Spatiotemporal evolution and ecological pathways of riparian forests within the ecosystem service cascade framework: a comprehensive analysis from the Irtysh River Basin, China

Abstract

Introduction Riparian forests in the valley area of the Irtysh River Basin (IRB) play a vital role in regulating regional hydrological and carbon processes, and they also serve as critical transboundary habitats for endangered species. However, these forests have been increasingly affected by human activities such as agricultural cultivation and livestock grazing. Methods This study examines the spatial distribution and temporal trends of land use and cover change, and vegetation greenness in the riparian forests in the valley area of the IRB from 1990 to 2020, and assessed four key ecosystem services (water retention, soil conservation, habitat quality, and carbon storage) with the InVEST model. In addition, the influences of land use and cover patterns, vegetation greenness, and other socio-ecological factors on integrated ecosystem services were quantified. Results The results showed that: (1) over the past 30 years, forest cover area declined substantially. Along the main stream of the Irtysh River, which has the largest forested area, the forested area has declined from 352.71 km2 to 163.10 km2. Forest land was primarily converted into sparse woodland and grassland; (2) high vegetation greenness grade exhibited a clear spatial pattern extending along both sides of the river channel. The multi-year mean maximum NDVI remained relatively high at 0.50, with an increasing trend; (3) except for soil conservation, the other three ecosystem services showed strong spatial heterogeneity. From 1990 to 2020, water retention and habitat quality remained relatively stable, whereas soil conservation and carbon storage both declined; (4) land use intensity and vegetation greenness exerted significant negative and positive effects on integrated ecosystem services, with path coefficients of −0.38 and 0.27, respectively. Discussion The findings reveal in clear detail the long-term dynamics and ecological functions of riparian forests in the valley area of the IRB, thereby offering important insights for their future conservation and restoration.