台灣南部南仁山長期生態研究區低地雨林的組成及植被類型

Species Composition and Vegetation Pattern of a Lowland Rain Forest at the Nanjenshan LTER Site, Southern Taiwan

為研究臺灣南部南仁山區的殘存低地雨林，於1989-1994年間在欖仁溪源頭及南仁山下的溪谷區分別設置3及2.1公頃的永久樣區，以比較兩區森林的物種歧異度、組成及結構。在欖仁溪樣區最優勢的科包含殼斗科、茶科、冬青科、八角茴香科、樟科及桃金孃科；在南仁山樣區最優勢的科則為大戟科、桑科、楝科、樟科，冬青科、蕁麻科、及千屈菜科，該樣區的森林在形相及結構上多少顯出熱帶雨林的特性。雙向列表比較法（TWINSPAN及DCA排序法將欖仁溪樣區切分出兩種生育地類型，但南仁山溪谷樣區則無此現象。欖仁溪樣區生育地的分化主要緣自東北季風的吹襲。隨著風力梯度的增強，樹冠高度由溪谷區的15-20m降至迎風坡面的3-5m；植株密度及樣區內的物種組成相似度則隨著暴露程度的加大而增高，但不同樣區間及生育地間樹榦的總胸高斷面積的差異不大。各森林的優勢度－歧異度曲線　均趨近於對數常態分佈曲線，物種歧異度則以隱避的溪谷及背風坡較高。

This study focused on a remnant of lowland rain forest in the Nanjenshan Reserve of southern Taiwan. During 1989-1994, two long-term plots of 2.1 and 3 ha were set up at Lanjenchi (hill) and Nanjenshan (valley) sites, and forest composition, structure and species diversity were compared between the two plots. In the Lanjenchi plot, the most important families (sum of basal areas of all species within that family) were Fagaceae, Theaceae, Aquifoliaceae, Illiciaceae, Lauraceae and Myrtaceae, while in the Nanjenshan plot, the most important families were Euphorbiaceae, following by Moraceae, Meliaceae, Lauraceae, Aquifoilaceae, Urticaceae and Lythraceae, which bore some similarities to the tropical rain forests both in physiognomy and structure. Both TWINSPAN classification and DCA ordination separated the windward forest from the leeward forest stands in the Lanjenchi plot, but no such pattern could be recognized for the Nanjenshan plot. In the Lanjenchi plot, both species composition and forest structure changed dramatically with exposure due to chronic monsoon wind-stress. As wind stress increased, canopy height decreased from 15-20 m in the creek bottom to 3-5 m in the most exposed windward habitat. Stem density increased steadily with increasing exposure, and mean similarity among quadrats become higher as well. Total basal areas were comparable between the plots and forest stands. Dominance-diversity curve for each of the forests conformed to a lognormal distribution. There was a strong tendency for species diversity to be higher in the less exposed forests.