Contrasting sensitivity and resilience to soil moisture and vapor pressure deficit between natural and planted forests under afforestation projects

Large-scale afforestation projects have significantly altered the temporal variability and spatial heterogeneity of regional water resources. The sensitivity of vegetation to hydrological changes and resilience are critical for understanding ecosystem adaptive capacity and stability. Clarifying how water resource variability and availability affect ecosystem sensitivity and resilience, and analyzing differences in ecological adaptation between planted and natural forests under afforestation, are essential for developing effective ecosystem management strategies and afforestation projects. This study constructed an ecosystem stability index based on sensitivity and resilience, and analyzed the controlling effects of water availability and variability on vegetation resilience from the perspectives of soil moisture (SM) and vapor pressure deficit (VPD). Results showed that ecosystems were more sensitive to SM variability than to VPD. Vegetation resilience was higher in areas with adequate moisture, whereas it was lower in regions with more pronounced moisture variations. Spatially, SM availability explained 55.6 % of the variation in vegetation resilience, while VPD availability explained 8.7 %. Natural forests had a higher sensitivity to moisture variability than planted forests (p < 0.05). The average resilience of natural forests was significantly higher than that of planted forests (p < 0.05). These results emphasize the importance of conserving and optimizing natural forest ecosystems. A comprehensive assessment of local soil moisture availability is recommended for future terrestrial ecosystem conservation projects.