Methane Emissions Offset Net Carbon Dioxide Uptake From an Alpine Peatland on the Eastern Qinghai‐Tibetan Plateau

Haijun Peng,Hanwei Ding,Hu Yao,Qian Guo,Bing Hong,Jinshu Chi,Yetang Hong,Jie Wang,Yongxuan Zhu

doi:10.1029/2021jd034671

Abstract

AbstractPeatlands store large amounts of carbon (C) and actively exchange greenhouse gases (GHGs) with the atmosphere, thus significantly affecting global C cycle and climate. Large uncertainty exists in C and GHG estimates of the alpine peatlands on Qinghai‐Tibetan Plateau (QTP), as direct measurements of CO2 and CH4 fluxes are scarce in this region. In this study, we provided 32‐month CO2 and CH4 fluxes measured using the eddy covariance (EC) technique in a typical alpine peatland on the eastern QTP to estimate the net C and CO2 equivalent (CO2‐eq) fluxes and investigate their environmental controls. Our results showed that the mean annual CO2 and CH4 fluxes were −68 ± 8 g CO2‐C m−2 yr−1 and 35 ± 0.3 g CH4‐C m−2 yr−1, respectively. While considering the traditional and sustained global warming potentials of CH4 over the 100‐year timescale, the peatland acted as a net CO2‐eq source (1,059 ± 30 and 1,853 ± 31 g CO2‐eq m−2 yr−1, respectively). The net CO2‐eq emissions during the non‐growing seasons contributed to over 40% of the annual CO2‐eq budgets. We further found that net CO2‐eq flux was primarily influenced by global radiation and soil temperature variations. This study was the first assessment to quantify the net CO2‐eq flux of the alpine peatland in the QTP region using EC measurements. Our study highlights that CH4 emissions from the alpine peatlands can largely offset the net cooling effect of CO2 uptake and future climate changes such as global warming might further enhance their potential warming effect.

Highlights

Carbon dioxide (CO2) and methane (CH4) are the two most important long-lived greenhouse gases (LLGHGs) and together contribute to over 80% of the radiative forcing caused by LLGHGs (WMO, 2018)
Large uncertainty exists in C and GHG estimates of the alpine peatlands on Qinghai-Tibetan Plateau (QTP), as direct measurements of CO2 and CH4 fluxes are scarce in this region
During the first half of the growing season, Tsoil at the depth of 10 cm decreased by 1.0°C from 2014 to 2015, forming a cooler and wetter soil condition over that period due to a slight increase in PPT

Summary

Introduction

Carbon dioxide (CO2) and methane (CH4) are the two most important long-lived greenhouse gases (LLGHGs) and together contribute to over 80% of the radiative forcing caused by LLGHGs (WMO, 2018). Peatland ecosystems have the potential to mitigate climate change by sequestering CO2 from the atmosphere into biomass and soils (Baldocchi & Penuelas, 2019; Nugent et al, 2019; Stocker et al, 2017); peatlands emit large amounts of CH4 to the atmosphere during the peatland forming and growing processes (Dommain et al, 2018; Kirschke et al, 2013), resulting in contrasting effects on radiative forcing Both pathways are sensitive to climate change and anthropogenic activities (Chen et al, 2013; Frolking et al, 2011); for example, drought caused by both peatland drainage and low precipitation (Fenner & Freeman, 2011; Swindles et al, 2019), peatland wildfires and burning (Turetsky et al, 2015), and conversion for agricultural uses (Carlson et al, 2013; Dommain et al, 2018) can shift the peatlands from net GHG sinks to sources. It should be noted that the historical, current, and future contributions of peatlands to the global C budget and radiative forcing are still uncertain due to limited knowledge of the synergistic feedbacks of CO2 and CH4 to climatic perturbation and anthropogenic activities (Luan et al, 2018; Petrescu et al, 2015; Stocker et al, 2017)

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