Spatiotemporal interaction and attribution analysis of ecosystem health and human activities in the Daxing'anling forest-grassland Ecotone, China.

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.