Scale Effects on Ecosystem Service Interactions and Driving Factors in the Three River Source Basin: Insights and Management Implications

Unveiling the scale effects on the interactions and driving factors of ecosystem services (ESs) contributes to the differentiated conservation of ESs across multiple scales. Utilizing models such as Integrated Valuation of Ecosystem Services and Trade-offs (InVEST), Self-organizing map (SOM), and Geographic Detector, we analyzed the spatiotemporal changes, interactions, and dominant driving factors of water yield (WY), soil conservation (SC), carbon storage (CS), and habitat quality (HQ) in the Three River Source Basin (TRSB) from 2000 to 2020 at both grid and sub-watershed scales; explored the impact of scale effects; and proposed ecological conservation strategies. The results indicated the following: (1) Over the 20 years, the average values of WY, SC, CS, and HQ in the TRSB were 146.12 mm, 10.95 t, 224.77 gC m−2, and 0.6942, respectively, which exhibited a distribution with lower values in the northwest and higher values in the southeast. Over the study period, WY and SC experienced declines at rates of −7.26 mm per 5 years and −0.08 t per 5 years, while CS and HQ showed increases at rates of 6.97 gC m−2 per 5 years and 0.007 per 5 years. (2) The relationships among WY, SC, and CS were primarily synergistic, whereas HQ exhibited more trade-offs with other ESs, and as the scale increased, the trade-off effects diminished, and synergistic effects were enhanced. (3) ESs were influenced by a combination of factors, and the interactions among these factors strengthened the explanatory power regarding ESs. Increasing vegetation cover and reducing irrational human activities were effective approaches to enhance the ESs in the TRSB. This study helps to expand the understanding of the relationships among ESs and the effects of scale, providing support for the protection and sustainable development of the TRSB ecosystem.