Impacts of human activities and vegetation cover on key ecosystem services in the Loess Hilly-Gully region of Northern Shaanxi, China.

Clarifying the impacts of human activities and vegetation cover on key ecosystem services (ESs) is of significance for promoting ecological management and achieving sustainable development in ecologically fragile areas. We quantified four key ESs (net primary production, water yield, habitat quality, soil conversation) of the Loess Hilly-Gully region of Northern Shaanxi. We analyzed the spatial and temporal variations of human activities, vegetation cover, and ESs, as well as the impacts of human activities and vegetation cover on ESs by using correlation analyses and segmented linear regressions. Human activities were quantified based on night-time lighting index, population density, and land use data. Results showed that soil conservation, water yield, habitat quality, and total ecosystem service (TES) of the study area had shown a fluctuating upward trend from 2000 to 2020, and that net primary productivity showed a significant increase. The human activity index (HAI) firstly declined and then increased, with an overall downward trend, and the average annual value declined by 17.1%. The fractional vegetation coverage (FVC) first increased and then declined, with an overall rising trend, and the average annual value rose by 9.2%. There was a negative correlation between human activities and ESs, and synergistic relationships between vegetation cover and key ESs, except water production. HAI on ESs firstly decreased and then increased. The impact of FVC on ESs was constantly increasing, and the adaptability of ecosystem services to vegetation changes was gradually strengthening. Our results could provide a reference for the formulation of ecological restoration strategies in ecologically fragile areas.