Constraints to Vegetation Growth Reduced by Region-Specific Changes in Seasonal Climate

Hirofumi Hashimoto,Long Cao,Ranga Myneni,Weile Wang,Govindasamy Bala,Andrew Michaelis,Sangram Ganguly,Cristina Milesi,Ryan Eastman,Ramakrishna Nemani,Tsengdar Lee

doi:10.3390/cli7020027

Abstract

We qualitatively and quantitatively assessed the factors related to vegetation growth using Earth system models and corroborated the results with historical climate observations. The Earth system models showed a systematic greening by the late 21st century, including increases of up to 100% in Gross Primary Production (GPP) and 60% in Leaf Area Index (LAI). A subset of models revealed that the radiative effects of CO2 largely control changes in climate, but that the CO2 fertilization effect dominates the greening. The ensemble of Earth system model experiments revealed that the feedback of surface temperature contributed to 17% of GPP increase in temperature-limited regions, and radiation increase accounted for a 7% increase of GPP in radiation-limited areas. These effects are corroborated by historical observations. For example, observations confirm that cloud cover has decreased over most land areas in the last three decades, consistent with a CO2-induced reduction in transpiration. Our results suggest that vegetation may thrive in the starkly different climate expected over the coming decades, but only if plants harvest the sort of hypothesized physiological benefits of higher CO2 depicted by current Earth system models.

Highlights

Climate change caused by increasing atmospheric carbon dioxide (CO2 ) concentrations has been extensively studied in the context of global warming, and the land carbon cycle feedback is recognized as one of the biggest sources of uncertainty in climate projection [1]
The multi-model ensemble mean shows pervasive future changes in vegetation structure and function by the end of this century under the high-emission Representative Concentration Pathway (RCP) 8.5 scenario: Leaf Area Index (LAI) increases by up to 60% and gross primary production (GPP) increases by up to 100% (Figure 2)
The percentage changes are higher in the high latitude regions for LAI, while changes in magnitude of LAI and GPP are higher in both the high latitude and tropical regions

Summary

Introduction

Climate change caused by increasing atmospheric carbon dioxide (CO2 ) concentrations has been extensively studied in the context of global warming, and the land carbon cycle feedback is recognized as one of the biggest sources of uncertainty in climate projection [1]. Global warming is proceeding with a greening trend of the Earth, as shown by satellite and ground observations of increases in leaf area index [2,3], canopy cover [4], and biomass [5]. Among the mechanisms supporting the greening Earth, CO2 fertilization is considered the dominant factor in enhancing vegetation, with evidence from free-air CO2 enrich (FACE) experiments [10], satellite observations [2,4], and ground observations [11]. Climate change is substantially contributing to the increase in global vegetation productivity because of the indirect effect of increasing CO2 concentrations [9]

Methods

Results

Discussion

Conclusion