Carbon and nitrogen storage under different forest ecosystems in mid-subtropical regions

A comparative study on carbon (C) and nitrogen (N) storages under different typical forest ecosystems in mid-subtropical regions was conducted in 2006 via a localized method. The results show that C and N storages are highest under natural secondary evergreen broad-leaved forests. C and N storages in mixed broad-leaved and Chinese-fir forests are greater than in pure Chinese-fir forests. First rotation of pure Chinese-fir stands has higher C and N storages compared with successive pure Chinese-fir stands. Spatial distribution of C and N storages is basically consistent, and declines across the layers from soil, to tree, root, understory and to litter．Soil layer C and N storages are respectively positively related with understory and litter biomass, but not obvious related with stand belowground biomass.