| Crop straw is an important biomass resource,which contains a lot of lignocellulose and nutrient elements.In terrestrial ecosystems,crop straw decomposition is an important source of soil organic matter,which is the link connecting the aboveground and underground ecosystem.Soil microorganisms are the main decomposers of crop straw,which play an important role in nutrient cycling in terrestrial ecosystems.The decomposition of crop straw lignocellulose will affect microbial activity and microbial community,meanwhile soil microorganisms can regulate soil physicochemical properties by decomposing crop straw to release nutrients.It is still unclear that the microbial mechanism of straw decomposition under different land-use soils.Moreover,it is also unknown that soil microbiota transplantation affects the straw decomposition under simulated conditions.Based on the above questions,in-situ rice straw decomposition experiments and indoor microbiota transplantation simulation were carried out in different experimental sites soil(ZJ forestland,QL farmland and BG wasteland).The purpose of this study was to clarify the characteristics of straw decomposition and the succession of microbial community during straw decomposition in different land-use soils.The main conclusions are as follows:(1)Rice straw degraded in different land-use soils(ZJ forestland,QL farmland,and BG wasteland),and the decomposition rate was 64.42%in ZJ forestland,which was significantly higher than that in QL farmland(54.77%)and BG wasteland(52.13%)(P<0.01,F=478.1).It was found that straw degraded rapidly in the early stage,especially in the first 2 week,then showed a slowly and stable trend in the later stage.Correlation analysis showed that straw decomposition rate was significantly negative correlation with total carbon of straw and ratio of straw C/N(P<0.001,R2 R2TC=0.424,R2CN=0.847),and there was a significantly positive correlation between the straw decomposition rate and the total nitrogen of straw(P<0.001,R2TN=0.652).(2)Results of straw decomposition experiment show that the content of soil total carbon(TC),total nitrogen(TN),available nitrogen(AN),available phosphorus(AP),available potassium(AK),microbial biomass as well as beta-xylanase,beta-glucosidase,cellobiohydrolase and laccase around each site with straw added in are all remarkably higher than CK(without straw)through straw decomposition.Meanwhile,AN,AP,AK shows a trend of rise first then fall.TC of ZJ also turns out to first rise and then fall,while it changes a little in QL and BG.Correlation analysis reveals an outstanding positive relationship between TC,TN,AN,AK and straw decomposition rate(PTC<0.05,FTC=4.93,PTN<0.01,FTN=8.21;PAN<0.05,FAN=5.63;PAK<0.05,FAK=7.81).(3)With the straw decomposition process in the different land-use soils,the populations of culturable bacteria and fungi on the straw showed a tendency of increasing first and then decreasing.The populations of bacteria was significantly higher than that of fungi.The populations of bacteria and fungi in the ZJ forestland were significantly higher than that in QL farmland and BG wasteland,which was in accordance with the results of RT-PCR result.The soil and straw bacterial communities showed significant differences,and straw bacteria mainly derived from soil.Soil bacterial diversity decreased firstly and then increased with straw decomposition,while straw bacterial diversity show a opposite trend.Moreover,soil and straw bacterial diversity in ZJ were markedly lower than QL and BG.However,the fungal diversity in ZJ were higher than QL and BG.Compared with bacterial diversity,the trend of fungal diversity is relatively mild and soil fungal diversity was significantly higher than straw fungal diversity.(4)With the decomposition process in the different land-use soils,soil microbial communities were significantly different from straw microbial communities and microbial communities in ZJ was significantly different from QL and BG.At phylum level,bacterial communities were dominanted by Firmicutes,Actinobacteria,Bacteroidetes,Chloroflexi and Proteobacteria in the decomposition process.The relative abundance accounts of these leading microorganism for more than 90%of the total.And the most dominant phylum was Proteobacteria which showed a decreasing trend with the decomposition process.And the fungal communities were dominanted by Ascomycota,Basidiomycota and Zygomycota.During the decomposition process,different microbial groups showed different response.At genus level,the abundance of Rhizobium,Shinella,Bacillus and Cellulomonas,Pyrenochaetopsis,Dokmaia,Zopfiella,Cercophora,Penicillium on ZJ straw were significantly higher than that on QL and BG straw.Correlation analysis showed that these microbial groups had significant relation with the straw,lignocellulose decomposition and soil enzyme activities.All these microbial groups had a ability to produce lignocellulose-degrading enzymes,which may be the reason that more straw decomposition rate in ZJ forestland.(5)Highly efficient straw-degrading microbiota community of ZJ soil was transplanted into sterilized QL and BG soil to delve simulated straw decomposition ability and the succession of microbial community.The results showed that straw decomposition rate,enzyme activities and culturable microorganism populations were higher in QL than BG under each gradient,which also increased with decreasing dilution gradient.Similarly,the decomposition process was fast in the early stage,and then tended to be stable.Correlation analysis showed that the microorganism population and soil enzyme activities had significantly positive relation with the straw decomposition rate,which indicated that the microorganism populations and enzyme activities were important factors of straw decomposition.(6)Simulating soil microbiota transplantation of straw decomposition experiment showed that Ascomycota,Proteobacteria,Acidobacteria,Actinobacteria and Chloroflexi were the dominant phylum.The genus of bacteria mainly includes Agromyces,Micromonospora,Microvirga,Mesorhizobium,Bradyrhizobium,Lysobacter and Variovorax.And Idriella,Chaetomium,Penicillium,Fusarium,Dactylaria,Plectosphaerella,Staphylotrichum,Aspergillus.,and Trichoderma were the dominant genus of fungi.Correlation analysis indicated that these microorganisms were positively correlated with soil enzyme activity,which could effectively promote the decomposition of straw and play an important role in promoting carbon cycling in soil.Under the same gradient conditions,the ZJ soil microbiota was transplanted into QL and BG soils,and the microbial community showed significant differences,indicating that the physical and chemical properties of the background soil were also very important for the decomposition of straw.In addition,different gradients(10-1,10-3,10-6)were transplanted into the same soil,and the soil microbial community composition also showed significant differences.Rice straw decomposition during 16 weeks in different land-use soils which can improve the soil carbon,soil nitrogen,available nutrient,microbial biomass and enzyme activities.The straw decomposition ability in different land-use soils were quite distinct,and ZJ forestland possess the highest decomposition efficiency.The straw microorganisms came from the soil,which was the main driving force of straw decomposition.With the straw decomposition process,the main components of straw changed,which had effect on soil and straw microbial community dynamics.The number of microorganisms on the surface of straw and the abundance of some microorganisms on the surface of straw in ZJ forestland were significantly higher than that in QL farmland and BG wasteland.Moreover,simulated straw decomposition of microbial transplantation showed that ZJ soil microbiota could continue to play its high-efficient ability to degrade straw in heterotopic soil,meanwhile the different gradients of microbial community had a significant impact on straw decomposition rate for their distinct microbial community.Therefore,both in the field conditions and indoor simulation conditions,the efficiently functional microbiota is an important guarantee of straw decomposition,thus shortening the straw decomposition period. |
