| Soil microorganisms,as an integral part of wetland ecosystems,play a key role in ecological processes such as material cycling,energy flow and ecological restoration.Wetland soil microbial community structure and diversity not only measure wetland soil microbial characteristics,but also are important indicators for predicting environmental quality and soil nutrient change trends.In this paper,the 9-year poplar woodland(P9),3-year poplar felling site(D3)and 6-year poplar felling site(D6)in Dongting Lake were used as research objects,and the native reed site was used as control(CK).By analyzing the change characteristics of soil microbial community structure,diversity and network stability,the following main results were obtained to reveal the mechanism of human activities on soil microbial communities in wetlands:(1)Soil physicochemical properties were significantly different among different sites,and Soil water content(SWC),Soil organic carbon(SOC),Total Nitrogen(TN),Nitrate nitrogen(NO3-),and Available phosphorus(AP)were significantly higher in CK than in P9,D3,and D6.In contrast,the Bulk density(BD)and pH were significantly lower than the contents of P9,D3 and D6.(2)Soil fungal and bacterial abundances did not differ significantly between the different sites,but the true-to-fine ratio was significantly different(p<0.05),and CK was significantly higher than the other sample sites.Alpha diversity was not significantly different between sites,but the similarity test showed that Beta diversity was significantly different(p=0.001).(3)The top 10 bacteria at the phylum level with significant differences were Bacteroides(5.90%),Planctomycetes(5.34%),Latescibacteria(3.31%),and Actinobacteria(3.25%).At the order level were Myxococcales(10.68%),Pedosphaerales(5.24%),Rokubacteriales(4.74%),Nitrospirales(4.97%),Desulfuromonadales(3.55%),SBR1031(3.96%).The top 10 fungal phylum levels with significant differences were Rozellomycota(2.80%),while the order level was Sordariales(24.04%).(4)Bacterial communities were significantly correlated with soil SOC,AP,BD,pH,NH4+(p<0.05).Fungal communities were significantly correlated with soil AP,pH,NH4+,SOC,TN,and water content(p<0.05).(5)The total number of nodes,total number of edges,mean path length and network diameter of the microbial network showed significant differences between the sites.the total number of nodes(320),total number of edges(220),mean path length(1.9111)and network diameter(9)were significantly higher in CK than in P9,D3 and D6,and D3 was the lowest in all four sites.(6)The relative abundance of the C-cycle functional group of soil bacteria was the highest and significantly different(p<0.05),followed by the N-cycle functional group and the S-cycle functional group.Except for the S-cycle functional group,the rest showed similar results in terms of correlation with environmental variables.Soil fungi,on the other hand,were dominated by Symbiotroph and Saprotroph.The above results indicate that the plantation of poplar plantations significantly influenced the complexity of soil bacterial and fungal communities and their symbiotic networks.However,the soil bacterial and fungal communities in the deforestation sites did not shift to the reedbeds,suggesting that deforestation alone may not be sufficient to restore the wetlands and that further measures and longer time are needed for the restoration of wetland soil ecosystems.The results of this study can provide important data support as well as scientific guidance for the ecological restoration of Dongting Lake. |
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