Abstract:The changes of soil fertility in a 70-year-old fast-growing, highyield Chinese fir stand, which was originally occupied by a broadleaved stand, were studied for 2 consecutive years in Anchaoxia, Qihou, Nanping The results showed that the soil fertility of the 70-year-old fast-growing, high-yield-Chinese fir stand had declined obviously. In comparison with the original broad-leafed forest stand, the Chinese fir site showed increased soil bulk density, decreased soil organic matter content and nutrient element concentrations, and diminishing soil enzyme and other biological activities. The reason that the 70- year-old Chinese fir stand still maintains relatively high fertility is that the increased undercanopy space facilitates the maintenance of high species diversity and biomass production.