Effects Of Biochars Addition On The Mineralization Of Soil Organic Carbon Under Different Incubation Conditions

Global warming has a huge impact on the carbon cycle of terrestrial ecosystems,and biochar has important implicatibns for reducing atmospheric CO2 concentrations.At present,domestic research mainly focuses on the effect of single factor addition of biochar on soil organic carbon mineralizatin.It is rare for comprehensive analysis of multiple factors.In this paper,we studied the effects of biochars addition on mineralization of soil organic carbon(SOC)under different incubation conditions using 13C-labeled and PLFA techniques.Biochars(produced from different raw materials or pyrolysis temperatures),soil types and incubation condition were considered and the influence of biochar to soil microbial community structure was also investigated in our study.This will provide the valuable information for the rational utilization of biomass resources and for the sustainable management of soil carbon sequestratioN.The main results were as follows:The CO2 release rates of soil decreased rapidly with the increase of incubation time with biochar addition and gradually stabilized,and the CO2 cumulative release of soil also rapidly increased and then slowly increased.The mineralization of native SOC was significantly accelerated during the first few days and subsequently suppressed after biochar addition compared to the control soil.After 112 days incubation,all the three Cunninghamia lancedata biochar(350?,550? and 750?)additions significantly inhibited the mineralization of native SOC.A similar trend was true for the two Schima superb biochar(350? and 550?)additions but not for the Schima superb biochar(750?)additioa The decomposition rates of Schima superb biochar and Cunninghamia lancedata biochar were 0.78%-2.77%after 112 days of incubation and decreased with the increase of pyrolysis temperatures.Under the same pyrolysis temperature,the decomposition rate of the Schima superb biochar was significantly fester than that of the Cunninghamia lancedata biochar.Soil total nitrogen content(TN)was increased more evidently with biochar at 350? than biochar at 750?,but soil total carbon(TC)and C/N was increased more evidently with high temperature biochar addition.Under the same pyrolysis temperature,the Schima superb biochar and Cunninghamia lancedata biochar had no significant effect on the composition of soil microbial community.However,the addition of low-temperature biochar produced from the same raw material significantly changed the composition of soil microbial community.Effects of biochar(350? produced from Cunninghamia lancedata)addition on mineralization of SOC were different for Cunninghamia Lanceolata plantation soil and sugarcane soil.The CO2 release rate and cumulative release of soil with biochar were significantly higher in Cunninghamia Lanceolata plantation soil than sugarcane soil.Biochar addition suppressed mineralization of native SOC in Cunninghamia Lanceolata plantation but promoted in sugarcane soil.Decomposition rate of biochar in Cunninghamia Lanceolataplantation soil was significantly different from sugarcane soil.Biochars addition significantly increased the content of TN,TC,C/N but reduced DOC for both soils,and the change was more evident in sugarcane soil than Cunninghamia Lanceolata plantation soilThe CO2 release rate and cumulative release of soil and decomposition rate of biochar at 35O? incubation temperature were higher than at 25?.The CO2 release rate and cumulative release of soil with straw addition or mixed straw and biochar addition were significantly higher than those of the control soil and soil with biochar addition alone.The sources of CO2 were identified by 13C stable isotope labeling method.Except for the first day,biochar addition inhibited the mineralization of native SOC,but straw addition significantly promoted the mineralization of native SOC both at 25? and 35 ?.While the mineralization of native SOC at 25? incubation condition was significantly promoted,but significantly inhibited at 35? with mixed straw and biochar addition.Straw or biochar addition at 25?and 35? also significantly increased soil TN and TC content Soil C/N ratio at 35? was lower than that at 25?.At 25? and 35? the content of soil DOC with straw addition was the highest and with biochar addition alone was the lowest At 25? incubation condition,straw addition alone and mixed straw and biochar addition significantly increased the abundance of soil fungal and Gram-negative bacteria.The abundance of soil Gram-positive bacteria with the control soil or biochar addition alone was significantly higher than that of straw additions(straw alone or mixed straw and biochar),and the abundance of soil actinomycetes also significantly increased due to biochar addition alone.At 35? incubation condition,straw addition alone and mixed straw and biochar addition significantly increased the abundance of Gram-negative bacteria but significantly reduced the abundance of Gram-positive bacteria and actinomycetes in soil.