The research was conducted with the goal to determine the variability of the quality parameters of the wood chips produced from the most favorable raw material (energy roundwood), and in the most controllable operational conditions (pellet factory), as the first step in identifying opportunities to optimize the wood chips’ quality monitoring. Four raw material types were tested: fir/spruce and beech debarked energy roundwood, as well as energy wood with bark of the same species. Sampling was conducted during six consecutive months along with laboratory testing, all according to the HRN EN ISO standards for solid biofuels. Interpretation of the results was done in relation to deviation from the first sampling results (as an indicator of the possibility to retain the quality of wood chips), and repeatability and reproducibility set in the standards (as an indicator of acceptable variability). The influence of the species and debarking process on the wood chips’ quality was analyzed as well. Relative deviation from the first sampling as well as the quality class change pointed moisture content as a normative property with the lowest possibility to retain initial values over the six-month period. Ash content results indicated a strong possibility to maintain the initial ash content class in the majority of the samples. In just three cases, the results of ash content were outside the reproducibility limits with first sampling as a reference. Gross calorific value results pointed only four samples outside the reproducibility limits with the first sampling results are set as a reference. Wood species influenced gross calorific value and the median value of the particle size distribution and debarking showed a significant positive effect on the moisture content reduction as well as on the ash content reduction. Presented findings are indicative for the investigated raw materials, however for the general conclusion on the subject of wood chips normative properties variation, various raw material types will have to be examined in further research.

This research was conducted to determine the cause, intensity and location of damage (stem, butt end, root collar, root) and the extent of damage to standing trees during felling and processing by an harvester and timber extraction by a forwarder (cut-to-length system). The research was conducted in the central part of the Republic of Croatia in the Management Unit (MU) “Bjelovarska Bilogora” during the thinning of Subcompartment 14b, area of 18.28 ha, in the stand of hornbeam (Carpino betuli—Quercetum roboris fagetosum Rauš 1975), age 70, and of Subcompartment 14c, area of 9.07 ha, in a stand of common beech (Carici pilosae—Fagetum Oberdorfer 1957) aged 79 years. The thinning intensity was 12.13% in Subcompartment 14b and 13.72% in Subcompartment 14c. Field measurements were carried out on sample plots—the first time in 2017 to determine the intensity and characteristics of the damage to standing trees with regard to the cause of the damage (harvester or forwarder), and the second time in 2018 to determine the overall intensity and features of the damage to standing trees after finishing harvesting operations. For all trees remaining in the stand after the harvesting operations, the following were determined: tree species, diameter at breast height (DBH), the position of the tree in the stand depending on the forest traffic infrastructure, and—if damaged—cause of damage, type of damage, the position of damage on the tree, and dimensions of damage. The intensity of the damage was expressed by the ratio of damaged and undamaged trees, with a detailed analysis of bark damage (squeezed-bark damage and peeled-bark injuries). The results of the research indicate the highest prevalence of peeled-bark injuries. In relation to the total number of standing trees, trees with peeled-bark injuries were more represented in Subcompartment 14c (39%) than in Subcompartment 14b (33%). In Subcompartment 14b, the harvester and the forwarder damaged an equal number of trees, while in Subcompartment 14c, the harvester damaged 59% of the damaged trees. In both subcompartments, an average of 83% of (peeled bark) injuries were up to 1.3 m above the ground. In both subcompartments, the most common (67%) were injuries up to 100 cm² in size, for which many authors claim the tree can heal by itself. Given the increasing use of harvester-forwarder systems in deciduous stands and research results that indicate possible damage to standing trees, it is necessary to pay attention to all phases of planning and execution of timber harvesting operations, thus minimising negative effects.

During forest harvesting operations, exhaust emissions from forest vehicles are released at different levels depending on several variables. This pollution released into the atmosphere is considered one of the main anthropogenic factors that negatively affect forest ecosystems. In this study, we analyzed exhaust emissions from a skidder diesel engine during various engine loads. Measurements were done on an ECOTRAC 140 V skidder with the water-cooling diesel engine and a built-in catalyst with an SCR system. The composition and amount of exhaust gases (CO, CO₂, O₂, NO_x,) at different loads of the diesel engine of the skidder and engine temperature were measured using a MAHA MET 6.3 measuring device. The amount of exhaust gases was analyzed in relation to the engine speeds, engine temperatures, and the European emission standards for engines used in nonroad mobile machinery (NRMM). Influences of catalyst systems and recommendations for more environmentally friendly forest harvesting practices are addressed. With the engine unloaded, the amount of CO₂ increased when engine speed was increased, while other amounts of exhaust gas decreased. During the cold start, the concentrations of hydrocarbons and nitrogen compounds were high. The composition of the exhaust gas was affected by the exhaust reduction system installed in the tractor and the amount of the exhaust gas was dependent on the engine load. The skidder engine met the requirements of the exhaust gas standards EPA/COM IIIB Tier 4 (I) under which it is declared. With a load engine during winch operation (2300 rpm), NO_x amounts mostly exceed the limit values of the standard. Exhaust emissions can be reduced at various operating levels by utilizing the most environmentally friendly technologies and following the correct procedures, such as warming the engine up to operating temperature prior to operation and operating in the most favorable mode with optimal speed. The regular reduction of exhaust limit values to newer stages of the standard therefore leads to the continuous development of engines and forest vehicles in general.

U radu su prikazane sastavnice strukture ukupne nadzemne biomase stabala divlje trešnje (Prunus avium L.) na području spačvanskog bazena u Upravi šuma Podružnica Vinkovci. Istraživanja su obavljena na 120 primjernih stabala divlje trešnje, prs...