| The straw is an important renewable resource,has great potential utilization value,improving the utilization rate of the straw has great significance to our country agriculture sustainable development.Straw returning to field is the main way of straw recycling in our country at present.Soil microorganisms play an important role in straw returning to field decomposition.Soil aggregate is an important part of soil,which is very important for soil carbon sequestration and nutrient retention.Although many studies have shown that straw returning to the field can change the composition and structure of soil microbial community,few studies have analyzed the effects of straw returning to the field on functional microbial groups involved in cellulose degradation from the perspective of different aggregates.In this study,the soil was separated into soil aggregates with different particle sizes by dry screening method,and the change process of microbial communities in different aggregates after straw returning to the field was analyzed through indoor straw incubation experiment,focusing on the microbial groups that may be involved in straw degradation.Then,through the simulated passage experiment,cellulose was used as the only carbon source to enrich the high cellulose degrading bacteria for different aggregates,isolate and screen out the high cellulose degrading bacteria,and the research results are as follows.(1)The particle size of aggregates is the main influencing factor of bacterial community structure.The dominant bacterial species of aggregates include Acidobacteria,Proteobacteria,Actinobacteria,Chloroflexi and Bacteroidetes.After the addition of straw,Bacteroidetes and Firmicutes were enriched significantly,and the diversity of small aggregates(SA)and original soil(OS)and microaggregates(MA)at the early stage of incubation was significantly changed,so that the diversity of bacterial community decreased.Different ecological structures in different aggregates affect the structure of microbial communities.Straw addition was the main influence factor on fungal community structure.Straw addition significantly reduced fungal community diversity and significantly changed community structure in the late incubation period,which mainly resulted in the increase of Ascomycota abundance,suggesting that this group played an important role in straw degradation in the late incubation period.(2)Bacterial communities of different aggregates showed obvious differences.In the enrichment process,the passage rate of each aggregate enrichment system was microaggregates(MA)>small aggregates(SA)>large aggregates(BA)>original soil (OS).The degradation rate of MA enrichment system was the fastest,and the cellulose filter paper was more completely degraded by MA enrichment system in the continuous passage process.The degradation efficiency of cellulose was higher,and Streptomyces accounted for the majority in MA aggregates.After continuous passage,the cellulose degradation ability of each aggregation enrichment line was enhanced,and the enrichment lines with high cellulose degradation ability were enriched through the passage of each aggregation.Proteobacteria and Actinobacteria were dominant in different aggregates,and Firmicutes were significantly enriched in MA and OS aggregates.(3)Three bacterial strains CCNWLXL 1-35~T,CCNWLXL 12-2 and CCNWLXL 21-a isolated from farmland soil were identified in terms of morphological,physiological,biochemical,genetic and chemotaxonomic characteristics.The results showed that the three strains could represent a new prokaryotic microorganism species.The strain CCNWLXL1-35~Twas named Arthrobacter rhizosphaerae.Strains CCNWLXL 12-2(=JCM 35018,=CCTCC AB 2021546)and CCNWLXL 21-a(=JCM 35019,=CCTCC AB 2021545)were isolated from the same source as additional strains of this species.In conclusion,the fungal community in different aggregates was mainly affected by straw addition,and the bacterial community was mainly affected by soil aggregates of different particle sizes.The microbial community structure of different aggregates resulted in different cellulose degradation functions,and microaggregates showed better potential for cellulose degradation.This experiment revealed the response of bacterial and fungal communities in different aggregates to straw addition,which played an important role in realizing efficient utilization of straw resources,and also provided a theoretical basis for the influence of soil structure change on straw returning to the field. |
