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Features of Assigned Beech Trees According to the Type of Felling in the Felling Areas of Bjelovarska Bilogora and their Influence on the Assortment Structure

Marinko Prka orcid id ; Hrvatske šume Direkcija Zagreb

Puni tekst: hrvatski pdf 2.526 Kb

str. 319-329

preuzimanja: 449



The subject of research were absolute and percentage share of assigned trees according to diameter class and type of felling and their influence on assortment structure of particular types of felling. The assigned exemplary trees were categorized according to the most prominent outward features into nine categories. The research was carried out on the total number of 36 areas of the economic unit Bjelovarska Bilogora. In the seeding felling areas data were collected on several occasions (felling). In that way, 2,308 assigned trees were categorized in the total of 46 occasions (felling). All the areas belong to ecological-economical type II-D-11 and structural class BEECH with the rotation of 100 years.
The aim of the process was gaining more insight into the factors that influence assortment structure of stands, as well as completing the information on principles and ways of forest management in the past and nowadays. Analysis of the number of trees of particular categories according to the type of felling (stand age) and diameter class was carried out with the aim of finding the answers to questions pertaining to the criteria of assignment of one type of felling, as well as the degree of damage to stands during the exploiting of forest in the area subject to research.
The assigned trees of group A (undamaged trees of normal growth) have, on the whole, extremely positive influence on assortment structure of particular type of felling. To these we can, to a certain extent, join pregrowth trees, i.e. group G, whose influence is limited mostly to thinning felling. Trees of all the other described groups have more or less negative effect on assortment structure of particular type of felling. The influence of suppressed trees (group H) on assortment structure is insignificant, and their importance for successful carrying out of seeding felling is considerable.
The percentage of trees with positive influence on assortment structure according to the type of felling, stands about 50 % in thinning and preparatory felling, while in seeding and final felling it is about 60 %.
Trees of medium diameter and large diameter, i.e. trees of diameter class between 41 cm and 60 cm, and those with breast diameter over 61 cm, have the greatest influence on the whole of tree assortment structure or particular types of felling. The reason for that is the fact that only those trees can potentially contain timber assortment of the highest quality (according to Croatian Standards of Forest Exploitation Products from 1995) because of the minimal dimensions prescribed for timber assortments of the highest quality. Percentage of those trees with positive and negative influence on assortment structure is almost identical in case of thinning and preparatory felling, while in case of seeding and final felling the share of trees with positive effect is considerably higher than the percentage of trees with negative effect on assortment structure.
It can be said that the percentage of trees with breast diameter larger than 41 cm, with the positive effect on assortment structure grows from 5.7 % in thinning felling to 57.5 % in final felling. If we focus on the relation (difference) between the trees with breast diameter larger than 41 cm, with positive and negative effect on assortment structure, we can easily say that this value ranges from – 2.9 % in thinning felling to 22.9 % in final felling.
Trees damaged as a result of our activities, or human influence, are contained within groups with description marks of C, D, E and I. The percentage of trees damaged by human activity increases from thinning felling to final felling. For thinning felling, this percentage amounts to 11.2 %, for preparatory felling it is 13.1 %, for seeding felling it is 15.8 %, while for final felling it amounts to 23.3 % of damaged trees. The increase in participation of trees damaged in that way towards the end of rotation can be attributed to intensifying of exploitation of forests at the time of seeding felling. However, as much as 23.3 % of damaged trees out of the assigned trees of final felling, i.e. almost one quarter of more or less damaged trees left for final felling, is the information which calls for some concern.
The quality of assortment structure of stand varies within a large scope and depends on different kinds of influence, from timely and high-quality cultivation activities, over influence of habitats, to the extreme abiotic influences of accidental character. Assortment structure of beech stands is the focus of our interest only in the sense of increasing the overall quality of beech trees, i.e. achieving the largest possible percentage of high-quality beech trees in the stand. The percentage of timber assortments in beech stands of particular age (except for final felling and clear felling) is not our primary interest.
The primary interest of forestry operational bodies (as well as science) is the quality and quantity of timber assortments that can be achieved through carrying out of particular type of felling, i.e. assortment structure of felling area. The share of timber assortments of particular type of felling is to a great extent a result of our decisions during the selection of trees for felling, by which we pursue the aim and the guidelines of stand management.
The principles (rules) we apply while assigning trees for particular type of felling lead us to “save” the high-quality trees for the end of the rotation (seeding felling, final felling). Having that in mind, it is to be expected that the percentage of the timber assortments of the highest quality (within the same diameter class) will increase from thinning felling towards final felling.
For that reason it is necessary to distinguish between the assortment structure of stand and the assortment structure of felling area (specific types of felling). The assortment structure of stand varies within a wide and unknown scope, and its quality is the result of the success of our management in the past. Only in that sense does the assortment structure of stand influence the assortment structure of felling area.
The increase in percentage shares of high-quality timber assortments according to diameter classes from thinning felling to final felling is a pattern determined by our decisions, i.e. expert conduct of cultivation activities of assigning trees for felling. This pattern is constant in the same measure as the principles of management and the manner of their implementation are constant.

Ključne riječi

assortment structure, beech felling areas, tree damages

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