposed as a strategy to mitigate greenhouse gas (GHG) emissions, its effectiveness in permafrost wetland soils under contrasting moisture regimes remains uncertain. We conducted a 100-day incubation experiment to examine the effects of pine-sawdust biochar produced at 300 or 800 °C and applied at five rates (0%, 1%, 3%, 5%, and 8%, w/w) on soil properties, enzyme activities, and CO₂ and CH₄ emissions under non-flooded and waterlogged conditions. Biochar addition altered soil pH, carbon and nitrogen pools, and enzyme activities, with responses varying between moisture regimes. Under non-flooded conditions, 300 °C biochar reduced soil pH and increased nitrate nitrogen (NO₃⁻-N), whereas under waterlogged conditions, biochar treatments increased soil pH and were associated with higher ammonium nitrogen (NH₄⁺-N) and lower NO₃⁻-N concentrations. Biochar generally reduced CO₂ emissions under non-flooded conditions and CH₄ emissions under waterlogged conditions. The 8% amendment of 800 °C biochar under waterlogged conditions yielded the lowest reported global warming potential (GWP; 5.49 ± 0.15 g·kg⁻¹). Enzyme responses also depended on moisture regime: dehydrogenase and urease activities generally declined under waterlogged conditions, whereas 300 °C biochar increased catalase activity. Pearson correlation and SHapley Additive exPlanations (SHAP) analyses identified NH₄⁺-N (29.3%) and catalase activity (17.4%) as the two leading predictors of GWP in the fitted model. These findings suggest that biochar amendment can reduce GHG emissions during laboratory incubation, although the magnitude and direction of the response depend on pyrolysis temperature, application rate, and moisture regime. Among the treatments tested, the 8% amendment of 800 °C biochar under waterlogged conditions produced the lowest GWP.

The Desert ecosystems are among the most vulnerable ecosystems globally, and maintaining their vegetation carbon balance is crucial for ensuring regional ecological stability and achieving the United Nations Sustainable Development Goals (SDGs) and Paris Agreement established the carbon neutrality target. For this purpose, this study focusing on China's arid regions, integrated GLASS NPP, soil, topographic, and meteorological data (including 16 extreme climate indicators) from 2000 to 2022. We employed trend analysis and geographical detectors to elucidate the spatiotemporal patterns and driving mechanisms of vegetation Net Ecosystem Productivity (NEP). The results indicated: (1) From 2000 to 2022, vegetation NEP exhibited an overall fluctuating upward trend. Spatially, carbon sinks decreased gradually from the relatively humid east to the extremely arid west, with carbon sources concentrated in localized areas of Xinjiang. (2) Absorbed photosynthetically active radiation (APAR) was the dominant driver of NEP changes, followed by precipitation, with both showing significant synergistic enhancement. While single extreme climate factors had a relatively weak influence across the entire region, their impact was pronounced in semi-arid zones, particularly the monthly maximum value of daily minimum temperature (TNX). Notably, the explanatory power of factor interactions increased significantly in these vulnerable zones. This study not only reveals the driving mechanisms and climate response patterns of ecosystem carbon sinks in China's arid regions under extreme climate stress, but also provides important scientific support for precise ecological restoration, maintaining regional ecological security, and implementing sustainable development goals.