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Relationship Between Soil Organic Matter And Microbial Communities After Adding Straw

Posted on:2019-09-13Degree:MasterType:Thesis
Country:ChinaCandidate:J R LiFull Text:PDF
GTID:2370330566979914Subject:Soil science
Abstract/Summary:PDF Full Text Request
Straw returning is of great significance to soil nutrient cycling and improvement of soil organic matter.Microorganism plays a decisive role in the decomposition and transformation of straw and the accumulation of soil organic matter.The corresponding changes of microbial community will be affected by the addition of straw and changes in water conditions.As a whole,soil,microorganism and organic materials will affect and restrict each other to determine the level of soil nutrients.The method of indoor simulation is used in this experiment.First,32 soil samples from 15 provinces in China were collected to compare the accumulation of soil organic matter and the changes of microbe related indexes under different water conditions after adding the same amount of straw.Secondly,the response of organic matter of the two soils to straw addition under different water conditions was compared between purple soil and paddy soil cultivated for a long time in the vicinity of the school.Furthermore,DNA high-throughput sequencing method was used to reveal the relationship between the succession of microbial communities and the accumulation of organic matter in the process of straw decomposition in different soils.The main conclusions are as follows:1.There was a significant negative correlation between the relative change rate of soil organic matter content and the initial SOM content(p < 0.05).After 90 days incubation in the mixed soil-straw system,the change of organic matter content of 32 soil samples from different regions of the country showed different regulation.Under aerobic condition,the organic matter increased except HLJ-1,and the range of increase was 1.34g/kg~17.39g/kg.Under flooding condition,the content of organic matter increased in 87.5% of soil samples and decreased in 12.5% of soil samples,ranging from-12.02 g / kg to 9.34 g / kg.Under two different water conditions,The number of culturable microorganisms,the content of microbial biomass carbon(MBCs)and the activity of soil cellulase in the soil treated with straw were higher than those in the original soil without straw,and there were significant differences between the two treatments.The increase of quantity is aerobic > flooding condition.The increasing range of culturable microbial communities in group L was : eukaryote > bacteria > actinomycetes group H was actinomycetes > eukaryotes > bacteria;2.In order to understand the effect of farming methods on soil organic matter accumulation after adding straw,the soil samples of adjacent paddy soil(group P)and purple soil(group D)were collected in this study,which were cultivated for a long time in the vicinity of the school.The 90-day aerobic and flooding tests were further carried out.Each group consisted of 2 treatments,aerobic gas was D1 and P1,flooding was D2 and P2.The initial organic matter content in group D was 65.41% lower than that in group P.During the 90 days of culture,the organic matter of both groups decreased at first and then increased.At the end of culture,the average increase of organic matter in group D was 1.55 times of that in group P.The results showed that low initial organic matter content was beneficial to the input and fixation of exogenous organic matter.The change trend of microbial biomass carbon in group D and group P was the same,which shows a trend of increasing at first and then decreasing.P group was higher than D group on each day of culture cycle.It peaked on the 3rd day.When the peak was reached,microbial biomass carbon in group P was 2.34 times that in group D,and there was a significant difference between group P and its initial content(p < 0.05).The increase degree of microbial biomass carbon in group D was significantly higher than that in group P at the end of culture(p < 0.05).In the early stage(0-14 days),the activity of cellulase increased,and the decomposition rate was faster.The activity of cellulase in soil decreased at 14-90 days with the decrease of easily decomposable substances in straw.The cellulase activity in group D was higher than that in group P during most of the culture cycle.3.The organic matter content of D1 was higher than that of D2 in the whole culture cycle.At the end of culture,the increase of organic matter in D1 group was 1.34 times than that in D2 group.The increase of organic matter in P1 was faster than that in P2 at the initial stage of culture(0-35 days),but the soil organic matter content of P1 and P2 tended to be similar gradually at the later stage of culture(35-90 days).Compared with the initial value,the order of organic matter increase was D1 > D2 > P2 > P1 in the end of culture.There was a significant positive correlation between soil respiration rate and soil microbial biomass.The order of soil respiration increase was P2>P1>D1>D2 in the end of culture.During the 90 days culture period,the respiration rate of D1 was higher than D2 at 0 to 21 days,but the soil respiration rate of D1 converged with D2 after 21 days.The soil respiration rate of P1 was lower than that of P2 in the whole culture cycle.The respiration rate of P1 was only 84.85% of P2 when the difference was the largest.The order of cellulase increase was D1>D2>P1>P2 in the end of culture.The results showed that the straw decomposition and the accumulation of soil organic matter were affected by the original cultivation methods.4.DNA high-throughput sequencing was performed on soil samples at representative time points such as 1 d,3 d,7 d,14 d,90 d.The results showed that bacterial diversity in group P was higher than that in group D.D1 and D2 showed an increasing trend during the culture period,especially the shannon index of D2 treatment continued to rise.P1 and P2 showed a decreasing trend,especially P2.The diversity of fungi in group P was higher than that in group D,and P2 was significantly higher than that in group D at the end of the experiment(p < 0.05).During the culture period,D1 and D2 continued to decrease,P1 and P2 fluctuated during the culture period,but returned to the original level at the end of the culture period.The bacterial abundance in group P was higher than that in group D,and the bacterial abundance in group P was significantly or extremely significantly higher than that in group D at the end of the experiment(p < 0.01).During the incubation period,D1 and P1 treatments were relatively stable,while D2 showed a continuous increase,reaching 137% of the initial abundance at the end of culture.P2 decreased after 14 days of culture and was only 75% of the initial stage at the end of culture.In terms of fungal abundance,group P was higher than group D,and at the end of culture,group P was significantly higher than group D(p < 0.01).Group D decreased significantly during the culture period.At the end of culture,the abundance of D1 and D2 were 64% and 60% of the initial values,respectively.The abundance of P1 was stable and P2 showed a decreasing trend,which was 86% of the initial value at the end of the culture.The above results showed that the microbial diversity and abundance of group P(paddy soil)were higher than those of purple soil in dryland,and the microbial microenvironment was more stable than that of the latter,and the change of water condition has little influence.Fungi in dryland soil decreased significantly under humid conditions.5.The dynamics of soil microbial community succession during the culture period highlighted the role of unknown Hypocreales.The ascomycetes fungi have strong ability of cellulose decomposition.unknown Hypocreales is the dominant group of D1.From the beginning to the end of culture,the abundance increased from 17.2% to 74.42%,which was the reason why D1 had high cellulase activity.After flooding treatment of(D2),Colpoda became the dominant group.The initial dominant group of P1,Bursaria,was 60.43%,which disappeared gradually in the process of culture,and 67.32% of the total were unknown Hypocreales,unknown Sordaria fimicola and Aspergillus.P2 Colpoda increased at first and then decreased,and reached the peak at the 7th day,which increased to 58.79%.At the end of culture,the dominance of Colpoda decreased.The abundance of dominant groups of P2 microorganisms was similar,which showed that another species of Hypocreales,unknown Sordaria fimicola and unknown Hypocreales.During the whole culture period,the difference of microbial community succession was not obvious.According to the RDA analysis of the relationship between microbial community and organic matter change,the results showed that the unknown Hypocreales made an important contribution to the accumulation of organic matter in D1 soil,and there was a positive correlation between the content of organic matter in P1 and Bursaria,and Colpoda played a certain role in the accumulation of organic matter of submerged treatment(D2 and P2).
Keywords/Search Tags:Straw, Soil organic matter, microorganism, purple soil, purple paddy soil
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