Abstract: Heihe River Basin is an area with important ecofunction. Changes of ecosystem services in this area greatly impact local socioeconomic development and ecological security. The society-ecology-environment problems have been highly concerned. Therefore, it is of great significance to examine the changes of ecosystem services and the synergies and trade-offs between them. In this study, ecosystem services and related synergies/trade-offs from 1990 to 2015 were quantitatively analyzed by the bivariate pixel by pixel correlation analysis based on time series. The results showed that there were synergies between ecosystem services at the whole region in the Heihe River Basin. There were 19 pairs of ecosystem services with synergy > trade-off: relationship between water yield, water conservation, soil conservation, N retention, P retention and carbon storage; 6 pairs with synergy = trade-off: food supply-water yield/water conservation/soil conservation, biodiversity maintenancewater yield/water conservation/P retention; 2 pairs with synergy < trade-off: biodiversity maintenance soil conservation/N retention. There were obvious regional variations in the synergy/trade-off relationship of ecosystem services. There was no synergy/trade-off relationship in 30% of the region. The spatial distribution of synergy/trade-off relationship varied greatly from north to south. The synergy/trade-off relationship was obvious in the south, being a long strip from southeast to northwest. By contrast, the synergy/trade-off relationship was not obvious in the north, the synergy/tradeoff areas were scattered in many points, flocculent and staggered, with low agglomeration.

Key words: Heihe River Basin, ecosystem services, spatial synergy or trade-off.