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行列疏伐對柳杉保留帶之樹輪生長影響

Effects of Row Thinning on the Residual Stand Tree-Ring Growth of Cryptomeria Japonica Plantation

摘要


本研究以棲蘭山地區45年生柳杉林為對象,此林分於1990年進行不同疏伐度之行列疏伐,包括砍2行留6行(T2)、砍3行留6行(T3)、砍4行留6行(T4)與砍5行留6行(T5),調查疏伐20年後之林分結構與生長變化,並以樹輪學分析方法評估疏伐效應。研究結果,以林木胸徑分布表現,未疏伐及T2與T3為常態分布,但T4與T5則呈現雙峰分布,且林木胸徑分布呈現變異較大的趨勢,可能與行列疏伐釋放空間之邊緣影響較強烈所致。未疏伐的林分(對照組)於24年生時直徑生長已持續降低,44年生林分平均胸徑為27.2±9.7 cm。疏伐對柳杉林木的年輪生長皆較未疏伐區有明顯的增加,以疏伐三行(T3)具顯著促進平均年輪寬增長,疏伐二行(T2)的效果較小。比較疏伐與未疏伐區的林木之各年度樹輪生長差異,以疏伐前5年(1986-1990年)為基準,未疏伐林分樣木樹輪寬平均生長皆較疏伐前減少,至2006-2010年第四期的樹輪寬生長差異比率為-54.2%。疏伐二行之T2,可維持林木的生長量與疏伐前5年之基準相似,但持續的時間效果則較疏伐三行以上(T3、T4與T5)者為短。T3對年輪寬生長促進最多,持續時間亦較長,最大可達42.6%,至第四期之差異比率則為22.5 %。T4與T5的樹輪寬生長差異比率變化趨勢相仿,亦具促進樹輪寬生長效益,但至第四期已降至0%與5.0%。以樹輪分析方法檢測疏伐強度的效應,以三次平滑曲線(cubic smoothing spline)所配適之生長趨勢,可增強檢定疏伐效應的能力。研究結果顯示24年生柳杉林經行列疏伐後5年才具明顯疏伐反應,以砍3行保留6行的疏伐對柳杉林木生長即具有顯著的促進功效,效應持續時間亦較久。然疏伐後20年,林木徑向生長已再次衰退,已可再次疏伐,調整林分結構,以改善柳杉林分生產力。

並列摘要


x The purpose of this research was to explore the strand structure and growth 20 yr after row thinning for Japanese cedar in Chilanshan, and effects of thinning was analyzed by tree ring method. Four row thinning treatments of strip cutting of 2 rows (T2), 3 rows (T3), 4 rows (T4), and 5 rows (T5) were applied; and 6 rows were retained on both sides of the cut strips. The average diameter of breast height (DBH) after the thinning treatments showed the following trend: T5 > T4 > T3 > T2 > control groups (trees in un-thinned stand, T0, DBH = 27.2 cm). The distributions of DBH classes in the T0, T2, and T3 regimes were normal distributions and the T4 and T5 regimes were bimodal distributions. The DBH of individual trees had significantly increased by near gap of thinning effects. The overall diameter growth of T0 regimes in the radial direction decreased gradually from pith outward to about 24-yr-old and then more slowly decreasing growth velocity. The trees growth with row thinning regimes increased in average ring width, as compared to those grown with unthinning regimes, and the effects of different row thinning on tree growth were compared by cubic smoothing spline method. The average tree growth in T3 regime was fastest and in T2 regimes was slowest among the 4 thinning treatments . According to compared standard growth rate, the overall diameter growth rate of > 24-yr-old tree was lower than that of 19-yr-old to 23-yr-old tree in unthinning regimes (-54.2%). In T2 regimes, the diameter growth rate of> 24-yr-old tree was about equal to that of 19-yr-old to 23-yr-old tree. In T4 and T5 regimes, the diameter growth rate of > 24-yr-old tree were adding to (0-5%) those of 19-yr-old to 23-yr-old trees. However, in T3 regimes, the diameter growth rate of > 24-yr-old tree was adding (42.6%) to that of 19-yr-old to 23-yr-old tree. After thinning, the free space increased GRRWD during the 1st period and decreased during the 4th period. The results suggested also that second thinning treatment should be practiced to improve the stand productivity.

被引用紀錄


鍾智昕(2017)。跨尺度分析與監測近熱帶人工林生長效應之研究〔博士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU201702931

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