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The focus of this paper is on the description of the openness of primary forest traffic infrastructure in the Republic of Srpska. The data were collected using Garmin Oregon 600 GPS devices across the entire territory of state forests, managed by the Public Enterprise „Šume Republike Srpske”, and the recorded traces were compared and corrected by orthophoto snapshots with a 0.50 m resolution. The tools used for the processing of collected data were software ESRI ArcGIS 10.2 and Quantum GIS 16.2. In addition, the analysis covers all forest roads that pass through state forests that can be used for forest management and enable the movement of trucks. Public roads are only taken as an overview of openness of this category of roads and forest openness is shown by forest categories. The analyses included 843,466.00 ha out of the total of 1,002,056.00 ha of state-owned forests. The final aim of this analysis was to obtain a clear insight into the quantitative status of primary forest traffic infrastructure in the Republic of Srpska. The data were collected during 2016. Based on the analysis, the total density of the network of primary forest traffic infrastructure for the research area was 9.28 m/ha without public roads, i.e. 11.21 m/ha with public roads. In addition, density of the network of primary forest traffic infrastructure was determined separately for each category of forests, and the highest density of forest road network was found in forest plantations (11.57 m/ha or 14.82 m/ha with public roads) and high forests with natural regeneration (11.13 m/ha or 12.49 m/ha with public roads).
Key words: Forest roads, Forest opening, Density of primary forest traffic infrastructure, a register of primary forest roads, GIS, GPS, Republic of Srpska
Uvod i prethodna istraživanja
The construction of a forest road network is considered a key element for successful forest management (Krč & Beguš, 2013). A well planned, designed, constructed and maintained system of forest roads is essential to facilitate forest management and protection of natural resources (Nasiri & Lotfalian, 2012). Open forests are gradually equipping the planned road network and forest stocks (Tucek and Suchomel, 1998). Primary forest roads provide access to forests for the production of wood assortments,

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but also for the needs of forests, monitoring, research, recreation, fire protection and other purposes (Eastaugh & Molina, 2011, Stefanović et al. 2016, Laschi et al. 2016). Planning a network of truck roads is preceded by a detailed analysis of the current qualitative and quantitative state of roads, and above all determines the spatial distribution of truck roads (Pentek et al. 2005; Lotfalian et al. 2008; White et al. 2010; Krč & Beguš, 2013; Danilović & Stojnić, 2014). The analysis of current spatial distribution reveals the part of the forest which does not allow access to the use of existing roads (Pellegrini, 2012). An analysis of the existing primary forest traffic infrastructure consists of a series of operations and procedures. Its task is to determine the quality, quantity and possible deficiencies of the existing road network, while it is also the first stage in the planning and optimization of a forest road network (Pentek et al. 2005).
Primary forest traffic infrastructure in the Republic of Srpska consists of forest roads that go through the forest and can be used for forest management. According to the Law on Public Roads (Official Gazette of RS, No. 89/13), forest track roads belong to the category of unclassified roads, together with rural, agricultural and industrial paths and roads on embankments for flood protection, access roads and others. In recent years, various studies on the state of the network of forest roads and perspectives of their development were carried out in the Republic of Srpska (Ljubojević, 2010; Potočnik et al. 2013; Danilović & Ljubojević, 2013; Petković et al. 2015; Dražić, 2016; Marić, 2016). During their research, the authors obtained a variety of information about the openness of forests and forest land at disposal. However, the information were mainly obtained on the basis of assessment or incomplete and unreliable evidence. So, Potočnik et al. 2009 reported that the density of the network of truck roads in Bosnia and Herzegovina and the Republic of Srpska was 8.7 m/ha in 2009, while three years later (Potočnik et al. 2012) the reported density of the network of truck roads was as low as 6.0 m/ha. However, in the report on the analysis of the forestry sector in Bosnia and Herzegovina (FAO, 2015) the density of the network of forest truck roads in the Republic of Srpska is 9.05 m/ha.
In 2016, an inventory of primary forest traffic infrastructure in the area of Public Enterprise „Šume Republike Srpske” was produced in order to gain a clear insight into the quantitative status of the network of truck roads in the Republic of Srpska. The inventory of primary forest traffic infrastructure was implemented using handheld GPS devices, and the data were processed using GIS softwares. Although it is clear that handheld GPS devices are not designed for accurate measurements, especially in forest conditions (Abdi et al. 2012), it was concluded that they could be used for the mapping of forest roads, since forest roads are mostly open areas where trees are removed. The development of the existing forest road cadastre is a prerequisite for conducting analyses and obtaining quality forest opening programs. Since the network of forest roads is dynamic and subject to constant changes, it is very important to regularly update the database (Talebi et al. 2015).
Područje istraživanja
The research was conducted in the territory of the Republic of Srpska, one of the two entities in Bosnia and Herzegovina. According to the Cadastre of forests (PFE, 2015), the total area of forests and forest land owned by the Republic of Srpska is 1,002,055.00 ha, and the total area of forests and privately owned forest land is 300,329.00 ha.
Table 1. An overview of forest areas and forest land by forest categories
Tablica 1. Pregled površina šuma i šumskog zemljišta prema kategorijama šuma
User forests and forest land owned by the Republic of Srpska are managed by the Public Enterprise „Šume Republike Srpske”, within 26 forest management units (FMU) and karst areas managed by the Center for karst management with headquarters in Trebinje. Areas of the national parks “Kozara” (3,530.00 ha) and “Sutjeska” (17,214.00 ha) belong to forests and forest land owned by the Republic of Srpska, while industrial plantations cover an area of 7,383.00 ha. In this paper, we analyzed an area of 843,466.00 hectares managed by 26 forest management units (FMU) without the Brčko District. These areas are not included in the analysis because forests and forest land in this region have a different purpose, which could have an impact on the results.

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Materijali i metode
As outlined in the previous section, the research was carried out in the area of 26 forest economic units. Forest engineers made Tracklogs using GARMIN Oregon 600 handheld GPS devices. All tracklogs were recorded in the form of polyline composed of 10 m-long segments, while the starting and ending points of each tracklog, as well as intersection locations were recorded as points. The recording was carried out in one pass, and the speed of movement of the vehicle during the recording was in line with the road category. The software used for data processing was GIS, ESRI ArcGIS 10.2 and Quantum GIS 2.16 „Nødebo“. The recorded track

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logs of truck roads were further controlled using orthophoto images with a 0.50 m resolution.
Primary forest traffic infrastructure that was taken for analysis, represents all forest truck roads that allow movement of trucks with and without trailers, regardless of the pavement condition. The following table provides technical standards that must be met by forest roads in the Republic of Srpska. All public roads that pass through the forest or its boundary which can be used for forestry purposes were included in the research. From the aspect of categorizing public roads (The law on public roads of RS, 2013), such roads are all local and regional highways and most of the arterial highways, but not fast roads and highways.
Density of the network of forest roads was calculated using the formula:
RD           – density of the forest roads network m/ha,
L             – Calculation length of forest roads,
A            – area.
The length of forest roads was calculated according to the following criteria. Entire length was taken into account for roads that pass through forest land. Half the length of the road was taken into account for roads that go to the edge of forest land or up to 300 m from the edge of forest land provided that they can be used for transport. In addition, roads coming perpendicular to the forest land were considered in the length of up to 500 m (Šikić et al., 1989).
In addition to the analysis of density of the network of truck roads, the paper presents a ten-year construction rate of truck roads by forest regions. The dynamics of truck road construction was obtained from the systematization of data of the “Research Development and Project Center” from Banja Luka, which designs truck roads for the purpose of the Public Enterprise „Šume Republike Srpske” and controls derivative works.
Since there is no precise analysis of the optimal density of truck roads in the Republic of Srpska, similar relief surfaces from neighboring countries were used as parameter in this case. The analysis of forest roads according to the relief characteristics of Croatia, which are similar to the characteristics in Bosnia, revealed that minimum openness required for the management of forests in RS starts from 15 m/ha, while the optimal value is about 20 m/ha (Šikić et al., 1989). The analysis of forest openness also included these parameters.
Rezultati istraživanJa
According to the categorization of roads, the roads that open forest regions in the Republic of Srpska are classified into public and forest roads. The total length of roads in the Republic of Srpska for the analyzed area amounts to 9,453.73 kilometers. The length of public roads is 1,628.16 kilometers or 17.22%, and of forest roads 7,825.57 km or 82.78%. Based on these data and the methodology applied to calculate the density of the network of truck roads, the result is that the average density of the primary forest traffic infrastructure in the Republic of Srpska is 9.28 m/ha and 11.21 m/ha of public roads.
An exceptionally low openness is evident in the “majevičko” forest management unit, whose openness amounts to 1.19

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m/ha. In this area, a large percentage of the forest is protected due to drinking water, so there is no intensive forest road construction and forest exploitation in this area. The municipality of Bijeljina finances the protected parts of the forest. The openness of public roads in terms of transport assortments is 8.61 m/ha.
According to the data of the “Research Development and Project Center” from Banja Luka for the period from 2006

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to 2016, 47.20 kilometers of forest truck roads are built on average in the Republic of Srpska each year. The total length of newly designed and constructed forest truck roads for this period reached 519.21 km. The average cost of construction of forest truck roads in the period from 2006 to 2016 amounted to 61,694.00 BAM/km (31,541.00 €/km).
Figure 9 shows the percentage share of road construction for each of the forest management areas for the period

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shown. Forest management units “ribničko” and “rogatičko” achieve the best financial results, so they are able to invest more financial resources than others.
Figure 10 shows the amount or length of constructed roads for each forest area in relation to the total road construction in the exploration area for the shown period.
The combination of GPS and GIS technology represents a global trend with an inexhaustible range of applications when it comes to collecting and analyzing spatial information (Drosos et al. 2014) and a fast, efficient and cost-effective method of forest roads inventory (Gumus & Acar, 2003). Due to possible defects occurring during the recording of forest roads, the precision of the GPS device and the signal quality, further analysis of the recorded data is necessary. Çalişkan & Karahalil (2017) applied GPS tracking and formed a database on every road, while Lepoglavec et al. (2015) made a correction of recorded data using orthophotos, in addition to recording a forest path track with a GPS device in one pass. Pentek et al. (2003) recommend recording the so-called “Feedback Methods, i.e., two-way shooting paths to minimize errors.
As already mentioned in this paper, a network of roads was created in the forests owned by Public Enterprise „Šume Republike Srpske” in 2016. Based on the analysis of the quantitative conditions in the network of truck roads in the Republic of Srpska, the density of primary forest traffic infrastructure is 9.28 m/ha and for public roads 11.21 m/ha. According to the above density of the network of truck roads, Republic of Srpska lags behind developed countries of Western Europe, in which the density of forest road networks reaches over 45 m/ha (Sokolović & Bajrić, 2009), but not so much behind the countries of the region. By comparison, the total length of roads used for forestry in Macedonia is 13,263.00 km, of which 3,326.00 km are public roads and 9,937.00 km are truck roads, which makes the density of truck road network of 13.43 m/ha (Trajanov et al. 2015). Based on data from 2009, the density of the network of primary forest traffic infrastructure in the Federation of BiH* (without the Herzegovina-Neretva Canton) was 10.9 m/ha (Sokolović & Bajrić, 2009). Pentek et al. (2014) reported that the density of forest roads in Croatian lowland regions was 9.05 m/ha, in hilly areas 11.26 m/ha, and 15.43 m/ha in the mountains, while in the karst area reached about 4.81 m/ha. Analyzing the network of forest and public roads that were used for forestry in Slovenia, Krč & Beguš (2013) point to the density of the road network of 24.8 m/ha. If we take only

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Radi potrebe unaprjeđenja mreže cesta u Republici Srpskoj, u ovome radu su prikazani određeni rezultati. Dinamiku izgradnje cesta i otvaranja šuma prate velike oscilacije, a posebice stagnacija početkom devedesetih godina. Izgradnja cesta u Republici Srpskoj nastavljena je vrlo slabo do 2006 godine, kada se krenulo intenzivno s projektiranjem i izgradnjom šumskih kamionskih cesta do danas. U ovome razdoblju na prostoru Republike Srpske izgrađeno je 519 km cesta, ili prosječno 47.20 km godišnje. S obzirom da ne postoji jasna analiza optimalne gustoće kamionskih cesta u Republici Srpskoj, u ovom slučaju su kao parameter poslužila slična reljefna područja iz okruženja. Pritom minimalna otvorenost koja je potrebna za gospodarenje šumama u RS uzeta je vrijednost od 15 m/ha, dok je optimalna oko 20 m/ha. Na osnovi ovih parametara učinjena je i analiza otvorenosti šuma. Otvorenost šuma šumskim kamionskim cestama iznosi 9.28 m/ha. Mnogi autori prikazali su otvorenost šuma, uključujući i javne ceste. Glede toga, i u ovome radu prikazana je otvorenost od 11.21 m/ha. Otvorenost javnim cestama možemo promatrati u smislu značenja ne samo za transport šumskih drvnih sortimenata, nego i za zaštitu šuma od požara i monitoring šuma, kao i za prijevoz radnika i opreme do šuma za potrebe izvođenja radova na pošumljavanju, uzgoju i korišćenju šuma. Gustoća šumskih kamionskih cesta za radoblje od 2006. do2016. godine je uvećana za 0.62 m/ha. Ovom dinamikom izgradnje cesta minimalna otvorenost bi se dostigla za 100 godina. Otvorenost šuma kreće se od 1.19 m/ha, pa sve do 14.75 m/ha. Svega jedno šumsko-gospodarsko područje (istočnodrvarsko) može se svrstati u minimalno otvoreno, što predstavlja 1.48% od ukupne površine državnih šuma Republike Srpske. Šumskogospodarsko područje “majevičko” ima najnižu otvorenost. Na ovome prostoru velika površina šuma je zaštićena kao vodozahvat pitke vode u općini Bijeljina, i na ovome prostoru nije dozvoljena intenzivnija eksploatacija šuma, pa samim tim i izgradnja šumskih kamionskih cesta. S obirom da je ovo područje malo površinom, ono nema veliki utjecaj na ukupnu otvorenost šuma i šumskog zemljišta. Iz rezultata ovoga istraživanja. dolazi se do zaključka, kao i u entitetu Federacija Bosne i Hercegovine, da su najvažnija pretpostavka i uvjet za unaprjeđenje šumske prometne infrastrukture i u Republici Srpskoj financijska sredstva. Nedostatak financijskih sredstava su osnovni uzrok zbog čega je realizirana novogradnja cesta značajno ispod preporučenog minimuma. Potrebno je značajno intenzivirati izgradnju šumskih kamionskih cesta, posebice obratiti pozornost na šumsko-gospodarska područja u kojima se skoro nikako nije gradilo. S obzirom da su parametri za utvrđivanje otvorenosti šuma uzeti iz okruženja, potrebno je provesti detaljniju analizu konkretnih utjecajnih čimbenika za ovaj prostor kako bi se odredio minimum i optimum.. Neophodno je u planskim dokumentima razraditi otvorenost šuma ili određenim studijama analizirati sve čimbenike koji utječu na otvorenost šuma, kako bi se postigli optimumi gustoće mreže šumskih kamionskih cesta za različite reljefne uvjete. Razvoj katastra postojeće šumske ceste je preduvjet za provođenje analize i dobivanje kvalitetnih programa otvaranja šuma. U radu je prikazana otvorenost šuma i šumskog zemljišta primarnom mrežom cesta u Republici Srpskoj. Podaci su prikupljeni GARMIN Oregon 600 GPS uređajima, na cijelom području, čiji je korisnik JPŠ “Šume Republike Srpske”, a snimljeni tragovi uspoređivani su i korigirani ortofoto snimkama rezolucije 0.50m. Za obradu podataka korišteni su GIS softveri, ArcGIS 10.2 i QGIS 2.16. GPS tragovi su razvrstani na javne i šumske ceste. Otvorenost šuma i šumskog zemljišta je prikazana po kategorijama šuma.
Ključne riječi: šumske ceste, primarno otvaranje šuma, gustoća primarne šumske prometne infrastrukture, registar primarnih šumskih prometnica, GPS, GIS, Republika Srpska

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forest roads into account, the network density is 10.6 m/ha, while in Austria it is as high as 45 m/ha (Ghaffarian & Stampfer, 2007). When we talk about the network of truck roads in Serbia, there are still no precise data on their quantitative and qualitative status (Danilović & Stojnić, 2014). The road network density in Bulgaria is 7.90 m/ha (Stoilov et al. 2014), and in Romania 13.73 m/ha (Bereziuc et al. 2014). In Czech Republic it amounts to 18.0 m/ha (Žáček & Klč, 2008), 10.1 m/ha in Ukraine (without public roads 7.8 m/ha) (Styranivsky et al. 2011), and in Slovakia it reaches 20.1 m/ha (Ambrušová et al. 2013).
Despite significant investment in the construction of primary forest traffic infrastructure in recent years, the density of the network in the Republic of Srpska is still not at a satisfactory level. In the past 11 years in the area of forests owned by the Republic of Srpska almost 519 km of truck roads and about 47.20 km per year were built. However, in addition to an underdeveloped network of truck roads, a major drawback is also the relatively low quality of the network of truck roads, and uneven density of the road network by forest regions. The dynamics of the construction of truck roads for a ten-year management period is envisaged in planning documents for all forest management areas, but looking at the results, it can be concluded that not everyone adhered to the dynamics of road construction, while in the forest region Doboj - Derventa, Trnovo, Lopare and Milići areas, forest truck roads have not been built at all.
Figure 11 shows the average openness of forest management units. It can be observed that higher openness can be found in forest management areas with high quality forests and those belonging to the hilly - mountainous belt. The top open areas are: 20 – petrovačko; 4 – dobojsko-derventsko; 25 – milićko and 24 - istočnodrvarsko. These are mostly hilly and mountain regions dominated by high forests with natural regeneration. The least opened areas are: 15 - posavsko, 14 - nevesinjsko - gatačko, 9 - kalinovičko and 12 – majevičko. The areas with a large share of high forests have higher openness, because the costs of forest road construction can be compensated by wood assortment production. Areas without a significant share of high forests have extremely low openness.
Based on data from the field and the processing of data collected from over 843,000.00 hectares in 26 forest management units which belong to different relief areas and over 9,450.00 kilometers of forest roads and public roads recorded, the density of forest road network of 9.28 m/ha was found in forests managed by the Public Enterprise „Šume Republike Srpske”, while in public roads it amounted to 11.21 m/ha. The newly built roads increased the density of primary forest traffic infrastructure by 0.62 m/ha. With this dynamics of construction, minimum openness would be achieved in 60 years including public roads, while minimum openness for primary forest truck roads would be achieved in 100 years. Only one forest area can be considered minimally open, representing about 1.48% of the total area of state forests in the Republic of Srpska. It is important to intensify the construction of primary forest road trucks, and especially focus on forest areas with almost no construction. The lack of financial resources and poor quality of forests in some forest management units result in inadequate openness. It is also necessary to carry out a more detailed analysis of specific impact factors for this area in order to determine the optimum. It is necessary that planning documents or specific studies elaborate on all the factors affecting forest openness, in order to achieve the optimum density of the forest road network for different relief conditions.
The data on the density of forest road network in the Republic of Srpska represent an exceptional value, obtained from the recording of the current state of the forest road network and systematization of the data collected, which represents the first study of this type in such a wide area. A completed inventory of forest roads represents the basis for developing strategies and plans for further development of the forest road network in the Republic of Srpska.
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