Roles of climate, vegetation and soil in regulating the spatial variations in ecosystem carbon dioxide fluxes in the Northern Hemisphere.

Zhi Chen,Jianping Ge,Xianjin Zhu,Guirui Yu,Zhiwei Xu,Qiufeng Wang,Xuhui Zhou

doi:10.1371/journal.pone.0125265

Abstract

Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60 % and 58 % of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45 - 47 % of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75 %. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary.

Highlights

Terrestrial ecosystems play important roles in modulating the atmospheric carbon dioxide concentration and mitigating global warming [1]
The datasets analyzed in this study included (1) the climate factors of mean annual temperature (MAT, °C), mean annual precipitation (MAP, mm), and mean annual solar radiation (MAR, W m-2); (2) the vegetation factors of the mean maximum enhanced vegetation index (EVImax) and mean annual enhanced vegetation index (EVImean); (3) the soil factors of soil organic carbon content at the depth of 0–30 cm (SOC30, %) and soil organic carbon content at the depth of 30–100 cm (SOC100, %); and (4) the ecosystem carbon dioxide fluxes of the mean annual gross primary production (AGPP, g C m-2 yr-1), mean annual ecosystem respiration (ARE, g C m-2 yr-1), and mean annual net ecosystem production (ANEP, g C m-2 yr-1)
The MAT and MAP accounted for 45–47% of the spatial variations in AGPP and ARE in the Northern Hemisphere

Summary

Introduction

Terrestrial ecosystems play important roles in modulating the atmospheric carbon dioxide concentration and mitigating global warming [1]. The net carbon exchange between terrestrial ecosystems and the atmosphere is approximately 15–21 Pg yr-1 [2]. This carbon exchange is 2–3 times greater than the annual anthropogenic carbon emissions [1]. Ecosystem carbon dioxide exchanges are highly variable across space [3,4]. To reduce the uncertainties in estimated carbon fluxes of terrestrial ecosystems in global carbon cycling, a better understanding of the mechanisms and processes underlying the spatial variations in ecosystem carbon dioxide fluxes is required [6,7]

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Conclusion