Volume 47 No. 2

Tree felling with a chainsaw is one of the most dangerous operations, but it cannot be replaced by machines in many areas. Operators are exposed to many hazards including accidents, fatigue, fumes, dust, noise and vibration. This research focuses on vibration exposure and on how it is affected by the accuracy of saw chain maintenance. Although chain sharpening must be carried out according to the manufacturer's instructions, it is common practice to make errors in sharpening angle and chain depth gauge lowering. The aim of the study is to investigate the variations in both cutting efficiency and vibration exposure, considering three different depth gauge lowering levels (standard: 0.65 mm, over-standard: 1.0 and 1.3 mm) when cross-cutting several square beams of two species: European beech (high density) and silver fir (low density). The results show that the increase in cutting efficiency at higher depths was statistically significant for silver fir beams but limited overall (about 10%). On the other hand, the over-standard lowering of the depth gauge did not reduce the cutting time on beech. On the contrary, vibration exposure increased significantly from a minimum of 64% to a maximum of 133% compared to the standard level. These results show that the practice of lowering the depth gauge beyond the standard level is dangerous for the operator and has no real benefit in terms of cutting performance.

During professional work, the forestry workforce is exposed to hazardous activities and numerous risks, which may result in everyday occupational accidents or illnesses. Networking and innovative thinking with the aim of developing new legislative solutions and certification systems, e.g. chainsaw qualification standard, represents an important link in supporting accident prevention in the national, European or even global forestry industry. The starting point for the preceding ideas is systematic recording, analysis and interpretation of basic indicators of the level of occupational safety in forestry. This study is focused on analysing the different occupational safety indicators for the period 2015 to 2024, with the aim of a comprehensive analysis of occupational accidents in the forestry sector of the Republic of Croatia at the national and regional level.

Data is gathered from occupational safety service databases of the Croatian Forests (CF) Ltd., which manages 2.024 million hectares of forests in the Republic of Croatia. Descriptive and inferential statistical methods were used in filtering, processing and analysing data. The inferential methods for data analyses included correlation analysis, Chi-squared test, and the Kruskal-Wallis H test to analyse the relationships between sampled variables.

In the ten-year period analysed, a total of 2,390 occupational accidents were recorded, of which 9 were fatal accidents. In the same period, 157 cases of occupational illness were recorded, of which 67.5% were caused by exposure to vibrations. The annual weighted average of the total number of accidents is 239 according to Croatian Forests Ltd. database (where the company cuts and processes less than 50% of the annual felling volume), while the same indicator for Croatia according to the Eurostat report is 264. The highest average number of accidents is recorded in the process of forest harvesting (58.1%). The riskiest work-related activity is felling and wood processing where on average 48.5% of the total number of accidents occur annually. The annual statistics are 0.37 fatalities per mil. m3, one occupational accident per 10,000 m3 of felled and processed wood (1.00/10,000 m3) and 30 accidents per 1000 employees. So, safety at work in Croatian Forests Ltd. can be assessed as partially satisfactory. Accident analysis from the perspective of the time curve (month, day, hour) shows the highest proportion of accidents occurring in the third annual business quarter, on a weekly basis on Tuesdays, and on a daily basis from 9 to 11 am. The key findings regarding analysis of data at the regional level indicated that medium-size Forest Administrations (FAs) as organizational components of the company CF Ltd. had the highest risk of accidents at work (41.60 accidents per 1000 employees). The indicators of the quantity of felled and processed wood per one accident (m3/accident) revealed an unsatisfactory result achieved by small-size FAs (19,943 m3/accident), and a more satisfactory result achieved by large-size FAs (28,335 m3/accident).

The range of numerical values and the weighted average value of occupational safety indicators for the sampled period did not show a decreasing trend, which indicates a similar or lower level of occupational safety in the forestry sector of the Republic of Croatia. The results obtained provide scientists and practitioners with an understanding of the level of occupational safety in Croatian forestry and form the basis for developing proposals for new measures in line with technological progress, as well as new educational programs for the development of work skills and competencies.

In today's modern forestry, which is founded on sustainable management and development, it is essential to carry out the design phase of forest roads with quality, both for financial and environmental reasons. The basis for this is high-quality field data. This research tested available and potentially suitable methods for field surveys in the process of designing a forest road, including the classical survey method, GNSS and total station survey, as well as structure from motion and airbone lidar scanning survey. A total of 23 forest road designs were created through 3 design methods. Four important forest road parameters were tested: cut and fill volume, carriageway value and roadway width. No statistically significant difference was found for any of the tested parameters between the methods. Total station and ALS-based designs showed the lowest values of cut and fill volumes, 2.41 m3 and 2.54 m3 for the total station design, and 3.20 m3 and 2.47 m3 for the ALS design. Although some deviations were found between SfM designs based on different flight parameters, they were not significant. The results indicate the possibility of using all tested methods in forest areas with steep terrain, after a salvage logging has been performed. Also, by using three design methods and testing their results provides guidance how to test different measurement systems in the future when designing forest roads.

Visual Place Recognition (VPR) enables robots to determine current location by comparing input image against previously stored reference images. It is essential in autonomous location and simultaneous localization and mapping (SLAM). A key task of VPR is evaluating similarity between images, as state-of-the-art deep learning-based approaches have achieved outstanding performance in standard indoor/outdoor scenes. However, the SOTA deep learning-based methods underperform in forestry robotic owing to two challenges, constrained computational capabilities and appearance variation due to seasonal shifts, weather/light/viewpoint variations, which substantially impair visual similarity computation. Consequently, this work proposes ForestsNet, a novel lightweight VPR network, to resolve this issue. First, a Binary Neural Network (BNN) was constructed to achieve considerable memory reduction. A novel binarization function, Leaky Sign, is proposed; it adaptively applies quantization factors to input activations, it retains richer feature information during binarization while significantly reducing accuracy degradation of place recognition. Second, Mixer Forests, a novel multi-layer perceptron-based aggregation method is introduced to integrate global context into feature maps, substantially enhancing the robustness against appearance variation. In addition, two novel evaluation metrics, Memory Allocation Efficiency and Balance Compression Recall, are designed to quantify the trade-off between memory efficiency and place recognition accuracy. Experimental results demonstrate that ForestsNet achieves substantially higher memory usage efficiency than full-precision networks. Compared to state-of-the-art BNNs, it presents superior performance in both memory efficiency and place recognition accuracy, establishing itself as a robust VPR solution for resource-constrained forestry robots.

A substantial percentage of global timber grows on challenging and steep terrain. This resource can be accessed with cable yarders or traction-assisted forwarders. When choosing which harvesting solution to employ for a particular logging job, its energy efficiency should also be considered, given the ever-rising energy cost. This theoretical study develops analytical models to determine and compare the fuel consumption of a cable yarder and a traction-assisted forwarder used for uphill extraction. Simulation results indicate that forwarding requires on average 69% more fuel per unit of transported payload across a range of work conditions (e.g. distance, slope gradient, payload size) and at least 47% more fuel under all simulated conditions. The efficiency advantage of cable yarding could be boosted further by transporting heavier loads. In cable yarding, a significant portion of fuel is consumed during standstill, when the engine runs idle or at low efficiency for extended periods of time. In forwarding, loading and unloading are particularly energy intensive. While cable yarders could greatly benefit from electrification, forwarders may see lower efficiency gains due to the challenges in electrifying linear hydraulic actuators in a cost-effective and robust manner.

In countries where private forest ownership prevails, wood mobilisation largely depends on the interest and commitment of private forest owners (PFOs) to manage their forests. In Slovenia, where 77% of forests are privately owned but insufficiently managed, this issue is particularly important. Governments not only in Slovenia, but also in other EU countries, have responded to this challenge of wood mobilisation by proposing various policy instruments, addressing the importance of PFO business cooperation both among themselves and with forest service providers. This study aims to find out: 1) whether there is a potential for business cooperation among PFOs; 2) which of the existing business organisational forms are appropriate for PFOs and 3) how property characteristics, forest management activity, forest management objectives and PFOs’ socio-demographic and economic characteristics influence PFOs readiness to engage into business cooperation. Based on the results, policy recommendations were developed to increase the share of PFO cooperating in business organisational forms in Slovenia. An online survey conducted in March and April 2022 among randomly selected Slovenian households owning forests provided data for two logistic regression models. The results show that PFOs are in general ready to engage in business cooperation; however, according to them, none of the currently existing forms of business cooperation is considered as very appropriate. The model »cooperation with other PFOs in business organisational forms« suggests that PFOs readiness to engage is influenced by forest management objectives related to carbon sequestration, wood and biomass production for personal use and for the market, as well as preserving forests as an investment for the future, PFO age and level of education. The model »cooperation with forest service providers« shows that PFOs readiness to engage is influenced by forest management objectives related to biodiversity conservation and wood and biomass production for personal use and for the market, as well as by PFO level of education. To motivate PFOs to engage into business cooperation, forest policy decision makers must take a holistic transformation of forest policy. To achieve the desired forest policy outcomes, the transformation should incorporate innovative and supportive policy instruments.

Forest road planning is a key component of sustainable forest management, as it ensures access to harvesting, transport, and protection activities while minimizing environmental impacts. Recent advances in digital terrain models (DTMs) and automated design tools have opened new possibilities for improving the efficiency of road alignment planning. This study evaluates the potential of an AI-driven corridor planning system (Path Explorer) integrated into RoadEng software compared with the traditional zero-line method in designing the forest road »Osmača–Compartment 56« in Bosnia and Herzegovina. Two DTMs with resolutions of 20×20 m and 90×90 m were used to generate alternative alignments, which were then refined in the Location module to produce preliminary projects and compared with the operational (field-designed) alignment. The results indicate that AI-driven preliminary designs achieved shorter alignments and lower estimated construction costs and earthwork volumes, suggesting potential cost savings under the tested conditions. The operational design, based on field measurements, remained the most accurate and suitable for final implementation in complex terrain. The study emphasizes that these conclusions are limited to the tested DTM resolutions and the specific case study area. Nevertheless, the integration of AI-driven corridor planning systems into early design phases can enhance the efficiency and objectivity of forest road planning, supporting more informed and sustainable engineering decisions.

Chainsaws are still a commonly used tool in the tending of young forests. The small volume of felled trees makes the use of powerful multi-operational machines economically unjustifiable. Moreover, the use of traditional petrol chainsaws carries a number of problems for the operator, such as noise, vibration, and exhaust fumes. Battery-powered tools can be an alternative to traditional petrol chainsaws. The purpose of this study was to determine the possibilities of using a battery-powered chainsaw during late thinning in terms of productivity and ergonomics. For the study, an ECHO ECCS-58V battery-powered chainsaw and a DOLMAR PS 5000 petrol chainsaw were used. Measurements were conducted in a 14-year-old pine stand. All measured noise level parameters were significantly higher for the petrol chainsaw. The average operating efficiency was 0.15 ha/h for the battery-powered chainsaw and 0.16 ha/h for the petrol chainsaw. The petrol chainsaw ran for an average of 42.0 minutes on a single tank of fuel, while the battery-powered chainsaw ran for an average of 41.0 minutes on a single battery. It was found that the battery-powered chainsaw achieved very similar productivity. With the availability of a sufficient number of batteries, it can successfully replace traditional petrol chainsaws during the tending of young forests. This will significantly reduce the negative impact of noise, vibrations, and exhaust fumes on the operator, while maintaining satisfactory productivity.