Assessing the response lag and vulnerability of terrestrial vegetation to various compound climate events in mainland China under different vegetation types

Abstract

In the context of climate warming, the compound dry-hot (CDH), dry-cold (CDC), wet-hot (CWH), and wet-cold (CWC) events have become more frequent and widespread in recent decades, causing severe but disproportionate impacts on terrestrial vegetation. However, the understanding of how vegetation vulnerability responds to these compound climate events (CCEs) is still limited. Here, we developed a multivariate copula conditional probabilistic model integrating the Standardized Precipitation Index (SPI), Standardized Temperature Index (STI), and Normalized Difference Vegetation Index (NDVI) together to quantify the vegetation response to each of CDH, CDC, CWH and CWC events under diverse climates in mainland China. Results show that CDC events result in the largest probability of vegetation loss relative to other three CCEs, with the probability of NDVI below the 40% percentile being 4.8%-13.0% (0.5%-2.6%) larger than individual dry (cold) events. In contrast, CWH leads to the lowest vegetation loss probability among all CCEs, with the probability of NDVI below the 40% percentile being 5.6% ~ 6.9% (4.2% ~ 5%) less than individual wet (hot) events. The response of vegetation vulnerability to CCEs varies considerably with ecosystems and climate types. Vegetation in Loess Plateau and northwestern Xinjiang (Inner Mongolia) is highly susceptible to CDC (CDH) events, while that in northeastern and southern China (eastern coastal and southwestern regions) is more vulnerable to CWC (CWH) events. Shrubland, grassland and cropland exhibit higher vulnerability to CDC and CDH events, while deciduous (evergreen) forests are more vulnerable to CWC(CWH) events, which may be related to vegetation physiological characteristics, survival strategies, and climatic adaptations. This study enhances our understanding on the response of various vegetation types to CCEs, and provides theoretical support for the development of measures to mitigate climate hazards.