Impact Four Years after Thinning on the Growth and Stand Structure of Taiwania Plantation in the Liukuei Experimental Forest

六龜試驗林台灣杉人工林疏伐四年後對生長和林分結構影響之分析

汪大雄(Dar-Hsiung Wang) ； 湯適謙(Shyh-Chian Tang) ； 邱志明(Chih-Ming Chiu)

《台灣林業科學》 21卷3期 (2006/09) Pp. 339-351

https://doi.org/10.7075/TJFS.200609.0339

摘要

本研究探討不同疏伐策略對林業試驗所六龜試驗林台灣杉人工林疏伐四年後對林木生長和林分結構之影響。調查結果顯示因受林分密度影響，強度疏伐對單位面積台灣杉斷面積和材積絕對生長量生長之促進效果較中度疏伐效果為低，但就相對生長來說，強度疏伐之促進效果較中度疏伐效果為高；傳播指數顯示，台灣杉人工林的林木位置之規整狀態會隨著下層疏伐作業之實施有所改變，而轉化成有朝向逢機分佈或群狀集合之趨勢；胸徑分化程度指標之分佈顯示疏伐作業縮短了其在林木胸徑差異空間上分佈之範圍，增加其差異屬於小階段之比例(0.83)，和減少位於程度中等階段之比例(0.17)。然疏伐4年後，因保留木間胸徑生長之速率不一，減少了差異位於程度小階段之比例(0.81)，並增加了差異屬於中等階段之比例(0.19)。

關鍵字

林分結搆 ； 空間分佈 ； 結搆指標 ； 林分生長

並列摘要

This paper examines the impact of thinning 4 yr after it took place on the growth and stand structure of Taiwania cryptomerioides plantations in Liukuei Experiment Forest in Southern Taiwan. Thinning to 3 residual levels in basal area were carried out in 1999, and three 0.09-ha plots were set up in each treatment for stand monitoring purposes.
The results showed that partially due to the stand density, the enhancements in the increments of basal area and volume by heavy thinning were less than those by medium thinning. However, enhancement of the growth rate was in a reverse order. The contagion index, which measures the spatial structure of a stand indicated that the regular pattern of individual trees in spatial locations in plantations was shifted toward a random or clumped one through individual tree thinning. The diameter differentiation index describing the spatial distribution of tree sizes indicated that the range of the difference in size of neighboring trees in the plantation was reduced through the thinning operation, with an increase in the proportions of trees having DBH differentiation of a small level (0.83) and a decrease in the average level (0.17). Due to variations in growth probably caused by competition among residual trees, 4 yr after thinning, the proportions of trees with a small difference level and average difference level were reduced (0.81) and increased (0.19), respectively.

並列關鍵字

plantation thinning ； spatial distribution ； structure index ； stand growth