| Soil erosion is serious on the Loess Plateau,especially in the Hilly and Gully Region.Alfalfa(Medicago sativa L)is a perennial legume forage with high quality and plays an important role in regional ecological environment construction and industrial structure adjustment.However,alfalfa continuous to be planted for many years,and its yield continuous to decline whiles the grassland is seriously been degraded.This experiment was undertaken on alfalfa(Medicago sativa L)that was cultivated under different growth years(7 a,14 a and 16 a)in a typical semi-arid area on the Western Loess Plateau.The Illumina MiSeq high-throughput sequencing technology was used to explore the structure and diversity of microbial communities in two soil layers(0-30 cm and 30-60 cm)under three treatments,and using statistical methods such as redundant analysis to explore the relationship between soil physical and chemical properties and microbial community structure and diversity.The aim of this study was to explore the response and mechanism of microbial community structure of alfalfa in different growth years,and to provide a scientific basis for the selection of suitable growth years of alfalfa.The main results are follows:(1)In the semi-arid Loess Plateau soil area,there are 36 phyla,90 classes,192 orders,375 families,716 genera of bacteria in the samples of alfalfa soil,and 6 phyla,23 classes,71 orders,148 families,291 genera of fungi.The distribution pattern and succession characteristics of bacterial and fungal communities were affected by the time of alfalfa planting.(2)Long-term cultivation of alfalfa in the rainfed area of the Loess Plateau significantly affected the diversity of the fungi community in the loessial soil,but did not significantly affect the richness and diversity of the soil bacterial community.(3)Actinobacteria(30.18%-34.73%),Proteobacteria(15.59%-21.33%),Acidobacteria(11.43%-13.41%)and Chloroflexi(10.84%-11.88%)were the dominant bacteria in alfalfa soil under different growth years on the loess plateau.In topsoil,the relative abundance of Actinobacteria decreased first and then increased with the extension of alfalfa growth years.The relative abundances of Proteobacteria and Chloroflexi increased first and then decreased with the extension of growth years.The highest abundance was 21.33% and 11.68%.The relative abundance of Acidobacteria appeared to increase with the extension of alfalfa growth years,and reached the highest in 16 a(13.41%).The dominant bacterial genera are classified as Gaiella(2.56%-4.99%),Nitrospira(1.55%-3.14%),Bacillus(1.01%-2.76%),and Pseudarthrobacter(0.49%-2.65%),Streptomyces(1.11%-1.82%).With the extension of alfalfa growth years,the relative abundance of Gaiella,Nitrospirillum and Paenibacillus gradually decreases,and Arthrobacter,Streptomyces,Blastococcus and The relative abundance of Nocardioides gradually increased,and the relative abundance of Sololibrobacter in 14 a was significantly higher than that in 7 a by 37.42%.(4)The dominant fungal phylum of alfalfa soil were Ascomycota(69.15%-91.45%),Zygomycota(5.23%-23.38%),and Basidiomycota(1.92%-5.48%).The relative abundance of Ascomycota was first decreased and then increased with the extension of planting years,and the relative abundance of Zygomycota and Basidiomycota was first increased and then decreased with the extension of planting years.The common dominant genus of alfalfa soil are Phaeomycocentrospora(10.49%-29.54%),Mortierella(5.21%-13.19%)and Beauveria(10.10%-13.02%),the relative abundance of 7 a Phaeomycocentrospora was significantly higher than that of 16 a and 14 a.The relative abundance of 14 a Mortierella was significantly higher than that of 16 a and 7 a.The relative abundance of Beauveria bassiana did not reach significant levels.(5)Redundant analysis showed that the two factors,soil organic carbon and Sucrase,were the key factors affecting soil bacterial community structure of alfalfa.While the alfalfa soil fungal community structure was affected by combination of environmental and biological factors. |
PDF Full Text Request