| Cyclobalanopsis elebaticostata is one of the rare and precious broad-leaf tree in subtropics area in China. It's trunk is big, it's lumber firm is solidity, it is resisted agaist wearing and it's machine capability is perfectly good.This species was found lately but was spoiled badly, and its distribution scope is narrow.This paper studied Cyclobalanopsis elebaticostata population using adjacent gridding after perspective investigation, and using the methods of mathematics, statistics and computer technology. The content includes population structure, natural regeneration, spatial distribution pattern, population life process and population growth tendency of Cyclobalanopsis elebaticostata and biomass, nutrient, fertility in the forest; it also includes the interrelationship(such as interspecific competition, inter-species joint, the niches of them)between the main species. It is no doubt of great significance and contribution to opening out population ecology adaption mechanism, enriching species diversity in FuJian, improving species frame and renew species in degeneration ecosystem. The results as follows:1．In this community, the species are rich, the trees are orderliness, the forest shade density is high, the kind of community is different, including conifer forest, latifoliate, forest, conifer and latifoliate forest and bamboo grove. The arbors of the forest are huge, nearly covered the whole community. The plants under the arbors are shaden trees. There are 25 families, 47 genuses, and 68 species in arbor layer. The main ones are Cyclobalanopsis elebaticostata, Castanopsis carlesll, Rhododendron simsii, Dendropanax chevalieri, Altingia gracilipes Hemsl, Neolitsea aurata, Castanopsis fabri Hance, Chinesse fir, Elaeocarpus chinensis Hook.f.ex Benth, Distylium racemosum Sieb. et Zucc, Diospyros morrisiana, Ilex asprella. There are 96 specieses in herbage layer. The main ones are Shibataea nanpingensis, Gahnia tristis, Pleioblastus amarus, Dicranopteris linearis, Smilax riparia, Potentilla tulens Wall, Pteris vuttata L., Woodwardia prolifera, Gleizheniaceae, Sarcandra glabra. In the community, Cyclobalanopsis elebaticostata is beautiful from the whole tree, and has high potential grow ability.2．From the age distribution, most of Cyclobalanopsis elebaticostata are in 1 to 6 age level. The proportion in age level 2 is the largest, second in age level 1 and 3, the smallest proportion is in 4,5,6 age level. There are seldom plants in age level 7 to 9．In the investigation area, most plants are in the middle age level, the younger plants are a little smaller, and the old plants are seldom. The community now in middle age dominant succession stage, and its renewal is good. In community 1, there are seldom old plants, and middle age plants are in dominant place. The young plants are smaller in community 1 and 2, the population has decline tendency. There are old plants in community 2 and 3, and in community 3, the age structure takes on obvious pyramid model. Its young plants are rich, population structure is integrity. In the whole investigation area, the number of young plants is not big, middle age plants is more, this population will go to old age in the future.3．The highest death rate came forth in age level 4, from 45．83% to 61．54%. The survival rates of Cyclobalanopsis elebaticostata population takes on decreasing tendency. In age level 4 and 5, the decrease rate is higher than the others. The trends between death rate and lethal power are coherence. The lethal power in age level 4 increases from 0．61 to 0．96．The main reason of this phenomenon is that the tree crown is large, so the resource availability is high, the competition between plants is acute, then comes on the scene of self-scanty then to balance. Interspecific competition is another main reason.4．All the indexes of aggregation indicate community 1 is aggregated distribution. Community 2 and community 3 is random distribution; The K value of community 2 is 13．3, it is not only aggregated distribution but also approaches to Poisson distribution.5．The Analysis indicates richness value of species is from 7 to 29, and diversity index D is from 0．64 to 0．94, and diversity index H is from 1．97 to 4．11, evenness index E is from 0．98 to 1．93, evenness index J is from 0．69 to 0．91．Community 2 plot 2 has the most kinds of species, community 3 plot 1 and 3 have high evenness. Community 3 is the most complex, the 2, last 1．The niche breadth order of 14 main arbors is: Cyclobalanopsis elebaticostata > Castanopsis carlesll > Rhododendron simsii > Dendropanax chevalieri > Castanopsis fabri Hance > Cunninghamia R.Br > Neolitsea aurata.> Distylium racemosum > Catalpa ovata D. Don > Ilex asprella> Diospyros morrisiana > Ilex macrocarpa Oliv > Ilex macrocarpa Oliv. > Machilus kwangtungensis Yang > Elaeocarpus chinensis.6．Analysis indicates Cyclobalanopsis elebaticostata and Cyclobalanopsis elebaticostata's niche breadth are wider, and the values of niche breadth are 0．96 and 0．83, which indicates the two species can adapt to the change of environment and can make use of resource of the community. The niche breadth of Rhododendron simsii, Dendropanax chevalieri, Castanopsis fabri Hance, Cunninghamia R.Br etc are lower than that of Cyclobalanopsis elebaticostata and Castanopsis carlesll, but is also around 0．5, which indicates they are superior in the moist environment that Cyclobalanopsis elebaticostata form; the niche breadth of Diospyros morrisiana, Ilex macrocarpa Oliv and Machilus kwangtungensis Yang are lower to 0．20, which indicates the degree of making use of the resource is lower.7．In the natural forest of Cyclobalanopsis elebaticostata, the most of niche breadth are from 0．2 to 0．4, and this extent is niche distribution peak. It accounts for 40% of trees. Most species in the region can't make full use of the resources, and the importance values of the species are relative lower, and niche breadth is lower than that of Cyclobalanopsis elebaticostata,Castanopsis carlesll and other tall tree. According to Niche breadth Table, the niche breadth of Cyclobalanopsis elebaticostata,Castanopsis carlesll are from 0．8 to 1．0．We can conclude the two species will be dominant and form a climax community. The niche breadth distribution percent of 0．6～0．8 is zero, the main reason is that the shade density is high in the community and illumination is insufficiency, so it is difficult for photophilous plant to survive.8．The percentage of similarity between main species in Cyclobalanopsis elebaticostata natural forest is high, the percentage of similarity between Cyclobalanopsis elebaticostata and other specieses is higher, and this indicates percentage of similarity is changes with niche breadth. Such as Rhododendron simsii-Dendropanax chevalieri, Cyclobalanopsis elebaticostata-Castanopsis carlesll, Cyclobalanopsis elebaticostata-Rhododendron simsii. Otherwise, the percentage of similarity is connected with life strategy, more similar much higher, such as Cyclobalanopsis elebaticostata-Castanopsis carlesll. There are 30 species-species whose niche overlap is more than 0．5, accounting for 28．57%; and there are 47 which niche overlap value is higher than equal value 0．35．The higher ones are Cyclobalanopsis elebaticostata-Ilex asprella, Castanopsis fabri Hance-Machilus kwangtungensis Yang, Castanopsis fabri Hance-Dendropanax chevalieri. There niche similarity is also higher than the equal value 0．15, it indicates that there is positive relationships between niches overlap and niche similarity.9．The arborous layer tree species in Cyclobalanopsis elebaticostata forest community display the state of mutual benefit growth, the competition between tree species favor vegetal interpromotion.. The value of PC=60% in the community accounts for 15．24%, 60%>PC=20% accounts for 74．28%, the value of the other species-species is under 20%. The value of PC of Cyclobalanopsis elebaticostata and other species is higher. Among the 105 species-species, there are 40 take on negative connection, account for 38．10%, and there are 62 take on positive connection, account for 59．05%. Positive connection is more than negative connection, indicates that the relationship between species is mutuality. From the value of X~2, the mutuality between every species-species is not deminant.10．The nutrition of Cyclobalanopsis elebaticostata above earth is leaf>twig>skin>stake> trunk.The nutrition of Cyclobalanopsis elebaticostata below earth increases with the diameter increasing. Because different apparatus work different in the process of growth, the Nutrient accumulation of apparatus is different. The nutrition of leaf is still higher than branch in the litter. The nitrogen content of defoliation is a little lower than freshness leaf, while kalium content of defoliation is much lower than freshness leaf because of kalium existing at the form of soluble salt. Decomposition of forest litter takes an active part in the improvement of soil nutrient. The plentiful defoliation in broadleaved forest can make the broadleaved forest keep well, and improve the ecological environment.11．Different community in the Cyclobalanopsis elebaticostata forest, the content of total nitrogen,total phosphorus and total potassium in upper layer of soil is more than lower layer. The dispersion of total nitrogen is the biggest, while the dispersion of total phosphorus is smallest. The content of total phosphorus is about 1%, which can offer potassium in the growth of Cyclobalanopsis elebaticostata.12．There are different biomass of Cyclobalanopsis elebaticostata in the verity community. Biomass in the community 1 add up to 98．17 t·hm-2, in community 2 is 69．86 t·hm-2, and in community 3 is 67．51 t·hm-2．The ratio of trunk biomass is from 49．08% to 52．54%, and that of leaf is from 4．79% to 7．52%. The biomass of branch is a little more than that of root. The leaf is the main assimilation apparatus, and there is the most nutrition in the leaf. The nutrition content of defoliation is the most in the litter.13．The defoliation of Cyclobalanopsis elebaticostata is the most: 0．28t·hm-2, accounting for 30．66%. The defoliation of Castanopsis carlesll is nearest to Cyclobalanopsis elebaticostata: 0．26t·hm-2, accounting for 28．38%. The two specieses can improve the soil fertility. |
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