Priming Effect Of Biochar Pyrolyzed At Varying Temperatures On Decomposition Of Soil Organic Carbon And The Related Microbialmechanism Of Poplar Plantations

Forest ecosystems are the largest and most stable carbon sinks.Carbon sequestration in plantation has become an important research topic.Soil carbon accumulation is an important approach to achieving to carbon sequestration in planted forests.In this study,a sample of soil ecosystem with 20-year-old poplar plantation was used to conduct the lab incubation experiment through the isotope labeling technique.Two kinds of rice straw biochar addition were prepared at300? and 500? respectively to researchthe priming effect on soil organic carbon decomposition.Meanwhile,the mechanism of biochar addition on the priming effect was discussed based on the availability of soil carbon sources and changes in microbial communities.The research is aiming to provide theoretical basis for enhancing soil carbon accumulation in poplar plantation.The results are shown as follow:?1?After 60 days of culture,biochar significantly changed the soil microbial community composition?p<0.05?,and the effect of biochar prepared at 500? was higher than that of biochar prepared at 300?.In the early culture period?0-7 d?,biochar increased the proportion of oligotrophic G⁺bacteria and decreased the proportion of fungi and actinomycetes;while in the later culture period?30-60 d?,biochar enhanced the trophic G^-The proportion of bacteria,and increase the proportion of fungi and actinomycetes.Moreover,biochar significantly reduced soil fungi/bacteria?p<0.05?,G^-bacteria/G⁺bacteria?p<0.05?and aerobic/anaerobic bacteria?p<0.05?only after 7 days of culture.?2?The effect of biochar on soil enzyme activities was mainly in the late culture period?30-60 d?.During this period,biochar increased the activity of soil glucosidase,cellobiosidase and phenol oxidase,but inhibited.Soil laccase activity.?3?Biochar prepared at 300? can significantly promote soil CO₂ emissions,and biochar at500? has a certain degree of inhibition on soil CO₂ emissions.Biochar prepared at 300? had a positive priming effect on soil organic carbon decomposition in poplar plantation,and biochar produced at 500? had a negative priming effect.CO₂ emissions from soils stimulated during culture were 5.55 and-25.3 mg C kg^-1,respectively.The relative sizes of the priming effects were3.35%and-15.2%,respectively.In summary,the addition of biochar affects the stimulating effect of soil organic carbon decomposition by affecting the soil microbial community structure,but in addition to the soil microbial community,biochar may also affectthe priming effect of organic carbon decomposition by changing the carbon source and chemical properties of the soil.