Niche differentiation of atmospheric methane‐oxidizing bacteria and their community assembly in subsurface karst caves

Abstract Karst caves are recently proposed as atmospheric methane sinks in terrestrial ecosystems. Despite of the detection of atmospheric methane‐oxidizing bacteria (atmMOB) in caves, we still know little about their ecology and potential ability of methane oxidation in this ecosystem. To understand atmMOB ecology and their potential in methane consumption, we collected weathered rocks and sediments from three different caves in southwestern China. We determined the potential methane oxidization rates in the range of 1.25 ± 0.08 to 1.87 ± 0.41 ng CH 4 g −1 DW h −1 , which are comparable to those reported in forest and grassland soils. Results showed that alkaline oligotrophic caves harbour high numbers of atmMOB, particularly upland soil cluster (USC), which significantly correlated with temperature, CH 4 and CO 2 concentrations. The absolute abundance of USC γ was higher than that of USC α . USC γ ‐OPS (open patch soil) and USC γ ‐SS (subsurface soil) dominated in most samples, whereas USC α ‐BFS (boreal forest soil) only predominated in the sediments near cave entrances, indicating niche differentiation of atmMOB in caves. Overwhelming dominance of homogenous selection in community assembly resulted in convergence of atmMOB communities. Collectively, our results demonstrated the niche differentiation of USC in subsurface alkaline caves and their non‐negligible methane‐oxidizing potential, providing brand‐new knowledge about atmMOB ecology in subsurface biosphere.