Vulnerability assessment and its driving forces in terms of NDVI and GPP over the Loess Plateau, China

Abstract

With the impact of climate change and the implementation of the “Grain-for-Green” ecological restoration project, the dynamics of water and heat transport and storage in the Loess Plateau (LP) have changed substantially. However, studies on the vulnerability of the LP ecosystem in response to ecological restoration are less concerned. Based on the normalized difference vegetation index (NDVI) and the gross primary production (GPP), this study assessed the spatial change of ecological vulnerability (EV) in the LP during 2001–2019. Results showed that (1) the annual mean NDVI and GPP was high in the southeast of LP and low in the northwest. The trend of NDVI and GPP presented a significant upward trend over approximately 85% of the regions; (2) the ecological vulnerability of LP displayed a low-to-high gradient from southeast to the northwest. Medium (0.3–0.45) and heavy (≥0.45) vulnerability levels occurred in the northwest of LP, which was attributed to less vegetation and serious land degradation; (3) forestland has the lowest vulnerability whereas grassland, sparse vegetation and urban land exhibited higher vulnerability, with the respective percentages of vulnerable areas of 63.8%, 90.4%, 70% in terms of NDVI and 87.1%, 49.8%, 38.4% in terms of GPP; and (4) the EV of LP was impacted by climate and terrain. The magnitude of vulnerability was negatively correlated with precipitation, temperature and slope, and positively correlated with drought. It is suggested that precipitation, slope and drought stress were the dominant factors of EV. The findings provide guidance for appropriate planning of ecological restoration in the LP.