Complex spatiotemporal responses of global terrestrial primary production to climate change and increasing atmospheric CO2 in the 21st century.

Shufen Pan,Xia Li,Qichun Yang,Chaoqun Lu,Chi Zhang,Hanqin Tian,Xiaoke Wang,Zhiyun Ouyang,Bo Tao,Wei Ren,Kamaljit Banger,Bowen Zhang,Shree R S Dangal,Jia Yang,Benjamin Poulter

doi:10.1371/journal.pone.0112810

Abstract

Quantitative information on the response of global terrestrial net primary production (NPP) to climate change and increasing atmospheric CO2 is essential for climate change adaptation and mitigation in the 21st century. Using a process-based ecosystem model (the Dynamic Land Ecosystem Model, DLEM), we quantified the magnitude and spatiotemporal variations of contemporary (2000s) global NPP, and projected its potential responses to climate and CO2 changes in the 21st century under the Special Report on Emission Scenarios (SRES) A2 and B1 of Intergovernmental Panel on Climate Change (IPCC). We estimated a global terrestrial NPP of 54.6 (52.8–56.4) PgC yr−1 as a result of multiple factors during 2000–2009. Climate change would either reduce global NPP (4.6%) under the A2 scenario or slightly enhance NPP (2.2%) under the B1 scenario during 2010–2099. In response to climate change, global NPP would first increase until surface air temperature increases by 1.5°C (until the 2030s) and then level-off or decline after it increases by more than 1.5°C (after the 2030s). This result supports the Copenhagen Accord Acknowledgement, which states that staying below 2°C may not be sufficient and the need to potentially aim for staying below 1.5°C. The CO2 fertilization effect would result in a 12%–13.9% increase in global NPP during the 21st century. The relative CO2 fertilization effect, i.e. change in NPP on per CO2 (ppm) bases, is projected to first increase quickly then level off in the 2070s and even decline by the end of the 2080s, possibly due to CO2 saturation and nutrient limitation. Terrestrial NPP responses to climate change and elevated atmospheric CO2 largely varied among biomes, with the largest increases in the tundra and boreal needleleaf deciduous forest. Compared to the low emission scenario (B1), the high emission scenario (A2) would lead to larger spatiotemporal variations in NPP, and more dramatic and counteracting impacts from climate and increasing atmospheric CO2.

Highlights

Net Primary Productivity (NPP), a balance between photosynthetic carbon (C) uptake (Gross Primary Productivity; gross primary productivity (GPP)) and losses due to plant respiration, represents the net C retained by terrestrial vegetation
4.1 Comparison of DLEM-simulated NPP with previous estimates The DLEM-simulated global terrestrial NPP is 54.57 PgC yr21 for the period 2000–2009, which is comparable to MODIS-based estimate of 53.5 PgC yr21 during the 2000s [16], and falls in the range of 44–66 PgC yr21 as estimated by 17 global terrestrial biosphere models [29]
Climate change in the 21st century would either reduce global NPP by 4.6% under the A2 scenario or slightly enhance NPP (2.2%) under the B1 scenario

Summary

Introduction

Net Primary Productivity (NPP), a balance between photosynthetic carbon (C) uptake (Gross Primary Productivity; GPP) and losses due to plant respiration, represents the net C retained by terrestrial vegetation. NPP is an important indicator of ecosystem health and services [2,3], and is an essential component of the global C cycle [4]. Terrestrial NPP is sensitive to multiple environmental changes including climate and atmospheric changes [5]. The IPCC Fourth Assessment (AR4) assessment indicated that global average temperature has increased by 0.74uC since the preindustrial times and that this trend is expected to continue through the 21st century [6]. Atmospheric CO2 concentration have increased from the pre-industrial level of 280 ppm to the 2005 level of 379 ppm [6]. The Representative Concentration Pathways (RCP’s) scenarios used in the IPCC Fifth Assessment

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Conclusion