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Stanislav Sever1 and Slavko Šunji2

1 IUFRO Deputy Coordinator, Faculty of Forestry Zagreb, Sveto Limunska 25, HR-10000 Zagreb, Croatia.

2 Forestry Adviser, "Hrvatske Lume" p.o. Zagreb, Vukotinovileva 2, HR-10000 Zagreb, Croatia.


The paper deals with problems of Croatian forest opening and of the attempts to increase the road density during the period 1991-1995. About 80 percent of Croatian forests and forest land are state forests. The public enterprise Hrvatske šume manages this national resource with its 16 Forest Administrations. Over the last five years total road density has increased from 6.6 m/ha to 7.0 m/ha (5.7%), and in some administrations from 2.2 to 22.2 percent. With six Construction Work Units Hrvatske šume has built about 48 percent of all new forest roads; 52 percent was built by contractors. Of 280 machines and devices available before the war, 178 construction units were left in 1995. The average age is between 6.7 years (backhoes) and 16.3 years (rollers). Investment in forest road construction in the last five years has been between 62 percent (1991) and 24 percent (1995) of the total invested funds.


The transition from a planned economy to a market economy is an extraordinary and complex process, not only from a political, but also from an economic, technological and biological point of view. Nowadays, unfortunately, the aim of forest opening is only to make a profit in a short time.

In this process Croatian forestry was additionally burdened by the war situation together with the disintegration of the former traditional central planning system, and generally even worse, with the former controlled way of thinking.

In general terms the transition affected all parts of forestry life, especially strategies for forest opening operations.

Seventy-nine percent of all Croatian forests are controlled by a public enterprise and only 20 percent are private. Starting a new life in 1990, Croatian forestry has inherited many problems of the past. Croatia is well forested with over 1.50 ha forest per caput. About 24 581 km2 (around 44%) of the territory is forest land. About 30 percent of the total area is covered with forest, of which more than 90 percent is natural forests. Forestry participates with 1.2 percent to the country's GDP, the wood industry with 2.5 percent, which make together 3.7 percent. Less than 5 percent of the total labour force is employed in this sector. Exports of forest products represent 10 percent of total exports (Sabadi 1994).

The task of forest opening and the reduction of logging transport costs are important and serious problems, as well as some ownership problems which it is hoped will be solved more easily than in other countries in transition. After Croatia declared independence in 1990, Hrvatske šume ("Croatian Forests") was established as a public enterprise with the responsibility to manage state forests (around 80% of total forests, about 1.95 million ha of forests and forest land; about 10000 employees; harvesting about 4.8 million m3 of allowable cut) (Sever 1995).

1. Forest opening and ownership

Forest opening in Croatia varies approximately from 20 m/ha in the mountainous areas (Gorski Kotar), to a few metres per hectare in other parts of the country. On average it amounted to 6.6 m/ha in 1991. In 1995 the state owned approximately 4/5, and private persons 1/5 of the forest land, and there were no financial resources to increase the road density. Woodlots are atomized into holdings of 0.5-1.5 ha (Anon. 1994a). However, subsequent privatization brought about new problems that may be solved partly by restitution and partly by compensation. This will probably be possible, because before the nationalization after the second world war, 24.3 percent of the forests were private.

Only a small proportion of forest roads building and maintenance is the responsibility of the public enterprise. It is mainly in the hands of contractors (52%).

In the pre-war time forestry building engineering employed about 280 machines and devices (Anon. 1994b).

Forest road construction in Croatia in the last five years

1. Forest opening status in Croatia

In the forests of the public enterprise Hrvatske šume (approximately 80% of total forests and forest land) there are 13 606.8 km of forest roads which, which is more than 50 percent of all Croatian public roads. Nevertheless forest opening is insufficient for rational forest management. Furthermore, in comparison with other developed European countries, road density is not satisfactory. On a total area of 1 945 998 ha of productive forests, the average forest opening by Hrvatske šume was 9.4 m/h, while for total forests and forest land it is 7 m/ha.

In the five-year period 1991-1995 the road density in the forests owned by Croatian Forests increased by 5.7 percent (Figures 1 and 2, Anon. 1994c, Anon. 1995a, Anon. 1995b. Anon. 1996).

Figure 2 shows the range of density of 15 forest administrations of 18 m/ha to 0.9 m/ha. The former refers to mountain terrain, the latter to the Mediterranean forests that are not production forests. Their purpose is recreational, environmental, and hunting. The data refer to all parts of Croatia -mountains, hills, lowland, and karst. On the other hand, one-third of the forest land has been inactive, and this is the reason of the low percentage of road building in some administrations. Some parts of land were occupied or near the front line (Sever 1995).

All data in Figures 1 and 2 refer to primary forest opening (forest or some public roads of all categories). Strip roads form the network of secondary forest opening. They are not treated in this paper.

Figure 1. Forest opening and administrations (district) of Hrvatske šume (Croatian Forests)

2. Forest opening strategy

The programme of Croatian forests development until 2025 plans intensive building of forest roads with an average density 0.3 m/ha or about 590 km per year. As result, within 20 years the road density in mountain and hilly areas will be about 20 m/ha and the skidding length (path) 300 m. In the lowlands the respective figures will be 15 m/ha and 267 m. The programme envisages the building of 150 km/a of forest firebreaks (Anon. 1993).

Figure 2. Forest road density in 1995. The percentage of increased density in the last five years

3. Technology and organization of forest road construction

The public enterprise Hrvatske šume has organized road building through six working units of forestry civil engineering. In 1995 about 48 percent of the roads were built with their machines and 52 percent by contractors.

The forest road building technology varies depending on geographical position, terrain topography and geologic structure of the soil. The most interesting terrain types are a) lowland, b) hill, c) mountain, and d) karst.

The basic characteristics of all technologies are high levels of mechanization, mainly consisting of heavy machines requiring minimum manual work.

Environmental implications of forest road construction, soil disturbance levels, effect on landscape, use of heavy equipment - all these are critical environmental issues with regard to the protection of the soil, water quality, and landscape.

Forest roads design takes into consideration slope (uphill/downhill) up to 8 percent, exceptionally 10 percent, width of road sub-base 4.5-6.0 m, minimum radius 15 m, longitudinal and lateral drainage, turning places, pass-by places and landings.

All forest roads are designed with an undersize roadway structure because of specific and changeable loads. During or after harvesting operations some damage is repaired with pebbles.

The fundamentals of forest opening theories in road design in Croatian conditions can be found in many papers (Kne evi 1991, Kne evi et al. 1991, Sever and Kne evi 1992) and in the form of computer design software.

Forest road construction is a specialization in forestry post-graduate studies.

4. Characteristics of forest opening in Croatian lowland

The lowland region of Croatia lies between the rivers Drava, Sava and Danube. It has a basic network of forest roads. Bulldozer is used for stump and humus clearings, and backhoes for water ditches. Graders and road-rollers are used to make the base layer (subgrade) and the surface layer. Some problems occur in the construction of forest roads in this region. Some examples are the high level of underground water, different soil structures - from pea to medium and high plastic clay, and the long distance (more than 100 km) of stone material transport. This is the reason why almost all roads are made with chemical or mechanical stabilization of the roadbed and the travelled way.

In the lowlands an increasing number of logging roads are built on geotextile and polymeric net. After levelling the terrain at an average width of 6 m, a roll textile or a 4 m net is placed. There is no need for additional tree felling. On the prepared base 35 cm thick stone material is laid.

5. Characteristics of foothilly and hilly terrain opening

Forest roads in foothilly and hilly regions are built mostly about 2/3 cut in the original ground and 1/3 in a dam. Heavy bulldozers are needed for route penetration for stump and humus clearing. Ditch excavations as ditch and fill slope are done with backhoes, and final levelling and rolling of the travelled way is done with graders and rollers. Transversal water is drained through concrete culverts.

There is often a need for rocks mining (A and B terrain category). Small drilling machines are used to make mine holes. Stone material comes from a medium distance although sometimes there are local materials near the roads.

6. Mountain terrain and forest roads construction

Subgrade construction on mountainous terrain is considerably expensive because compact rocks are predominant and a large volume of hole drilling with much explosive is needed to finish the subgrade. Roads are normally built one-way with extensions on curves and passing places.

On permeable soil (limestone) there is no longitudinal drainage On impermeable soil there is no need for it.

Local materials from route cutting and mining are mainly used on the travelled way. The best solutions are little self-walking stone breaking machines.

There are many reasons to change technology from mining to backhoes with hydraulic hammers.

7. Karst terrain

Forest road construction on karst is similar to the technology used on mountain terrain. Machines, bulldozers and backhoes also have the same technical features. Environmentally friendly equipment and its behaviour must be carefully chosen. These roads are of a temporary character.

8. Investment in road construction

The level of investment in road construction, as well as in equipment in the 1991-1995 period, was influenced by the war since the occupied forest land was a real economic power. There is an increasing portion of contractors employed inroad construction jobs. In 1995, 48 percent of forest roads, strip roads and firebreaks was built by the public construction work units while 52 percent was built by contractors.

Figure 3 shows all investments of Hrvatske šume and Figure 4 illustrates the investment structure classified in three groups: forest roads, multi-storey construction, and machines and equipment.

As can be seen, there was an evident increase between 1991 and 1993 (fourfold), which dropped to one-half in 1995. The investments in forest roads at the beginning of the period were 62 percent and decreased in 1995 by about 25 percent.

Figure 3. Total investment vs. total income (1991 -1995)

Fewer investments in machines and equipment have resulted in their amortization. Figure 5 shows the number of the main construction machines in the period 1991-1995, and Table 1 gives their average age.

Figure 4. Structure of investment (1991-1995) with a portion of forest roads investment

Table 1. Number and age of typical construction machines in 1995



Average age

























Construction trailers



Figure 5. Numbers of typical construction machines in the period 1991-1995


Additional criteria for forest road building

Except for the known criteria of forest road construction, there are many other requirements to be met. With regard to forest road building machines the following criteria must be defined (Sever 1995):

· effective system of supervising the quality of environmental care;

· interdependent obligations for the protection of the forests from bulldozers and backhoes which could endanger its production;

· supply of auxiliary materials without environmental risk;

· choice of work method accompanied by the best selection of alternative techniques, e.g. bulldozer vs. backhoes, mining vs. hydraulic hammer;

· improved utilization of mechanized forest building engineering;

· improved criteria and guidelines to redesign high-serial road building machines for forestry purposes;

· clear definition of the requirements of forest technologies;

· development of secondary processing structures (preparation of machine tools, maintenance).


Anon. 1993. Program razvoja "Hrvatskih šuma" 1991-2025. god., Zagreb, str. 164

Anon. 1994a. Public enterprise "Hrvatske šume" '93 - "Croatian Forests" '93, Yearbook in Woods, Pictures and Figures, Zagreb, p. 45

Anon. 1994b. Priopcenje u svezi s raspravom o hrvatskom šumarstvu i JP "Hrvatske šume" (A report on the discussion on Croatian forestry and the "Croatian Forests" public association. Meh. šumar., Vol. 19, No. 1: 1-10

Anon. 1994c. Poslovno izvješce 1993, "Hrvatske šume" Zagreb, pp. 93

Anon. 1995a. "Hrvatske šume" - poslovno izvješce 1994, Zagreb, pp. 75

Anon. 1995b. "Hrvatske šume" 1991 - 1994. - poslovno izvješce, Zagreb, pp. 36

Anon. 1996. "Hrvatske šume" - poslovno izvješ e 1995, rukopis (Manuscript), Zagreb, str. 62

Knezevic, I. 1991. Prilog istrazivanju odredivanju optimalne gustoce šumskih prometnica u prebornim šumama Gorskog Kotara (A supplement to the determination of the forest road optimal density in the selection forests of Gorski Kotar), Meh. šumar., God. 16, br. 1-4, pp. 11-15

Knezevic, I., Picman, D. & Jakovac, H. 1991: Utjecaj nacina gospodarenja na optimalnu gustocu šumskih prometnica u prebornim šumama Gorskog Kotara (The impact of management methods on the forest road optimal density in the Gorski Kotar selection forests), Meh. šumar., God. 16, br. 1-4, pp. 16-19

Sabadi, R., ed. 1994. Review of forestry and forest industries sector in Republic of Croatia. Zagreb, pp. 120

Sever, S. & Knezevic, I. 1992. Computer-aided determination of optimal forest road density in mountainous areas. Proceedings of Workshop on Computer Supported Planning of Roads and Harvesting Workshop. Feldafing, Germany, pp. 13-25

Sever, S. 1995a. Cestitamo hrvatskim osloboditeljima (We congratulate our liberators!), Editorial, Meh. šumar 20(3): 127-128

Sever, S. 1995b. Logging strategies in Croatia, a country in transition. IUFRO XX World Congress, Tampere, Finland. Proceedings of the Technical Sessions of Subject Group 3.06 Forest Operations Under Mountainous Conditions, pp. 217-226.

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