Acceleration of global vegetation greenup from combined effects of climate change and human land management

Abstract

Global warming and human land management have greatly influenced vegetation growth through both changes in spring phenology and photosynthetic primary production. This will presumably impact the velocity of vegetation greenup (Vgreenup, the daily rate of changes in vegetation productivity during greenup period), yet little is currently known about the spatio-temporal patterns of Vgreenup of global vegetation. Here, we define Vgreenup as the ratio of the amplitude of greenup (Agreenup) to the duration of greenup (Dgreenup) and derive global Vgreenup from 34-year satellite leaf area index (LAI) observations to study spatio-temporal dynamics of Vgreenup at the global, hemispheric, and ecosystem scales. We find that 19.9% of the pixels analyzed (n = 1,175,453) experienced significant trends toward higher greenup rates by an average of 0.018 m m day for 1982-2015 as compared to 8.6% of pixels with significant negative trends (p < 0.05). Global distribution and dynamics of Vgreenup show high spatial heterogeneity and ecosystem-specific patterns, which is primarily determined by the high spatial variation in Agreenup, while the temporal dynamics of Vgreenup are directly controlled by both changes in Dgreenup and Agreenup. Areas with the largest Vgreenup and largest positive trends are both observed in deciduous and mixed forests as compared to nonforest ecosystems showing both lower Vgreenup and trends. For nonforest ecosystems, human-managed ecosystems (e.g., rangelands and rainfed croplands) exhibited higher Vgreenup and positive trends than those of natural counterparts, suggesting strong imprints of human land management on terrestrial ecosystem functioning. Globally, warming has accelerated Vgreenup in temperature-constrained high latitude forest ecosystems and arctic regions, but decelerated Vgreenup in temperate and arid/semiarid areas. These results suggest that the combined effects of climate change and human land management have greatly accelerated global vegetation greenup, with important implications for changes in terrestrial ecosystem functioning and global carbon cycling.

Sensitivity of Vegetation on Alpine and Subalpine Timberline in Qinling Mountains to Temperature Change

“…This is similar to the conclusion of this study. From this is can be seen that globally, warming has increased Vgreenup in temperature-constrained high latitude forest ecosystems and arctic regions, but decreased Vgreenup in those areas known to be temperate and arid/semi-arid [27].…”

Accelerated rate of vegetation green‐up related to warming at northern high latitudes

“…Therefore, this study could overestimate the influence of CO 2 on the RVG trends. Previously, Wang et al (2018) suggested that human land management played an important role on the acceleration of green-up velocity on a global scale. In the present study, we focus on high-latitude regions where human-managed ecosystems are minor, but this anthropogenic influence or other environmental factors could exert an effect on the long-term RVG trends.…”

“…These studies suggest that the RVG is a dynamic factor which responds to the changes in environmental conditions and transforms the entire shape of the green-up stage together with the growth onset (Kern et al, 2020;Klosterman et al, 2018;Park et al, 2015). Wang et al (2018) presented that the RVG accelerated over the past several decades from a global perspective. They pointed out that global warming could be the reason of the acceleration based on correlations of the RVG with temperature and precipitation.…”

Vegetation Change and Driving Factors: Contribution Analysis in the Loess Plateau of China during 2000–2015

“…It is an important link that connects climate change, human activities, and ecosystems. Climate and human activities are the basic drivers for controlling and affecting the spatial distribution of vegetation and its changes [1][2][3]. Climatic factors control the growth process of vegetation on a long-term scale, restrict the geographical distribution of terrestrial vegetation, and determine the type and magnitude of regional ecosystem services.…”