Quantitatively linking ecosystem service functions with soil moisture and ecohydrology regimes in watershed

The ecohydrological processes of terrestrial and riverine systems in watershed under changing environments exerted significant pressure on ecosystem service functions. However, the response directions of these functions to the magnitude, frequency, duration, timing, and rate of change in ecohydrological conditions remain largely unknown. Beginning with the water yield and confluence mechanism of the terrestrial system in the watershed, we integrated ecohydrological theory with apportionment entropy theory to establish linkages between ecohydrological processes and ecosystem service indicators. Coupling physical hydrological models with machine learning methods, we quantified the differences in the contributions of driving forces to hydrological conditions at seasonal and monthly scales. At the grid scale, the study determined that human activities enhanced the correlation between water levels and soil moisture by affecting the water yield and runoff processes in the watershed. The dynamic characteristics of the interaction types of climatic factors deepened the spatial heterogeneity of water yield functions. Additionally, the flattening process of water level fluctuations under changing environments had varying impacts on different ecosystem service functions. The water level duration and timing corresponding to ecosystem service functions in the current watershed required urgent attention. Notably, the changes in the five sets of established ecosystem service function parameters were 13.16 %, 7.42 %, 66.47 %, 33.99 %, and 24.47 %, respectively. Human activities accounted for 51 % of water level changes on an annual scale, 65 % during the second quarter of the year, and reached 86 % in September. The emptying effect caused by reservoir storage must not be overlooked in its impact on ecosystem service functions. This study, which focuses on the response mechanisms between hydrological processes and watershed ecosystem service functions, establishes a quantitative evaluation framework for assessing the impact of water level changes on ecosystem services, thereby providing a foundation for future exploration of the cascading effects of ecosystem services centered on ecohydrological processes.