Journal
ISME JOURNAL
Volume 6, Issue 6, Pages 1115-1126Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/ismej.2011.179
Keywords
methane-oxidizing bacteria; methanotrophs; upland soil cluster alpha; atmospheric methane; seasonal dynamics; grassland soil
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Funding
- European Science Foundation (METHECO) [018]
- Deutsche Forschungsgemeinschaft [LI 455/3-1]
- University College Dublin
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Microbial oxidation is the only biological sink for atmospheric methane. We assessed seasonal changes in atmospheric methane oxidation and the underlying methanotrophic communities in grassland near Giessen (Germany), along a soil moisture gradient. Soil samples were taken from the surface layer (0-10 cm) of three sites in August 2007, November 2007, February 2008 and May 2008. The sites showed seasonal differences in hydrological parameters. Net uptake rates varied seasonally between 0 and 70 mu g CH4 m(-2) h(-1). Greatest uptake rates coincided with lowest soil moisture in spring and summer. Over all sites and seasons, the methanotrophic communities were dominated by uncultivated methanotrophs. These formed a monophyletic cluster defined by the RA14, MHP and JR1 clades, referred to as upland soil cluster alphaproteobacteria (USC alpha)-like group. The copy numbers of pmoA genes ranged between 3.8 x 10(5)-1.9 x 10(6) copies g(-1) of soil. Temperature was positively correlated with CH4 uptake rates (P<0.001), but had no effect on methanotrophic population dynamics. The soil moisture was negatively correlated with CH4 uptake rates (P<0.001), but showed a positive correlation with changes in USC alpha-like diversity (P<0.001) and pmoA gene abundance (P<0.05). These were greatest at low net CH4 uptake rates during winter times and coincided with an overall increase in bacterial 16S rRNA gene abundances (P<0.05). Taken together, soil moisture had a significant but opposed effect on CH4 uptake rates and methanotrophic population dynamics, the latter being increasingly stimulated by soil moisture contents >50 vol% and primarily related to members of the MHP clade. The ISME Journal (2012) 6, 1115-1126; doi:10.1038/ismej.2011.179; published online 22 December 2011
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