台灣地區人工林地位生產力指數模式之建立

Investigation of a Site Productivity Index for Plantations in Taiwan

汪大雄(Dar-Hsiung Wang) ； 王兆桓(Chao-Huan Wang) ； 陳家玉(Chia-Yu Chen)

《台灣林業科學》 16卷4期 (2001/12) Pp. 307-315

https://doi.org/10.7075/TJFS.200112.0307

摘要

地位指數為國內外應用最廣泛的一種作為衡量生育地生產立木材積潛能的指標，其方法是以立木高度或林分高度和林齡之間的關係為基礎而建立。由於此種關係之約束，使得地位指數在應用上受到許多的限制，而只能適用於單一樹種或呈同齡林之人工林分。在混淆或異齡林之林分，由於其樹高和年齡間之關係並非如單純林那樣明確，使得以樹高-年齡為基礎所導出的地位指數無法理想地適用於混淆人工林內。鑑於台灣地區的人工林地易受天然樹種的侵入，或因造林成活率不佳經多次補植的情況下而呈現類似混淆林狀態，或因林分之林齡紀錄不全無法得到正確的林齡，使得傳統之地位指數無法應用於該類林地。為期能發展出一適用於混淆、異齡林分內測定地位生產力之替代方法，本研究選用地位生產力指數之概念，並以修正的三參數Weibull函數來建立優勢木與次優勢木之“樹高-胸徑”方程式，以推導出台灣地區各主要樹種的地位生產力指數，則似為目前最為可行之方法。結果顯示檜木林型扁柏、松類林型的臺灣二葉松、杉木、柳杉和相思樹等樹種皆可獲得顯著的地位生產力指數。

關鍵字

地位指數 ； 地位生產力指數 ； Weibull函數

並列摘要

Site index, defined as the average of height of the dominant (or dominant and codominant) trees in a stand at a specified reference age, is the measure that is probably the one most widely used in the world to estimate the potential capacity of timber production. While methods for constructing site index curves have become increasing complicated and diverse, the foundation of site index equations, the height-age relationship, remains unchanged. Due to restrictions of the height/age relationship, site indices, therefore, can only be reasonably applied to even-aged and pure-species stands. In mixed or uneven-aged stands, due to the lack of a height/age relationship, the site index is not a reasonably reliable site productivity measurement. Owing to the fact that plantations in Taiwan are easily invaded by seedlings generated naturally with the consequence of becoming mixed species stands, and the lack of age record in survey, it is not appropriate to use a site index to evaluate site productivity. An alternative site productivity measure, based on the relationship between total tree height and diameter at breast height of dominant and codominant trees was used to quantify site productivity for major tree species in Taiwan. The results of this study show that for species of Chamaecyparis obtusa var. formosana, Pinus taiwanensis, Cunninghamia lanceolata var. lanceolata form lanceolata, Cryptomeria japonica var. japonica, and Acacia confusa, based on data available, a site productivity index model with a significant fit for all parameters can be obtained.

並列關鍵字

site index ； site productivity index ； Weibull function