Abstract: Sanjiangyuan National Park is one of the most sensitive and fragile ecosystems in China. Assessing and simulating ecosystem service value (ESV) can fill the knowledge gap for ecological protection and restoration. We constructed an ESV assessment model based on economically modified equivalent factor method and land use data to explore the spatial-temporal variations of ESV in Sanjiangyuan National Park from 2005 to 2020. The Patch-generating Land Use Simulation (PLUS) model was used to predict the characteristics of ESV under four scenarios (i.e., natural evolution, water protection, forest and grassland vegetation protection, and ecological protection) in 2035. The ESV of Sanjiangyuan National Park showed an increasing trend from 3.77×10¹¹ yuan in 2005 to 3.93×10¹¹ yuan in 2020. The ESV was affected by water, grassland, snow/ice and barren land. The change of water area had a significant impact on the change of ESV (with an average contribution rate of 67.8%). Under the four scenarios simulated by PLUS model, the ESV values in 2035 were higher than that of 2020. The ecological protection scenario had the highest ESV, reaching 4.21×10¹¹ yuan, an increase of 7.2% compared to 2020. Our findings suggest that the comprehensive ecological protection of forests, grasslands, and water areas should be emphasized in the resource protection planning of Sanjiangyuan National Park to promote the improvement of ESV.

Key words: ecosystem service value, spatial-temporal evolution, scenario simulation, Sanjiangyuan National Park