Threshold effect of ecosystem services in response to climate change, human activity and landscape pattern in the upper and middle Yellow River of China

Abstract

Identifying spatiotemporal heterogeneity and impact mechanism of ecosystem service value (ESV) is critical for enhancing ecosystem management and regional sustainability. However, the existing findings have failed to investigate the synergetic effect of multiple drivers on ESV, nor have considered the threshold effects under different conditions, which is important to understand the complex and frequently interacting ecosystem. In this study, we applied the improved ESV calculation method, Pearson correlation analysis and conditional inference tree model to depict the dynamic changes of ESV, to explore separate and synergetic effects of various factors, and further to identify key thresholds under combined effects in urban agglomerations along the upper and middle Yellow River area (UMYRA). The results showed that: (1) The total ESV of the study area increased by 5936.63 million CNY over the study period. With the exception of the urban agglomeration along the Yellow River in Ningxia (YRNX), four types of sub-services in Hulunbeier-Baotou-Erdos-Yulin urban agglomeration (HBEY) and Taiyuan urban agglomeration (TY) showed a rising trend. Spatially, the greater growth of ESV mainly concentrated in the northern desert belt, whereas the major grain production areas and urban areas presented different degrees of degradation. (2) Climate factors and land use intensity are the main factors affecting the total ESV, followed by economic density and terrain condition, while landscape metrics exert a relatively small impact on ESV. But the influences of these factors on single ESV show distinct internal differences. (3) Synergetic effects of multi-factors showed that: ①When the evapotranspiration and precipitation are at a certain threshold (1277 mm＜PET＜1317 mm and PRE＞417.55 mm), rising temperature can effectively promote the growth of ESV. The same effect is also observed on steep slopes under matched hydrothermal conditions; ②When economic development is at a high level, intensifying human activities within a certain range (0.11＜HAI＜0.29 and 184.32＜LUI＜210.6) could greatly promote the ESV, but the opposite effect was also true when the thresholds were breached; ③Fragmented landscapes with low diversity (SHDI＜0.86) can promote ESV improvement, but high diversity fragmented landscapes (PD＞0.14 or SHDI＞0.85) would lead to ESV decline. Our research sheds light on the key thresholds under synergetic effect of multiple factors on ESV from a novel perspective, which provide a specific and practical guidance for achieving sustainable management.