DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
| ŠUMARSKI LIST 1-2/1966 str. 31 <-- 31 --> PDF |
at 144 crowns per m3f of raw wocd. The diference of 48 crowns per m3f is only slightly reduced when felling and other costs are taken into account. Basic density plays an important role also in the quality of saw-logs. Moreover, the stand, which is to produce saw timber, yields pulpwood when it is young. Pulpwood is obtainded from the upper part of the stem of timber trees; and the waste from sawing is used in the production of pulp. Consequently, we must also consider the production of timber from the point of view of pulp. Variations in basic density are caused to a great extent by variations in environment; and these environmental differences can be considerable even in a small stand. The most important environmental factor seems to be stand density, a rough estimate of which can be obtained indirectly by measuring the width of the annual rings of the tree. The next most important environmental factor appears to be the temperature, which for Swedish habitats is quite well defined if the latitude and height above sea level of the site is known. Figure 6 shows how, in principle, the assessment of the basic density of the proposed plus trees is made. By means of regression function the mean basic density is calculated which can be expected for different widths of the annual ring in wood samples from habitats at a certain latitude and height above sea level. The regression functions have been calculated for material HEIGHT CURVE FOR PLUS TREES OF NORWAY SPRUCE INCLUDED IN THE SEED ORCHARD No31 IN CENTRAL SWEDEN 31 !Mean height of the plus and check trees in m. 30 29 28 27 26 25 24 23 22 21 PLUS TREES CHECK. TREES 20 X **´/ 80 90 100 110 120 130 W0 150 years The age of the plus and check trees at breast height. Fig. 4. |