Damage of Forest Trees and Quality of Timber Assortmets of Pedunculate Oak on Spačva Area

Pojava propadanja i odumiranja stabala hrasta lužnjaka jedan je od najznačajnijih gospodarskih i ekoloških problema u šumarstvu Hrvatske. Gospodarski problemi odnose se na smanjenje kakvoće drva, poremećaje u potrajnom gospodarenju te povećanje troškova gospodarenja i smanjenje prihoda. Ekološki problemi odnose se na stalne promjene stanišnih uvjeta i smanjenje stabilnosti šumskih ekosustava. Cilj istraživanja bio je analizirati iskorištenje drvnog obujma različito oštećenih stabala hrasta lužnjaka. Prosječna osutost stabala uz cestu Županja - Lipovac iznosila je 57 %, a na području spačvanskih šuma 24 %. Utvrđeno je intenzivno odumiranje sta bala hrasta lužnjaka uz cestu Županja-Lipovac u 2003. godini, koje je iznosilo 30 %. U svim stupnjevima osutosti utvrđena su stabla s biotskim oštećenjima. Kod stabala sa značajnom osutošću krošanja (>25 %) utvrđeno je smanjenje udjela tehničkog drva za oko 10 %, odnosno isto toliko povećanje otpada. Udio furnirskih trupaca kod stabala male i srednje osutosti bio je 50 % veći u odnosu na jako osuta i odumrla stabla. U radu je raspravljena problematika ukupnog iskorištenja drva pri sječi i izradbi te vrijednost drvnih sortimenata vitalnih stabala u odnosu na oštećena i odumrla stabla hrasta lužnjaka.Management with forests of pedunculate oak, the principal commercial tree species in Croatia, is burdened with increasing instances of tree decline and dieback. A combination of factors, such as decreased height and diameter increment, lower value of wood assortments, disturbances in planning and management and rising management costs, have made this the most important management and ecological problem in Croatian forestry. Tree decline is a gradual, continuous, or in some cases, rapid loss of tree vita lity. In forestry, tree decline is assessed on the basis of the exterior appearance of a tree, i.e. on the basis of tree damage assessment. Tree damage relates to crown, stem and root damage. Crown damage assessment is based on crown defoliation and changes in leaf colour. Tree dieback is sudden death of trees due to diseases or a complex action of adverse factors. It can often stem from a continuous decline of trees and a disturbed stability of forest ecosystems. In Croatia, the most severely affected tree species are the two principal ones: pe dunculate oak and silver fir. Tree decline and dieback incur high financial los ses, amounting to as much as 40 % of the potential market value of forest assortments. However, a decrease in non-market forest functions is much more serious. The economic consequences of tree decline are reflected on the quality and lower value of wood assortments. Dieback of pedunculate oak trees leads to sapwood degradation and a decrease in assortment diameter, which may amount to as much as 33 % of the diameter. The goal of research was to determine the impact of pedunculate oak da mage on the structure and volume of wood assortments. Research was con ducted on tree samples from four management units in Vinkovci ForestAdministration, along the Županja - Lipovac road. Wood volume utilization of dead and differently damaged trees of pedunculate oak was analyzed. Tree crowns along the Županja - Lipovac road were found to be more defo liated compared to those in the “Spačva basin” area. Crown defoliation of pe­dunculate oak was about 60 %, which indicates decreased tree vitality. Severely defoliated and dead trees manifested significantly higher biotic da mage in relation to slightly and moderately defoliated trees. The percentage share of veneer logs and class I logs, as well as stacked wood, was higher in trees with the first and second defoliation class. The share of lower class logs (II and III class), as well as the percentage share of waste was higher in trees with higher defoliation classes. Of the total wood volume, there were 20 % of veneer logs in defoliation classes 1 and 2 (slight and moderate defoliation), and 10 % of veneer logs in defoliation classes 3 and 4 (severe defoliation). Ac cording to the percentage share of assortments in the total technical roun dwood, there were 37 % of veneer logs in trees with defoliation classes 1 and 2, and 18 % of veneer logs in defoliation classes 3 and 4. The proportion of lower-class technical assortments was higher in higher classes of crown defo liation. The proportion of second class logs in defoliation classes 1 and 2 was 11 %, and in defoliation classes 3 and 4 it was 19 %. The proportion of third class logs in defoliation classes 1 and 2 was 15 %, while in defoliation classes 3 and 4 it reached 19%. There was more waste in defoliation classes 3 and 4 (30 %), and slightly less in defoliation classes 1 and 2 (27 %). Tree damage lowers the quality of logs and lessens the income from pedun culate oak management. Tree damage assessment may reduce the amount of snags and increase management yields. Timely and appropriate tree damage assessments have a positive effect on overall management with pedunculate oak. The selection of damaged trees for felling is a key factor that ensures the quality of the wood matter in disturbed and unstable forest ecosystems