engleski

DEFINING ASSORTMENT STRUCTURE OF EVEN-AGED BEECH STANDS ACCORDING TO STANDARD HRN EN 1316-1:1999

Research was carried out in even-aged beech stands in continental part of Croatia, at Forest Administration Bjelovar, “ Bjelovarska bilogora” management unit. In Croatia, share of beech is 36% in ratio of mixture and a similar share is in growing stock and year’ s timber mass marked for felling. The subject of research was probability of appearance of roundwood timber assortments in trees according to the type of felling and the difference between shares of roundwood timber assortments according to diameter class and type of felling. On the basis of the research results, new assortment tables were made according to Croatian Standards HRN EN 1316-1:1999. Research was carried out on a sample consisting of 787 trees in thinning felling, 788 trees in preparatory felling, 862 trees in seeding felling and 645 trees in final felling. An overall number of 3082 exemplary trees were included in the research. The age of the felling areas studied was between 59 and 91 years in the preliminary yield (thinning), 94 to 110 years in preparatory felling, 100 to 112 years in seeding felling, and 98 to 114 years in final felling areas. Using random selection, a sample of exemplary trees was made. Sample consisted of all beech trees marked for felling on predetermined azimuth lines. This way, shares of trees marked for felling were: 14.5% in thinning felling, 12.3% in final felling, 11.3 % in seeding felling and 10.7% in preparatory felling. Also, it was explored the probability of appearance of trees consisting of A, B, C and D assortment quality classes. Share of A class assortment quality was only 3.2% in thinning felling and 8.0% in preparatory felling. However, share of A class assortment quality was higher in seeding felling – 40.3% and 53.0% in final felling. Probability of appearance of B class assortment quality in seeding felling was 79.2% and in final felling was 86.7%. In thinning felling, share of B class assortment quality was 34.5% and in preparatory felling 44.2%. Probability of appearance of C and D classes of assortment quality was similar in all felling types. Total shares of C class assortment quality were 88.9%-95.4% and share of D class assortment quality was 97.6% in thinning felling and 99.7% in final felling. The average participation of assortments in diameter classes and in different felling types was calculated using parabolic regression equation: A quality class: Thinning felling and preparatory felling: y = - 0.0014x&sup2 ; + 0.0248x + 0.0209, R&sup2 ; = 0.7297 Seeding felling and final felling: y = 0.0008x&sup2 ; + 0.004x - 0.0014, R&sup2 ; = 0.8934 B quality class: Thinning and preparatory felling: y = - 0.003x&sup2 ; + 0.0586x - 0.0844, R&sup2 ; = 0.7897 Seeding felling and final felling: y = - 0.0027x&sup2 ; + 0.468x - 0.0752, R&sup2 ; = 0.7749 C quality class: Thinning and preparatory felling: y = 0.0006x3 - 0.0182x&sup2 ; + 0.159x – 0.167, R&sup2 ; = 0.7254 Seeding felling and final felling: y = 0.0013x3 - 0.0344x&sup2 ; + 0.2582x – 0.2800, R&sup2 ; = 0.8544 D quality class: All felling types: y = 0.0012x3 - 0.0281x&sup2 ; + 0.1768x – 0.0165, R&sup2 ; = 0.3585 Fuelwood: Thinning and preparatory felling: y = - 0.0035x3 + 0.0779x&sup2 ; - 0.5357x + 1.4263, R&sup2 ; = 0.9746 Seeding felling and final felling: y = - 0.0015x3 + 0.0424x&sup2 ; - 0.3701x + 1.2265, R&sup2 ; = 0.9192 Waste: All felling types: y = - 0.0004x&sup2 ; + 0.0094x - 0.0059, R&sup2 ; = 0.9593 Timber assortment tables which take into consideration type of felling as one of the inputs, provide a more reliable estimate of assortment structure of the felling area and more precise planning of timber mass marked for felling. In this case, as a distinguishing factor, we took the selection criterion for marking trees for felling which is applied for the types up to, and including, the preparatory felling. For that reason, timber assortment tables were made separately for thinning and preparatory felling, and separately for seeding and final felling. Seeding and final felling show by ca 11% higher shares of top quality timber assortment (A and B class) than thinning and preparatory felling. On the other hand, thinning and preparatory felling show by ca 11% higher shares of lower quality timber assortment (C and D class) than seeding and final felling.

common beech; assortment structure; Croatian Standard HRN EN 1316-1:1999

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