In recent years, digital aerial photogrammetry has emerged as an alternative method to airborne laser scanning in three-dimensional modelling of forest areas, especially for the generation of digital surface models (DSMs). In forest inventory, DSM is usually used in combination with the corresponding digital terrain model for the generation of canopy height model (CHM), which is then used as a basis for deriving various tree and forest attributes.

The main aim of this research was to examine the vertical accuracy of DSMs of different spatial resolutions over the forest area, and with new findings contribute to the application of digital photogrammetry in forest science and practice. For that purpose, DSMs with spatial resolution (pixel size) of 0.3 m (DSM0.3), 0.5 m (DSM0.5), 1 m (DSM1), 2 m (DSM2) and 5 m (DSM5) were generated by image matching of digital aerial images for the area of lowland pedunculate oak forests (management unit Kunjevci, Forest Administration Vinkovci). The vertical accuracy of DSMs was evaluated by comparing manually stereo measured elevations of 294 tree tops with the elevations of planimetrically corresponding DSMs points.

As expected, the highest accuracy was obtained for DSM0.3 (root mean square error, RMSE = 0.76 m; mean error, ME = –0.03 m). Almost equal accuracy was obtained for DSM0.5 (RMSE = 0.76 m; ME = –0.05 m) and DSM1 (RMSE = 0.76 m; ME = –0.07 m), slightly lower for DSM2 (RMSE = 0.84 m; ME = –0.16 m), whereas the lowest accuracy was obtained for DSM5 (RMSE = 1.31 m; ME = –0.54 m).

The accuracy comparison showed that the decreasing of spatial resolution (pixel size) of raster based DSMs from 0.3 m to 1 m, does not significantly affect their vertical accuracy. With further decreasing of spatial resolution to 2 m, and especially to 5 m, the vertical accuracy of DSMs also decreases. In the light of the obtained results, further studies should be focused on research of possibilities of application of DSMs of different spatial resolution in forest inventory, namely: DSM0.3 and DSM0.5 for obtaining information at tree level, DSM0.5 and DSM1 at plot level, and DSM1, DSM2 and DSM5 at stand level.

Keywords: digital surface model (DSM), digital photogrammetry, aerial images, image matching, forest inventory

The aim of this research was to evaluate the accuracy of photogrammetrically estimated mean tree height for the main tree species (sessile oak, common beech, common hornbeam) of the mixed privately-owned forests in Central Croatia. Within this research, digital aerial images of ground sampling distance of 30 cm and national digital terrain data for digital terrain model (DTM) creation were used. Stereo-photogrammetric measurement was conducted on photogrammetric plots overlaid upon the aerial images based on the spatial coordinates of the plot centres recorded by the GPS receiver during field survey. Photogrammetric heights of each tree on the plot were calculated as a difference of tree top determined on aerial images and corresponding tree bottom obtained from DTM. The accuracy of the photogrammetrically estimated mean tree height of each species was evaluated with reference field data. For that purpose, the photogrammetric and field mean stand heights of the main tree species were calculated for each subcompartment. Mean stand heights were calculated as averages of all measured trees within specific subcompartment.

Very similar errors of photogrammetrically estimated mean stand heights in relation to field estimates were obtained for all three observed species (sessile oak, common beech, common hornbeam). However, the most accurate estimates were obtained for common hornbeam (MD = –1,97%, RMSE% = 8,29%), whereas slightly lower accuracy was obtained for common beech (MD = 2.16 %, RMSE% = 10.16 %) and sessile oak (MD = 3.06 %, RMSE% = 10.27 %). The results of this research confirmed the great potential for the application of digital aerial images of high spatial resolution in forest inventory, especially for the mean tree height estimation.

Keywords: stereo photogrammetry, digital aerial images, tree height, mixed forest stands, forest inventory

Described biotechnical measures focus on the use of woodchips in the formation of a structural reinforcement layer on forest roads in the places with high levels of groundwater. These are often short sections of roads which can thus block off entire forests. In history, these sections were overcome using corduroy roads. Currently, there are tendencies to revive the biotechnical technology and replace logs used for corduroy roads with woodchips. This study investigates the possible reinforcement of a waterlogged section using woodchips in a forest road of multifunctional character, which serves for cycling as well as timber transport. In total, three different types of reinforcement were constructed using woodchips in combination with geotextile and crushed stone. The reinforcement was tested by common operations using a timber extraction tractor with tandem axle trailer. The modulus of deformation was measured on the surface and the deformation characteristics of the layer were determined. Subsequently, the shape of the reinforcement cross-section was surveyed. The results have shown that, even with very low modulus of deformation values, the shape of the reinforcement cross-section does not change statistically in two types of the reinforcement technology. These two types of reinforcement can be successfully used for forest roads that perform the recreational function or for timber transport by tractor. The main advantages are that renewable material is used and no extraction and moving of the ground occur during its production.

Keywords: Forest road, reinforcement, corduroy road, woodchips, waterlogging, trafficability

The aim of the research was to explore in detail the impact of selected features of the raw material (diameter of energy roundwood and wood species/water content) on the efficiency of individual work elements; especially crosscutting and splitting, which are, based on the results of previous research, expected to have a correlation with these raw material features.

In order to determine the efficiency of Posch Spaltfix S-360 firewood processor in mechanized production of chopped firewood, a method of continuous chronometry was applied. Time consumption was determined and analyzed providing work elements of effective time and delays. Multiple regression analysis was used to investigate the dependence of time consumption of individual work elements on the round fuelwood diameter and wood species/moisture content. A model for the calculation of firewood processor productivity was developed based on the significant influence parameters.

The study found that the diameter of the energy roundwood has a positive effect on productivity of the investigated processor Posch Spaltfix S-360 in accordance with the »piece-size law«. In addition to the positive impact on productivity, a statistically significant effect of energy roundwood diameter on the increase of time consumption for work element cross-cutting was determined.

The opportunity for a substantial increase in quality, and thus the price of fuel wood, lies in optimizing the natural drying of raw material in order to achieve 25% or less of water content. However, both the natural drying and sorting of input raw material for the purpose of uniforming the final product dimensions require uniform and constant supply of sufficient raw materials

The research results should be used to optimize the production system whose backbone is the investigated processor, but also to point out the general principle of the impact of selected features of raw material to the expected productivity of chopped firewood production by firewood processors.

Keywords: diameter, cross-cutting, splitting, European beech, European hornbeam, product quality

During the transport of stacked wood for processing (pulpwood), it is essential to know the total load mass because the sale of these products is based on mass. The main goal of the research is to determine the mass distribution of fir pulpwood load that can be transported with different types of truck units and to compare it with the permitted axle load limits and the total mass of the loaded truck unit. Forest truck units IVECO Trakker 500, manufactured in 2012, and MAN TGS 33.440, manufactured in 2014, were used in this research. Both truck units are equipped with the same hydraulic crane Epsilon Palfinger M110Z and trailers PSM 200.

During the research, axle loads were measured by a portable measuring system of four measuring weighing scales DINI ARGEO WWSC. Measurement accuracy of the measuring system is 1 kg. For research purposes, the portable weighing system was calibrated using certified standards for calibration of scales.

The axle loads of the empty truck unit IVECO were measured six times, and MAN truck unit eight times during the study. The mass of MAN truck unit is smaller on average by 570 kg. In both unloaded truck units, the highest axle load is on the second truck axle. Based on the comparison with legal limits, it has been determined that the payload of MAN and IVECO truck units is 21 341 kg and 20 771 kg, respectively.

A total of 24 measurements of axle loads on loaded truck units were conducted with different loads of fir pulpwood – 11 times on the truck unit IVECO and 13 times on the truck unit MAN.

The distribution of total axle loads in both truck units is about equal. 60% of the total load is on the truck, and 40% on the trailer. Slight deviations of 1–2% have been found between axle loads on the investigated trucks units. Masses of the loads are calculated from the difference between the axle loads of loaded truck units and the average value of the axle loads of unloaded truck units. The lowest values of the load mass are distributed to the front truck axle, and they account on average for 21% and 17% of the mass of load of IVECO and MAN truck unit, respectively.

Based on the collected data, differences were established between methods of stacking wood in the loading space of the truck. It was also determined that these differences did not affect the occurrence of overloading. The occurrence of overloading or exceeding the permissible total mass of truck units during transport on public roads is primarily affected by the total mass of the load. The results of the research point to the guidelines for the development of truck units and lead to certain conclusions regarding the application of truck units in the timber transport.

Keywords: forest truck unit, mass of the load, axle load, legal restrictions, fir pulpwood

Gabions are wire baskets filled with stone; however, the filling can also be made of other materials (brick, wood, decorative glass). The use of such systems began with the earliest civilizations, and nowadays they are still in use. Gabions come in three basic forms: gabion baskets, gabion mattresses and bag gabions. Gabion baskets are mainly used (Brooks and Nielsen 1992) as a sustaining or retaining wall, and rarely as stabilization. Gabion mattresses are a kind of wire mesh »pillows« filled with stone material used for lining the river beds, canals, streams and torrents. They are used for the control of watercourses and prevention of soil erosion. Bag gabions (gabion sacks) have lately been used in the works to strengthen river beds and dam bases. Today, gabions are used in many aspects of human activities, but their most important contribution is the protection function in the regulation of watercourses and road slopes. The stabilization and embankment fortification with gabions have confirmed their widespread use. An additional contribution is their decorative function for which they are used in landscaping. Because of its wide range of applications, gabions are recognized nowadays by most engineers worldwide as a standard construction material. Advantages and disadvantages of the use of gabions are the starting point for their use and encouragement for further research.

Keywords: gabions, slope protection, low-volume roads, landscaping, watercourse control

Austrian forests and forest management have undergone great change during the past 500 years. From the 16th century on, the unregulated extraction of wood in order to cover the needs for energy in iron industry and saltworks as well as the increasing demand for firewood in the growing cities led to deforestation in great parts of the country. Since 1961, when the first forest inventory data of Austrian forests has been collected, the total forest area in the country has increased by 300,000 ha. Today, with an area of nearly 4 million ha, 47.6% of Austria is covered with forests. With a share of 61.2%, spruce is the most common tree species in Austrian forests. The vulnerability of these trees to climate change and the resulting damages by storms and bark beetles is currently leading to a change in the forest structure. The Austrian state forests are focused on more resistant but still fast-growing tree species like larch or Douglas fir.

Keywords: Austrian forest management, spruce, Austrian forests, forestry overview

Use of biomass in the energy sector is a unique opportunity for forestry. In addition to ensuring the price and the market for the product that is considered the lowest quality from the technical aspect (long wood), it enables a considerably more effective exploitation and a more intensive caring for forests. Diverse works of caring for forests, such as pollarding and the first tending, as well as silvicultural activities in degraded stands could become cost–effective, since there is a local market and a continuous long–term demand for wood biomass. Moreover, the planting of fast– growing forest cultures and their establishment on uncovered forest land could increase the attractiveness of investment into forestry, since the rate of return and the period of return on investment is significantly shorter compared with classical forestry. The program package developed by Lega d.o.o. was used in the paper in order to perform optimization calculation for two types of cogeneration plants (CHP and ORC), and hence a comparative analysis of the results of optimization calculation was performed. Evaluation of cost–effectiveness of investment or capital budgeting was performed upon reaching a decision on involvement into long–term investment projects. The surface that met the annual requirements of the plant was calculated based on the annual yields of forest culture, annual requirements for wood chips, the length of the rotation period, calorific value of wood chips, as well as calorific value of willow grown in short rotation cultures.

Keywords: biomass, energy production, cost–effectiveness, cogeneration, capital budgeting

Na trideset i osmoj sjednici Radne skupine o statistici, ekonomici i gospodarenju šumama ECE/FAO-a, održanoj u Ženevi 23. i 24 ožujka 2016. godine, prihvaćen je prijedlog da Republika Hrvatska bude domaćin trećega sastanka Ekspertnoga tima za energiju drva UNECE/FAO-a. Organizacija je sastanka, uz potporu Ministarstva poljoprivrede Republike Hrvatske i Hrvatske komore inženjera šumarstva i drvne tehnologije, povjerena Šumarskomu fakultetu Sveučilišta u Zagrebu.

Ekonomska komisija za Europu Ujedinjenih naroda (UNECE) osnovana je 1947. godine kao jedna od pet regionalnih komisija Ujedinjenih naroda. Glavni cilj Ekonomske komisije za Europu, koja uključuje pedeset i šest zemalja članica u Europi, Sjevernoj Americi i Aziji, unaprjeđenje je paneuropske ekonomske integracije. Značajna je pažnja Ekonomske komisije za Europu tradicionalno posvećena i šumarstvu i drvnoj industriji, i to praćenjem stanja šuma u regiji, pružanjem pomoći u razvoju politika potrajnoga gospodarenja šumama i širenjem svijesti o šumskim proizvodima i općekorisnim funkcijama koje šumski ekosustavi pružaju društvu…

U organizaciji Društva za športsku rekreaciju Salinovec te pod ponovnim pokroviteljstvom Grada Ivanca i Šumarskoga fakulteta Sveučilišta u Zagrebu 4. i 5. lipnja u parku stare škole Salinovec održan je 2. hrvatski festival kiparenja motornom pilom. Festival je otvorio gradonačelnik grada Ivanca Milorad Batinić, dipl. ing. šumarstva.
Svoje umijeće kiparenja motornom pilom predstavilo je sedam natjecatelja iz Hrvatske te četiri iz Slovenije. Na festivalu su sudjelovali ovi kipari…

U Varšavi je od 4. do 7. rujna 2016. godine održano 49. međunarodno znanstveno savjetovanje udruženja FORMEC pod naslovom »From Theory to Practice: Challenges for Forest Engineering« u organizaciji varšavskoga Prirodoslovnoga sveučilišta (SGGW) pod vodstvom predsjednika Organizacijskoga odbora profesora Tadeusza Moskalika.
Glavni je cilj savjetovanja bio naglasiti sve izazove s kojima se susreću brojni sudionici u šumarstvu, a posebice vezano uz različite sječne sustave, otvaranje šuma, prijevoz drva, okolišnu pogodnost radova pridobivanja drva, uporabu šumske biomase za energiju te sigurnost pri radu. Kao i svake godine, ideja je savjetovanja FORMEC-a povezivanje znanstvenika, istraživača i praktičara iz cijeloga svijeta radi izmjene iskustava, znanja i vještina u području šumarskih tehnika i tehnologija…

U Planici je od 21. do 23. rujna 2016. godine održano 3. međunarodno znanstveno savjetovanje »Gozdarsko inženirstvo jugovzhodne Evrope – stanje in izzivi«. Organizator je savjetovanja bio Odsjek za šumarstvo i obnovljive šumske resurse Biotehničkoga fakulteta Sveučilišta u Ljubljani. Savjetovanje je održano u Olimpijskom sportskom centru Planica, a sudjelovalo je preko trideset sudionika iz zemalja regije. Među sudionicima bili su znanstvenici i istraživači šumarskih fakulteta iz Skoplja, Sarajeva, Banje Luke, Zagreba, Ljubljane i Beograda, zatim predstavnici sponzora Tajfun, Uniforest, Husquarna, Vilpo i Pahernikova ustanova. Predstavljeno je više od dvadeset znanstvenih, stručnih i preglednih radova…

U Zadru je od 21. do 24. rujna 2016. godine održan 6. međunarodni stručno-znanstveni skup »Zaštita na radu i zaštita zdravlja«. Cilj je skupa bio pružanje i razmjena najnovijih informacija i postignuća iz izrazito multidisciplinarnih područja, kao što je zaštita na radu, zaštita zdravlja i sigurnost u zemlji i inozemstvu. Okupljanje stručnjaka iz područja sigurnosti i zaštite na radu potaknulo je Veleučilište u Karlovcu još 2006. godine u okviru prvoga ovakvoga stručno-znanstvenoga skupa…