Inter-Annual Variations of Methane Emission from an Open Fen on the Qinghai-Tibetan Plateau: A Three-Year Study

Huai Chen,Xu Wang,Ning Wu,Qiu’An Zhu,Changhui Peng,Dan Zhu,Yanfen Wang,Yongheng Gao,Gang Yang,Xiuqin Fang,Gil Bohrer

doi:10.1371/journal.pone.0053878

Abstract

The study aimed to understand the inter-annual variations of methane (CH4) emissions from an open fen on the Qinghai-Tibetan Plateau (QTP) from 2005 to 2007. The weighted mean CH4 emission rate was 8.37±11.32 mg CH4 m−2 h−1 during the summers from 2005 to 2007, falling in the range of CH4 fluxes reported by other studies, with significant inter-annual and spatial variations. The CH4 emissions of the year of 2006 (2.11±3.48 mg CH4 m−2 h−1) were 82% lower than the mean value of the years 2005 and 2007 (13.91±17.80 mg CH4 m−2 h−1 and 9.44±14.32 mg CH4 m−2 h−1, respectively), responding to the inter-annual changes of standing water depths during the growing season of the three years. Significant drawdown of standing water depth is believed to cause such significant reduction in CH4 emissions from wetlands in the year 2006, probably through changing the methanogen composition and decreasing its community size as well as activating methanotrophs to enhance CH4 oxidation. Our results are helpful to understand the inter-annual variations of CH4 emission and provide a more reasonable regional budget of CH4 emission from wetlands on the QTP and even for world-wide natural wetlands under climate change.

Highlights

Methane (CH4) is an important greenhouse gas, about 25 times more powerful in warming the atmosphere than carbon dioxide (CO2) for the time horizon of 100 years [1]
Comparing the threeyear means of each stand, we found that CH4 emission from C. muliensis and E. valleculosa stands was significantly higher than that from K. tibetica stand, with no significant difference between the former two (Fig. 3a)
Seasonal and Inter-annual Variations of CH4 Fluxes In this study, we found CH4 emissions of the year of 2006 (2.1163.48 mg CH4 m22 h21) were significantly lower than that of 2005 and 2007 (13.91617.80 mg CH4 m22 h21 and 9.44614.32 mg CH4 m22 h21, respectively), with no significant differences between 2005 and 2007 for all the three stands (Fig. 3b)

Summary

Introduction

Methane (CH4) is an important greenhouse gas, about 25 times more powerful in warming the atmosphere than carbon dioxide (CO2) for the time horizon of 100 years [1]. CH4 is regarded as an important greenhouse gas only second to CO2. Wetlands represent one of the most important sources for methane emission, and the most uncertain one. Such uncertainty arises primarily from the large spatiotemporal variation that occurs in different scales and the limited data of specific wetlands [1,5]. We need to fill into place the jigsaw pieces of data on specific wetlands from different regions, if we want to get the whole picture of CH4 emission from wetlands

Methods

Results

Conclusion