Study On Comparison Of Seed Plants Flora Of Dipterocarp Forest Between Xishuangbanna And Tongbiguan Natural Reserve

Dipterocarp forest is used to signify that the species from the Dipterocarpaceae is dominant in the composition of the upper forest. The species of the Dipterocarpaceae are the most luxuriant and representative in the tropical rain forests in Asia. Dipterocarp forest in Xishuangbanna nature reserve was typical tropical rain forest vegetation which was found in 1970s and caused great attention in the plant realm. Its area is about 800 hectare. Dipterocarp forest in Tongbiguan nature reserve was found by the experts of Southwest Forestry University in 1950s. There is the biggest area with about 4000 hectare and the most centralized distribution in China. This paper selected the two typical regions of the Dipterocarp forest, studied on the wilding seed plants which growed there and researched into their flora.There were 119 families, 390 genera and 782 spieces (including subspecies) of seed plants in the Dipterocarp forest of Xishuangbanna nature reserve. The dominant families (contains 10 species and more) were: Rubiaceae, Moraceae, Orchidaceae, Euphorbiaceae, Annonaceae, Lauraceae, Apocynaceae, Papilionaceae, Meliaceae, Myrsinaceae, Araceae, Rutaceae, Acanthaceae, Zingiberaceae, Asclepiadaceae, Palmae, Vitaceae, Verbenaceae, Urticaceae, Caesalpiniaceae, Sterculiaceae, Piperaceae, Fagaceae. The dominant genera which contained more than 6 species were: Ficus, Litsea, Lindera, Tetrastigma, Ardisia, Fissistigma, Psychotria, Ixora, Syzygium, Calamus, Garcinia, Millettia, Amomum, Maesa, Combretum, Dalbergia, Castanopsis, Beilschmiedia, Mycetia, Bauhinia. According to the distributional pattern, it showed that the families of tropical distribution took up 73.11%, with genera of tropical distribution accounting for 92.31% and species of tropical distribution accounting for 58.70% in the Dipterocarp forest of Xishuangbanna nature reserve. The flora of seed plant in the Dipterocarp forest of Xishuangbanna nature reserve was belonged to tropical flora because of the dominant composition of the tropical flora. At the level of genus, Tropical Asia type occupied 32.82% of the total number of genera. At the level of species, Tropical Asia type occupied 53.20% of the total number of species. With the strong Indo-Malesia characteristic, it showed that the flora belonged to one part of tropical Asia. Whereas the especial location in Xishuangbanna, this forest flora is showed the distinct character with northern margin of tropical SE Asia.There were 115 families, 405 genera and 797 spieces (including subspecies) of seed plants in the Dipterocarp forest of Tongbiguan nature reserve. The dominant families (contains more than 10) were: Orchidaceae, Rubiaceae, Annonaceae, Moraceae, Euphorbiaceae, Papilionaceae, Lauraceae, Zingiberaceae, Araceae, Apocynaceae, Palmae, Acanthaceae, Urticaceae, Asclepiadaceae, Sterculiaceae, Rutaceae, Meliaceae, Piperaceae, Cucurbitaceae, Gesneriaceae, Caesalpiniaceae, Myrsinaceae, Verbenaceae, Combretaceae, Menispermaceae. The genera that contained more than 6 species were: Ficus, Piper, Elatostema, Calamus, Millettia, Combretum, Fissistigma, Ixora, Dendrobium, Dalbergia , Syzygium, Mycetia, Psychotria, Aeschynanthus, Beilschmiedia, Alpinia, Bauhinia, Ardisia. In the floristic composition of this forest, the families of tropical distribution make up 73.91%; the genera of tropical distribution make up 93.33%. So the flora of seed plants in the Dipterocarp forest of Tongbiguan nature reserve was belonged to tropical flora, because of the dominant composition of the tropical flora. In the genera distributional pattern ,the genera of Tropical Asia is the most type with 34.07%. In the species distributional pattern, the species of Tropical Asia distribution and its sub-patterns occupy 52.20% of the total species. These showed that the flora have the characteristic of tropical Asia. As Tongbiguan natural reserve is located at the northern margin of SE tropical Asia, the temperate component is about 10% in the distributional pattern of families and genera, and more than 17% in species. So the flora of seed plants in Dipterocarp forest of Tongbiguan nature reserve is showed the distinct character with the nature of northern margin of tropical SE Asia.With the comparison, it showed that there are some comparative features between the flora of seed plants in two regions as follows:(1) Dipterocarp forest in the two regions both have high richness of species. However, there are poor gymnosperms in two regions with 2 families, 2 genera, 2 species in Xishuangbanna nature reserve and 2 families, 2 genera, 4 species in Tongbiguan nature reserve. According to the species richness, Dipterocarp forest in Tongbiguan nature reserve is enriched than Xishuangbanna.(2) Two regions both have high percentage of single-species families (containing only 1 species), single-species genera (containing only 1 species), few-species families (including 2 to 9 species) and few-species genera (including 2 to 5 species). This data indicated that the seed plants flora of two regions are both deficient.(3) In the distribution patterns, whether in the genus level or species level, the Tropical Asia pattern both have occupied the highest proportion in two regions. It indicated that the present flora of seed plants in the two regions both have fixed historical origins with Tropical Asia. The tropical distribution of species in Dipterocarp forest of Xishuangbanna nature reserve is higher than that of Tongbiguan, but the temperate distribution is lower. It showed that the floristic characterist of seed plants in the Dipterocarp forest of Xishuangbanna nature reserve has become more greatly influenced by tropical floristic elements than that of Tongbiguan.(4) The two regions have 109 families, 320 genera and 522 species in common. The coefficient of similarity of families and genus are both high, and the floristic similarity of families, genera and species between two regions has gradual decreased. The results showed that they had the same floristic origins, but the relative relation has weaken through time.(5) The flora of the Dipterocarp forest of Xishuangbanna nature reserve is more closely linked with that of Indo-Chinese Peninsula than the flora of the Dipterocarp forest of Tongbiguan nature reserve, and the flora of the Dipterocarp forest of Tongbiguan nature reserve is more closely linked with that of the east Himalayans.