| Climate change characterized by warming and elevated CO2 concentration has a significant impact on the stability of soil organic carbon in rice-wheat rotation,while the sequestration and stability of soil organic carbon could has great feedback on it.Therefore,studies on the effect of climate change on different components and stability of soil organic carbon,microbial dynamics and the role of microbial residues in the accumulation of organic carbon could provide theory basis for accurate evaluation of the carbon sequestration potential of paddy soil under future climate change.In this study,the field experiment with long-term climate change was set up on a typical paddy soil from Tai Lake Region.Four treatments included the environmental conditions as controls(CK),the elevated atmospheric CO2 concentration by 500 mg·kg-1(CE),and the atmospheric temperature(crop canopy)increased by 2? on the environmental basis(WA),the elevated atmospheric CO2 concentration by 500 mg·kg-1 and the atmospheric temperature increased by 2?(CW).Topsoils(0?15 cm)were collected for incubation to investigate the response of soil organic carbon mineralization to different moisture regimes,analyze soil amino sugars and their impact on the contribution of soil organic carbon accumulation,and microbial community by high throughput sequencing.The results would classify the effect of long-term climate change soil organic carbon sequestration potential and its stability.The results are as below:1?Soil organic carbon mineralization intensity was affected by long-term warming and elevated CO2 concentration.The soil organic carbon mineralization showed the trend of increasing firstly and then decreasing to the change of moisture regimes basically.The organic carbon mineralization rate increased with moisture regime under the condition of less than 50%WHC,and decreased with the soil moisture over 50%WHC.Under the same moisture level,the CO2 production in CE,WA and CW treatments were significant lower than in CK treatments.2?The sensibility of the SOC mineralization to soil moisture had a significant difference under long term warming and elevated CO2 concentration.The four treatments have different sensitivities to moisture regimes.Compare with the CK treatment,under high moisture condition,the sensitivity of the soil organic carbon mineralization to moisture in CE,WA,and CW were decreased 76.3%,8.7%and 85.2%,while under low moisture condition,the moisture sensitivity in the three treatments were increased by 62.4%,10.3%and 22.1%,respectively.3?Long term warming and elevated CO2 concentration affected the content of amino sugars and their components in the soil.Compared with the CK treatment,the total amino sugar content and the content of each component in the CE treatment was increased significantly by 6.5%to 28.9%.The total amino sugar content and the accumulation of Glucosamine in the WA treatment had no significant change,but the Muramic Acid content increased by 22.1-29.1%significantly.The content of total amino sugars and each component in CW treatment was increased significantly by 17.3-39.98%.The contribution of microbial residue carbon to soil organic carbon was affected by warming and elevated CO2 concentration.Compared with CK treatment,CE treatment increased the contribution to microbial residual carbon to soil organic carbon pools by increase of the accumulation of fungal-derived carbon.WA treatment significantly increased the proportion of bacterial-derived carbon in organic carbon,but there was no significant change in the contribution to total microbial residual carbon to soil organic carbon pool.Contribution to total microbial residues and fungal residues to soil organic carbon storage in CW treatment did not change.4?Long-term warming and elevated CO2 concentration significantly afected the community structure of bacteria and fungi in the bulk soil and aggregates.Compared with the CK treatment,the OTUs and Chao1 indexes of bacteria in CE,WA and CW treatments were increased significantly by 2.23?2.55%and 1.13?3.11%respectively,while the OTUs and Chao1 indexes of fungi were decreased significantly by 10.21?14.59%and 4.31?10.49%.There were significant difference in OTUs and Chao1 indexes between different aggregates sizes in the same treatment.The OTUs and Chao1 indexes of bacteria in the macro-aggregates were higher than that in micro-aggregates and silt and clay fraction in CK,CE and WA treatments,while the CW showed that the micro-aggregates and the silt and clay fraction were larger than macro-aggregates.In CK and CE treatments,the OTUs and Chao1 indexes of fungi showed the highest in macro-aggregates,but WA and CW showed highest in silt and clay fraction.The relative abundance of major phylum levels in soil aggregates were significantly affected by long-term climate changes.Compared with CK treatment,CE treatment significantly reduced the relative abundance of Proteobacteria and Basidiomycota in macro and micro-aggregates,decreased by 8.44%and 52.31%,24.35%and 52.09%,respectively.WA treatment reduced the relative abundance of Proteobacteria and Basidiomycetes significantly in the silt and clay fraction,which were 12.66%and 58.21%,respectively.CW treatment increased the relative abundance of Acidobacteria in microaggregates by 12.05%,and decreased the relative abundance of Ascomycetes and Basidiomycetes by 11.32%and 54.03%,respectively.In summary,long term warming and elevated CO2 concentration could significantly change the soil organic carbon composition and its stability.Under the condition of future water pattern change,lower soil water content would help to reduce the decomposition of organic carbon,while the change of microbial community structure and the accumulation of soil stable components(microbial necromass carbon)may contribute to enchancing the stability of soil organic carbon under the condition of CO2 and warming.However,the interaction mechanism between stability of soil organic carbon and microbial change still need to be further studied. |
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