Spatial Distribution Characteristics Of Community Structure Components In Evergreen Broad-leaved Forest Of China

Evergreen broad-leaved forest(EBLF)has complex community structure and high biodiversity. It plays an irreplaceable role in maintaining the balance and stability of the ecosystems. EBLF in China is distributed in densely populated and economic development areas, subject to destruction severely. Therefore, it's necessary to carry out comprehensive, systematic and in-depth study to EBLF in China. In the study of plant communities, the community structure is often an important aspect of the research. By studying the structure,we can not only understand the plants'adaptation to the environment, tracing the evolution of the genetic relationship, but also help to understand their function, succession and classification.In this study, we analyze leaf type, leaf margin, leaf texture, leaf arrangement, leaf size, leaf size class, sexual system of flower, fruit type, fruit size and tree height of the species in the tree layer and shrub layer of the community. Study their gradient by longitude and latitude and the reason why it shows such trends. Following are the conclusions:In the latitudinal gradient, leaf type, leaf arrangement, leaf texture and flower sexual system shows a parabola change patten. In the vicinity of latitude 28°, simple leaves, alternate leaves and sclerophyll has the highest proportion. While bisexual flower reach the highest proportion in the vicinity of latitude 24°. Leaf margin, leaf size and fruit size is negatively correlated with latitude. In terms of fruit types, drupe which is in dominant position reaches a minimum value in the vicinity of latitude 28°, while the proportion of capsule reaches its peak here. In the change of leaf size class, the propotion of microphyll increased with the latitude, while the proportion of mesophyll decreased.In the longitude gradient, leaf type has similar changes with leaf arrangement. Simple leaf and alternate leaf has the highest proportion in the vicinity of longitude 114°. Leaf margin and tree height shows similar changes, presented the parabola change in the longitude range. Entire margined leaves reach the highest proportion at longitude 114°and tree has the highest height here too. It reaches the highest proportion of bisexual flower at longitude 102°, and it shows a parabola change in the area of longitude 110°-120°, reaching the peak at longitude 118°. In regard to leaf texture, the proportion of sclerophyll in the range of longitude 110°-120°is winding rise. Leaf size and fruit size decreases with the increased longitude. At longitude 102°, the proportion of drupe is larger than that in the longitude range 110°-120°, while capsule shows the opposite change. With respect to the change of leaf size class, microphyll and mesophyll are the two main components, as one falls, another rises. Microphyll shows a parabola change in the area of longitude 110°-120°, has the maximum in the vicinity of longitude 118°.Between the eastern and western part of EBLF, the ratio of simple leaf and alternate leaf in eastern part is higher than which in the western. In terms of fruit types, drupe has the highest proportion in both parts, and the ratio of capsule is higher in the eastern part, while aggregate is higher in the western. Concerning leaf size class, the eastern region dominated by microphyll, while the western region has slightly higher proportion of mesophyll. But because of the higher rate of nanophyll in western region, there is no significant difference within leaf size beween the two parts.Within the components of community structure we studied, leaf form is combined to the synthetic effects of many environmental factors. Leaf texture is mainly affected by frost-free season and extreme temperatures. Flower sexual system is mainly affected by extreme temperatures. Entire margined leaf is mainly affected by the mean annual temperature(MAT). Fruit type is mainly affected by MAT and the mean annual sunshine duration.Leaf size is mainly affected by frost-free season, the mean annual sunshine duration and the highest (lowest) mean monthly temperature. Fruit size is mainly affected by MAT and frost-free season. Leaf arrangement and tree height is not closely related to the environmental factors surveyed.In summary, species which have simple leaf, alternate leaf, sclerophyll, bisexual flower and freshy fruit are in the dominant position of EBLF in China. This reflects the warm and humid climate there.