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ŠUMARSKI LIST 5-6/2020 str. 49     <-- 49 -->        PDF

Data Collection and Calculations – Prikupljanje podataka i izračuni
In 2015, ten years after planting, data were collected in sampling quadrats of 20 × 20 m (44‒130 trees) at the center of each experimental plot. Diameter at breast height (DBH), tree height, height to lowest dead and lowest live branch and maximum diameter of live and dead branches were measured, after which the height/DBH ratio (H/D), live crown ratio, stem volume, form quotients and aboveground dry biomass were calculated.
The DBH of all trees was measured with a tree caliper in the sampling quadrats of the plots. Tree height, height to lowest dead branch and lowest live branch were measured using a combination of a laser rangefinder and a clinometer. Maximum diameters of live and dead branches were measured with a digital caliper on the five thickest tree branches. The H/D ratio was determined by dividing the height of the tree by the DBH. The live crown ratio for each tree was determined by the ratio of live crown length to the total tree height.
In addition, 16 trees representing the diameter class (0‒3.9 cm, 4‒7.9 cm, 8‒11.9 cm, 12‒15.9 cm) in each plot were cut down (48 trees for each planting density) for determination of stem volume and aboveground dry biomass. After the branches were stripped from the stem, diameters were measured at the heights of 0.30 m, 1.30 m, 3.30 m, 5.30 m… using calipers, and  the stem volume with bark of each tree was calculated using the Smalian formula. The billet volumes were calculated by the cylinder and the end parts by the cone formula  (Kalıpsız 1999). Double-bark thicknesses of each of the cut trees were also measured.
Form quotients of the trees were determined using the following formula (Assmann 1970; Kalıpsız 1999):
where, q is the form quotient, d1.30 the diameter at breast height (cm), and d3.30 and d5.30 the tree diameters (cm) at 3.30, 5.30 m… of tree total height.                                                                  In order to determine the aboveground biomass of each felled tree, branches were weighed after removal from the stem. In addition, two branch samples (10 cm-long) were taken from the lower and upper parts of the length to the crown and these were also weighed. The stem was then divided into three equal parts and weighed. A 5-cm-thick stem section was taken from the middle of each piece and weighed. Branch and stem samples were dried in the oven at 105 ºC for 48 h, and weighed on 0.01 g precision scales. The stem and branch dry biomass of each tree was determined using these dry weights (Saraçoğlu 1998). Leaf biomass was not calculated because biomass measurements were carried out during the leafless period. Therefore, aboveground dry biomass was calculated from total stem and branch dry biomass.
Volume and aboveground dry biomass equations for individual trees depending on the DBH were obtained by regression analysis for all initial planting densities (Table 2). These selected models were used to estimate the volume and dry biomass of the remainder of the trees.