Dynamics Of Soil Microbial Communities In Revegetation Areas On The Loess Plateau Of China

Revegetation has been widely adopted on the Loess Plateau for its effective application in controlling soil erosion and restoring degraded environments.Vegetation restoration and succession are markedly impacted by plant-soil feedbacks,and the microbial communities play a key role in the feedbacks and the structure shaping of plant communities.By using high-throughput sequencing,the dissertation mainly focused on the taxonomic and functional responses of soil microbial communities and interactions between above-and below-ground communities in the process of revegetation on the Loess Plateau,and aimed to reveal the potential effects.Firstly,the structure of bacterial and fungal communities was significantly altered by revegetation,and the statistical analysis,which based on Bray-Curtis and Unifrac distance,demonstrated that the composition of both bacterial and fungal communities was markedly different among revegetation sites.The most abundant phylum of bacterial communities was Actinobacteria,and then followed by Proteobacteria,Acidobacteria and Chloroflexi,and the fungal communities mainly included Ascomycota,Basidiomycota and Zygomycota.The taxonomic alpha diversity of both bacteria and fungi was significantly increased with the vegetation succession,and their community similarities were dramatically decayed with time.The structure,composition and diversity of bacterial and fungal communities were significantly influenced by environmental variables;and the soil p H,organic matter and total nitrogen were the best predictors shaping their community structure.Secondly,the metagenomic sequencing suggested that there was a significant difference between the functional alpha and beta diversity of both grasslands and farmland,and the grassland converted from farmland for 30 years hold the greatest functional alpha diversity.Among all the measured environmental variables,the soil organic matter was the main driving force for those variations.Moreover,compared with the farmland,the grasslands had significantly increased the abundance of genes associated with energy metabolism,carbohydrate metabolism and xenobiotics biodegradation and metabolism according to the KEGG database;however,the farmland had greater abundances of genes associated with amino acid metabolism,glycan biosynthesis and metabolism,replication and repair and cell growth and death.When annotated to the CAZy database,the grasslands had higher abundance of carbohydrate degradation enzyme genes,including the GH3,GH13 and GH15 subfamilies.At last,there were significant interactions between above-and below-ground communities during the process of revegetation,and the alpha diversity of bacteria and fungi was found increasing with the plant alpha diversity,thus the plant alpha diversity can be a striking predictor for their alpha diversity.The beta diversity of bacterial and fungal communities was significantly correlated with plant beta diversity,and the soil variables also had obviously impact on their communities.The plant communities and soil variables had distinct influence on bacterial and fungal communities,for plant communities had a stronger impact on fungal communities than bacterial communities,and conditions were opposite for soil variables,suggesting different select processes for shaping bacterial and fungal commuities.