| As a new form of soil tillage,conservation tillage is an inevitable choice for modern agriculture to walk the road of sustainability.Its main contents include mulching,no-tillage,rational utilization of water resources and rational rotation tillage technology,which is to improve the soil conditions,less land exposed,reduce pollution,maintain moderate roughness and moderate water and poss a sole benefit for ecology.Conservation tillage can cut down farming costs,increase yield of crops and improve the ecosystem of cropland.To study its effect on microbial diversity has important theoretical significance and practical value.The long-term controlled field experiment in Henan province is located in the Fengqiu national agro ecological experiment station,which was began in 2006.It was set up with tillage with mulching(CntWtS),no-tillage mulching(CntWntS),tillage without mulching(CntWt)and no-tillage without mulching(CntWt)treatments.Soil samples were gathered in 2013 November.Soil microbial diversity of four treatments,cellulose-decomposing microorganisms diversity of four treatments and the genetic variation of cellulose degrading fungal cellulase gene were studied.The results are as follows:1)The measurement of the physical and chemical properties showed that,the quantity of total nitrogen,organic carbon,total phosphorus,total potassium,nitrogen,phosphorus and potassium in the four treatments were as follows:CntWntS>CntWtS,CntWnt>CntWt,CntWntS>CntWnt,CntWtS>CntWt?The soil PH were weak alkaline and had no significant differents.2)Measurement of the number of microorganisms in the four different soils showed that,the number of bacteria,fungi and actinomycetes in no-tillage mulching were higher than others.Mulching improved the number of bacteria,fungi and actinomycetes.no-tillage increased the number of fungi in no-mulching.3)High-throughput sequencing analysis about diversity of microbial community structure showed that,the composition of soil microbial in four treatments in door classification level basically remained unchanged,but the number of microbe proportion had changed.Diversity index showed that mulching for long-term increased species richness,but long-term no-tillage mulching reduced the microbial diversity.OTUs analysis showed that 70.24%of OTUs common exists in four kinds of soil,OTUs in mulching treatments was proportion of 85.49%of the total OTUs,OTUs in no-tillage treatments was proportion of 78.74%of the total OTUs.Beta diversity analysis showed that four treatments microbial community structure changed dramatically.The long-term no-tillage and mulching has affected the soil microbial community structure.4)PCR-RFLP analysis about cellulose-decomposing microorganisms community diversity showed that,mulching significantly improve their diversity,no-tillage to a certain extent affect their diversity.Two mulching treatments had similar degree community diversity,other two no-mulching treatments had similar degree community diversity.Phylogenetic analysis showed that the sequences respectively belong to Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes,which contained the sequence number were 15,6,7 and 5,The dominant species was Proteobcteria.Redundancy analysis showed that cellulose-decomposing microorganisms in four treatments showed a significant difference in spatial distribution and that cellulose-decomposing microorganisms community structure changed greatly.5)The TRAP-PCR analysis about cellulose enzyme gene genetic variation of cellulose-decomposing fungi showed that,there were 19 primer combinations which had clearer electrophoresis bands,they were CBH ?-me1,CBH ?-me2,CBH ?-em2 and CBH ?-em3;CBH ?-me1;CDH1-me1,CDH1-me2,CDH2-mel and CDH2-me2;EG1-me1,EG2-me2,EG1-me2 and EG2-me1;Lac1-me1,Lac1-me2,Lac2-me2,Lac2-em2 and Lac1-em3.The PCR products by agarose gel electrophoresis results showed that the total number of bands were 942,the total number of polymorphic bands were 670.The percentage of polymorphic bands was 71.13%,they had high genetic variation. |
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