| As a transitional ecosystem between land and water,wetland is closely related to human activities.Its ecological environment has been seriously degraded especially due to the rapid urbanization,agricultural reclamation and water pollution,which further affects soil nutrient cycle and distribution characteristics,and causes changes in soil ecological function.In the process of degradation and ecological restoration of urban lakeside wetland,microorganisms are very sensitive to the changes of soil parameters caused by natural and human disturbance,and respond to the soil environment through the shifts of community functional metabolism characteristics and structural composition diversity.In the study,we took different ecological restoration patterns as the research object,based on the Biolog-EcoPlate and 16S rRNA sequencing technologies,analyzed comprehensively the effect of ecological restoration on soil physicochemical properties,carbon sequestration and labile organic carbon fractions,soil microbial metabolic characteristics and bacterial community composition diversity,which was to provide experiment basis for revealing the interaction between vegetation,soil and microorganisms.The main conclusions were lists as follows.(1)In the four different ecological restoration patterns of farm land(FL),forested wetland(PL)and grass land(GL)and reed land(RL),there was obvious effect of the surface in soil organic carbon,dissolved organic carbon,particulate organic carbon,hot-water soluble organic carbon and microbial biomass carbon content,which presented downtrend with the deepening of the soil.However,the variation of easily oxidizable organic carbon between soil layers was not in sync with other labile fractions,especially in the growing season,the easily oxidizable organic carbon content was evenly distributed between different soil layers and different restoration patterns.Besides,significant or extremely significant positive correlations were found between soil organic carbon and labile organic carbon fractions(P<0.01 or 0.05).(2)Soil carbon storage was mainly distributed in the surface layer(0-10 cm)in different patterns,and the change trends were as follows:FL>PL>GL>RL in the dominant season and FL>GL>PL>RL in the growing season.In addition,the carbon storage in FL,GL and RL decreased with the deepening of soil layer,while that in PL showed a trend of firstly decrease and then increase.Moreover,taking GL type as the reference,the carbon pool management index of PL,RL and FL in the 0-20cm soil layer of vegetation dormant and growing seasons were higher,showing a decreasing trend with the deepening of soil layer.Consequently,the soil quality of PL,RL and FL patterns were batter than GL pattern.(3)The utilization of single carbon source by soil microbial communities in different soil layers and restoration patterns was different.In the surface 0-10 cm soil,the seasonal difference in the overall metabolic activity of the soil microbial community was not obvious.The average well color development value of the community was the highest in RL and the lowest in GL in both the dormant and growing seasons.However,the average well color development values of 10-20 cm soil were significantly different from the surface.In the second layer,the metabolic activity in FL soil was the strongest in both seasons,while the lowest was in RL(dormant season)and GL(growing season).In addition,the diversity index differences of soil microbial communities among different restoration patterns were mainly reflected by the season,especially for the second layer of 10-20 cm.According to principal component analysis,the main types of carbon sources playing a differentiation role in the metabolic characteristics were carbohydrate and carboxylic acids.(4)The diversity index and structure composition of surface soil bacterial community were different with the shifts of seasons and restoration patterns.In the vegetation dormant season,all diversity indices in GL were the lowest.While In the growing season,the indices in RL were the lowest,and in FL were the highest.Analyzing from the phylum level,Proteobacteria,Acidobacteria and Actinobacteria were the three main categories of soil bacteria in both seasons in the four recovery patterns,while the relative abundance of Chloroflexi was higher than that of Actinobacteria in the growth season.At the genus level,the differences became prominent--in the first 20 genera with the highest relative abundance,only the relative abundance of Gpl,Gp7 and Ktedonobacter in the dormant season was not significant among the four patterns,while the other 17 genera were all significantly different;18 genera and Others have significant difference in the growing season,except the Latescibacteria_genera_incertae_sedis(P<0.05).Besides,at the phylum level,Verrucomicrobia and Chlorobi were simultaneously affected by different ecological recovery pattern,season and their interactions.In addition,Latescibacteria was significantly affected by the interaction between patterns and seasons,but the effects of the two alone were not significant.At the generic level,Gp4 and Gp7 are influenced by patterns,seasons and their interactions.(5)Ecological restoration induced changes in soil environmental factors,thereby affecting the relationship between soil carbon cycle,microbial carbon source utilization and bacterial community composition diversity.Among the soil environmental properties,the contents of dissolved organic nitrogen,nitrate nitrogen,total nitrogen and magnesium were significantly positively related to soil organic carbon and labile carbon fractions(P<0.05 or 0.01).The result of redundancy analysis and Pearson's correlation analysis demonstrated that there existed obvious differences of carbon source utilization and structural characteristics of soil microbial communities under different restoration patterns,and the dominant soil factors significantly affected the microbial functional and compositional diversity.On the one hand,ammonium nitrogen content in soil had a significant impact on microbial carbon source metabolism level,among which ammonium nitrogen was positively correlated with the utilization of carboxylic acids.On the other hand,we found ammonium nitrogen content was significantly positively related to the relative abundance of Acidobacteria,and negatively to TM7 in both seasons,which indicated ammonium nitrogen significantly influencing the structure and composition of soil bacterial communities. |
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