Key words: methane oxidation rates; community of soil prokaryotes; artificial moisture gradient; methanotrophs. Response pattern of soil prokaryotic community to enhanced methane concentration along artificial moisture gradient

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.

甲烷氧化菌（methanotrophs）对甲烷的氧化作用是大气甲烷唯一的生物汇，约占大气甲烷总清除量的10%。近期研究表明，在局地尺度上，土壤性质会影响土壤原核生物的分布与活性。然而，在分类学层面上，土壤原核生物对甲烷浓度升高的响应模式仍未明确。为解决这一科学问题，本研究设置了培养实验，将土壤置于不同湿度梯度下，并设置甲烷浓度升高前后的分组处理。实验前三个月，土壤样品在大气甲烷浓度下、不同湿度梯度中进行培养；在不同湿度条件下培养三个月后，向体系中加入300mL浓度为20000ppm的甲烷。本研究结果显示，在人工设置的湿度梯度下，甲烷浓度升高会引发原核生物群落的显著变化。在经高浓度甲烷培养的土壤中，α多样性指数显著降低。Chao指数仅在人工湿度梯度下呈现显著变化，不受甲烷浓度水平的影响。β多样性模式在不同湿度处理组以及甲烷添加后均存在显著差异。基于零模型的甲烷添加后沿海拔梯度的平均NTI与RNI预测值显示，确定性因子与随机性因子同时对群落构建发挥作用。土壤原核生物的相对丰度在甲烷添加后发生改变。土壤原核生物的相对丰度对升高的湿度梯度呈现正负双向响应。甲烷氧化菌的相对丰度在湿度梯度升高以及甲烷添加后均发生显著变化，但甲烷氧化速率并未随土壤湿度的改变产生响应。