DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 3-4/1966 str. 29 <-- 29 --> PDF |
The volume tables were prepared only for stands of the shade-loving tree species, i. e. for Fir/Spruce and Beech (stands managed by the selection method). For the sake of better illustration of Šurić´s interpolated tables it was presented on an example also the course of the computation of volume and volume increment. Computed were data relating to Fir species in the experimental plot »Jasle«, forest region of Gorski Kotar (Klepac, 4). In the example special attention was paid to the determination of the tariff series of the stand and of the mean annual diameter increment. The tariff series was determined on the basis of the height of the central basal- area tree. In order to select with 95°/o of reliability the tariff sei´ies, the size of the height sample (nh) of the central basal area tree was determined on the ground of Tippett´s Table (Tab. 1) and Table 2 which we ourselves prepared. Tippett´s Table (Tab. 1) is representing the average relations of the standard deviation (oh) and the ranges, for a definite size of the samples (with the understanding of the normal distribution of frequences). In Table 2 are represented sizes of the sample for different estimates of the standard deviation (oi,) and different height intervals (/) h = height difference between two different boundary height curves within the diameter-class gradation of the central basal-area tree) with 95°/o limits of confidence 1.96*0,2 nh > Ah ( )2 2 We determined the estimate of the standard deviation of heights ( instance measurements of nine heights) and Tippett´s Table. On the basis of the thus determined standard deviation and the tariff height inerval (A h) read from the tariff (in order to obtain greater safety we take the interval of the fifth tariff series of Šurić´s interpolated tables, see tariffs), we have read from Table 2 the necessary size of the height sample (nh), from wich we determined the height of our central basal-area tree. The annual diameter increment was determined by moans of the increment core method. The number of increment sample trees (cores) was distributed proportionally to the sum of diameters b. h. within an individual diameter gradation (Tab. 3). Under such a distribution of increment sample trees the total error of the growing- stock volume increment will be the least (Emrović, 1). The average annual diameter increment (i,i) was computed for each diameter gradation. For the needs of practice it will suffice to smooth the diameter increment (i(1) graphically, taking care that the smoothed curve satisfies all conditions of a well situated line. The thus adjusted diameter increment was used for the computation of the volume increment. The bark increment was neglected for the purpose of greater elbow-room when calculating the volume. The computation of the growing stock and volume increment of the stand was performed in two ways, which can serve also as a control to each other. In the first instance (Tab. 4) we obtain the volume of the growing stock according to diameter gradations by multiplying the total basal area of the individual diameter gradation |