南仁山區亞熱帶雨林樹種的組成和分佈類型

Abstract

在南仁山區萬?得山東側支稜海拔300公尺處設立1公頃長方形連接樣區。對樣區中胸高直徑1公分以上的木本植物加以調查，記錄樹種名稱、胸高直徑；並圖示其在樣區中的位置；同時每一株樹均給予調查號碼，以做為日後追蹤複查的依據。 由1公頃樣區樹種的組成及優勢度觀之，樣區中的優勢種是屬於台灣中海拔地區的樹種，以殼鬥科為主。而熱帶植物（如桑科植物）在本樣區中已極稀少；作者並比對前人的研究，將200—300公尺以上劃歸亞熱帶雨林楠櫧林帶的範圍。 藉由聚類分析法（cluster analysis）比較樣區中樹種及優勢度的差異所得結果，可將樣區分為三群。第一群存在於迎風陡坡風力極強處，以嶺南椆、台灣柃木等為代表。第二群存在於溪穀附近，以江某佔最優勢。第三群是南仁山地區的代表性植物，存在於風力中等至小處，主要以長尾栲、紅花八角、革葉冬青等為主。三群植物在樹種組成、優勢度曲線、高度、密度上都有明顯的不同。迎風陡坡不論在單位元密度、單位元種數都居三群之冠，認為是由於風力不斷幹擾的結果，即整個樣區的植群是以鑲嵌體的狀態存在。此事實支持植物社會不均衡理論學說。 依樹種在樣區上的分佈類型（distribution pattern）上可分為四大類型。一是迎風陡坡型，如嶺南椆、台灣柃木。二是溪穀型，如山龍眼、山刈葉。三是風力中等處型，如長果木薑子、九節木。四是廣泛分佈型，如長尾栲、革葉冬青。其中迎風陡坡型和溪穀型的植物可以截然區別。12個同屬內的植物在分佈類型上產生分化，即適應了不同的生育地而不相重疊，此事實支持哈欽遜（Hutchinson）對於物種因競爭而產生生態位分化的學說。

In 1989 a permanent 1-ha plot of lowland subtropical rain forest was established in the Kenting National Park in southern Taiwan. All free-standing woody plants in the plot with dbh?1 cm were identified, measured, tagged, and mapped. A total of 105 tree species (10902 stems) was recorded. The community structure was characterized by a relative dominance of Castanopsis carlesii in the canopy, Illicium arborescens in the middle story, and Calamus formosana in the understory. However, tropical species such as Moraceae were rare. Thus, floristic composition of this area was comparable with that found in some of the subtropical rain forests or even warm-temperate rain forests of the Central Range in Taiwan. Cluster analysis revealed three distinct groups of samples. Group 1 was dominated by Eurya hayata, and was located at windward slope which was highly disturbed by strong wind. Group 2 occurred along the streamside and was dominated by Schefflera octophylla. Group 3 from gentle leeward slope was dominated by Castanopsis carlesii, Illicium arborescens, and Ilex cochinchinensis. Moreover, considerable distinctions occurred in density, canopy height, and dominance-diversity curves between windward and leeward portions of the plot. Based on distribution pattern of the species, most species were patchily distributed and many were random. Among the patchily-distributed species, Cyclobalanopsis championii and Eurya hayata only occurred in the windward slope, while Helicia formosana and Evodia merrillii occurred along the streamside. Species which appeared to be randomly or near-randomly distributed over the plot included Castanopsis carlesii and Ilex cochinchinensis. However, there was another type of distribution pattern such as Litsea acutivena and Psychotria rubra that occurred randomly in the plot except the windward slope. The distribution pattern of species also suggested that there were strong niche differentiation among species in the same genus, and it seemed to conform to the Gause's competitive exclusion principle.