Abstract: Comparative studies on the soil physical and chemical properties and Chinese pine growth in Chinese pine pure forest and Chinese pine-N fixers mixed forest show that the contents of organic matter, total N, total P. O lsen-P and available Nwere higher in mixed than in pure forest soil. In mixed forest soil, its bulk density and hardness decreased. and the initial penetration speed increased; thc growth of height and diameter at breast height of Chinese pine wasfaster in mixed forest, indicating that this forest was more effective on soil improvement. Basedon thc measurement of soil cnzyme activity and N-fixing capacity, the soil fertility 1evel of different water and soil conservation forests was evaluated comprehensively.

Key words: Water and soil conservation forest, Soil improvement, Soil enzyme activity, Nfixing capacity, baseline, marine ecosystem, stable isotope, compound specific stable isotope