Abstract: In this study, the effect of vegetation on soil fertility was researched so as to guide the local vegetation construction. Nine pieces of planted forest in the northeast sandy area of the Ulanbuh Desert were taken as the study area,and 16 indicators of soil physical, chemical and biological properties were selected through the sensitivity analysis and principal component analysis to derive the integrated fertility index (I_IF)calculated with the fuzzy comprehensive evaluation approach. The content of physical clay < 0.01 mm, degree of aggregation, organic matter content, total N content, bacterial population and urease activity were selected as the soil fertility indicators, which could reflect the most information of soil fertility, and the coefficient of determination was 0.940 5. Holistically, the value of soil fertility was in an order of shrubbery > woodland > sandy land, shrubbery could improve soil, and I_IFof Caragana korshinskii was the highest. Therefore, the native nitrogenfixing shrubs should be considered as the dominant planted species, and some tree and herb species should also be selected, however, it is not suitable to plant trees in large area.

Key words: planted forests, soil fertility, principal component analysis, fuzzy comprehensive evaluation approach, Ulanbuh Desert