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題 名 | Silvicultural Thinning Intensity Effects on Increasing the Growth of Planted Loblolly Pine (Pinus Taeda L.) Stands in Northern Iran=疏伐對伊朗北部德達松林分生長之效應 |
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作 者 | Bonyad, Amir; | 書刊名 | 臺灣林業科學 |
卷 期 | 21:3 民95.09 |
頁 次 | 頁317-326 |
分類號 | 436.254 |
關鍵詞 | 裏海; 德達松; 多變量分析; 生長率; 疏伐; Caspian sea; Loblolly pine; Multivariate; Growth rate; Thinning; |
語 文 | 英文(English) |
中文摘要 | 德達松是伊朗北部經濟林主要外來之造林樹種,這些人工林位於伊朗之裏海林區,和裏海南岸為界,面積有1.9百萬公頃。本試驗選擇未疏伐、弱度和中度疏伐之三個林分,由不同之林分密度,總共收集180株林木,量測93個樣區之斷面積進行分析。變數有胸高直徑、樹高、材積、樹皮厚、每公頃斷面積、樹冠長和樹冠幅。弱度和中度疏伐之林分和未疏伐林分胸高直徑生長之比率分別為1.09及1.18,胸高斷面積平均年生長率分別為1.186和1.20。中度疏伐林分比未疏伐林分約可增加20.6%之林分材積。這分析顯示中度疏伐可明顯的增加胸高斷面積和材積之生長率。疏伐後,活樹冠變得較長,枝條也較多,未疏伐、弱度及中度疏伐三個林分活樹冠比率分別為41.23、43.87和44.52%。生長率詮釋藉由Wilk’s (Λ) 和Hotelling’s T22測驗之多變異統計分析,Wilk’s測驗使用三個林分之6個變數平均向量進行分析,F值14.435大於P = 0.01之F值4.37,此結果顯示中度疏伐對提升德達松人工林之生長速率有顯著之效果。 |
英文摘要 | Loblolly pine (Pinus taeda L.) is 1 of the main exotic species in commercial plantations in northern Iran. These plantations are situated in the Caspian forests of Iran, which border the southern coast of the Caspian Sea and cover an area of 1.9×106 ha. For the present experiment, unthinned, and lightly and moderately thinned stands were selected as 3 populations. Data were collected from a total of 180 trees among the different stand densities. For basal area analysis, 93 plots were measured. Variables such as diameter at breast height (dbh), total height, tree volume, bark thickness, basal area per hectare, crown length, and crown diameter were measured. The growth rate ratios of dbh in the lightly and moderately thinned stands were 1.09 and 1.18, while the mean annual increments of basal area growth rates in the 2 thinned populations were 1.186 and 1.20, respectively. Moderate thinning increased the volume of stands by about 20.60% of the stand volume. This analysis indicated that moderate thinning drastically affected the basal area and the growth rate of volume. After thinning, dimensions of live crowns increased and more branches were evident. Percentages of live crown ratios in the 3 study populations were calculated to be 41.23, 43.87, and 44.52%. Growth rate interpretations were supported by statistical multivariate analysis of variance using Wilk’s (Λ) and Hotelling’s T22 tests. Wilk’s test was carried out on a mean vector of 6 variables in the 3 study populations. The null-hypothesis (Fc = 14.435 > Ft = 4.37) was rejected at the 0.01 level of significance. Thus, the results indicated that moderate thinning significantly influenced increased growth rates of planted loblolly pine stands. |
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