This study compared oak butt-log volume estimations gained through terrestrial measurements in the forest stand with a remote approach using an unmanned aerial system (UAS) and photogrammetric ...post-processing. Terrestrial measurements were conducted in the lowland part of Croatia after a completed motor–manual final felling of a 140-year-old even-aged oak stand. Butt-logs’ volumes were estimated with four methods: the sectioning method and Huber’s, Smailan’s and Riecke–Newton’s methods. Measuring diameters and lengths and estimating volumes remotely were based on orthophotos using four different software: ArcGIS, QGIS, AutoCAD and Pix4D. Riecke–Newton’s method for volume estimation had the smallest relative bias of +1.74%, while for Huber’s method it was −8.07% and with Smailan’s method it was +21.23%. Log volume estimations gained remotely via ArcGIS and QGIS were, in the case of Huber’s method, at +3.63% relative bias, and in the case of Riecke–Newton’s method at +1.39% relative bias. Volume estimation using the sectioning method resulted in a total of 51.334 m3 for the whole sample, while the sectioning method performed with the help of AutoCAD resulted in 55.151 m3, i.e., +7.43% relative bias. Volume estimation of thirty oak butt-logs given by Pix4D software (version 4.8.4) resulted in +9.34% relative bias (56.134 m3). Comparing terrestrial measurements and the volume estimations based on them to those gained remotely showed a very high correlation in all cases. This study showed that using a UAS for log volume estimation surveys has the potential for broader use, especially after final felling in even-aged forests where the remaining trees in the stand would not block photogrammetric analysis.
Rutting measurements are a significant part of scientific research on the impact of forest vehicles on the forest soils and damage to the forest transport infrastructure. Although photogrammetric ...methods of measurement or measurements based on LiDAR (light detection and ranging) data are increasingly being used for rutting measurements, the previous research conducted using these methods indicated the challenge of recording water-filled ruts. For this reason, it is necessary to define a reliable method of rutting field measurement in lowland forest stands characterized by a high level of groundwater that fills the ruts shortly after the passage of forest vehicles. This research analyzed the measurement accuracy using a total station and a GNSS RTK device with a CROPOS correction base in relation to the measuring rod that represented the reference method. Based on recorded and processed data, ruts are displayed in two ways: as net and as gross value of rut depth. The analysis of net rutting revealed a statistically significant difference between the calculated rut depths based on measurements with a GNSS RTK device and other methods. On average, the net rutting measured by the GNSS RTK device was 2.86 cm smaller than that of the reference method. When calculating the gross rutting, which consisted of the net rut depth and the bulge height, no statistically significant difference was found between the measurement methods used. Based on this result, the bulge height was also analyzed, and showed a statistically significant difference between the data recorded by the GNSS RTK device and other methods. It can be concluded that measuring the depth of ruts with a total station gives accurate data and represents the optimal modern field measurement method for the same or similar terrain conditions. In contrast, the GNSS RTK device, which constantly gives higher elevation points, can be used to measure gross rutting.
Bark beetle outbreak sites were analysed before sanitary logging in Gorski Kotar County during spring, summer and autumn 2021. Downed European silver fir trees were inspected for red-listed ...saproxylic entomofauna. Among other species, the fir pinhole borer (Treptoplatypus oxyurus, Dufour, 1843) (Coleoptera: Platypodidae) was observed and studied on-site and in the laboratory. Symptoms of T. oxyurus presence were recognised as white filamentous bites of sawdust on the bark of the fir trees and the surrounding soil. Every tree infested infested with T. oxyurus was measured (diameter at breast height, height/length), and its position was recorded. Segments were collected for laboratory analysis to evaluate the layout and position of T. oxyurus gallery system. The results showed that individual corridors of T. oxyurus, as a rule, never intersect, cross or connect. Each family of beetles (male, female and their offspring) lives separately in its corridor system. There were examples of corridors that were very close to each other but did not touch. T. oxyurus is still completely unknown to forest operatives in Croatia, who do not recognise symptoms of its occurrence.
During the seven-year research period, the average annual removal was by 3274 m3 higher than the average annual removal prescribed by the existing management plan (MP). The main reason lies in the ...high amount of salvage felling volume at 55,238 m3 (38.3%) in both the main and the intermediate felling due to oak dieback. The analysis of forest accessibility took into account the spatial distribution of cutblocks (with ongoing felling operations) and the volume of felled timber for two proposed factors: (1) the position of the cutblock and (2) the position of the removal. Cutblock position factor took into account the spatial position of the felling areas/sites, while removal position factor besides the spatial reference took into account the amount of felled timber (i.e., volume) both concerning forest infrastructure network and forest operations. The analysed relative forest openness by using geo-processing workflows in GIS environment showed four types of opening areas in the studied management unit (MU): single-opened, multiple-opened, unopened and opened areas outside of the management unit. Negative effects of the piece-volume law and low harvesting densities on forest operations are highlighted in this research due to high amount of salvage felling particularly in the intermediate felling by replacing timber volume that should have come from thinnings.
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.
The accuracy of the positioning of the data collected by remote sensing platforms is of great importance in forest and wildlife surveys, salvage logging, soil disturbances after felling operations, ...fire risk management and many other forestry-based research. The significance of bark beetles in silver fir and Norway spruce stands is an essential factor that can affect the increase in biomass quantity and the reduction of its quality. Due to an Ips typographus (L.) outbreaks in the central part of Croatia from 2016 to 2021, salvage logging was performed in an area of 11,940 ha, with terrain slopes varying from 0 to 172.83%. Two plots of similar sizes (<5 ha) and different terrain conditions (flat vs. sloped terrain) were chosen and were measured in June 2022. Measurements included a total station, a real-time kinematic (RTK) GNSS (Global Navigation Satellite System) terrestrial receiver and an unmanned aerial system (UAS) in order to determine the accuracy of a digital terrain model (DEM) generated by a photogrammetric UAS. In total, 175 checkpoints were marked in the field. Four different GCP (Ground Control Point) classes (5, 10, 15 and 20) were used to compare validation points acquired from the original point clouds, imagery and orthophotos to the reference positions. This study showed that, in terms of a forest area recognition after conducted salvage logging, the use of 10 GCPs for terrain evaluation is necessary even in small areas below 5 ha and regardless of terrain slope.
Forest roads, as a prerequisite for high-quality forest management, should be optimally distributed in order to avoid negative environmental impacts and to best fulfill their task. In the design ...phase of forest roads, it is necessary to know which factors influence most the volume of earthworks to enable the designer to best adapt to the terrain requirements. In this paper the impact of an average cross terrain slope and carriageway value of a forest road on cut and fill volume is analyzed. The research was carried out in the area of the management unit Trovrh–Kik, characterized by irregular terrain with slopes ranging between 27 and 58%, and on some micro locations even up to 84%. On eight forest roads, based on standard cross-section profiles, the influence of the average cross terrain slope and carriageway value (difference between ground level and grade level) of the forest road on the cut and fill volume per 1 m of the forest road route was analyzed. The obtained coefficients of determination indicate a strong correlation between the cut volume and carriageway value (R2 = 0.6841), and a moderate correlation between the fill volume and carriageway value (R2 = 0.5619). Unlike the influence of carriageway value on the cut and fill volume, the correlation between the cross terrain slope and fill volume is weak (R2 = 0.2076) or moderate in the case of the cut volume (R2 = 0.3167). On the basis of the analyzed standard cross-section profiles, it was determined that the carriageway value was 0.051 m, where the difference between the cut and fill volume was minimum and the average actual carriageway value was determined to be −0.09 m. It can be concluded that, on terrains with large and varying slopes, there is no unique model or terrain factor that could describe the earthworks required in the construction of a forest road. However, it is beyond doubt that the increase in the carriageway value and cross terrain slope caused the increase in the aforementioned volumes.
The use of forestry vehicles in mechanised harvesting systems is still the most effective way of timber procurement, and forestry vehicles need to have high mobility to face various terrain ...conditions. This research gives boundaries of planning timber extraction on sloped terrain with a cable skidder, considering terrain parameters (slope, direction of skidding, cone index), vehicle technical characteristics and load size (5 different loads) relying on sustainability and eco-efficiency. Skidder mobility model was based on connecting two systems: vehicle-terrain (load distribution) and wheel-soil (skidder traction performance) with two mobility parameters: (1) maximal slope during uphill timber extraction by a cable skidder based on its traction performance (gradeability), and (2) maximal slope during downhill timber extraction by a cable skidder when thrust force is equal to zero. Results showed mobility ranges of an empty skidder for slopes between −50% and +80%, skidder with 1 tonne load between −26% and +63%, skidder with 2 tonne load between −30% and +51%, skidder with 3 tonne load between −34% and +39%, skidder with 4 tonne load between −35% and +30% and skidder with 5 tonne load between −41% and +11%.These results serve to improve our understanding of safer, more efficient timber extraction methods on sloped terrain.
Today, LCA is one of the leading and most used tools for environmental management, but the application of LCA in forestry is still in an initial phase. Due to a high amount of different wood products ...which can be produced in forestry sector, production of raw material itself is not included enough in the whole LCA process. Raw wood products and biomass used to be widely declared as >>carbon neutral<< and renewable, but production steps have a significant influence on the environmental impact depending on machinery used, opening forest with new roads, management type (clear-cut, even-aged management or selective cut), etc. This paper gives a review of LCA studies in forestry based on three segments: * harvesting operations * biomass for energy * road construction and maintenance. Keywords: life cycle assessment, energy consumption, GHG emission, carbon neutral, wood products.
Background and Purpose: Terrain trafficability and vehicle mobility during timber extraction are highly influenced by terrain characteristics, as well as by soil bearing capacity. Insufficient ...planning, too heavy vehicles, excessive traffic, poor soil knowledge, together with bad weather conditions, cause severe disturbance to forest soil. Damage to the forest ecosystem arises due to felling and timber extraction operations, regardless of the technical means used in this process. Traffic intensity plays an essential role in soil compaction because deformations can increase with the number of passes, which may lead to excessive soil disturbance.
Materials and Methods: The research was conducted in Zalesina, a hilly and pre-mountainous part of Gorski kotar, Croatia, in two management units (MUs) comprising of 569.64 ha of selective beech and fir forests. Physical and mechanical properties of forest soil, essential for vehicle mobility and terrain trafficability during timber extraction are based on measuring the following soil parameters: 1) soil penetration resistance, 2) soil shear strength, and 3) current soil moisture. Measurements were made during one calendar year, on five sampling plots (three in MU "Belevine" and two in MU "Kupjački vrh") chosen on the prevailing soil types in both MUs.
Results: The highest values of cone index and shear strength were recorded in July which was the warmest and driest month with only 7 rainy days. Current soil moisture was the lowest in July at φ=15.26% vol, while the lowest values of cone index were from October to January with precipitation at its climax from September to January with cumulative 1232 mm of rain and 846 cm of snow. Lower values of penetration resistance were in MU "Kupjački vrh" at 0.96 MPa, which is related to overall terrain structure of high karst and surface roughness, making the sampling of plots difficult. By comparing cone index values (CI15) and the mean values between 5 and 25 cm of depth (CI5-25), the variation coefficient indicates a lower variability of CI5-25 values on four out of five sampling plots. However, t-test showed no statistically significant difference between these soil parameters.
Conclusions: Data regarding soil bearing capacity in a map form as an additional layer to other maps of stand characteristics would ensure better opportunities for planners or operators to reduce and avoid rutting and soil compaction. Measured data on penetration resistance, soil shear strength and current soil moisture have not only given in a simple and a fast manner the in situ stand conditions, but they have also shown their dependence on climatic conditions.
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