Number of soil microorganism and enzyme activity and their relationship with soil nutrients were investigated with the density change of subalpine Fargesia denudate under the primitive Fargesia denudata-Picea purpurea forest in Western Sichuan.The results showed that with the density increasing

the number of soil microorganism and enzyme activity decreased which led to the decomposed rate of the forest floor decreased and the standing pool increased gradually.The storage of total and available P decreased significantly with the density increasing but there had no notable change for the storage of total and available N and K among different densities.There were significant correlation between the amounts of soil microorganisms and soil enzyme activities and soil organic matter

total N

total P

alkali-hydrolyzable N and available P.Therefore soil biological index can be used as evaluation index of soil fertility.In order to avoid soil degeneration and accelerate subalpine coniferous plantation succession and building the food base for panda

keeping suitable Fargesia denudate density would be a good measure for subalpine Fargesia denudata-Picea purpurea forest management.