Abstract: The cycling of C, N and P is important in functioning of forest ecosystem. By applying the method of spatial sequence instead of time successional sequence, the contents and stoichiometric ratios of C, N and P in soil and root of larch (Larix spp.) in young (10 a), middleaged (25 a) and mature plantation (50 a) located in the montane region of eastern Liaoning Province, China were studied. The results showed that the contents of soil C, N and P decreased significantly with the increasing stand age. The soil C∶N and C∶P increased with the increase of stand age. The stand age had no significant effect on N∶P in soil. The N, P, C∶N and C∶P in roots changed significantly with the increase of stand age. The contents of N and P in roots decreased significantly with the increasing stand age. The root C∶N and C∶P increased with the increasing stand age. The stand age had no significant effect on the content of C and N∶P in roots. Our results suggested that the soil fertility of larch plantation declined with the increase of stand age. In order to improve soil fertility, regulation of stand structure by thinning and reasonable fertilization should be applied.

Key words: environmental efficiency, carbon emission, SBM model,  , Western China.