Characteristics And Microbial Mechanism Of Soil Organic Carbon Mineralization Under Submerged And Aerobic Conditions

Soil organic carbon is an important component of soil,which plays an important role in soil fertility.The balance of CO2 in the atmosphere was impacted by the stability of soil organic carbon pool.On the one hand,the mineralization of soil organic carbon was conducive to the release of soil nutrients,which had a positive effect on the high yield of crops,but was not conducive to the maintenance of soil fertility.On the other hand,the concentration of CO2 in the atmosphere was increased by the mineralization of soil organic carbon.This change had a significant impact on global climate.At present,most of the researches on the mineralization of soil organic carbon were concentrated on the additional materials,mineralization of the soil original carbon was ignored,and only few studies focus on the chemical structure of organic carbon and the changes of soil microbes in the process of mineralization.In this paper,the mineralization of soil organic carbon under flooding and aerobic conditions was studied by using Biolog eco-board,16 S high-throughput sequencing technology and NMR solid-state nuclear magnetic resonance technique.The soil organic matter Chemical structure and bacterial community structure,the coupling relationship between the chemical structure of soil organic carbon and microbial community structure was explored.The results showed that(1)The total organic carbon in the soil was decreased by 8.68% under the submerged condition,while the total organic carbon in the aerobic condition decreased by 6.23% after360 d culture.The soil water-soluble organic carbon was significantly higher under submerged condition than that under the aerobic condition(p <0.05)during the whole incubation period.The mineralization rate constant of SOC was 0.0095 under submerged condition,which was significantly higher than that under aerobic condition.(4)The chemical structure of soil organic carbon was obviously different in submerged and aerobic conditions.The percentage of alkyl carbon was increased under the submerged condition,whereas the percentage of o-alkyl carbon was elevated under aerobic conditions.More o-alkyl was mineralized under the submerged conditions.The aromatics,A/ OA and BH / HI of soil organic carbon under the submerged condition were higher than that under the aerobic conditions.Due to a large number of easy mineralization components were mineralized to recalcitrant compounds under the submerged condition,and thus increased the stability of soil organic carbon.(2)The average well color development at 96h(AWCD96h)in submerged conditionswas significantly lower than that under the aerobic conditions from 0 to 15 d,no significant differences from 30 to 60 d,and significantly higher(P < 0.05)than that in aerobic conditions from 180 to 360 d,respectively.The carbon resources used by soil microorganism were mainly from amino acids at the beginning of incubation,then gradually evolved to phenolic acids(30-60 d)and amino acids(180-360 d)carbon in waterlogged conditions,while it was evolved to polymer carbon sources(60-360d)in aerobic conditions.(3)16S high-throughput study of bacteria showed that Shannon index and Equitability index of soil bacteria under the submerged conditions significantly higher than that under the aerobic conditions.The community structure of soil microbes was the same in different directions under submerged and aerobic conditions.The community structure of soil microbes was similar in 180 and 360 days incubation under both the submerged and aerobic conditions,but the community structure of soil microbes were evolved to different groups under the submerged and aerobic condition.It mainly dominated by Cryptosporidium,Phytophthora,Candidatus Nitrososphaera and Rhodospirillae under the submerged,while it are mainly Kaistobacte,Gaiellaceae,Ellin6067,Chitinophagaceae,Ellin5301 under aerobic conditions(4)The content of soil soluble organic carbon and the activity of soil microbes were improved under the submerged condition,and the community structure of soil microbes was changed,and the contents of soil microbial community were improved.The anaerobic microorganisms including Karyomonas,Phytophthora,Candidatus Nitrososphaera,Bacteria promoted cellulose,fatty acids and other substances in soil organic carbon degradation,then speed up the mineralization of soil organic carbon.