継続的な森林調査法に関する研究(I) : 地上調査法の比較
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概要
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The aim of this study is to establish a nation-wide continuous forest inventory system, and this paper describes a comparison among the four survery-methods of sampling on the ground (point sampling, line sampling, circle plot method with constant radius, and circle plot method with two different radii) carried out on the basis of the sampling errors of present value estimation. In case of point sampling, d.b.h. and tree height of the counted trees by basal area factor (k=4) were measured. In line sampling, the line of the length 15m was located and the measurement of the counted-trees by k=4 was conducted the same as in point sampling. In circle plot method with constant radius, the plot area was fixed on 0.02ha and in circle plot method with two different radii, they were fixed on 0.15 and 0.03ha, respectively. Each method was carried out in Sugi (Cryptomeria japonica) stand of 55 years old, of kagoshima university forest in Kagoshima pref., Japan (Table 1). Fifteen points were located systematically in this stand, and at each point each sampling method was conducted (Fig. 1). The estimators and its confidence-intervals of average of d.b.h., average of tree height, total basal area and total volume by each method were denoted in Table 2,and its sampling errors were denoted in Table 3. According to the Table 3,point sampling denotes relatively high percentage of samplimg error in all the estimations except the total volume one. Circle plot method with two differemt radii, denotes higher sampling error in the volume-estimation. In this paper, Line sampling seems to be more useful. In Switzerland, the same comparison was conducted and its result is denoted in Table 4. The sampling methods, supplied with larger plot area than in this study, were tested. Based upon this result, the circle plot method with two different radii has been adopted in Swiss CFI system. As you know, the condition of forest resources in Switzerland is the best in the world. It may be troublesome, if not impossible, to adopt the same plot-area and method conducted in Swiss directly in Japan. In the next paper, based on the sampling error of change estimation and the sampling efficiencies (inevitable time-loss or number of surveyors e.t.c), a comparison among the above four survey-methods of sampling on the ground is going to be conducted.
- 鹿児島大学の論文
- 1991-03-15
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