臺灣東南部亞熱帶常綠闊葉林之油葉石櫟─長尾尖葉櫧林型植群動態研究

Vegetation dynamics in the Lithocarpus konishii- Castanopsis carlesii forest type of subtropical evergreen broad-leaved forest in Southeast Taiwan

本研究於2004年設立的太麻里試驗林油葉石櫟—長尾尖葉櫧林型1 ha動態樣區進行複查，分析15年後的植群變化，提供探討臺灣東南部亞熱帶常綠闊葉林的動態變化。從2004到2019年間，樹種的組成從61種增加為63種，原記錄之61種均仍存在，新記錄2種。DBH≧1 cm的立木數量從5,972株增加為6,703株，淨增加率為12.2%，其中98.9%的新增立木為DBH＜5 cm的個體。胸高斷面積從723,889.00 cm^2增加為732,957.50 cm^2，淨增加率為1.3%。比較2004年與2019年的兩次調查，立木數量與胸高斷面積最優勢的前二十種，發現樹種組成的相似度頗高，僅排名稍有變動。顯示在15年當中，樹種的族群結構略有變化，但樹種組成的改變很少；此現象小徑木的大量增加顯示當地所形成的冠層孔隙大於單一樹倒所形成的孔隙，但因樹種豐富度、立木數量和胸高斷面積均沒有減少的跡象，且中、大級徑木仍持續有徑級生長，故可推測林分在15年間處於相對穩定的狀態，屬於演替中後期階段森林。

This study aims to reexamine the 1 hectare of Lithocarpus konishii- Castanopsis carlesii dynamic plot in the Taimali experimental forest established in 2004, in order to analyse the vegetation changes of the subtropical evergreen broad-leaved forest in southeastern Taiwan after 15 years. We discovered that, from 2004 to 2019, tree species composition had increased from 61 species to 63 species, including the original 61 species and two new species. Standing trees with DBH ≧ 1 cm had increased from 5,972 to 6,703 (net increase rate 12.2%) and 98.9% of the new standing trees were measured DBH < 5 cm. The basal area at breast height had increased from 723,889.0 cm^2 to 732 ,957.5 cm^2, with a net increase rate of 1.3%. Comparing the two surveys in 2004 and 2019, the top 20 species with the highest number of standing trees and basal area at breast height were found to have a quite high similarity in tree species composition, with only a slight difference in ranking. It meas, from 2004 to 2019, the population structures of tree species had changed slightly, but the compositions of tree species had changed very little. The large increase of small-diameter trees shows that the locally-formed canopy gaps are larger than those formed by a single tree fall. However, since there was no sign of decreasing in the tree species richness, the number of standing trees, and the basal area of breast height, and the medium-large diameter size trees continued to grow progressively, we could presume that the stand was in a relatively stable state for 15 years (2004-2019), and belonged to the mid-late succession stage.