Microbiological Mechanism Of Impacts On Methane Production Potential Of Marsh Wetland Reclamation In Sanjiang Plain

Methane(CH₄)is the second most important greenhouse gas after carbon dioxide,so it is focus of nowadays'research.Wetlands are the largest natural source of methane emissions,and the Sanjiang Plain contains the largest freshwater wetland in China.With the development of science and agriculture,a large amount of wetlands have been reclaimed for crop cultivation.Wetland reclamation has a great impact on soil physical and chemical properties,microbial properties and carbon cycle.Although a number of studies have conducted for these,how wetland reclamation affects methane production potential along soil profiles remains under investigated.Here,we sampled soil cores form cropland and typical natural wetland in Sanjiang Plain Marsh Wetland Ecological Experiment Station and then conducted laboratory cultural experiment to explore the microbiological mechanism of impacts on microbial properties and methane production potential of wetland reclamation.Main conclusions showed as follows.(1)Wetland reclamation significantly reduced the concentrations of total carbon(TC)and total sulfur(TS),but significantly increased p H along soil profiles.Wetland reclamation significantly reduced the total nitrogen(TN)content at the surface soil(0-30 cm).Moisture and decreased due to wetland reclamation.The impacts on chemical properties along soil profiles of wetland reclamation varied insignificantly with season.(2)Wetland reclamation homogenized microbial properties along soil profile,in which the microbial biomass and phospholipid fatty acid(PLFA)content at surface soils significantly decreased by 80-90%,but the microbial biomass and PLFA content at increased deeper soils(30-100 cm).Wetland reclamation changed the vertical distribution of microbes along the soil profile,with decreasing the microbial proportions of surface soil.Wetland reclamation increased the C stress of surface soil microbial groups,but decreased the C stress of soil microbes from 60 to 100 cm.The impacts of wetland reclamation on microbial properties at surface soil in winter was greater than that in spring,summer and autumn.TC and p H dominated the variations of microbial abundance and community structures along soil profiles.Wetland reclamation strongly changed TC and p H and then influenced microbial properties.(3)The methane production potential of the wetland soil profile in Sanjiang Plain decreased significantly with soil depth.The methane production potential of the surface soil was significantly higher than that of the deep soil in cropland.Both in cropland and wetland,methane production potential in winter was significantly lower than that in autumn,spring and summer.Wetland reclamation significantly reduced the methane production potential along soil profiles.(4)Wetland reclamation affected surface soil methane production potential mainly through influencing microbial characteristics.It also affected methane production potential by affecting TC,TN and p H.Wetland reclamation significantly reduced the contents of TC and TN,increased p H,and then significantly reduced microbial abundance.In addition,drainage activities of reclamation suppressed the metabolisms of methanogens.The decrease of microbial abundance caused the decline of methane production potential.In 30-100cm,wetland reclamation affects methane production potential by affecting soil chemical properties.Wetland reclamation significantly reduces TC and increases p H.The decrease of TC content reduces the content of organic matter available to methanogens,and the increase of p H reduces the availability of these organics.