| Napahai plateau wetland,located in the southeast margin of Qinhai-Tibet Plateau,is an importantly international karst wetland with an origin of limestone type.It is one of the hot spots in global biodiversity conservation for its rich biodiversity bred by habitat diversity.However,Napahai wetland has suffered a widespread degradation to form a series of stages such as swamp wetland(SW),swamp meadow(SM),meadow(M)and reclaimed wetland(RW)due to human activities(e.g.,tourism,farming and drained).The degradation in Napahai plateau wetland can induce a significant change in soil physical and chemical properties and soil ecological process,which affects the composition and structure,diversity and ecosystem function of soil microbial community.In this study,a series of different degradation stages(i.e.,SW,SM,M and RW)were employed to explore the composition(bacteria and fungi),structure and diversity of soil microbial community during soil degradation processes,using the metagenomic and high-throughput Illumina platform sequencing technology.We analyzed the effect of changes in spatial-temporal characteristics of soil physiochemical properties on soil microbial community which caused by wetland degradation,and the response characteristics and mechanism of soil bacteria and fungi community to the wetland degradation.The results may are help to understand the response direction,degree,mode and characteristics of soil microbial community to wetland degradation,and can provide the interpretation for wetland degradation mechanism and guide the protection and control of wetland degradation.The main research results were as follows:(1)The degradation in Napahai wetlands significantly affected the spatiotemporal characteristics of soil physical and chemical properties.Along the degradation process from marshy grassland to the meadow or reclaimed wetland,soil water content gradually decreased,soil organic matter(SOM)and total nitrogen(TN)reduced,and C/N ratio increased.The results suggested that wetland degradation has led to the decrease in the sink of soil carbon and nitrogen.The vertical distribution of soil physiochemical properties was generally distributed in soil surface soils at the different degradation stages in the plateau wetland.Soil physical and chemical indexes decreased along the soil depth except for soil waster content(MC)and C/N.The physiochemical properties of soil had certain seasonal variations during the degradation process of plateau wetland.The total phosphorus(TP),total potassium(TK)and C/N were greater in the dry season than in the wet season,while other soil indexes were lower in the dry season than in the wet season.The seasonal variation in SM was more obvious in 0-20cm soil layer than in 20-40 cm soil layer,while that in M was no difference between the two soil layers,and that in RW was significant higher in 20-40cm soil layer than in 0-20cm one.(2)The degradation in Napahai wetlands significantly affected the composition,structure and diversity of soil bacterial communities and their spatial and temporal changes.The composition and structure of soil bacterial community in different degradation stages were different in the phylum,class and genus level.The dominate groups of soil bacteria were proteobacteria and Acidobacteria gate level,but there differences in relative abundance between the subdominant bacteria group and of other groups.The class was dominated by various subclasses in Proteobacteria,but differences existed among dominant subgroups.There was a significant difference in the classification levels among the different wetland degradation stages.The main genera in M was spartobacteria bacteria in verrucomicrobia,GP6 genera in Acidobacteria for RW,povalibacter and fusobacterium genera for SW,and bacillus cereus in Firmicutes and Xanthomonas in bacteroidetes for SM.In general,the degradtation caused an increasing trend in abundance and diversity of soil bacteria.Wetland degradation significantly affected the composition,structure and spatial and temporal dynamics of soil bacterial communities.In the vertical change,the composition and abundance of dominant soil bacteria in different degradation stages were significantly different at the the levels of phylum,the class,the genus,and the diversity of soil bacteria decreased along soil depth.In the seasonal variation,the soil bacteria in different degradation stages showed different changes in the abundance and composition at the levels of phylum,class,and the genus:the values of phylum,class,and the genus in SW and SM were ranked as dry season>wet season;the dominate phylum and the genus in M,and the dominate phylum and class in RW were dry season>wet season;the dominant class and genus in M and the dominate genus in RW were wet season>dry season;the bacterial diversity in 0-20cm soil layer in SW was wet season>dry season,and that in 20-40cm soil layer was the opposite;those in SM were wet season>dry season;those in M and RW were dry season>wet season.(3)The degradation of Napahai wetlands significantly affected the composition,structure and diversity of soil fungi communities and their spatial and temporal changes.There were significant differences in the composition and structure of soil fungi community at the phylum and class levels in different degradation stages.The dominate phylum and class in SW and SM were uncerrtain fungal classification fungi,while those in M were ascomycetes,archaeomycetes,ascomycetes,and basidiomycetes.The degradation of Napahai wetlands resulted in a decrease in the abundance of uncertain fungal classification fungi,but an increase in ascomycetes,basidiomycetes and zygomycetes.Fungal abundance and diversity generally increased with the degradation level of wetlands.The degradation of wetlands affected the spatiotemporal variation of soil fungal structure and diversity.The group composition of dominant fungi community and class in different soil layers at different degradation stages was basically stable,but there were significant differences in the abundance for dominant group(abundance>1%).The diversity of soil fungi in SM and M decreased along the soil layer,while that in SW and RW had no significant differences.The fungi diversity in two soil layers was wet season>dry season,while that in RW was dry season>wet season.There was no significant difference of seasonal variation in the diversity in two soil layers in M.(4)The changes in soil physiochemical properties caused by degradation of Napahai wetlands can significantly affect the structure and diversity of soil bacteria and fungi community,but there was a certain difference between seasons and between soil layers.The impact factors of soil bacterial community structure for 0?20cm soil layer in dry season were MC,SOM,TN,AN and TP,while those in 20?40cm soil layer were MC,SOM,TN,AN,TP,PH and C/N.The impact factors of soil bacterial community structure in wet season were TK and AK in 0?20 cm soil layer,while those in the 20-40cm soil layer were SOM,TN,AN and C/N.The impact factors of soil bacterial diversity in dry season were C/N,pH,TK,MC in 0-20 cm soil layer,while those in 20--40cm soil layer were MC,SOM,TN,pH,AN and TK.The impact factors of soil bacterial diversity in wet season were C/N,pH,AN,AK,TP,TK in 0?20cm soil layer,while those in 20?40 cm soil layer were MC,SOM,TN,pH,AN,TK and C/N.The impact factors of soil fungal community structure in dry season were C/N,pH,TK and MC in 0?20cm soil layer,while those in 20-40cm soil layer were MC,SOM,TN,AN,TP,pH and TK.The impact factors of soil fungal community structure in wet season were C/N,pH,AN,AK,TP and TK in 0?20 cm soil layer,while those in the 20?40cm soil layer were MC,SOM,TN,pH,AN and C/N.The impact factors of soil fungal diversity in dry season were MC,SOM,TN,AN,TP,AP and AK in 0?20 cm soil layer,while those in 20?40cm soil layer were TP,AP,AK and TK.The impact factors of soil fungal diversity in wet season were C/N and TK in 0?20cm soil layer,while those in 20?40 cm soil layer were TP,TK,AP,AK,SOM,C/N and AN. |
PDF Full Text Request