Abstract: With more than 200 years old primitive Korean pine and broad?leaved climax forest and its two 20 and 80 years old secondary Populus davidiana and Betula platyphylla forests in Changbai Mountains as test objects,this paper studied their root biomass and underground C and N storage.The results showed that the root biomass of 20 years old,80 years old,and climax forests was 2.437,2.742 and 4.114 kg·m^-2,respectively. with forest succession,the root C storage was 1.113,1.323 and 2.023 kg·m^-2,soil C storage was 11.911,11.943 and 12.587 kg·m^-2,and underground C storage was 13.024,13.266 and 14.610 kg·m^-2,respectively,while the root N storage was 0.035,0.032 and 0.038 kg·m^-2,soil N storage was 1.207,1.222 and 0.915 kg·m^-2,and underground N storage was 1.243,1.254 and 0.955 kg·m^-2, respectively, which indicated that along with forest succession,forest underground became a potential “carbon sink",whereas underground N storage did not change obviously.

Key words: Dissolved organic matter, Extraction method, Origin, Composition, Bioavailability, Environmental significance