| Wetlands are considered to be the largest natural sources of methane (CH4),accounting for20-40%of total CH4emissions. The oxidation of CH4could effectivelyreduce the methane emission and subsequently alleviate the greenhouse effect byconverting CH4to carbon dioxide (CO2). After methaneogens occurrence at anoxiczones in wetland, CH4consumption by anaerobic methanotrophs (ANME) ispredicted to occur near the oxic-anoxic interface where CH4diffusing and emission toatomosphere. Therefore, anaerobic oxidation of methane is a potential CH4sink inwetlands. In this study, to investigate the anaerobic oxidation of methane and thecommunity structure of ANME archaea, soil samples with five layers (0-10、10-20、20-30、30-40、40-50cm)derived from Phragmites australis and Taxodium distichumplantation were collected in Chongxi Wetland, Shanghai. In this study, combined withincubate method and quantitative PCR, Denaturing Gradient Gel Electrophoresis(DGGE) and clone library analysis techniques, the physicochemical properties ofdifferent soilsnds, as well as anaerobic methanothophic potential and the abundanceand community structure of the functional microorgansims were analyzed. The mainresults are as follows:1) Total organic carbon (TOC), total nitrogen (TN) and microbial biomass carbon(MBC) content in the topsoil (0-20cm) of Phragmites australis and Taxodiumdistichum plantation wetland were higher than that in subsoil (30-50cm). The SO2-4content decreased with the increase of soil layer in Mudfalts and Phragmites australisplantation, while it was constant in Taxodium distichum.in addition, plant significantlyinfluenced soil physicochemical properties except total inorganic carbon and totalcarbon: TOC, TN and MBC content in Phragmites australis and Taxodium distichumplantation were significantly higher than that in Mudfalts. For the two plantations, nosignificant difference of TOC and TN content was observed between Phragmitesaustralis and Taxodium distichum, and MBC content was higher in Phragmitesaustralis plantation. Compared to mudfalts, higher total Fe content was observed insoil of Taxodium distichum plantation. The content of SO2-4in the layer0-30cm soil of Mudfalts and Phragmites australis was significantly higher than that in the layer0-30cm soil of Taxodium distichum, while it is reverse in layer30-50cm. Theseresults suggested that the soils were characterized differently might due to plant type,soil layers and soil microorganisms.2) There is a significant difference ofanaerobic methanotrophic (AOM) potentialbetween different soil layers and plants: the AOM potential in the topsoil (0-10cm)varied from12.0to24.0nM/g.d, and affected by different vegetations as Mudfalts>Phragmites australis> Taxodium distichum. In the layer10-50cm soil, the AOMpotential variation was varied as Taxodium distichum> Phragmites australis>Mudfalts. Furthermore, the AOM potential in Taxodium distichum plantation wassignificantly (P<0.05) higher than that in Mudfalts and Phragmites australis, rangingfrom12.0to35.0nM/g.d. The linear regreassion analysis suggested that plant type,soil layer and TN significantly influenced AOM potential, and TN was negativelyrelated with AOM potential。3) The fingerprint of DGGE showed that more bands in Phragmites australiscommunity and Taxodium Distichum community were appeared in the20-50cm soillayer than that in0-10cm soil layer. In mudflats, there was no significant differenceof the bands among different soil layers, and there were only several bands in40-50cm layer. All the bands were clustered into several groups as0-10cm,10-40cm and40-50cm. The diversity index of ANME communities increased with increasing ofsoil depth, and the indexs in Phragmites australis and Taxodium Distichumcommunity were remarkable higher than that in mudflat.4) Based on16S rRNA gene clone library, the ANME mainly belonged to Eurarchaeotaand Crenarchaeota. For mudflats, the ANME species in0-10cm was mainly belongedto Thermoprotei. For Phragmites australis commmunities, the species in40-50cmsoil layer only belonged to Crenarchaeota, while the ANME in10-20cm and20-30cm mainly clustered to the two phylums Eurarchaeota and Crenarchaeota. ForTaxodium Distichum community, Eurarchaeota species only existed in the layer30-40cm, while Crenarchaeota dominated all the other layers. The shannon indexs of 20-40cm soil layers were significantly higher (P<0.05) than that of the other layers inall three plant communities. Although the diversity of ANME in the mudfalts weresignificantly higher than that in Phragmites australis and Taxodium Distichumcommunity, the abundance was in reverse. So we could conclude that the depth of soiland vegetation played an important role in the distribution of microorganism species.5) The quantitative analysis based on16S rRNA gene showed that the abundanceof16S rRNA gene were ranged from9.1×104to6.8×105copies/g DNA, and the0-10cm layer of mudflats appeared as the most abundant with4.44×105copies/ng DNA.For Phragmites australis community, significantly more gene copies were obtained inboth layer10-20cm and20-30cm. the gene abundance in Phragmites australis andTaxodium Distichum community were4.67×105copies/ng DNA and4.80×105copies/ng DNA, respectively, which were significantly more than that in mudflat. Thevariation tendency of16S rRNA gene copies in40-50cm of different plants was asfollowed: Phragmites australis> Taxodium Distichum>Mudflat. While the variationtendency of16S rRNA gene copies in the layer0-10cm was as followed: Mudflat>Phragmites australis and Taxodium Distichum, but in10-50cm, the trend was opposite.The analysis of linear regression suggested that soil depth significantly affected theabundance of microorganism communities, and TN and MBC were negativecorrelated with the gene abundance. |
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