Increasing influence of compound dry-hot events on vegetation in northern China in recent years

Abstract

Based on the Copula function in combination with the standardized precipitation index (SPI) and the standardized temperature index (STI), the compound dry-hot index (CDHI) was developed to evaluate the compound dry-hot events (CDHEs) in northern China. The spatiotemporal variations in CDHEs during summer from 1982 to 2020 were investigated to explore the response of vegetation to CDHEs. The results revealed that under the influence of global warming, the CDHEs intensified markedly in eastern Xinjiang, Gansu, southern Qinghai, central and eastern Inner Mongolia, northern Hebei and Beijing. The extent of areas where STI contributes more than 50 % to CDHEs is significantly greater than SPI. In most regions, detrended and standardized normalized different vegetation index (SNDVI) and SPI are positively correlated, with grasslands exhibiting the highest correlation, followed by farmlands and forest. However, the relationship between SNDVI and STI exhibits spatial heterogeneity, which is possibly affected by altitude. Different vegetation types have varying loss to CDHEs, 0.51 (farmlands) > 0.50 (grasslands) > 0.31 (forest). The rate of vegetation loss in arid and semi-arid regions is significantly higher than humid and semi-humid areas. These findings contribute to a deeper understanding of vegetation responses to climate extreme events, providing critical scientific support for ecosystem risk management under climate change.