|Sažetak (hrvatski)|| |
Zdravstveno se stanje jele obične u preborno gospodarenim sastojinama utvrđuje praćenjem stanja krošnje pojedinih stabala, odnosno osutosti iglica. Republika Hrvatska je od 1992. godine uključena u praćenje zdravstvenog stanja šuma u okviru Međunarodnog programa za procjenu i motrenje zračnog onečišćenja na šume. Motrenje se ponavlja na stalnim plohama posrednom (vizualnom) procjenom osutosti krošanja pojedinih stabala. U 1999. godini bilo je 63,8 % značajno oštećenih, a 2004. godine zabilježeno je visokih 88,4 % značajno oštećenih stabala. Istraživanjem je obuhvaćeno 200 stabala jele srednjeg prsnog promjera 48 cm i prosječne visine 29,4 m u odsjeku od 36,00 ha, a od toga 44 stabla u "3b" i 156 stabala u "4" stupnju posušenosti. Ukupni obujam doznačenih stabala prema Schumacher-Hall-u iznosi 570,95 m3, a srednji obujam stabla 2,85 m3. Postotak iskorištenja kretao se od 35,79 % do 87,10 % s prosjekom od 71,97 %, a otpad je u prosjeku iznosio 28,03 %. Prema neto izrađenom obujmu stabla u "3b" stupnju bilo je 66,18 % tehničke oblovine, a višemetarskog prostornog drva 33,82 %. Kod stabala u "4" stupnju posušenosti na tehničku oblovinu otpada svega 37,69 %, a na višemetarsko drvo 62,31 % izrađenoga neto obujma. Relativna vrijednost jediničnog drvnog obujma u razredu oštećenja krošnje "3b" manja je za 10 % do 30 % od jedinične vrijednosti neoštećenih stabala. Kod razreda oštećenja krošnje "4" vrijednosti jediničnog obujma smanjene su za iznose od 30 % do 45 % u odnosu na neoštećena stabla.
|Sažetak (engleski)|| |
Silver fir (Abies alba Mill.) is naturally distributed in mountainous regions of central, southern and parts of western Europe (Figure 1). Ecologically, commercially and traditionally, silver fir is the most important Croatian conifer species, participating in the total conifer growing stock with about 35 % (Prpić and Seletković 2001). It occurs in selection forests, which represent an important ecological stronghold of the most forested region in the Republic of Croatia. The stand´s health status is assessed by monitoring the crown condition of individual trees. Dobbertin and Brang (2001) showed that mortality rates increase exponentially with increasing defoliation. Crown damage can be monitored indirectly and directly, but neither of these methods is completely objective (Redfern and Boswell 2004). The health status of forests in Europe is monitored on an annual level within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests, ICP FORESTS. The programme was launched in 1985, and the Republic of Croatia joined in 1992. Monitoring is repeated in permanent plots by indirect (visual) assessment of crown defoliation of freely grown trees. According to the assessment of forest condition in Croatia (ICP FORESTS) for the year 1999, undamaged fir trees accounted for only 14.3 %, whereas severely damaged trees accounted for as much as 63.8 %. Severe damage denotes crown needle loss ranging from 26 % to 99 % (Potočić and Seletković 2000). Particularly high participation of damaged fir trees of 81.6 % was recorded in Gorski Kotar in 1999, while only 3.8 % were healthy fir trees. The results of field research suggest that the portion of damaged fir trees is constantly increasing. Thus, as much as 88.4 % of severely damaged trees were recorded in 2004 (Vrbek et al. 2008). The value of wood assortments of dead trees from salvage cuts is lower compared to those obtained from regular silvicultural treatments in healthy selection stands. The goal of this research is to analyze the quantity, quality and value of wood volume obtained from salvage cuts of silver fir in a selection forest. The research was conducted in the area of Gomirje forest administration within the management unit of "Potočine - Crna Kosa". The management unit extends over northern and north-eastern slopes of Mt. Velika Kapela at altitudes between 339 and 1,200 m. The compartment covers an area of 36.00 ha. The management class is a managed forest of silver fir and common beech with a total growing stock of 339 m?/ha. The growing stock of fir is 112 m?/ha. There are 304 trees per hectare, of which 157 are silver firs. To investigate fir trees during salvage cuts, breast diameters and heights were measured on every blazed tree and crown damage was directly assessed using the ICP FORESTS methodology. Trees marked for cutting were divided into two classes (degrees) of crown damage ("3b" and "4"). Crown damage for class "3b" ranges between 81 % and 99 %, while class "4" represents completely dry trees (Figure 3). The volume of each marked tree was calculated according to the Schumacher-Hall expression. Values of wood and timber assortments change in accordance with changes in the society, on the market and in economic relations, and in accordance with the application of new technologies and impacts of other factors (Rebula 1996). Value analysis of the obtained wood volume is made by determining the price of every single timber assortment. The price of every single piece of roundwood corresponds to the valid pricelist of the main forest products. The pricelist is used to calculate the price of roundwood from forests owned by the Republic of Croatia during the sale of standing trees ("on the stump") to contractual buyers. Value coefficients were established in accordance with mutual relations of price classes in relation to the most represented price class, which was taken as 1.00. The results were expressed by the relative value ratio of timber assortments produced from trees in crown damage classes "3b" and "4". Figure 3 shows distribution of dead silver fir trees in compartment 7b with regard to crown damage degree. Diameter classes range from 17.5 cm to 77.5 cm. The lowest number of trees, i.e. only one tree, was in the largest diameter class, while the majority of the trees were in the diameter class of 47.5 cm. A total of 200 trees with average breast diameter of 48 cm and average height of 29.4 m were marked and processed. A comparison of the total marked volume determined with the Schumacher-Hall form and the volume taken from the mentioned tables is given in Figure 5. The comparison was made on the basis of individual and total tree volume. According to Šurić, the total volume of marked trees was 491.93 m?, according to Schuberg it was 570.32 m?, and according to Schumaher-Hall it was 570.95 m?. Statistically significant differences (for p<0.05) were found in Šurić - Schuberg and Šurić - Schumacher - Hall relations, whereas insignificant difference was found in the comparison of volume of Schuberg - Schumacher-Hall. The utilization percentage of wood volume is determined as the ratio of the produced wood volume and the volume of large wood over bark according to Schumacher-Hall (Table 2). In the sample, the utilization percentage ranged from 35.79 % to 87.10 % with an average of 71.97 %, or 73.54 % (Median). Wood waste amounted to 28.03 % (26.46 %) on average. In the "3b" damage class the average breast diameter was 53 cm and height was 31 metre. Overall marked volume was 157.31 m?, the volume of processed wood over bark was 137.07 m?, and that under bark was 120.42 m?. The average percentage participation of bark was 12.69% and was lower by 0.6 % than that in the "4" damage class. With regard to the net structure of 116.54 m? of roundwood, technical roundwood accounted for 77.13 m? (66.18 %), and pulpwood for 39.41 m? (33.82 %). Within overall utilization, 49.03 % related to technical roundwood and 25.05 % to pulpwood. With regard to the quality of felled trees, only logs in class I, II and III were produced, while the remaining volume related to pulpwood. In the structure of produced wood assortments, class I accounted for 19.85 %, class II for 43.78 %, and class III for 36.37 %. Of the total number in the sample, 156 trees were in the crown damage class "4". These trees had an average breast diameter of 46 cm and a height of 29 m. The total volume of marked trees was 413.64 m?. The volume of processed wood over bark was 356.60 m? and volume under bark was 312.56 m?, which shows that bark participates with 13.31% in the total wood volume. A quantity of 302.51 m? of wood assortments was produced, of which technical roundwood accounted for 114.01 m? and pulpwood for 188.51 m?. The percentage share of wood waste was 26.86 %. Overall utilization was lower than in class "3b" and amounted to 73.14 %. Within total utilization, 27.56 % related to technical roundwood and 45.57 to stacked wood. In terms of structure, technical roundwood accounted for only 37.69 % and pulpwood for 62.31 % of the net volume. Only logs in class I, II and III were produced. In the structure of produced wood assortments, only 5.02 % related to class I, 30.39 % to class II and as much as 64.59 % to class III. Monetary value of trees is determined on the basis of volume of a particular diameter class and the price of principal forest products. The price of forest assortments made from standing trees ("stump price") was used to calculate monetary value of wood volume. According to the pricelist, monetary value of assortments was divided into three price classes based on the mean saw log diameter. The largest number of assortments was in the price class of pulpwood, for which an index of 1.00 was determined. Value indices given in Table 3 were established on the basis of the price ratio of other price classes and the mentioned one. Multiplying the price class index with assortment volume resulted in the assortment value index. The sum of all assortment value indices of individual trees is the relative value of the produced wood volume, i.e. relative tree value. Stem value rises with an increase in breast diameter. The value of damaged trees (Figure 7) in crown damage class "3b" is lower by more than 20 %, and the value of trees in class "4" is lower by more than 35 % in relation to the value of undamaged trees from regular selection cuts. Value increases per wood volume unit (Figure 8) in accordance with an increase in tree breast diameter. The reason is the absence of certain quality classes in the thinnest trees and division of monetary value according to the prescribed assortment diameter. The relative value of wood volume unit in crown damage class "3b" is lower by 10 % to 30 % than the value unit of undamaged trees. In crown damage class "4", the values of volume unit are lower by 30 % to 45 % in relation to undamaged trees.