The storages,densities and spatial patterns of carbon in bamboo(Pleioblastus amarus) and birch(Betula platyphylla) forest ecosystems which had been converted by farmland 5 years ago were studied to understand the contribution of forests converted by farmland(FVF) to carbon sink.The results indicated that:(1)the carbon density of different bamboo organs varied from 0.348 5 gC/g to 0.518 6 gC/g,and the carbon density of different birch organs varied from 0.4519 gC/g to 0.513 7 gC/g;(2)the carbon density in litter layer were 0.341 7 gC/g and 0.395 3 gC/g beneath bamboo and birch forests,respectively;(3)the carbon storage was significantly and positively correlated with the biomass of the corresponding organs,the biomass carbon storage accounting for 48.87% and 53.06% of the total biomass and carbon storage in the bamboo forest,and for 57.25% and 57.27% in the birch forest,respectively;(4)in the forest,the soil held the largest carbon storage,the second was plant organs,and the smallest was the litter layer;(5)the soil carbon storage decreased because of the artificial disturbance during the initial of FVF;(6)the land of FVF would develop an important carbon sink.