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題 名 | 三種面積圓形樣區及二種係數值水平樣點法等五種地面測計方法調查精度之研究 |
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作 者 | 吳英陵; | 書刊名 | 宜蘭農工學報 |
卷 期 | 10 1995.06[民84.06] |
頁 次 | 頁57-67 |
分類號 | 436.713 |
關鍵詞 | 圓形樣區取樣法; 水平樣點取樣法; 樣本數; 精度; Circular plot sampling; Horizontal point sampling; Sample size; Precision; |
語 文 | 中文(Chinese) |
中文摘要 | 採用五種不同地面測計方法,實地調查並探討對不同林型材積調查精度最高的地 面測計方法為本研究直接目的。 研究地區面積4,091公頃,海拔高從778.4公尺到3,461.8公尺不等,依林型經濟價值設定 不同的容許取樣誤差,共140個地面樣區;每一個地面樣區均各有五種地面測計方法,分別 為三種固定面積圓形樣區以及水平樣點取樣法畢特立希氏角度係數值為2(R2)及4(R1)的 二種測計方法;為簡化測定作業,同一株樣木的胸高直徑僅作一次測定,樹高僅測0.0125公 頃樣區內全部樣木,其餘未測樣木之樹高依樹種(群)別樹高曲線式推算。 試驗結果得下列重要結論: 1. 樣本數固定時,人工林林木材積調查精度隨其樣區(點)平均株數之增多而提高,與使 用固定面積樣區調查或水平樣點法無關。 2. 樣本數固定時,天然林林木材積調查採用水平樣點法所得精度遠高於固定面積樣區調查 法,且固定面積樣區調查法精度亦未必因樣區面積擴大為0.05公頃而提高。 3. 純就林木材積調查精度而言,林分為桿材林分或疏林分情況之一者,應使用係數值為2或 較小的畢特立希氏角度係數值;使用係數值為2較諸係數值為4者,95%機率水準取樣誤差10- 20%時,可以減少之樣點個數在10%以上。 4. 天然林採用係數值為2之水平樣點法(R2)所得調查精度最高,人工林採用0.05公頃圓形 樣區(C3)所得材積調查精度最高。 |
英文摘要 | Three kinds of fixed-area circular plot sampling and two forms of horizontal point sampling ard adopted for field enumeration to explore the optimum method to timber volume survey precision for various forest types. With elevations ranging from 778.4 meters up to 3,461.8 meters and a total area of 4.091 ha, the 140 observations are allocated to the strata accordingto the degree of precision desired for the particular strata. Three kinds of circular plot sampling and two forms of horizontal point sampling are enumerated with the common center or point in every 140 observations. The results of this case study are summarized in the following conclusions: 1. For fixed sample size in artificial plantation, the horizontal point sampling is not more efficient than the circular plot sampling for precision concerned. Furthermore, precision themselves are much more influenced by the average number of trees per plot or point. 2. For fixed sample size, precision studies have shown that the horizontal point smapling is more efficient than those of circular plot sampling. Also, the circular plot with a plot size of 0.05 ha does not guarantee any higher precision than those of smaller ones for fixed sample size. 3. For horizontal point sampling concerned, the optimum basal area factor is 2 in open stands or pole-timber stands; With 10-20% sampling error at 0.95 probability level, the sample size of BAF 2 is 10% or more less than that of BAF 4. 4. The optimum results could be expected with horizontal point sampling, with BAF2(R2), to natural forest and circular plot sampling, with 0.05 ha (C3) plot size, to artificial plantation. |
本系統中英文摘要資訊取自各篇刊載內容。