台灣目前森林經營注重於森林資源保育，因此許多早期造林的人工林都已陸續達到甚至超過其預設之伐期齡，這些人工林將來會如何發展，以及未來應如何經營，需要先瞭解其林況隨林齡之變化發展。本研究根據林務局永久樣區調查資料，分析羅東林區33處林齡介於7至56年之柳杉人工林林況及林下胸徑＞5cm闊葉樹生長情形。分析結果顯示柳杉人工林截至56年生，株數減少速度逐漸趨緩，而平均直徑、平均樹高、胸高斷面積仍持續成長，然而各林分之立木度具有很大差異。柳杉林下闊葉樹的株數、平均直徑、平均樹高、胸高斷面積則隨林齡增加而增加，但就相對密度以及相對優勢度而言，杉林下闊葉樹雖然相對密度隨林齡漸高，但相對優勢度尚遠不及柳杉，推論柳杉應仍能持續維持優勢，短期間不會要被闊葉樹所演替取代。
Nowadays in Taiwan, the management of national forest emphasizes resource conservation. As a result, the ages of many plantations have exceeded their designated felling ages. How would these plantations become, and how should they be managed, require the knowledge of the long term development of stand conditions. This study used data of 33 plots collected by the Forest Bureau at the Lo-Tung Forest district to analyze the stand conditions of Japanese cedar (Cryptomeria japonica) plantations ranging from 7~56 years old. The results showed that for the Japanese cedar, the mortality rate decreased, and tree size, mean tree height and basal area increased with stand ages. However, stocking levels of varied among stands. On plantations with larger diameter understory hardwoods (DBH＞5cm), the amount, tree size (diameter and height), and basal area of the hardwoods, as well as their percentages relative to the whole stand, increased exponentially with the plantation ages. However, in terms of relative dominance, the understory hardwoods had not yet outcompeted the Japanese cedar, and Japanese cedar would remain dominant in the long term. Total recovery of hardwoods through natural succession would be unlikely within a short period of time.
