| In this study,we used the method of time-space mutual substitution in order to explore the variation characteristics of soil organic carbon and its fractions under different restoration years and different restoration modes in the process of vegetation restoration,the content of soil organic carbon,soil labile organic carbon and black carbon was studied in Larix gmelinii plantation of different restoration years,Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation in severely burned areas of Greater Xing'an Mountains.Results indicated that:(1)Whether different restoration years or different forest stands,the vertical distributions of soil organic carbon and its fractions were consistent,and that decreased with soil depth increasing.The soil carbon pool of Larix gmelinii plantation was greatly affected by the restoration years in the progress of vegetation restoration.The content of soil organic carbon ranged from 20.58 to 90.24 g/kg,which increased significantly during 5~18 years of vegetation restoration,but almost remained unchanged during 18~23 years of vegetation restoration and then began to rise.The soil organic carbon pool of Larix gmelinii plantation got better recovery after 26 years of vegetation restoration.The content of soil organic carbon ranged from 46.43 to 90.24 g/kg,from 27.95 to 74.05 g/kg and from 17.55 to 40.03 g/kg in Larix gmelinii plantation,Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation respectively,and the difference reached a significant level among different forest stands(p<0.05).(2)The content of readily oxidizable carbon,microbial biomass carbon and water soluble organic carbon ranged from 3.92 to 28.19 g/kg,from 117.20 to 859.15 mg/kg and from 28.33 to 123.39 mg/kg in Larix gmelinii plantation of different restoration years,which showed an increasing trend with the increase of restoration years.The content of readily oxidizable carbon ranged from 16.05 to 28.19 g/kg,from 9.24 to 23.92 g/kg and from 8.00 to 16.92 g/kg,and the content of microbial biomass carbon ranged from 397.26 to 859.15 mg/kg,from 154.78 to 464.76 mg/kg and from 94.65 to 186.24 mg/kg,and the content of water soluble organic carbon ranged from 82.54 to 123.39 mg/kg,from 46.65 to 76.20 mg/kg,and from 27.52 to 47.90 mg/kg in Larix gmelinii plantation,Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation respectively.The content of labile organic carbon was highest in Larix gmelinii plantation,followed by Betula platyphylla secondary forest,which in Pinus sylvestris var.mongolica plantation was lowest.(3)Regression analysis indicated that readily oxidizable carbon,microbial biomass carbon and water soluble organic carbon were extremely significant correlated with each other(p<0.01),which demonstrated that all of them can represent labile organic carbon to a certain extent,and the correlation between microbial biomass carbon and water soluble organic carbon was the highest.The ROC/SOC showed an increasing trend with the increase of restoration years as a whole.The ROC/SOC was lowest at 0—5 cm soil layer in Larix gmelinii plantation,followed by Betula platyphylla secondary forest,which in Pinus sylvestris var.mongolica plantation was highest.Soil microbial quotient increased in the early period of restoration,but decreased a little during 23~26 years of vegetation restoration.Soil microbial quotient was highest in Larix gmelinii plantation,but the difference did not reach a significant level between Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation(p>0.05).The WSOC/SOC increased with soil depth increasing,which firstly increased then decreased with the increase of restoration years,and was highest in 23 years of vegetation restoration.There was significant difference in WSOC/SOC at 0—5 cm soil layer among different forest stands(p<0.05),with the maximum WSOC/SOC for Larix gmelinii plantation.(4)The content of black carbon ranged from 3.63 to 21.70 g/kg in Larix gmelinii plantation of different restoration years,which showed an increasing trend with the increase of restoration years.The content of black carbon ranged from 8.88 to 21.70 g/kg,from 5.51 to 18.01 g/kg,and from 2.43 to 5.51 g/kg in Larix gmelinii plantation,Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation respectively,with the maximum black carbon content for Larix gmelinii plantation,followed by Betula platyphylla secondary forest and Pinus sylvestris var.mongolica plantation successively.And there was significant difference in black carbon content among different forest stands(p<0.05).The BC/SOC showed an increasing trend with the increase of restoration years at 0—5 cm soil layer,which in Larix gmelinii plantation and Betula platyphylla secondary forest was significantly higher than those in Pinus sylvestris var.mongolica plantation(p<0.05).Regression analysis indicated that the soil organic carbon displayed an extremely significant linear correlation with black carbon(p<0.01),which demonstrated that black carbon was an important component of soil organic carbon. |
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