Assessing the Responses of Ecosystem Patterns, Structures and Functions to Drought Under Climate Change in the Yellow River Basin, China

Abstract

Understanding how ecosystems respond and adapt to drought has become an urgent issue as drought stress intensifies under climate change, yet this topic is not fully understood. In this study, we systematically explored the relationships between ecosystem patterns, structures and functions changes and drought, taking a typical climate change-sensitive area and an ecologically fragile area—the Yellow River basin—as a case study. The drought indices (including the standardized precipitation evapotranspiration index (SPEI), streamflow drought index (SDI), and humidity index (HI), the ecosystem pattern, structure (landscape fragmentation index (F)) and function indicators (including gross primary productivity (GPP), water use efficiency (WUE), and ecosystem service value (ESV)) were determined, and their spatiotemporal changes were identified using 20-year long MODIS data and observed data. The relationships between ecosystem changes and meteorological and hydrological drought and the mechanisms underlying ecosystem responses to drought were further investigated. The results showed that the Yellow River basin has experienced meteorological and hydrological drought during most of the last two decades, predominantly characterized by medium and slight droughts. Moreover, cropland and forest ecosystems have expanded, but grassland ecosystems have significantly decreased in size. As the ecosystem structure became more complex, F continuously increased. The ecosystem functions also exhibited an obvious upward trend in GPP, a downward trend in WUE, and a W-shaped increase in total ESV, with significant regional differences. The ecosystem indicators F, GPP, and ESV exhibited positive correlations with the SPEI, SDI, and HI, while the WUE exhibited a negative correlation at the watershed scale. Specifically, the GPP-SDI exhibited a significant positive correlation (p < 0.05). The responses of some functions to drought in wetland ecosystems and grassland ecosystems vary from those in else ecosystems. This study enhances the understanding of this responses and will help stakeholders formulate drought mitigation policies and protect ecosystem health.

Keywords: drought, Ecosystem pattern-structure-function, Response, Yellow River basin