| Reevesia rotundifolia, a species of Reevesia genus from Sterculiaceae family, and a endangered species only natived in China, is distributed only in the south area of the Shiwandashan Mountain in Fangchenggang city, Guangxi. Based on thoroughly wild investigation, this paper statistically described the distributing status of R. rotundifolia resource, and analysed characteristics and structure of the population by methods of synecology and population ecology , and discussed the basic biological and ecological factors bringing on the species'danger; meanwhile, we did some breeding experiments and tried to found out the most suitable conditions and ways for artificial breeding. These results would serve as evidence for the conservation of the population and community diversity of R. rotundifolia, and also had reference values for studies of other endangered species in Sterculiaceae.Owing to excessive human disturbance for past years, the R. rotundifolia population had been dramatically decreasing. Investigation showed there were only 1387 individuals in total with the distributing area about 5.67hm2, just occurring sparsely in 4 towns of Nasuo, Naliang, Fulong and Nadong in Fangcheng area.Severe and frequent human activities had lead the habitat fragmental and vegetation retrogress, so the community with R.. rotundifolia was obviously secondary with simple community structure of only one arbor stratum , and reflected something of transitiveness from tropic rainforest to subtropic evergreen broad-leaf forest . According to the important values of the main species, the communities with R. rotundifoli can be divided into 10 associations, which were named Ass. Reevesia rotundifolia + Eurya ciliate + Miscanthus. floridulus, Ass. Reevesia rotundifolia + Syzygium championii - Psychotria rubra, Ass. Reevesia rotundifolia + Pleioblastus sp. + Dendrobenthamia hongkongensis + Camellia. euryoides, Ass. Reevesiarotundifolia - Brassaiopsis glomerulata + Ardisia depressa, Ass. Reevesia rotundifolia - Rhodomyrtus tomentosa + Psychotria rubra, Ass. Reevesia rotundifolia + Rhaphiolepis indica + Miscanthus floridulus,Ass. Ficus auriculata + Elaeocarpus sp. + Camellia oleifera - Ilex godajam , Ass. Machilus sp. + Leioblastus sp. - Eurya ciliata-Strobilanthes cusia, Ass. Ilex godajam + Rhodomyrtus tomentosa-Melastoma candidum-Arthraxon hispidus and Ass. Ilex godajam + Eurya quinquelocularis-Melastoma candidum-Arthraxon hispidus. Among them the former 8 types were due to tropical evergreen monsoon forest, but with a few heliophyllous trees such as Pinus massoniana,Liquidambar formosana,Alniphyllum fortunei in some plots. The Shannon-Weiner and Simpon's diversity indexes of the communities were between the tropical mountain rain-forests and subtropical evergreen broad-leave forests; the later 2 were tropical scrub types, usually located in the top of mountains, and were secondary vegetation formed by interference of severe human activities, the diversity index of them are relatively low.The niche breadth indexes of R. rotundifolia population were a little greater than the others'in dimensions of latitude and rate exposure of rocks. Some invaded heliophyte species had a narrow niche breadth value, even equal 1, but have great niche overlap with Reevesia rotundifolia, such as Pinus massoniana, which showed that they were similar in some extent of their requirements for soil elements or light.Estimating the relation of R. rotundifolia and other main species in the community by combination of PC and AC demonstrated that most of the relation was positive but weak. Only one from 19 species took a relatively stronger positive association with Reevesia rotundifolia is Brassaiopsis glomerulata with AC value of 0.43; Pinus massoniana,Liquidambar formosana,Alniphyllum fortunei had very weak relativity but quite large niche overlap index with R. rotundifolia,which maybe reflected that there are strong inter-specific competition between them. The positive association between shrub species and R. rotundifolia, were a little stronger than trees, including Psychotria rubra ,Ilex godajam, Rhodomytrus tomentosa.The population dynamical model and survival curve reflected that the whole R. rotundifolia population in Fangcheng area was steady in theory, but the structure of DBH or height in most populations were not continuously, especially seedlings and big trees have a high mortality, which would affect swinging the population development and update in deep greed, even result in retrogression. So, on the populations, diminishing types are dominated, their percentage wais 72.7%. As well, the structure of all populations show that R. rotundifolia at aging level were often distributed in different vegetation. Generally, seedlings and adults lived in evergreen monsoon forest, and the youth distributed in tropical scrub, which demonstrated that the population in different development stage have different requirements for illumination.The result of distribution pattern showed that R. rotundifolia population have the transition from clump to random with growing of individuals. The distribution patterns were affected by different environmental conditions, too. Young trees were mainly distributed contagiously and have the highest degree of congregation when sampled in a area of 25m2, and the m*/m index dynamics curve variety was rising, but decreases sharply after 700m.To know biological characteristics of R. rotundifolia more roundly, and to find the endemic causes and the most suitable way for protection, we have done artificial experiments of seeding besides wild investigation, such as cottage, seedling transplanting, and so on. Among them seeding and seedling transplanting did the trick. The optimal temperature for seed germination was about 25℃and water was needed greater, freezing had obvious effect for elevating germination rate, and sand or loess were better germination texture than filter paper, perhaps sand and loess could offer more sufficient water and air for seeds.Based on integrated research of R. rotundifolia population, community, and biological characteristics, we found that the most important factor causing the species in danger was the excessive human disturbance which not only destroyed the habitat retrogression but also caused the individuals dramatically decreased or even extincted in partial region. Secondly, the biological characteristic of the species'ownself was a quite factor, such as low rate of fruiting, germinating, and seedling surviving. The influences of genetics or pollination etc were needed further research. So, avoiding human destroy is the key for protecting R. rotundifolia population and natural habitats; meanwhile, breeding to increase the quantity of seedlings is valuable for enlarging the wild population.
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