Ján Tucek1 and Josef Suchomel1
1 Assistant Professor, Faculty of Forestry, of Technical University in Zvolen, Department of Exploitation and Forest Mechanization, T. G. Masaryka 24, 960 53 Zvolen, Slovak Republic.
Abstract
This paper discusses the possibilities of using computer techniques, digital terrain models and geographical information systems in the planning of forest roads.
Priorities of technological requirements for the location of forest roads are presented in relation to other requirements and the possibilities for solutions, forest operations planning and modelling are discussed.
The latest trends and solutions in this field studied by the Department of Exploitation and Forest Mechanization of the Faculty of Forestry, Technical University, Zvolen, are presented.
Keywords: Opening-up of forests, forest road and landing locations, technology optimization, computerized methods, GIS.
Introduction
Opening up of forests and related optimization of forest technologies use are very interesting and important for forest management. Forest roads are sustainable in the long term and their location has an influence on all management activities in forest stands. Efficiency and economics of forest operations are influenced significantly by road location. Forest road building is also extremely costly. The impact on the natural environment is significant in three ways:
· influence of road building,· influence of the road or landing itself,
· influence of the equipment and technologies used depending on the parameters and location of the road and landing network.
The solution of this complex problem also depends on the natural, economic, social and management conditions of the forests in the different countries.
Overall characteristics of forestry in Slovakia
Slovakia covers an area of 49 036 km2, its altitude varying from 92 to 2 655 m a.s.l. The forests in Slovakia represent approximately 40 percent of the territory. Mountain forests with the area of 550 000-600 000 ha represent about 30 percent of the total forest area. There are no common criteria for the delimitation of mountain conditions. Frequently they are characterized by an altitude higher than 700 m, a significant slope degree and typical geobotanical characteristics, which in Slovak conditions are ecosystems from the fifth to the eighth altitudinal vegetation zones. Beech, fir and spruce are the prevailing tree species there, frequently in mixed stands. Of the annual harvested volume, about 50 percent is located on the mountains and about 30 percent is in stands with a slope higher than 50 percent (they also occur in areas at lower altitudes).
Conditions are very specific in areas with flysch geology. Low bearing capacity of the soil is typical there, as well as its sensitivity to climatic changes (moisture). About 23 percent of the forests belong to this "flysch geology belt". The mountain area also includes Swiss mountain pine stands in the subalpine degree with an area of approximately 18 000 ha, practically without management activities.
The relief of Slovakia is generally hilly and steep, so the most important beneficial forest functions are ecological, related soil, water and air conservation. According to existing legislation, the functions of forest stands fall into two basic groups which serve substantially to a different purpose: a production function (i.e. exclusively wood production) and non-production function (i.e. the so-called public interest functions). Each forest stand always performs more than one function but, according to the needs of society, emphasis is given to one or more of them. On this basis forest stands are divided into three categories:
· protection forests - 14 percent;
· special purpose forests - 14 percent; and
· production (commercial) forests - 69 percent.
Specific rules exist for the management of stands in the different function categories.
Coniferous tree species represent 43 percent, broadleaved species 57 percent. Natural regeneration occurs in 15-20 percent of forests although, depending on natural conditions, it is possible to reach 30 to 40 percent. A significant fact is the vast damage to the forests by emissions, especially in the area surrounding local emission sources but also from remote sources (Czech Republic, Poland). The total growing stock in stands is 365 million m3.
The largest changes in the ownership tenure of forest lands occurred between 1920 and 1948. There were significant changes in the right of use of forest land after 1948. Legislation promoted the right of use above the rights of ownership. Thereafter, reprivatization has been taking place since passing the Act on Land and the Act on the Property of Municipalities and Churches in 1992. The State owns about 42 percent of the forest area. societies 23 percent, private owners 17 percent, villages and towns 10 percent, churches and other owners 8 percent.
The cultivation policies, which were applied in Slovak forests till the end of nineteenth century, included "nature friendly forest management". Attempts to keep forest's natural characters dominated (in all-aged forests and in forests which had changed from the original tree species). Regeneration methods were based on small-area shelterwood cutting, sometimes in combination with border cutting. This positive trend resulted from the Forest Act of 1960 and the small-area shelterwood system became the basic way of management. Clear-cutting was limited. But actual implementation did not correspond to the declared orientation. In the 1980s, for example, clear-cuttings were realized on 74 percent of the area, border cuttings on 20 percent and small-area shelterwood techniques only on 6 percent of area.
The volume of wood harvesting is established on the basis of exploitation balance and sustained forest production. Annual harvesting is about 4.5 million m3. Of this 3.3 million m3 of the wood come from regeneration cuttings and 1.2 million m3 from tending cuttings. A high portion of irregular harvesting due to snow, wind, pest and emission disasters has an important influence.
Felling and delimbing is carried out mainly by chain-saws. The average time needed for these two operations is 1.1 hour/m3. Trees are delimbed mainly in the stands. Only about 2 to 3 percent of the harvested volume is logged with delimbing at roadside or at a forest landing by a processor.
Crosscutting (assortment production) in stands is only about 10 percent. Timber is dragged to the roadside or landing mainly in whole-stem status - 85 percent by different means. Details on the equipment used are presented in Table 1. About 70 percent of the assortments from whole-stem timber are made at the roadside or landing by chain-saws. Twenty-five percent is processed at central timber yards nearby the railway and about 5 percent directly at the customer's yards. Hauling (transport) of timber is largely mechanized. About 70 percent of the harvested volume is transported by hauling rigs (truck and trailer). Hydraulic booms are frequently used for loading.
The forest roads network consists of hauling roads, permanent skidding roads and so-called skidding lanes. The average density of hauling roads (paved) is about 10 m/ha, the density of permanent ground skidding roads is about 6 m/ha. The road density in the different forest categories varies. Details are presented in Table 2. The density of temporary skidding earth roads and lanes is about 30-50 m/ha2. The building of new roads is presently limited due to insufficient capital available to forestry in general.
Important factors for the opening up of forests in Slovakia
In Slovak conditions opening up of forests and forest roads location is influenced or limited by:
1. Natural conditions
A big portion of forests lies in the mountains. There are steep terrains with broken topography, and long slopes where slope roads cannot be built cable systems must be used. An additional problem arises in the opening up of areas with flysch geology. The main problem is the low ground bearing capacity of the soil, its tendency to logging and post logging erosion and to landslipping. It is proposed to eliminate earth roads in this area and to use ground skidding, or to avoid it in rainy periods. Forests damaged by emissions need very fine and detailed opening up due to the use of selective harvesting and the high sensitivity of the ecosystems. Influences on the natural environment should be as sound as possible. The high broadleaved species composition has had an influence on the technologies used because it is impossible to use machine delimbing.
2. Function typical of forests and detail management planning
The prevailing officially declared silviculture system is the small-area shelterwood system. Very specific requirements exist for the location of roads; access to the stands; possibility to drag trees, stems or logs very carefully; protection of advance regeneration, etc. Additional problems are faced in the opening up of protection forests and special purpose forests. A detailed verbal description of the proposals must be prepared for opening up forests in the different function categories to fulfil the main objectives of the respective category. But a system for their application on a non-subjective and really quantitative basis still does not exist.
3. Changes in forest ownership
Reprivatization of forests is in progress. New owners have limited investment capacity for building forest roads. Their possibility to use of developed mechanized technologies is also limited. On some occasions, they use very simple motomanual technologies and a universal (agricultural) tractor for timber logging. The creation of contractor companies specialized in forest operations could bring positive changes. But this process is starting only now. Some law acts are still in force, which regulate the duties of the owners in the opening up of forests and in the use of environmentally sound technologies.
4. Logging technologies
The main problem is the discrepancy between the large areas of steep mountain terrain and the low use of cable technologies. The problem originated from the lack of quality cable systems in the past and the lack of a law regulating the disturbances to the natural environment during and after logging operations. Cable systems are substituted by skidders, which need to build a dense network of earth roads with negative influences on the natural environment.
The use of mechanized technologies is also very poor. It is important to mention that access of machines to the stands is limited. They should be used at the roadside or at a landing (forest yard). The location of landings or forest yards is very important from this point of view. It is not possible for labour productivity of motomanual technologies to increase significantly in the future since the top has probably been reached.
5. Forest road building
There are practically no unopened areas in Slovakia. But the efficiency of the forest roads network varies greatly. Roads are mainly built in valleys. There is a problem of how much detail is needed to build hauling roads. A second problem is how to connect them to the skidding roads, or how to connect cable system traces to them. A special problem is the location of landings or forest yards in a roads network for the processing of trees or stems.
6. Legislation on opening-up planning
A system for the planning and evaluation of transport conditions in every forest complex has been in use for years. The institute for planning of forest management (Lesoprojekt) is the authority responsible for this task, which includes the complex evaluation of the condition of the forests; their production and harvesting possibilities; and natural, social and techno-economic conditions of management. Forest management plans for each stand for a 10-year period are prepared on the basis of this knowledge.
Details on the terrain and technological characteristics of each stand are also part of this material. It covers slopes (categories 0-20%, 21-40%, 41-50%, 51% and over) and traffic-bearing capability of the terrain. The edge-bearing capacity of soil for tractors is 50 kPa. The existence of obstacles, rocks, holes, roughness higher or deeper than 0.5 m over distances less than 5 m, is also evaluated. On this basis, slope categories are divided into three classes:
P = allows transit permanently,
P/N = transit potentially possible during good climatic conditions,
N = transit permanently impossible.
Terrains with slopes of more than 50 percent are evaluated as permanently not allowing transit to tractors. The quality of this classification system is discussed frequently with regard to the bearing capacity of the soil. A second problem is its practical implementation, as mentioned before.
7. Insufficiently detailed knowledge and lack of a quality application system
There is insufficiently detailed knowledge for the quantification of the impact of different equipment, methods and technologies on the soil, brush (especially advance regeneration) and trees in stands under different conditions. The relations between terrain conditions, function type of the forests, planning activities, technologies, disturbance to the environment, and road and landing locations should be investigated. A system for evaluating, processing and application of this knowledge in the planning process for individual stands on an independent objective basis is still missing.
Actual problems in the planning technologies of forest roads and potential and perspectives of computerized methods
Opening up of forests means gradual planned equipping of forests with a roads and landings network. Forest technologies should be used for efficient stand management. Requirements for location, structure and parameters of a roads and landings network are different under variable terrain conditions and with variable proposed technologies and management activities. These requirements and also approaches to the planning process can be related to economic, ecological, management and technological issues.
From an economic point of view, roads and landings should be located on the area with the target of minimizing costs for roads and landings and costs for timber skidding or processing. Many theoretical works exist in this field. The density of the road network and the theoretical skidding distance are used in the calculations for a given period of road use. They are quite clear for simple plain conditions. Other costs for supplementary management activities - costs for workers transport, hauling of timber, or equations for more detailed skidding costs calculation - are frequently included. Many of the coefficients used in the equations are modified for actual or for mountainous conditions.
Ecological requirements can be expressed as the need to minimize disturbances to the soil, brush and tree stands during the management process. Very simply, there is a need to minimize the overall length of the road network. But skidding and processing of trees in stands has also a significant influence on the natural environment. These requirements are discussed very frequently but still are not quantified and practically used in road planning technologies.
Management requirements deal with possibilities and efficient use of forest roads in "other" management activities in the forests, such as for dividing the forests into management units, for using the roads for the protection of forests against fire, for social needs, and for touristic and recreation activities. They are not included in the primary planning activities. Only after the fact occurs, they are evaluated and checked. They are important in protection forests and in forests of special purposes.
From a technological point of view, technical and technological parameters of logging (processing) equipment, terrain and stand characteristics and also transport distances are evaluated in planning process according to the real conditions in the stands. The location of landings and their connection to different road types (skidding, hauling) are very important mainly in conditions where access of machines to the stands is impossible. It should be in harmony with the gravity situation (direction of moving the timber) and with the parameters of the proposed equipment used. Landing location influences the location of skidding and hauling roads, the way they are connected, the length of every road category and the volume of timber. Nitami (1995) discusses the importance of technological aspects and landing locations in the planning process in relation to regeneration techniques. The basic scheme of relationships in this system is shown in Figure 1. The most important technological criteria to be considered in roads and landings location are:
· possibility to use effectively different equipment methods in relation to terrain and stand characteristics (length of slopes, inclination, topography, possibility of transit, obstacles, soil ground bearing capacity and age of stands, species composition, quality of timber);· optimization of skidding distance - optimization of skidding costs and minimization or optimization of environment disturbance by skidding (forest operations);
· possibility to employ proposed tending or regeneration techniques (access to stands, dragging of stems or logs, protection of advance regeneration or trees);
· concentration of a sufficient amount of timber over time and area in relation to the equipment used.
In real conditions there is a need to evaluate all requirements in their complexity. Many factors and alternatives should be evaluated and checked in this process, and this is traditionally supported by computerized methods. There are no common criteria and methods. Every "optimization" is also a problem of definition of criteria and priorities for special conditions. Historical development in opening up of forest and traditions in logging technologies used in different countries also play an important role.
Computerized methods are very useful in the solution of these problems. For planning where economic approaches dominate they bring the possibility to describe and quantify conditions more realistically. But "clear" utilization of this approach is probably limited to relative simple plain conditions with homogeneous tree species and technology composition. It is not possible to evaluate in detail ecological parameters. Beneš (1973). for example, discussed the influence of terrain topography on the quality of the planning process and relative forest accessibility. It seems that approaches, which originate in technological and ecological evaluation of more alternatives, are more effective for mountains where conditions change frequently. It is possible to evaluate traffic bearing capacity of the terrain and efficiency of use of different means for less or more "real" terrain and stand conditions and proposed roads and landings location. The ecological impact should also be evaluated and checked in this process. Many alternatives may be checked and compared in a DTM and GIS environment before roads building and technologies using the evaluation of many parameters (economic, ecological, and technological). This approach is not new but still interesting. In the past Kanzaki (1966) published similar proposals and recently also Epstein et al. (1994).
For the purpose of systemization of knowledge, we can identify several layers in the use of computerized methods in the planning process - for example, overall approach to the problem, data structuring and software tool use, methods use. and thematic orientation. A more detailed discussion on this subject can be found in Tucek (1995). The Proceedings of the workshop on computer supported planning of roads and technologies of Subject groups 3.05 and 3.06 of IUFRO in Feldafing (1992) and the International NEFU/IUFRO/FAO/FEI Seminar on forest operations under mountainous conditions in Harbin (1994) provide a very well documented picture. The meeting of Subject group 3.06 IUFRO at the XX. World Congress in Tampere (1995) also adds to the knowledge in this field.
Heinimann (1995) presents a "philosophy" for the understanding of forest operations as a scientific discipline, discusses its place in forestry in wider natural, social and economic relations. The place and role of computerized methods are also analysed in connection with future needs.
Discussions in this area are strongly influenced by the development in computer technology, both hardware and software. We can see that this development is extremely fast. So we can expect rapid employment of new knowledge and products.
Important developments are also made in data structuring and processing. We can expect employment of object structuring and programming in this area. Commercial DBMS systems, GIS and DTM systems have own environments for convenient data structuring and development of user-defined applications. Under these new operation systems it is possible to use multiple applications (multitasking) and to export and import data from and to environment or application. These possibilities for integrating data and environment types should be extremely important for development of new applications and processing of data and relations, which were not processed previously.
Increased focus should be placed on environment and human protection questions (Gjedtjernet 1994. Suchomel and Lukac 1995). To obtain valid and actual information, we can expect the employment of remote sensing methods (Shiba 1995).
To derive maximum profit from forest roads, technologies planning systems and evaluation systems should move from a static approach to a dynamic system with regard to operational management and control in forestry enterprises.
Computer networks and access to remote databases should be important too, mainly to obtain data. use of big computing capacity or exchange of information. This is extremely important for the development of research activities.
Latest solutions at Department of Exploitation and Forest Mechanization in Zvolen
Recently we have carried out some special projects in this field at our Department. They were part of actual research projects. Work in this area is oriented toward three main branches: possibilities of using of computerized methods in the planning of forest roads location planning; possibilities of using computerized methods in the evaluation or optimization of forest technologies; and the study of the influence of equipment and forest technologies to the natural environment.
The new method for preliminary technological evaluation of forest road location was verified on the territory of Vrchdobroc with the object of water conservation and research (see Tuèek 1994) and more recently on the territory of Kyslinky valley in the Polana Mountain (see Tuèek 1995).
We have concluded that raster DTM is a very good tool for the analysis of slopes, for profile analysis, for the calculation of Euclidean distances, and for various display purposes. We used the Idrisi GIS environment in calculations. Its data structure is very convenient for user-defined module building. So we designed modules for several processing alternatives. It is possible to calculate the "map of area accumulation" - version AKUM; distances from each cell of raster image to the nearest defined object (valley line, mountain ridge, road) "on the surface of the DTM in direction of maximum slope gradient" - version DOWN; the same, but against direction of maximum gradient -version UP; "shortest distance from each DTM cell over the DTM surface to the defined object" with visibility and aspect of cells checking under this line down and up - versions STRDOWN and STRUP; map of number of straight reachable cells" in defined distance for every cell of DTM -version REACH. Modules DOWN and UP should model tractor skidding distances, modules STRDOWN and STRUP should calculate skyline skidding distances. These modules are able to work with raster images in Idrisi format. Equally, their outputs are useful in an Idrisi environment. Our programme modules were created in TURBO BASIC language.
Output from module AKUM - the map of area accumulation - may be a source of supplement information for decision-making in locating a new road. Cells that accumulate the largest area are potentially the most suitable for road location. On the other hand, cells that accumulate no area are places of gravitational boundaries. These lines are technologically important for the creation of working units. We can use the outputs from modules UP and DOWN and also STRUP and STRDOWN for conditions without roads on the slope for decision-making on where to locate the road on the slope without exceeding the limiting distance from the valley line or ridge line.
It is possible to draw every raster image with one or more vector files in a GIS environment. For example, the map of distances by a map of contours, or by map of stand boundaries or by map of existing roads and so on. They can be meaningful and supplementary for decision-making on where to locate a new road. We can suggest alternatives for the location of new roads. Then for every alternative we can calculate distances by modules DOWN or UP or STRDOWN and STRUP and extract a value of "average skidding distance" for skyline or tractor skidding in stands. The solution for each alternative can be displayed, printed and compared and then the best alternative chosen.
There is a possibility to create many other information layers in a GIS environment. We can use them as supplementary source of information for decision-making. Positive or negative places in the territory may be located in them - for example, suitable or not suitable geological underground, ground-bearing capacity of the soil, geomorphologic characteristics, extreme slopes, barriers, rockiness, and places for landings. Yoshimura and Kanzaki (1995), for example, present very interesting methods for the evaluation of slopes in a GIS environment. Characteristics important for environmental protection may also be located.
The main idea of the method described is the possibility to propose some alternatives for road location. For each alternative we can calculate the distance of every raster cell from the roads (for defined skidding method) and extract average or maximum values for defined stands. The value of the skidding distance should be used in the technological evaluation of the proposed technologies and of the road and landing locations. Solutions for each alternative can be compared, displayed or processed in a GIS environment (in combination with supplementary information). Skidding distance is the most important technological characteristic for road location. But in a GIS environment we can define many others - overall length of the road network, road density, etc. The method described is not an automatic method for opening up. It is only a tool to create supplementary information for the user to make more objective decisions. Only the user, who has a basic knowledge in opening up and in the use of technologies can create, modify and use this information efficiently.
Nowadays attention is paid to the efficiency and quality of the work performed by harvesting and logging machines, especially to its influence on the forest environment and the functionality of the forest - hence the requirement to describe many interactions inside the "man-machine-environment (forest)" system.
The work presented aims to contribute to the task of solving the problem of multi-criteria analysis and the description of selected harvesting methods in regeneration fellings. This approach presumes to create the open model of limiting factors (criteria) and the model of technological variants of harvesting technologies.
Based upon the analysis of the evaluation and the influence of criteria on modelling production and transport technologies, we have selected several significant criteria that we are able to quantify so far. These criteria belong to the open system, which is operational or being realized. The architecture of the open system is shown in Figure 2.
Because of the wide extent of the problem we aimed our effort at the part of the harvesting process from a stump to a roadside. This section is mainly affected by the mutual interaction of human activity, machines and environment. The selection and realization of a particular variant of harvesting has the dominant influence of a final result from the point of view of ergonomic, ecological and economic criteria. The variant can be described as the sequence of harvesting, skidding and logging operations carried out by relevant machines in a particular space (trail) and at a particular time. Each operation is determined simultaneously by the space, the machine and the level of finalization of products.
The criteria chosen for the modelling and optimization of harvesting methods are the following:
A. Ergonomic criteria:1. Risk of an accident: the influence of this criterion is expressed through concrete and quantified number of accidents related to a particular operation carried out with a particular technical method;2. Energy consumption - degree of difficulty and hardness of work.
B. Ecological criteria:
To assess the influence of selected harvesting methods in a forest stand, on a forest ground and soil, we carried out:
1. An analysis of the damage to trees, undergrowth and harvested logs by the use of chain saws;2. An analysis of the influence of the logging machines selected to the forest stands and undergrowth;
3. An analysis of the damage to the soil and soil compaction.
C. Economic criteria:
1. Direct costs of harvesting variants were obtained as the sum of partial direct costs of machines and overall expenditures of each machine included in a variant, respectively;2. For the calculation and evaluation of time consumption of harvesting methods we used standard time-tables. The standard time-tables were developed by an enormous effort on the part of the team of researchers. They divided a working process into smaller parts called operations. These operations are basic parts of our optimization model.
There are several other criteria that could be taken into account, but we have not enough information about them. Our system is open, which means if there is research carried out and new information available, we have no difficulties in attaching it to the existing structure or in creating a brand new criterion.
A software has been developed to meet the requirements of the described methodology. The software named "TVDT" has been written in programme language called MUMPS (DataTree, version 3.0.10). The current version of TVDT 2.0 is now tested and we are preparing new modules to cover new technologies and machines that appear on the Slovak market. TVDT consists of three major parts (Figure 2):
1. The database stores all the data available about machines and technologies, the standard timetables (split into operations), and many other essential data required for the calculations. Another tool from the database enables the input of spatial data; we prepared an interface for the transfer of required data from several sources: GIS, supervisor's databases and portable computers.2. Calculations: after the database is filled with appropriate data about a forest stand, terrain descriptions and other data, which a user can change, the calculations begin. The programme first calculates all the operations from the database of operations, then calculates the entire variants from the database of predefined and user-defined variants.
3. The outputs can be presented in several ways. For forestry practice there is a predefined template, which shows to the user the entire variant and tells him/her about each operation included in this variant.
For the decision-making there are other templates from which a user can derive essential data. At this moment no module for the decision-making is implemented in the programme; therefore we used another software developed at the Technical University of Zvolen. This software takes all the above-mentioned criteria and results from the templates and is able to carry out multi-criteria analysis. The modelling and optimization of harvesting variants creates a large potential for the increase of quality, effectiveness and speed of management of technological processes.
The credibility of the results obtained depends on the data from the database introduced in the calculations. We assume that data coming from a specific forest enterprise are more reliable than average data calculated for entire Slovakia. The results are usable in many ways: for operative management, for the purchase of new machines, for the analysis of acceptability of technical means in particular conditions and for their further development. The open model of technological variants is a valuable tool for the management of forest enterprises. Management can decide on the basis of the results of this programme, of their own knowledge and of the knowledge of other experts which harvesting variant is best for the conditions under consideration.
Study of the environmental impact of different means and technologies is third area of research in our Department. Conditions of access for skidding means, efficiency of their use and also their impact on the natural environment in different function types of forests are analysed. Disturbance and compaction of soil are studied in different geologic and climatic conditions. The amount of logging and post-logging erosion is also evaluated. The requirements of different techniques depending on the system of road location are also evaluated in relation to efficiency and labour productivity of the technology used. Disturbances of advanced regeneration and tree stands are evaluated for different skidding means, road location conditions and regeneration methods. We propose to use this knowledge as a basis for the quantification of ecological and economic parameters of different technologies.
References
Beneš, J. 1973. The effect of topography on forest opening by road systems. Lesnictví No. 6. pp 479-492 (In Czech only with English summary).
Epstein, R. et al. 1994 Planex - Software for operational planning. Proceedings of Int. NEFU/IUFRO/FAO/FEI Seminar. Harbin.
Gjedtjernet, A.M.F. 1994. Forest operations and environmental protection. Proceedings of Int. NEFU/IUFRO/FAO/FEI Seminar. Harbin.
Heinimann, H.R. 1994. Conceptual design of a spatial decision support system for harvest planning, Proceedings of Int. NEFU/IUFRO/FAO/FEI Seminar. Harbin.
Kanzaki, K. A planning of the road network by the theory of graphs. J. Jap. For. Soc. 48(10): 365-371
Nitami, T. 1995. Optimizing of forest harvesting system, the sustainable forest management and operational efficiency XX IUFRO Congress. S3.06 Meeting, Tampere.
Shiba, M.: Imagery data processing system using aerial photography for sensitive investigations in the route selection process. XX. IUFRO Congress, S3.06 Meeting, Tampere.
Suchomel, J. & Lukac, D. 1995. Modelling and optimizing of harvesting methods - Multicriterional analysis. XX IUFRO Congress, S3.06 Meeting, Tampere.
Tucek, J. 1994. Using of the GIS environment for opening up of forests. Proceedings of Int. NEFU/IUFRO/FAO/FEI Seminar. Harbin.
Tucek, J. 1995. Computer aided forest roads (localization) and forest operations planning. XX IUFRO Congress, S3.06 Meeting, Tampere.
Yoshimura, T. & Kanzaki, K. 1995 Method of planning a forest road network using slope failure potentials. XX IUFRO Congress, S3.06 Meeting, Tampere.
1994. The Forestry of Slovak Republic, Poly kontakt.
Table 1. Use of skidding equipment
|
Skidding equipment |
Share of skidded volume (%) |
|||
|
1980 |
1985 |
1990 |
1993 |
|
|
Crawler skidders |
19.4 |
11.2 |
6.8 |
3.3 |
|
Agricultural tractors |
23.2 |
25.2 |
26.0 |
30.7 |
|
Skidders |
45.4 |
55.1 |
57.4 |
58.5 |
|
Cable systems |
0.6 |
2.7 |
2.7 |
2.2 |
|
Horses |
10.3 |
6.7 |
5.4 |
3.8 |
|
Other |
1.1 |
0.1 |
0.1 |
0.4 |
Table 2. Forest roads density for different function categories of forests
|
Function category of forests |
Road type |
Average density m/ha |
|
Protection forests |
Hauling roads |
7.95 |
|
Permanent skidding roads |
3.99 |
|
|
Total |
11.95 |
|
|
Forests for special purposes |
Hauling roads |
8.78 |
|
Permanent skidding roads |
3.80 |
|
|
Total |
12.58 |
|
|
Commercial forests |
Hauling roads |
9.87 |
|
Permanent skidding roads |
8.21 |
|
|
Total |
18.09 |
Figure 1. Harvesting and stand regeneration relationships
Figure 2. Structure of software for forest technologies evaluation - TVDT 2.0
