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A large permanent plot was set in a primary broad-leaved forest, which located in the west area between 9.5 and 10 K at Nantzuhsienchi Trail. The 3.5ha of the large permanent plot, from west to east, contains various topographies from sub-ridge to valley. It’s a proper area to study the composition, structure, variation of vegetation and distribution pattern of species in the valley of median elevation. And it also provides the basic study of vegetation change and erosion of streams. The study was recorded 8,939 stems of woody plants(DBH≧1cm), 2,554 stems/ha, and the total transactional area at breast height was 205.57m2, 58.73m2/ha including 26 families, 46 genera, and 58 species. According to the calculation of stems, the dominance families are Lauraceae, Fagaceae and Theaceae. The species which have most individuals are Litsea acuminata, Machilus japonica, Castanopsis carlesii and Eurya leptophylla. According to the calculation of transactional areas at breast height, the dominance family is Fagaceae, and the next is Lauraceae. The most dominance species include C. carlesii, Cyclobalanopsis stenophylloides, Pasania kawakamii, M. Japonica and L. acuminate. Both of stems and transactional areas at breast height are higher in the upper or steep slope. For the importance value, the dominance families are Fagaceae, Lauraceae and Theaceae. The dominance species are C. carlesii, M. Japonica, L. acuminate, C. stenophylloides, P. kawakamii and E. leptophylla. Among all shrub species, the highest percentage of offshoot is Viburnum taitoense. Litsea akoensis and M. Japonica are higher among all tree species. Both of Cinnamomum insulari-montanum and C. stenophylloides have the most offshoots in the average of stems with offshoots. The species which have the highest percentage of the main stem dead (MD) are C. insulari-montanum and M. Japonica. The forest structure as the dominance species in canopy are C. carlesii, C. stenophylloides and P. kawakamii with Fagaceae. The dominance families in sub-canopy are Lauraceae and Fagaceae, such as L. acuminate, M. Japonica and C. carlesii. The dominance families in shrub layer are Lauraceae and Theaceae, such as M. Japonica, E. leptophylla and L. acuminate. The analysis of structures of diameter classes shows four types: 1. reverse J type, 2. L type, 3. wave type, 4. bell type. Relatively dominance species have much number of small-diameter trees, and it shows that the main species of the forest have good reproduction. By the analysis of TWINSPAN, five types of vegetation are revealed and shows a higher relation between vegetation and topography. The types and dominance species are mentioned as following: Ⅰ. Disturbing ridge type, in which the dominance species is Alnus formosana; Ⅱ-1. upper slope type, in which the dominance species are C. carlesii, L. acuminate, E. leptophylla and Schima superba; Ⅱ-2. mediate-slope type, in which the dominance species are C. carlesii, C. stenophylloides and L. acuminate; Ⅲ-1. lower slope type, in which the dominance species are M. Japonica and L. acuminate; Ⅲ-2. disturbing lower-slope type, in which the dominance species are M. Japonica, P. kawakamii and C. stenophylloides. The distribution patterns of species above 10 stems can be divided into 6 types: 1. disturbing upper-slope type (1 species, e.g. A. formosana); 2. nun-disturbing upper-slope type (11 species, e.g. Vaccinium randaiense); 3. nun-disturbing sharp-slope type (5 species, e.g. C. insulari-montanum); (4) nun-disturbing upper-slope widespread type (6 species, e.g. L. acuminate); (5) nun-disturbing whole area widespread type (6 species, e.g. Neolitsea sericea); (6) disturbing lower-slope valley type (5 species, e.g. L. akoensis). For the properties of the recorded species, the percentage of shrub and endemic species are higher than other permanent plots in Taiwan. By comparing with the plots of Mt.Peitungyen and Chungtzekuan area belonging to Quercus Zone in the mediate elevation, the studied plot is the highest in an accumulative total of importance value with the pre-five species. Among the dominance composition of forest, all of them, from upper to lower Quercus Zone, shows an intermediate quality, and the variation from valley to ridge.
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