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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

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





( )2

We determined the estimate of the standard deviation of heights (diameter gradation from the range of the sample of heights (in the field we took for
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