Effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions

Zhiyuan Zhang,Jukka Pumpanen,Kentaro Takagi,Takashi Hirano,Georg Wohlfahrt,Juan Zhu,Lutz Merbold,Alessandro Cescatti,Nina Buchmann,Fernando Moyano,Guanhong Chen,Renduo Zhang

doi:10.1038/s41598-017-03386-5

Abstract

The net ecosystem CO2 exchange is the result of the imbalance between the assimilation process (gross primary production, GPP) and ecosystem respiration (RE). The aim of this study was to investigate temperature sensitivities of these processes and the effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions. A database of 403 site-years of ecosystem flux data at 101 sites in the world was collected and analyzed. Temperature sensitivities of rates of RE and GPP were quantified with Q10, defined as the increase of RE (or GPP) rates with a temperature rise of 10 °C. Results showed that on the annual time scale, the intrinsic temperature sensitivity of GPP (Q10sG) was higher than or equivalent to the intrinsic temperature sensitivity of RE (Q10sR). Q10sG was negatively correlated to the mean annual temperature (MAT), whereas Q10sR was independent of MAT. The analysis of the current temperature sensitivities and net ecosystem production suggested that temperature rise might enhance the CO2 sink of terrestrial ecosystems both in the boreal and temperate regions. In addition, ecosystems in these regions with different plant functional types should sequester more CO2 with climate warming.

Highlights

The ecosystem CO2 exchange is controlled by fluxes associated with assimilation and respiration processes, corresponding to the rates of gross primary production (GPP) and ecosystem respiration (RE), respectively[1]
The results of the comparison demonstrates that temperature sensitivities of both RE and GPP can be well characterized by the exponential model
The approximate intrinsic temperature sensitivity indexes of GPP (Q10sG) and RE (Q10sR) were determined on all site-years using the procedure of Mahecha et al.[17] described in the section of Methods

Summary

Introduction

The ecosystem CO2 exchange is controlled by fluxes associated with assimilation and respiration processes, corresponding to the rates of gross primary production (GPP) and ecosystem respiration (RE), respectively[1]. There is still no consensus over the magnitude and directions of the response to climate change of the physiological processes underpinning the ecosystem CO2 exchange[4] This uncertainty often limits the ability to predict the carbon balance of terrestrial ecosystems[5]. Q10 values fitted to measured field data with statistical models are normally used to characterize the temperature sensitivity of ecological respiration process. The Q10 approach is on the base of the relationship between reaction rates and temperature described by van’t Hoff[19] As shown above, this exponential model has been widely used to study temperature sensitivity of RE at the subcellular and individual levels, as well as at the ecosystem level[13, 17, 20, 21], including calculations of apparent and intrinsic temperature sensitivity indexes of RE. Applicability of the exponential model to temperature sensitivity of GPP needs to be further demonstrated

Objectives

Methods

Results

Conclusion