Effects Of Plant Types On The Diversity Of Soil Microbes And Bacterial Laccases Genes In Desertification Grassland

As the active participants in element cycling and energy flowing,soil microorganisms are responsible for the mineralization of more than ninty percents of the organic matter in the ecosystem.Laccase,which is in relationship to the degradation of organic matter and carbon cycling,can decompose lignin completely.In order to understand the effects of plant types on soil properties,microbial community structure and the diversity of bacterial laccase genes in desertification steppe,seven typical plant communities including Syringa pinnatifolia var.alanshanica,Ulmus Glaucescens,Amygdalus mongolica,Ephedra rhgtidosperma,Convolvulus gortschakovii,Salsola laricifolia and Reaumuria soongorica were selected to collecte soil samples.The physical and chemical properties and enzyme activities of the samples were measured and the effects of plants on soil microbial diversity as well as community structure were studied via high throughput sequencing.The effects of plants on the diversities of bacterial laccase genes were further investigated by cloning and sequencing the fragments of bacterial laccase-encoding genes.The main research contents and results are as follows:(1)The enrichment effect of soil nutrients caused by the desert plants was quite different among the seven desert plants,and the difference was related to the size of plant individuals.The soil nutrients of S.pinnatifolia var.alanshanica,U.Glaucescens,A.mongolica,S.laricifolia and R.soongorica shrubs showed obvious enrichment effect but the enrichment effect was not obvious in the soil of E.rhgtidosperma and C.gortschakovii.(2)The effects of different plants on the richness,diversity and community structure of soil microorganisms were quite different.The abundance of bacteria in the soil was significantly increased by E.rhgtidosperma and C.gortschakovii;E.rhgtidosperma significantly increased soil fungal richness,while U.Glaucescens significantly decreased soil fungal richness.The bacterial diversity was increased significantly by S.laricifolia,A.mongolica,E.rhgtidosperma,and C.gortschakovii.The fungal diversity was increased significantly by S.laricifolia,but decreased significantly by R.soongorica.The dominant fungi were Ascomycota,Zygomycota and Basidiomycota in all the soil samples.All the other six plants decreased Basidiomycota and Chytridiomycota except S.pinnatifolia var.alanshanica,but the content of Zygomycota was enhanced by R.soongorica,U.Glaucescens,and A.mongolica,significantly.Actinobacteria was the most dominant bacteria in the soils from the shrubs of S.laricifolia,R.soongorica,E.rhgtidosperma,and C.gortschakovii,while Proteobbacteria was the most dominant bacteria in the soil of A.mongolica,U.Glaucescens,and S.pinnatifolia var.alanshanica.All the seven desert plants reduced the Actinobacteria content.Except S.pinnatifolia var.alanshanica,the other six desert plants increased the contents of Proteobacteria and Bacteroidetes.(3)The bacteria containing laccase genes in all the soils were distributed in 14 phylums and the proportion of Proteobacteria,Actinobacteria and Fimicutes was the largest in the bacterial laccase community.The biodegradation of organic matter in the soil of desertification grassland was dominated by bacteria rather than fungi.All the seven desert plants could increase the activity of soil laccase and change the richness and diversity of laccase producing bacteria in soil,which resulted in the acceleration of organic matter decomposition and carbon cycling in desert soil.(4)The litter from desert plants caused the increase of organic matter in desert soil,which enabled plants to enrich the functional microbiota such as Bacillus,Sphingomonas,Variibacter,Beauveria,Metarhizium,Volutella in the soil or to inhibit the growth of some microorganisms such as Fusarium,Alternaria,Leptosphaeria.As a result the microbial community structure was remarkably changed,which washelped to improve the stress resistance of desert plants.The increase of the abundance of dominant groups in bacteria and fungi enhanced the activities of urease,sucrase,and alkaline phosphatase,which contributed to accelerating the circulation of carbon,nitrogen,and phosphorus in the desert soil.