Effect Of Pyrogenic Carbon Accumulation On Carbon Mineralization In Peatlands Of The Da Xing’an Mountains

Peatlands are an important component of terrestrial ecosystems,which contain rich soil carbon stocks and play an important role in the global carbon cycle.With climate change and rising global temperatures,peat soils tend to become drier and peatland fires occur more frequently.Fire not only directly cause the release of large amounts of carbon stored in peat soils but also generate large amounts of pyrogenic carbon(PyC)during the burning process.PyC has been of interest as a stable part of the soil carbon pool due to its chemical stability and slow decomposition in the soil.However,the mechanism of post-fire PyC entering the peatland soil and its effect on soil carbon release is still unclear.To address this issue,this experiment selected peatland soils in the Bilahe state-level nature reserves in the Da Xing’an Mountains as the research object,and used incubation experiments to study the carbon mineralization,microbial biomass carbon(MBC),available N,and soil enzymes in peatland soils under two incubation environments,aerobic and anaerobic,as well as PyC burning temperatures(250°C and 600°C)and cumulative concentrations(5% and 10%).phenolics,and soil enzymes to investigate the effects and driving mechanisms of PyC accumulation on the carbon pool of forest bog soils under different fire intensities.The main results are as follows:1.Changes in physicochemical indexes of peatland soil under the conditions of PyC accumulationDuring the incubation process,soil MBC and available N showed a decreasing trend,in which the MBC content was higher under aerobic incubation than anaerobic incubation,but the available N content was lower under aerobic incubation than anaerobic incubation.Under the aerobic culture condition,PyC-250°C increased the available N content and PyC-600°C increased the MBC content.Meanwhile,PyC-600°C increased the activity of β-D-glucosidase,which may be due to the fact that PyC accumulation promoted soil microbial activity,resulting in enhanced soil enzyme activity.In addition,the high concentration(10%)of PyC accumulation decreased the phenolic concentration in soil,which probably will reduce the inhibition of phenol oxidase in soil and increase the phenol oxidase activity.2.Change pattern of carbon mineralization in peatland soil under the condition of PyC accumulationDuring the incubation process,the total carbon mineralization of peatland soil showed an overall increasing trend.Compared with the control,PyC-250°C cumulative concentrations(5%and 10%)significantly increased soil carbon mineralization rate(22.3% and 45.2%),while PyC-600°C cumulative concentrations(5% and 10%)decreased soil carbon mineralization rate(8.48%and 12.3%).Differences in the nature of PyC produced at the two temperatures during incubation and in the cumulative concentrations altered carbon mineralization in peatland soils.3.Pyrolytic carbon accumulation affects enzyme activity and carbon mineralization by changing soil physicochemical propertiesUnder the conditions of PyC accumulation,the soil MBC content was significantly and positively correlated with the C mineralization rate in both aerobic and anaerobic culture incubations,and the soil available N content was significantly and positively correlated with MBC.This indicates that soil available N,MBC content and soil C mineralization rate are closely related,and the effect of PyC on available N content in soil and soil microbial activity is an important factor in changing soil C mineralization rate during incubation.In addition,soil MBC content was significantly negatively correlated with phenol oxidase,and phenol oxidase was significantly negatively correlated with soil C mineralization rate during aerobic incubation,but soil phenolics was significantly positively correlated with phenol oxidase.This indicates that phenol oxidase is also an important factor affecting soil carbon mineralization under aerobic incubation,while PyC accumulation may alter soil C mineralization by affecting soil microbial activity as well as phenolic content.High temperature PyC had a negative effect on soil C mineralization in peatlands,and wildfires caused loss of soil carbon pools,but high temperature PyC may have protected soil carbon pools.In summary,under the conditions of PyC accumulation,soil MBC,available N,phenolics,soil enzymes and soil carbon mineralization are closely linked,and the effect of post-fire PyC on carbon mineralization in forest bog soils should be paid attention to.Future research on the carbon pool of forest bogs should be oriented towards "carbon neutrality" and clarify the response mechanism of PyC to carbon release from bogs.In addition,this study provides a theoretical basis for the conservation of forest bog soil carbon pools through fire management,which is important for the conservation and management of peatland.