Studies On Community Characters Of The Mid-montane Evergreen Broad-leaved Forest In Baishanzu Mountain

Baishanzu Mountain, which lies in Qingyuan County, the southwest of Zhejiang Province is an important part of Baishanzu-Fengyang National Nature Reserve. For nature and human disturbing, the typical evergreen broad-leaved forest of the low mountainous zone almost disappeared in this area. Large areas of evergreen virgin forest only exist in the mid-montane zone at its northern slope, with the altitude ranging from 1300 to 1700m. Virgin forests in mid-subtropical region in China were severely destroyed in most cases, but the forest of northern slope in Baishanzu Mountain is well-reserved.To survey the vegetation and analyse the floristic composition, physiognomy, community structure and species diversity, a 5 hm~2 permanent plot was established in the mid-montane evergreen broad-leaved forest in Baishanzu Mountain.1. Floristic composition There are 319 species of vascular plants in the plot (including subspecies, varieties and forms), belonging to 75 families and 156 genera, in which the pteridophyte accounted for 9 families, 12 genera and 15 species, the gymnosperm 4 families, 4 genera and 5 species, and the angiosperm 62 families, 140 genera and 299 species respectively. Families and genera (containing only one species) are various. Dominant species are significant, i.e. Lithocarpus brevicaudatus and Cyclobalanopsis multinervis are dominant within the forest community. The proportion of evergreen species is higher than that of the deciduous species. Characteristic species in subtropical mid-montane region, i.e. Lithocarpus brevicaudatus, Cyclobalanopsis multinervis and Camellia cuspidata are abundant and important.2. Flora characteristics Areal-type of species suggests that the forest is highly related to tropic components, while temperate components occupy fairly high percentages. Chinese endemic species give priority to East China-type, South China-type and Southwest China-type, while the non-endemic elements of this flora are Asia and East Asia region. All indicates that the forest is a mid-montane evergreen broad-leaved forest in the northern subzone of the middle subtropic.3. Individual quantitative traits-Abundance Lots of rare-species exist in the community, and the dominance of the dominant species is high. Common species, which stand for species with characteristics of the east part of subtropics in China, show high fitness to local environment. Some common species have strong abilities to clone and occupy most resources; thereby they are important in the community. Although it's on the climax stage of succession process, the distribution of the abundance is not even.4. Compositive quantitative traits-Importance value The dominant species are significant in the tree-layer, and they are Rhododendron latoucheae, Lithocarpus brevicaudatus, Cyclobalanopsis multinervis, Camellia cuspidata and Schima superba. Rhododendron latoucheae and Camellia cuspidata are also dominant in shrub-layer. In herb-layer, pteridophyte, i.e. Plagiogyria japonica is overwhelming both in quantity and importance.5. Physiognomy Meso-phanerophytes and micro-phanerophytes occupy the dominant position. Liane-phanerophytes and geophytes have higher percentage, while chamaephytes and therophytes are few. With regard to the leaf characteristics, the community is mainly composed of mesophyll and microphyll, orthophyll, simple leaf and non-entire leaf. It reveals that the forest is an old-growth middle-subtropical humid evergreen broad-leaved one.6. DBH class The DBH class distribution of stems shows as an "L", which means the seedlings have the highest dominant, and with DBH value increasing the number of stems decrease gradually. Large amount of the seedlings and saplings exhibit good regeneration, and as a result of the effects of intraspecific and interspecific competition and typhoon few individuals have super DBH. Distribution of the diameter's frequency is detected as exponential distribution, which indicates the stems are continuous distribution on the vertical space, and the community is on the climax stage of succession process.7. Vertical structure The community structure is complex, and the delamination is not obvious. The dominant species distribute in different two sub-layers of trees, and it lessens the competition on a certain extent. Upper canopy is discontinuous, and it is far from the under-layer. The dense shrub-layer contains many species, and it is the seedling pool of the community. Herb-layer is sparse but with rich species, and liana is various but lack of large individuals. In conclusion, the community is a typical middle-subtropical evergreen broad-leaved forest.8. Species diversity Among three layers, the Margalef index, Simpson index and Shannon-Wiener index in the shrub-layer are the highest, and the lowest for tree-layer. It demonstrates a consistent to the common phenomena of species diversity in subtropical forest ecosystem.