Abstract
Heat and drought stress, which often occur together, are the main environmental factors limiting the survival and growth of vegetation. Studies on the response of gross primary production (GPP) to extreme climate events such as heat and drought are highly significant for the identification of ecologically vulnerable regions, ecological risk assessments, and ecological environmental protection. We got 1982–2017 climatic data from the University of East Anglia Climatic Research Unit, Norwich, England, and GPP data from National Earth System Science Data Sharing Service Platform, Beijing, China. Using Theil–Sen median trend analysis and the Mann–Kendall test, we analyzed trends in temperature and the standardized precipitation/standardized precipitation evapotranspiration indices in the eight vegetation regions of China. Additionally, the response of GPP to the single and combined impacts of heat and drought were analyzed using multidimensional copula functions, and GPP reduction probabilities were estimated under different drought levels and heat intensities. The results showed that the probability of a drastic GPP reduction increases with increasing drought levels and heat intensities. The combined impacts of heat and drought on vegetation productivity is greater than the impacts of either drought or heat alone and presents a nonlinear superposition of the two extremes. The impact of heat on GPP is not evident when the drought level is high. The temperate grassland and warm temperate deciduous broad-leaved forest regions are the most sensitive regions to drought and heat in China. This study provides a scientific basis for the comprehensive evaluation of the risk of GPP reduction under the single and combined impacts of heat stress and drought stress.
Highlights
Introduction published maps and institutional affilGross primary production (GPP) refers to the total carbon amount fixed by green vegetation per unit area per unit time through photosynthesis and is the material basis for the survival and development of human society; changes in gross primary production (GPP) affect the entire terrestrial carbon cycle [1,2]
According to the 2D copula model of GPP and drought/heat, this study found that when the drought level/heat intensity increases, the ENAG probability in each vegetation region increases, and the higher the drought level/heat intensity is, the more the probability increases
In this study, based on GPP data from the EC-LUE model and CRU TS 4.04 climatic data, we analyzed the trends of temperatures and drought indices (SPI/SPEI) in China and investigated the impacts of extreme climatic conditions on GPP by constructing multidimensional copula functions between
Summary
Introduction published maps and institutional affilGross primary production (GPP) refers to the total carbon amount fixed by green vegetation per unit area per unit time through photosynthesis and is the material basis for the survival and development of human society; changes in GPP affect the entire terrestrial carbon cycle [1,2]. CO2 fertilization and extensions of the growing season are expected to enhance vegetation growth because of ongoing global warming [2], and there is evidence of increased vegetation coverage worldwide, even in some semiarid regions [3,4]. The frequency, persistence, and magnitude of extreme climate events such as droughts, storms, floods, heat, heat waves, extremely low temperatures, and heavy rains are projected to further increase in the mid-to-late 21st century [1,2,5,6,7] and may pose potential threats to vegetation growth and terrestrial carbon uptake [8,9,10]. Understanding the responses of terrestrial GPP to extreme climate events such as heat and drought in the context of the potential aggravation of climatic extremes is of great significance for iations.
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