Abstract. After clear-felling of a first generation Chinese fir (Cunninghamia lanceolata) forest, mixed stands of Chinese fir and Michelia macclurei (a broadleaf tree) (MCM), pure M. macclurei stands (PMS) and pure Chinese fir stands (PCS) were established in 1983. The effects on soil were evaluated 20 years after planting by measuring physicochemical, microbiological and biochemical parameters. Both broadleaf monoculture and mixtures of broadleaf and conifer exerted a favourable effect on soil fertility. A soil quality index (SQI) decreased in the order: PMS (0.62) > MCM (0.57) > PCS (0.41). Improvement in soil quality, enhanced biological activity and forest productivity demonstrated that mixed stands are an effective measure to maintain sustainable forest productivity, as well as to control soil degradation under successive stands of Chinese fir. In addition, since the microbiological and biochemical parameters measured were sensitive to the forest management, they may be potential indicators for assessing the sustainability of different management systems. The results also showed that total organic carbon, cation exchange capacity and microbial biomass carbon are effective indicators of the improvement or deterioration of soil quality under forest.