Study On Soil Enzyme Activity And Microbial Diversity Of Wetland In Zoige Plateau

Wetland is a transitional ecosystem between terrestrial and aquatic ecosystems.It plays an important role in maintaining biodiversity and ecological balance.Its unique hydrology,soil,vegetation,and biological characteristics play important roles in protecting species and sustaining biodiversity.The microbial community in the wetland has a large number of species,active ecological functions,and plays a key role in the wetland ecosystem.The Zoige plateau wetland is located in the eastern part of the Tibetan Plateau,a sensitive area of global climate change.The Zoige County and Hongyuan County of Sichuan Province(101°30'E-103°30'E,32°20'N-34°08'N,elevation 3400-3900 m)is the main aera of Zoige plateau.It is the largest plateau peat bog central distribution area in China.The climate conditions are special,only divided into cold(November to April)and warm(May to October)season.This study aims to analyze the effects of changes in climate and geographical locations on the soil enzyme activity and microbial diversity in Zoige plateau wetland to fully understand the diversity of wetland microbial resources and provide a scientific basis for the protection and utilization of microbial resources.The wetland soil in Zoige County(Huahu),Hongyuan County(Qiongxi)and its transitional area(Maiwa)were selected to detect soil enzyme activity.BIOLOG microanalysis was used to analyze the functional diversity of microorganisms.The population diversity of culturable microorganisms was studied,the strains with cellulose and lignin degradation activity were further screened.The results are listed as below:(1)The activity of the six enzymes(catalase,polyphenol oxidase,urease,acid phosphatase,cellulase,invertase)and soil physicochemical properties were determinated and their correlation were analyzed.The catalase activity what was significantly lower in warm season than in cold season.The activity of polyphenol oxidase,urease,acid phosphatase and invertase in Huahu were all significantly higher in the warm season than in the cold season.There was no significant difference in polyphenol oxidase,acid phosphatase and cellulase activity of Maiwa and Qiongxi between cold and warm seasons.Catalase,polyphenol oxidase and cellulase activity showed no significant differences between the three sampling sites since the low temperature in the cold season is not conducive to the enzyme activity.In the warm season,the activity of polyphenol oxidase,urease and acid phosphatase in Maiwa and Qiongxi were significantly lower than in Huahu.The water,organic matter,available nitrogen and available potassium content in Huahu had significant differences between the cold and warm seasons,but there was no significant difference between Maiwa and Qiongxi.There was no significant correlation between enzyme activity and physico-chemical properties in the cold season,while the correlation was significant in the warm season,especially the correlation between polyphenol oxidase,urease,acid phosphatase,cellulase activity and organic matter,water content,sampling temperature,pH.The correlations between urease,acid phosphatase activity,and available nitrogen,available phosphorus content were significant.Therefore,it could be concluded that the change of enzyme activity is closely related to physical and chemical properties(eg.temperature)in Zoige wetland.(2)The BIOLOG microanalysis method was used to measure the total metabolic capacity of microbial communities,the metabolic ability of different carbon sources,the diversity index,and the utiliztion of dominant carbon sources for analysis metabolic function diversity.The total metabolic capacity of microbial communities was arranged from higher to low as Huahu>Qiongxi>Maiwa in the cold and warm seasons.The microbial carbon metabolism of different subregions was significant difference in the warm season,but it was not significant in the cold season.The carbon source metabolic capacity was higher in Huahu and Qiongxi in the warm season than that in the cold season,while the differece of Maiwa is not significant.In the cold and warm season,the three sampling sites had the lowest metabolic capacity for alcoholic carbon sources.Huahu had higher metabolic capacity for other carbon sources than alcohol,while Maiwa and Qiongxi has high utilization rate for sugars,amino acids and esters,and low utilization rate for alcohols,amines and acids in the cold season.The species evenness,richness,and diversity of the soil microbial communities in the warm season were better than those in the cold season,and the three sampling sites represented Huahu>Qiongxi>Maiwa.The dominant carbon sources for soil microbial utilization are sugars,amines and acids in the cold season,while sugars,amino acids and acids are dominant in the warm season,with some differences.(3)Flat colony counting method was used in quantity calculation of bacteria(4?,15? 25?,37?),fungi(25?)and actinomycetes(15?).The results of bacterial count analysis showed that bacteria quantity at different temperatures all was generally 4?,15?>25?>37? in the cold season.In the warm season,the number of bacteria at 37? was still the smallest,the overall number of bacteria is low in Maiwa.There was no significant difference between 4? and 15? in both cold and warm seasons.The results of fungal quantity analysis showed that the number of fungi for Huahu and Qiongxi were higher in the warm season than that in the cold season,and there was no difference in Maiwa.The number of fungi all showed that Huahu is the largest,while Maiwa is the smallest in the cold and warm seasons.Actinomycetes quantitative analysis results showed that the number of actinomycetes in warm season was more than that in the cold season only Huahu.The number of actinomycetes was highest in Huahu,and there was no significant difference between Maiwa and Qiongxi.The Maiwa showed low levels in the numbers of bacteria,fungi and actinomycetes may be due to the special geographic location of Maiwa and its high altitude,which is blocked by the mountain and is not separated in the warm and cold season.(4)Thirty seven strains of bacteria with degrading activity were isolated using cellulose and lignin degradation bacteria screening medium,they belong to three different phylums:Proteobacteria,Firmicutes,Enterobacteria.Among them,32 strains belong to five different genus,seven strains belong to cupriavidus,19 strains belong to bacillus,two strains belong to serratia,two strains belong to lelliottia,and two strains belong to enterobacter,and the remaining five strains can not be identified for the genus,the further identification is required.The +H1 strain was identified as cupriavidus metallidurans,the YX2 strain was bacillus velezensis,and the X8 strain was bacillus licheniformis based on morphological observation,physiological and biochemical analysis,16S rDNA sequence homology comparison,and phylogenetic analysis.The YX2 strain and +X8 strain are bacillus.Probablly,the spore-forming bacteria are more able to adapt the high altitude and low temperature in the Zoige plateau.This is consistent with the basic characteristics of microorganisms.The +H1 strain is a bacterium belonging to the cupriavidus which has the ability to transform heavy metals.This may be closely related to the heavy metal content in the soil of zoige wetland.