Effects Of Different Intensity Burning On Soil Black Carbon Of Natural Forests In Great Xing’an Mountains

Black carbon (BC) is an important component of soil inert carbon library and plays an important role in soil organic carbon cycle. In this paper, mild and severe burned areas in Great Xing’an Mountains were studied. Through comparative study of contrast plots, the effects of different intensity burning on soil organic carbon and black carbon of natural forests in Great Xing’an Mountains were explored, the results showed that:(1) Mass fraction of soil organic carbon and black carbon in contrast plots, mild and severe burned areas decreased with soil depth. Whether mild or severe burning, the changes of soil organic carbon mass fraction was not significant. After mild burning, the changes of soil black carbon mass fraction was not significant. After severe fire, black carbon mass fraction of 0-5cm soil layer significantly increased from 13.66 g/kg to 35.03g/kg. Which indicated that the surface soil coking incomplete combustion of plants litter residues after severe fire made an important contribution to black carbon accumulation of surface soil. In three stands, mass fraction of soil organic carbon and black carbon showed a significant linear relationship (p <0.01). Which indicated that black carbon played an important role in forest soil organic carbon fixed process in Great Xing’an Mountains. In mild and severe burned areas, the proportion of BC/SOC was higher than control plots.(2) Mass fraction of soil light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), light fraction black carbon (LFBC) and heavy fraction black carbon (HFBC) in contrast plots, the mild and severe burned areas decreased with soil depth. In three stands, SOC of 0～5cm soil layer mainly existed in light components, LFOC/SOC were 68.19%, 67.77% and 79.79%. Compared with control plots. After a mild fire, the changes of soil LFBC mass fraction was not significant. After severe fire, the LFBC of 0～5cm soil layer significantly increased to 30.25 g/kg. The HFBC mass fraction of 0～5 cm soil layer in contrast plots was 6.45 g/kg, which significantly decreased to 4.41 g/kg after mild burning and significantly reduced to 4.79 g/kg after severe fire. The LFBC/BC of 0～5cm soil layer in contrast plots was 50.85%, after the mild and severe burning fire, LFBC/BC significantly increased to 71.73% and 84.74%, which made BC of 0～5cm soil layer mainly existed in light components.(3) The changes of LFBC/SOC in contrast plots, the mild and severe burned areas were 7.2%～8.27%,12.16%～15.24%,7.58%～23.83%. The changes of HFBC/SOC were 5.74% ～10.92%,6.09%～9.43%,4.19%～9.97%. The changes of LFBC/LFOC were 11.52%～ 18.73%,22.6%～31.45%,16.86%～29.82%. The changes of HFBC/HFOC were 24.32%～ 10.68%,10.32% 18.73%,19.21%～20.67%. LFBC showed a significant positive correlation with LFBC/SOC and LFBC/BC respectively (p<0.01), which showed a significant negative correlation with HFBC/SOC and HFBC/BC(p<0.01). HFBC showed a significant negative correlation with LFBC/LFOC (p<0.05), which showed a significant positive correlation with HFBC/HFOC(p<0.01). LFBC showed highly significant linear relationship with SOC (R2= 0.7854, p=0.000), and showed a significant linear correlation with LFOC (R2=0.8292, p= 0.000). HFBC showed a very significant linear relationship with SOC (R2=0.3674, p=0.001) and HFOC (R2=0.7872, p=0.000).