A study on ecohydrological mutual feedback relationship of the Shangdong River basin based on hydrological connectivity

Investigating eco-hydrology in desert grasslands is pivotal to comprehend the dynamic evolution patterns of vegetation. Nonetheless, a research void persists in understanding the eco-hydrological mutual feedback mechanisms associated with hydrological connectivity and the corresponding health index evaluation of a small watershed. This study is centered on the Shangdong River watershed in Inner Mongolia and uses SWAT (Soil and Water Assessment Tool) to simulate hydrological processes. The hydrological connectivity index (IC) was employed as a link to conduct Pearson correlation analysis and Granger causality tests on ecological and meteorological-hydrological factors. Additionally, the PSR model was utilized to assess the ecological health status of the watershed. Key findings reveal the following: (1) The NDVI in the Shangdong River watershed showed an overall upward trend from 2007 to 2018, while IC exhibited an overall downward trend. Temporally and spatially, there was a significant negative correlation between IC and NDVI. (2) During the vegetation growth season, IC serves as a pivotal link in the feedback loop of eco-hydrological processes. Temperature drives vegetation growth, which in turn affects IC. IC regulates soil moisture content and evaporation, further influencing vegetation growth, thus forming a feedback mechanism. (3) Over the study period, the Grassland Health Composite Index (GHI) demonstrated a consistent rise, averaging 0.44, signaling a suboptimal state for the grassland ecosystem. Furthermore, a negative correlation was observed between GHI and IC. Consequently, regulating IC could play a crucial role in safeguarding and rejuvenating the grassland ecosystem. This study offers theoretical and data support for understanding eco-hydrological processes and effective pasture management of the desert grassland watershed.