Abstract: We examined the vertical distribution characteristics of soil organic carbon (C), total nitrogen (N), total phosphorus (P) and their ecological stoichiometric ratios in 0-80 cm soil profile under three forest stand types in the middle and lower reaches of the Beijiang River, including broad-leaved forest, coniferous forest, and mixed coniferous and broad-leaved forest. The results showed that soil C, N and P contents of the three forest stand types were 12.17-14.25, 1.14-1.31, and 0.27-0.30 g·kg^-1, respectively. The contents of C and N decreased with the increases of soil depth. The content of C and N in each soil layer showed that coniferous and broad-leaved mixed forest > coniferous forest > broad-leaved forest. There was no significant difference in P content among the three stand types, and there was no obvious variation in the vertical profile. The soil C/N, C/P, and N/P of the three forest types were 11.2-11.3, 49.0-60.3, and 4.5-5.7, respectively. There was no significant difference in soil C/N among the three stand types. The highest soil C/P and N/P were found in the mixed forest. There was no interaction between soil depth and stand type in affecting soil C, N, P contents and their stoichiometric ratios. There was significant positive correlation between C and N, and between N and C/P in each stand type and soil layer. Soil C/P and N/P had stronger ecological indicating effects on stand types. The coniferous and broad-leaved mixed forest was strongly limited by P availability.

Key words: stand type, soil nutrient, ecological stoichiometry, vertical distribution