Key words: methane oxidation rates; community of soil prokaryotes; artificial moisture gradient; methanotrophs

Oxidation of methane by methanotrophs is the only biological sink for atmospheric methane, accounting for up to 10% of the total removal of atmospheric methane. Recent studies indicated effect of soil properties on distribution and activity of soil prokaryotes at local scale. However, response pattern of soil prokaryotes at taxonomic level to elevated methane addition remains still unclear. To address this, we established an incubation experiment exposing soils to varying levels of moisture and before and after increased methane concentration. In the first three months soil samples were incubated at different moisture levels at atmospheric methane. After three months of incubation at various moisture regime, 300 ml of methane in concentration of 20000 ppm was added. Our results showed significant changes of prokaryotic community under increased methane concentration along artificial moisture gradient. Alpha diversity indices significantly decreased in soils incubated with elevated methane. Chao index indicated significant changes along artificial moisture gradient but was unaffected by methane level. Beta diversity pattern differed significantly among various moisture treatments as well as after addition of methane. Null model expectation of mean NTI an RNI after methane addition along elevation gradient showed simultaneous effect of deterministic as well as stochastic factors. Relative abundances altered after methane addition. Relative abundances of soil prokaryotes showed both positive as well as negative response to elevated moisture gradient. Relative abundance of methanotrophs altered significantly along elevated moisture gradient as well as after addition of methane, but methane oxidation rates did not respond to changes in soil moisture.