Effect Of Precipitation Exclusion On Castanopsis Carlesii Natural Forest Soil Methane Uptake And Methanotrophs Community Structure

Methane is an important greenhouse gas and has a relative global warming in the world and its warming potential is25times that of CO2on a century time scale. The contribution of atmospheric methane to the current level of global warming is up to20%. Uptake of methane by forest soil is the sink and plays an important role in the carbon and carbon budget of forest ecosystems, so it’s a great approach to mitigate greenhouse gas emission. Climate change, which is changing with precipitation reduction ways and its controlling mechanisms, plays a significance role in calculation of regional forest ecosystem carbon balance and forest carbon sink.Castanopsis carlesii natural evergreen broad-leaved forest was selected, located at the same site at nature reserve of Castanopsis in Sanming City. A field experiment was conducted to study the effect precipitation exclusion treatments (i.e.30%precipitation reduction,60%precipitation reduction and control) on methane uptake and methanotrophs community structure. The results showed that C. carlesii natural forest was the sink of methane, and the soil methane uptake rates with variation of precipitation exclusion showed significant difference among seasons, the maximum was in summer and autumn, then the minimum was in winter and spring. With precipitation exclusion intensity increased, the soil of methane uptake rate was increased. Compared to control, the60%precipitation reduction and30%precipitation reduction was increased by21%and5%, respectively. The soil water content could describe20%-29%variation of soil methane. After precipitation exclusion, soil methanotrophic bacteria diversity and richness appear increasing trend, like60%precipitation reduction of type Ⅰ methanotrophic bacteria richness and diversity index were significantly higher than30%precipitation reduction and control, but30%precipitation reduction of type Ⅰ methanotrophic bacteria richness and diversity index increased was not obvious. In addition, type Ⅱ of soil methanotrophic richness and diversity index was significantly higher than control’s, and30%precipitation reduction of type Ⅱ soil methanotrophic richness and diversity index and60%precipitation reduction showed no significant difference. Type Ⅰ of methanotrophic bacteria and soil total organic carbon, type Ⅱ of soil methanotrophic bacteria and soil dissolved organic carbon existed significant correlation, respectively. Our result indicated that the change of soil total organic carbon and dissolved organic carbon content had an important influence on soil methanotrophic community structure with precipitation exclusion. Furthermore, the richness and diversity of soil methanotrophs increased were the vital factors to increases soil methane uptake.