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題名 | Taper Modeling on Calocedrus formosana Plantations in Lienhuachih, Central Taiwan=蓮華池地區臺灣肖楠人工林林木尖削度模式之建立 |
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作者 | 汪大雄; 鍾智昕; 謝漢欽; 湯適謙; | 書刊名 | 臺灣林業科學 |
卷期 | 33:2 2018.06[民107.06] |
頁次 | 頁163-171 |
分類號 | 436.25 |
關鍵詞 | 樹幹剖面模式; 變動形數模式; 分段式多項式; Stem profile; Variable form; Segmented polynomial; |
語文 | 英文(English) |
中文摘要 | 林木尖削度模式又稱為樹幹剖面模式(stem profile),是描述樹幹連皮或去皮直徑隨著某特定高度之變化情形。尖削度可以計算一株樹在不同利用標準下之木材利用材積。因此,對木材工業而言,良好之尖削度模式可以在不同標準規格下提供準確有效之木材利用率。一般言之,尖削度模式種類甚多 其配置之方式亦不同。本研究使用高階多項氏、二段式多項式、三段式多項式和變動形數模式等4種模式,探討蓮華池地區台灣肖楠人工林木尖削度模式之建立,並就各模式之推估能力進行比較。研究結果顯示雖然就總體之推估能力(含偏差與精密度)言之,各模式間之差異不大,以變動形數模式最佳,但描述各不同段位之能力則有明顯之差別。以從根株至10%樹高高度之部位觀之,變動形數模式之預測能力最佳,其次為三段式多項式。由於變動形數模式和三段式多項式能較有效描述各段位之尖削度變化,不但其總體之偏差百分比小於6%,其幹材較低部位之偏差亦為最低,因比,變動形數模式和三段式多項式是為比較理想之尖削度模式。 |
英文摘要 | Taper is used to measure the rate of decrease in stem diameter from the bottom upwardly. Taper equations express the expected stem diameter outside or inside the bark, as a function of the height above ground level, total tree height, and diameter at breast height. Four tapering modeling approaches were used to estimate the stem diameter at a given height above the stump in Calocedrus formosana plantations and compare their accuracy and precision. The results indicated that while there was little difference in describing the overall tapering performance, based on 3 criteria considered simultaneously, the variable-form stem profile was the best at describing the taper of the total tree bole, followed by 3-segmented polynomials. The mean relative biases for these models on the fitted trees were < 6%, except for the polynomial form with a higher-order approach. The butt swell (segment from 0.3 to 1.3 m in height) is a part of the stem that is the most difficult to predict in tapering modeling for all models used. However, the precision and accuracy in the prediction of the tree butt swell can be impressively improved using variable-form taper models. |
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