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

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.