engleski

Impact of Sustainable Management of Natural Even-Aged Beech Stands on Assortment Structure of Beech in Croatia

Within a comprehensive research of assortment structure of beech felling sites, the effects were investigated of sustainable management of even-aged beech stands on the quality of beech forest wood assortments by type of cut. In the period 1997 to 2007, field research covered a total of 3776 model beech trees in the area of Bjelovar, in stands of ecological-management type II-D-11 and management class BEECH with a 100-year rotation. The research was carried out with the application of two standard systems: Croatian Standards for Forest Harvesting Products of 1995 and Croatian Standard: Hardwood Round Timber – Qualitative classification - Part 1: Oak and beech HRN EN 1316-1:1999. According to the requirements of the Croatian Standards for Forest Harvesting Products of 1995, the sample for the development of assortment tables involved 3001 model trees, and assortment tables were made in accordance with the requirements of the Croatian Standard HRN EN 1316-1:1999 based on samples made of 3082 model trees. The tables showing the share of wood assortments, determined in accordance with the requirements of these two standards, were developed separately for thinning and preparatory felling, and separately for seeding and final felling, due to numerous reasons caused by type of management. The average percentage shares of wood assortments maintain the same ratios by quality classes (of course not the same percentage values) regardless of the applied standard (HRN or HRN EN) or norm. This research identified problems in production of assortments, reasons for the need of developing separate tables for thinning and preparatory felling, and for seeding and final felling, as well as the impact of type of management on the quantity and quality of beech forest assortments. By managing beech stands, meeting scientific and professional requirements, the said impacts on the quantity and quality of forest wood assortments may be directed to a certain extent, through the life cycle, to the target production. False heartwood, as the phenomenon considerably affecting the quality of industrial wood of beech trees, has been the object of professional and scientific interest for more than 100 years. Occurrence and characteristics of false heartwood were investigated depending on diameter class of average trees and type of cut in beech stands on a sample of 2308 trees. The age of trees in thinning operations ranges between 50 and 91, in preparatory cuts between 96 and 111, in seeding cuts between 101 and 112 and in final cuts between 98 and 112. In thinning 11, 7 % of trees were found with false heartwood, in preparatory cut 54, 7 %, in seeding cut 71, 3 % and in final cut 84, 6 %. The length of industrial roundwood, and absolute shares of false heartwood in trees, increase from thinning to final cut, while the volume percentage of false heartwood in trees for all types of cuts, except final cut, decreases. With seeding and final cuts approximately 15 % of volume of wood assortments of the highest quality (A and B quality class) has an excessive share of sound false heartwood for A and B quality class. With respect to the volume of large wood, depending on diameter class, the share of quality subclass A–s ranges between 0, 3 and 2 % and the share of quality subclass B-s between 1, 1 and 3, 2 % of large wood volume. With the application of tending procedures (negative and positive selection) and regeneration of beech stands, with passing of time, the value of the stand and wood assortments produced by individual type of cut increases. In biological (physiological) and economic context, the development of false heartwood with beech trees has an opposite trend, and the positive selection of trees that carry the development of the stand and natural regeneration provide the transfer of the best properties to future generations. This is a compromise that must be accepted by proper management and determination of harvesting rotation of beech stands.

forest management by thinning, forest regeneration by preparatory, seeding and final felling, Croatian standards, false heartwood, quality of forest wood assortment

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