| Qinling Mountains, as the main natural boundaries of north-south climate and vegetation types, are typical regions of vegetation transition zone.So the study of plant community characteristics and bio-diversity are valuable. Foping state level natural reservation, located in the middle of the southern slope of the Qinling Mountains, is one ofthe regions with the highest, most sensitive and most remarkable biodiversity. It has typical and representative characters in both floristic composition and community types.Foping natural reservation was chosen as the study target, we conducted the first system research to community characteristics, distribution, species, biodiversity and endangered species. The results are shown as follows:The plant communities of Foping natural reservation have abundant diversity of species. The investigation indicates that there were 467 species in 283 genera of 113 families, including 276 genera of 107 families of seed plants and 7 genera of 6 families of Pteridophyta in investigated area. The members of the same genera and family show significant differences, which reflects the diversity feature of seed plants. The temperate properties of the flora are obvious and the geographic elements are complicated. The temperate elements dominate the whole community, and the species endemic to East Asia or China took large proportion. The results also show that the vertical structure of the community is obvious, which is composed of tree layer, bush layer and grass layer. In the life form spectrum of species, Phanerophytes and Chamaephytes hold superiority.Plant communities in Foping natural reservation were studied by the methods of TWINSPAN (Two-Way Indication Species Analysis) in this paper. The plant communities of Foping natural reservation were divided into 7 vegetation types and 24 community types.Using richness index, evenness index, and diversity index analyzed 24 communitytypes of Foping natural reservation. The results showed: (1) the analysis ofαdiversity index showed a consistent trend-grass layer>bush layer>tree layer, which was becau se plant diversity depend on its richness and evenness. (2) The indexes were related to the type of plant community. The diversity, richness and evenness among different community types had significant difference. The diversity index became much higher with more complexity of community structure and more richness of species. (3)The diversity was influenced by multiple factors, including community type, altitude, interference and habitat condition and so on. Theβspecies diversity indexes of Foping natural reservation had marked change with the increase of altitude. Theβspecies diversity indexes between 1200m and 1900 were highest, to which the main causes were few artificial interference and good environmental conditions. The biggest values ofβwh(Whittaker index) andβwi(Wilson index) dropped in the altitude between 1550m and 1650m, which reflected a transition from bush community to plant community. The maximum values ofβwh(Whittaker index) andβwi(Wilson index) dropped in the altitude between 1850m and 1950m, which reflected a transition between broad-leaved trees and coniferous trees. The differences among theβdiversity indexes of Foping natural reservationare significant, which indicated that there are few common species in different communities of Foping natural reservation, which was because most community types of Foping natural reservation exist as climax communities.There are 17 endangered species in Foping natural reservation. Among them, 1 species belonged to the first national grade protected plants and 16 species, the second.
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