Abstract: In this paper,theforests of Genhe city in Greater Khingan range as the research objects.Among forests of different ages and located in the same region,the effects of fires of different intensity on the different physical and chemical properties of soil black carbon and organic carbon were analyszed.The conclusions are as follows.With the change of fire intensity,the content of black carbon in soil changed accordingly.Compared with the control sample,at the primary stage of the formation of severe forest fires,soil black carbon content was 146.29 g/kg,an increase of 118.3%.Soil organic carbon content was 105.31 g/kg,an increase of 189.3%.Lightly burned soil black carbon was 110.93 g/kg,an increase of 65.5%;while the organic carbon content was 52.30 g/kg,an increase of 43.7%.In the forest fire after several years,variations of black carbon content and organic carbon content in soil were different,but the overall trend was still increasing.Compared with the control plots,after the severe burn of soil black carbon sites were increased by 88.8%in 2015 and 32.3%in 2014;and organic carbon content increased by 61.6%in 2015 and 9.4%in 2014.Lightly burned soil black carbon content increased by 24.5%and 9.5%;and organic carbon content increased by 11.7%and 8.4%.Compared with the control plots,the content of black carbon and organic carbon in soil held relatively constant over the thirteen years following the fire.There is a relationship between the contents of black carbon and organic carbon content in soil.Organic carbon content will be increased with the increase of the content of black carbon.The analysis of the changes of soil black carbon content and organic carbon content in the aftermath of forest fire can help to deepen the understanding of the process of carbon cycle in the biosphere.

Key words: Fire;Soil black carbon;Soil organic carbon