| Manglietia yuyuanensis Law is one of the wood tree specie of Magnoliaceae family,and also is the eminent local broad-leaf tree specie in Fujian province. It plays a important role in the development of broad-leaf tree forestation. So the systematically study on M.yuyuanensis Law is very imminent and important.This paper, basing on the natural forest of M.yuyuanensis Law located in Qingzhou Town and mixed forests of M.yuyuanensis Law and Chinese fir. located in Zhenhuo County.Fukou Town and. Shuinan County respectively, Shaxian city, Fujian province, gives a series of studies including the characters of community ecology of M.yuyuanensis Law, the endangered reasons, growth characteristics, forest density and mixed proportion, the relationship between interspecific competition and growth and the regulation of interspecific correlation. 1 .The niche breath of Manglietia yuyuanensis Law is more narrow,and M. yuyuanensis Lanv only distributes sparsely for the human's destruction. The results shows that the species in community are considerably rich, and the species diversity index, species richness index and dominant index of the stratum layer are higher, but the evenness is lower.2. The study on population structure and spatial distribution patterns of the dominant species shows that M.yuyuanensis Law had a stable structure and belonged to a mature type of population structure,but the amout of seedlings were more less and it's dynamic development wasn't optimistic,The population structure of Castanopsis Lamontii and Choerospondias axillaries were all inverse pyramid types and Castanopsis fargesis was a pyramid shape of population structure . The spatial distribution patterns of M.yuyuanensis Law and Castanopsis Lamontii in community were all aggregated.3.Using variance ratio (VR^ x2 text by "2 X 2"contingency table, the association coefficient (AC) and the other two formulae,i.e. PCC and r,the interspecific correlations of 23 major varieties of the tree-layer and the shrub-layer in the community were analysed. The study showed that the dominant populations,such as M.yuyuanensis Law* Castanopsis Lamontii and Castanopsis /argey/5, formed more species pairs of positive association than those of negative assocition;there was remarkable positive relation among the major shrub-layer.4. By using the Lokta-Voherra equation of competition, the final results of competition of inter-species are analyzed and show that when reaching competitive balance ,the relative dominant degrees of M.yuyuanensis Law and its associated species are 78.23% and 21.77% respectively,which also shows that M.yuyuanensis Law population is controlling the whole community.5.The endangered reasons for M.yuyuanensis Law were follows:there were fewer mature seeds in the fruits,the intervention of human activities was severe, animals' destruction and it's lack of stronger competition so on.6. Basing on the research, it can conclude that M yuyuanensis Law grows fast and its stem is straight and full. Though in early, the growth rate is lower than Chinese fir. , about 10 years later the stem growth of M. yuyuanensis Law reaches its highest rate. The growth discrepancy of M yuyuanensis Law in mixed plantation was significant by different thinning measures. Thinning in time, the fast-growing period of DBH, height, and volume of M yuyuanensis Law prolonged about 3 years. And now M. yuyuanensis Law of 17-year-old are still in fast-growing period and3its average DBH and average height are 21.8cm, 13.8m respectively. But not thinning timely, the growth of the M. yuyuanensis Law is pressured and its fast-growing period ended in advance. 7. The crown characteristics of 17-year-old M.yuyuanensis Law in two mixed stands were explored. There were significant difference of crown characteristics among different diameter scales. The difference of the vertical distribution of foliage was greatly attributed to leaf number. The study by the means of path analysis method showed that the favorable crown characteristics for growth of M.yuyuanensis Law wa...
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