Abstract: The Changes of flora, species diversity, predominance and age structure of the forest in Spirit Valley, Nanjing were studied, based on the data collected in 1951, 1981 and 1991 from the same plot. During the 40 years, the number of species has been changed from 75 to 56, being 50 in 1981. The number of individuals from 5 097 to 20 585 and then to 3 344. Meanwhile, little variation was shown in both Simpson index and Shannon-Wiener index. All the distribution curves of predominance fit log series type, indicating important function of the dominant species. In fact, the predominance of the first 6 species respectively accounted for 75.4% ,96.2% and 84.4% of the total. Population of the pioneer species, Pinus massoniana Lamb., showed a declining trend owing to its low survival rate of its seedlings. Instead, the age structure of Pistacia chinensis Bge. Forcasted its potential dominance in the future. Occurrence of ever-green broadleaved tree populations with advancing age structures not only showed the improvement of the habitat, but also the possibility of community development to zonal vegetation.

Key words: pecies diversity, Population, Species-abundance, North subtropics