Investigation Of Microbial Communities Structure In Biological Soil Crusts Of Desert

Biological soil crust has an important role in arid area, which usually can be divided into three stage of microbiotic crust, lichen crusts and moss crusts. In this thesis, Large number of microbiotic crust were collected from desert soil. The Development process of microbiotic crust was studied and microbial communities in different developmental stages of microbiotic crusts was analyzed. The results are as follows:(1) In the process of development of microbiotic crust, it was a significant positive correlation among the thickness of crust, content of chlorophyll a and content of microbial biomass. With the development of microbiotic crust, the content of organic matter and total nitrogen in crusts soil were increased, water holding capacity was enhanced, and water permeability was decreased.(2) The development of microbiotic crust showed a obvious character of stage. The process of microbiotic crust development can be divided into four stage of formation stage, junior stage,middle stage and mature stage.(3) The results of high throughput sequencing showed that in the4development stage, the unique OTU of16S rDNA were21、30、18and33respectively and the common OTU of16S rDNA was157. The unique OTU of18S rDNA were all1and the common OTU of18S rDNA was39. In the development process of microbiotic crusts, the diversity and uniformity of prokaryotic microorganisms were increased, and reached the maximum uniformity of prokaryotic microorganismsis increasing, reached the maximum at the end of abundance at the mature stage. The diversity and uniformity of fungal community was basically stable in the process of microbiotic crusts development.(4) The main group of bacteria and actinomyces in microbiotic crusts were in31classes. In which, Bacillus and Cyanobacteria had obvious advantage in every stage, relative abundance of Cyanobacteria increased in middle and mature stage, and the populations of Actinobacteria, Chloroplast, Alphaproteobacteria and Bacilli which are near genetic relationship to Cyanobacteria had higher relative abundance in each stage. The main group of fungi in microbiotic crusts were in16classes. In which, Dothideomycetes and Pezizomycetes had obvious advantage in every stage, while Phomopsis, and Blyttiomyces were disappeared in the final two stages of development.