The Forest Community Classification, Ordination And Niche Of Major Tree Species In Dazhu Mountain In Jiaonan City

The forest community classification, ordination and niche of major tree species are fundamental for vegetation retoration, and there are great significance in managing sea coastal protective forest. In this paper, the method of quantitative analysis using sofeware TWINSPAN and CCA ordination were used to analyze the community classification, and to find the major environmental factors which restrict the distribution of major populations in Dazhu mountain in Jiaonan. For each environmental factor, the niche breadth and niche overlap of major populations were analyzed. The aims are to identify the relationships among the major trees and environment resources, and provide with theoretical basis for managing sea coastal protective forests optimally, and improve the forest ecosystem servises. The main results are as follows.1,TWINSPAN analysis shows that the vegetation can be classified into 7 association groups in Dazhu mountain. They are Robinia pseudoacacia cv.Inermi + Pinus densiflora Sieb et Zucc., R. pseudoacaccia L. + P. thanbergii Parl. + P. densiflora Sieb et Zucc., P. densiflora Sieb et Zucc. + Tilia amurensis Rupr. + R. pseudoacaccia L. , R. pseudoacaccia L. + P. thanbergii Parl. + Rhus chinensis Mill., P. thanbergii Parl. + Pistacia chinensis Bunge., P. thanbergii Parl. + R. pseudoacaccia L. + Pyrus betulaefolia Bunge. and R. pseudoacaccia L. + Castanea mollissima Bl . + P. thanbergii Parl. repectively. Among them, the habitat of last association is the best because of higher soil moisture and nutrient contents. The second one and 6th one take the second place. The poorest is 5th one which soil water content is only 0.32%.2,The results of CCA ordination analysis show that the major environmental factors are gradient, altitude, soil thickness, available N, available K and organic matter in Dazhu mountain. The traverse axis interprecipates the informations of gradient, altitude and soil thickness; the vertical axis interprecipates that of available K and altitude.3,There are little differences among niche breadth of major populations in Dazhu mountain. Generally speaking, the niche breadth of R. pseudoacaccia L.and P. thanbergii Parl. are larger as compared with other in 20 arbor polulations, their niche breadth are 3.390 and 3.234 repectively. The next are P.s betulaefolia Bunge. (2.974), Ailanthus altissima (Mill) Swingle. (2.942) and P. densiflora Sieb et Zucc.(2.618). The populations who have narrower niche breadth are R. pseudoacaccia L., C. mollissima Bl., T. amurensis Rupr., P. chinensis Bunge., Crataegus pinnpatifida Bunge. and Quercus dentata Thunb.; their niche breadth are 0. That ot the rest 9 populations are between 1.051 and 2.727. The order of the Niche breadth in shrub populations is Lespedeza bicolor Turcz(3.608), Rosa multiflora Thunb.(2.940), Dutzia grandiflora Bunge(2.727), Rhododendrom simsii Planch(2.344), Forsythia suspensa Vahl.(2.333), Grewia biloba G.Don(1.017), Lindera obtusiloba Bl., Vitis amurensis Rupr., Weigela florida A.DC. and Bismarckia nobilis Hildebr. Et H.(0). Because the populations with larger niche breadth have stronger adaptability. So it is the first choice to choose tree species with larger niche breadth in constructing coastal protective forest.4,There are two kinds of couple species which niche overlap are higher. One is the couples with wider niche breadth. There are higher overlap on each resource dimension between P. thanbergii Parl.×P. betulaefolia Bunge., R. pseudoacacia L.×A. altissima (Mill) Swingle. and P. betulaefolia Bunge.×A. altissima (Mill) Swingle. . The overlap indexes are bigger than 0.6. Another is the couples with narrower niche overlap in the same resource position. when the niches of couples are narrower and not in the same resource position, the niche overlap are lower.In a word, it is the first choice to choose tree species with larger niche breadth when constructing coastal protective forest. Because the populations with larger niche breadth have stronger adaptability in rocky coast. It is the first choice to choose tree species who have the lower niche overlap with larger niche breadth in tree species arrangement..Such as arbor trees: R.pseudoacacia L., P. thanbergii Parl., P. betulaefolia Bunge., A. altissima (Mill) Swingle., A. julibrissin Durazz ., P. spectabilis Ait., Q. acutissima Carruth., P. densiflora Sieb et Zucc. and Lythrum salicaria. Shrub trees: L. bicolor Turcz, R. multiflora Thunb., F. suspensa Vahl., Dutzia grandiflora Bunge, Rhododendrom simsii Planch. These population with larger niche breadth , they have the higher overlap in some resource dimensions. But they have the lower overlap in other resource dimensions. They ustilize different resource position, and there are not direct competition among them. Instead, they can ustilize environmental resource primely.