Abstract: It is of significance to understand trade-offs and synergies of ecosystem services (ESs) for ecosystem management and efficient resource allocation. Based on data of land use, meteorology, soil and normalized vegetation index (NDVI), we analyzed the spatiotemporal variations of four ESs (i.e., soil conservation, net primary productivity (NPP), habitat quality, and water yield) in Yan’an City from 2000 to 2020. Moreover, hot spot regions of four ESs were identified. The trade-offs and synergies among ESs were analyzed at city, county, and basin scales. The amount of ESs in different land use types was calculated. The results showed that soil conservation increased greatly, carbon sequestration decreased firstly and then increased, habitat quality was slightly declined, and water yield increased firstly and then decreased, and thus the spatial pattern of the four ESs remained basically unchanged from 2000 to 2020. The proportion of non-hot spot areas, Ⅰ areas and IV areas decreased significantly, the proportion of the Ⅱ areas and Ⅲ areas increased greatly. The relationship among ESs in Yan’an as a whole was mainly synergetic, whereas such relationships at county and watershed scales were different from that at the whole city scale. Forest land was a major land use type that provided ESs in Yan’an region. The combination of land use type, soil type, climate, and terrain were the main factors driving the scale effects on the relationships between ESs tradeoffs and synergies.

Key words: ecosystem services, spatiotemporal variation, hot spot, multi-scale representation.