Abstract
Water stress is one of the primary environmental factors that limits terrestrial ecosystems’ productivity. Hense, the way to quantify gobal vegetation productivity’s vulnerability under water stress and reveal its seasonal dynamics in response to drought is of great significance in mitigating and adapting to global changes. Here, we estimated monthly gross primary productivity (GPP) first based on light-use efficiency (LUE) models for 1982–2015. GPP’s response time to water availability can be determined by correlating the monthly GPP series with the multiple timescale Standardized Precipitation Evapotranspiration Index (SPEI). Thereafter, we developed an optimal bivariate probabilistic model to derive the vegetation productivity loss probabilities under different drought scenarios using the copula method. The results showed that LUE models have a good fit and estimate GPP well (R2 exceeded 0.7). GPP is expected to decrease in 71.91% of the global land vegetation area because of increases in radiation and temperature and decreases in soil moisture during drought periods. Largely, we found that vegetation productivity and water availability are correlated positively globally. The vegetation productivity in arid and semiarid areas depends considerably upon water availability compared to that in humid and semi-humid areas. Weak drought resistance often characterizes the land cover types that water availability influences more. In addition, under the scenario of the same level of GPP damage with different drought degrees, as droughts increase in severity, GPP loss probabilities increase as well. Further, under the same drought severity with different levels of GPP damage, drought’s effect on GPP loss probabilities weaken gradually as the GPP damage level increaes. Similar patterns were observed in different seasons. Our results showed that arid and semiarid areas have higher conditional probabilities of vegetation productivity losses under different drought scenarios.
Highlights
The Intergovernmental Panel on Climate Change (IPCC) report shows that the world will continue to warm in the 21st century [1]
By comparing with the FLUXNET gross primary productivity (GPP) site data, we found that different light-use efficiency (LUE) models have a good fit in estimation of LUE GPP
From 1982 to 2015, the global average annual GPP of terrestrial vegetation continued to increase at a mean rate of 0.134 Pg C a −1 (p < 0.001), but its growth rate declined after the mid-1990s (Figure 1a)
Summary
The Intergovernmental Panel on Climate Change (IPCC) report shows that the world will continue to warm in the 21st century [1]. This indicates that as the future temperature rises, the occurrence and frequency of extreme weather and climate, such as heatwaves and droughts, will increase rapidly [2]. This trend and its associated adverse effects on natural and social ecosystems are expected to increase further [3]. In arid and semiarid regions, water stress is the primary environmental factor that limits terrestrial ecosystems’ productivity [5].
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