Abstract: By using space-time substitution method, an investigation was made on the species composition, density, and regeneration mode of woody plant seedlings in the primary moist evergreen broad-leaved forests and different type secondary vegetations in Xujiaba region of Ailao Mountains, Yunnan. The woody plant seedlings were of 46 species, including 31 tree species and 15 shrub species. Their density in virgin grassland, secondary Populus bonatii forest, Lithocaupus re-growth forest, and primary forest was 421.9±59.5, 34.4±8.1, 31.6±7.2, and 18.5±6.6 stems·25 m^-2, respectively. With the progress of succession, the proportion of shrubs decreased, while that of trees increased gradually. In the process of succession, the sprouting of shrub species was the dominant regeneration pattern at the early stage (grassland) whereas that of tree species was the major regeneration strategy at the late stage (primary forest), the density of woody plant seedlings decreased gradually, and the life-form and regeneration modes of the seedlings changed.

Key words: Vegetable, Nitrite, Pollution