title: Holocene variations in peatland methane cycling associated with the Asian summer monsoon system.
abstract: Atmospheric methane concentrations decreased during the early to middle Holocene; however, the governing mechanisms remain controversial. Although it has been suggested that the mid-Holocene minimum methane emissions are associated with hydrological change, direct evidence is lacking. Here we report a new independent approach, linking hydrological change in peat sediments from the Tibetan Plateau to changes in archaeal diether concentrations and diploptene δ(13)C values as tracers for methanogenesis and methanotrophy, respectively. A minimum in inferred methanogenesis occurred during the mid-Holocene, which, locally, corresponds with the driest conditions of the Holocene, reflecting a minimum in Asian monsoon precipitation. The close coupling between precipitation and methanogenesis is validated by climate simulations, which also suggest a regionally widespread impact. Importantly, the minimum in methanogenesis is associated with a maximum in methanotrophy. Therefore, methane emissions in the Tibetan Plateau region were apparently lower during the mid-Holocene and partially controlled by interactions of large-scale atmospheric circulation.
authors.affiliation: 1] Organic Geochemistry Unit, Cabot Institute and School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK [2] State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Meteorology, University of Reading, Earley Gate, PO Box 243, Reading, RG6 6BB, UK.
authors.forename: Joy S
authors.initials: JS
authors.lastname: Singarayer
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Bristol Research Initiative for the Dynamic Global Environment, Cabot Institute and School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Valdes
authors.affiliation: Organic Geochemistry Unit, Cabot Institute and School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Pancost