Abstract: Artificial C. lanceolata stand dominates in the forest ecosystems of subtropical zone in China and occupies very important status in the production of timber. However , long term's practices and researches have manifested that, pure C. lanceolata plantations exha usted large amount of nutrients during the period of growth and development, and si multaniously, the amount of soil microbes declined year by year, the biochemical activity and oxidative-metabolic capacity got weaker, the degradation of forest land quality and productivity was brought about. Furthermore, repeatedly planting C. lanceolata trees in curred the land capability to decline gradually, and the toxic vanillin-like substances accumulated. Hence, the environment of soil became worse, and worse, and the produc tivity was cut down by mort than30 percent. Experiments confirmed that the mixed plantation of C. lanceolata and Michelia macclurei not only dispeled many defects of pure C. lanceolata stand, but also had better performances on ecological and economical effici ency. It is one critical way to solve the problems just related.

Key words: Pure C. lanceolata stand, Forest ecosystem, Quality of forest land, Productivity