Current issue: 53(4)
Under compilation: 54(1)
To assess the quality of results obtained from heuristics through statistical procedures, a number of independently generated solutions to the same problem are required, however the knowledge of how many solutions are necessary for this purpose using a specific heuristic is still not clear. Therefore, the overall aims of this paper are to quantitatively evaluate the effects of the number of independent solutions generated on the forest planning objectives and on the performance of different neighborhood search techniques of simulated annealing (SA) in three increasing difficult forest spatial harvest scheduling problems, namely non-spatial model, area restriction model (ARM) and unit restriction model (URM). The tested neighborhood search techniques included the standard version of SA using the conventional 1-opt moves, SA using the combined strategy that oscillates between the conventional 1-opt moves and the exchange version of 2-opt moves, and SA using the change version of 2-opt moves. The obtained results indicated that the number of independent solutions generated had clear effects on the conclusions of the performances of different neighborhood search techniques of SA, which indicated that no one particular neighborhood search technique of SA was universally acceptable. The optimal number of independent solutions generated for all alternative neighborhood search techniques of SA for ARM problems could be estimated using a negative logarithmic function based on the problem size, however the relationships were not sensitive (i.e., 0.13 < p < 0.78) to the problem size for non-spatial and URM harvest scheduling problems, which should be somewhat above 250 independent runs. The types of adjacency constraints did moderately affect the number of independent solutions necessary, but not significantly. Therefore, determining an optimal number of independent solutions generated is a necessary process prior to employing heuristics in forest management planning practices.
A new sampling design, the local pivotal method (LPM), was combined with the micro stand approach and compared with the traditional systematic sampling design for estimation of forest stand variables. The LPM uses the distance between units in an auxiliary space – in this case airborne laser scanning (ALS) data – to obtain a well-spread sample. Two sets of reference plots were acquired by the two sampling designs and used for imputing data to evaluation plots. The first set of reference plots, acquired by LPM, made up four imputation alternatives (varying number of reference plots) and the second set of reference plots, acquired by systematic sampling design, made up two alternatives (varying plot radius). The forest variables in these alternatives were estimated using the nonparametric method of most similar neighbor imputation, with the ALS data used as auxiliary data. The relative root mean square error (RelRMSE), stem diameter distribution error index and suboptimal loss were calculated for each alternative, but the results showed that neither sampling design, i.e. LPM vs. systematic, offered clear advantages over the other. It is likely that the obtained results were a consequence of the small evaluation dataset used in the study (n = 30). Nevertheless, the LPM sampling design combined with the micro stand approach showed potential for improvement and might be a competitive method when considering the cost efficiency.
The nature areas surrounding the capital of Norway (Oslomarka), comprising 1 700 km2 of forest land, are the recreational home turf for a population of 1.2 mill. people. These areas are highly valuable, not only for recreational purposes and biodiversity, but also for commercial activities. To assess the impacts of the challenges that Oslo municipality forest face in their management, we developed four optimization problems with different levels of management constraints. The constraints consider control of harvest level, guarantee of minimum old-growth forest area and maximum open area after final harvest. For the latter, to date, no appropriate analyses quantifying the impact of such a constraint on economy and biomass production have been carried out in Norway. The problem solved is large due to both the number of stands and number of treatment schedules. However, the model applied demonstrated its relevance for solving large problems involving maximum opening areas. The inclusion of maximum open area constraints caused 7.0% loss in NPV compared to the business as usual case with controlled harvest volume and minimum old-growth area. The estimated supply of 20-30 GWh annual energy from harvest residues could provide a small, but stable supply of energy to the municipality.
This study examined the relationships between forest management planning units and patches formed by forest habitat components. The test area used was a part of Koli National Park in North Karelia, eastern Finland. Forest management planning units (i.e. forest compartments) were defined by using a traditional method of Finnish forestry which applies aerial photographs and compartment-wise field inventory. Patches of forest habitat components were divided according to subjective rules by using a chosen set of variables depicting the edaphic features and vegetation of a forest habitat. The spatial distribution of the habitat components was estimated with the kriging-interpolation based on systematically located sample plots. The comparisons of the two patch mosaics were made by using the standard tools of GIS. The results of the study show that forest compartment division does not correlate very strongly with the forest habitat pattern. On average, the mean patch size of the forest habitat components is greater and the number of these patches lower compared to forest compartment division. However, if the forest habitat component distribution had been considered, the number of the forest compartments would have at least doubled after intersection.
This paper deals with the testing of dynamic stratification for estimating stand level forest characteristics (basal areas, mean diameter, mean height and mean age) for a 117 ha study areas in Finland. The results do not show possibilities to achieve more accurate estimates using only Landsat TM principal components as auxiliary data opposed to static stratification. It was found that in dynamic stratification non-measured observations should be assigned the mean characteristics of the measured observations that belong to the same cube (class) instead of stratification variable classes until a certain limit. If only one principal component is used the number of classes has, however, little influence. Low field values are overestimated and high values underestimated.
The only successful results were obtained using two variables of different origin – the qualitative development stage class and the quantitative 1st principal component. The lowest root mean square error in estimating basal area was 6.40 m2/ha, mean diameter 3.34 cm, mean height 2.65 m and mean age 14.06 years. This increase of stratification accuracy is mainly resulted by the use of development stage class as an auxiliary variable.
The paper discusses the principles of forest management in the state forests of Finland, and the contradictions in choosing between the different land uses. These principles of the forest management are sustainable use of natural resources, economic and effective management, and taking in account nature conservation, protection of environment, recreation services and employment issues in all activities of the Forest Service. Even regional policy affects the management planning in the state forests.
Forest balance is a comparison between the growing stock volume at the beginning and end of a balance period and the gross increment and drain during that period. The forest balance of Finland during that period 1967-1973 and the increment and drain balance during the period 1953-1977 are used as examples in the paper. Forest balance is a check of the accuracy of basic estimates. If the discrepancy between the calculated growing stock at the end of the balance period and the growing stock estimated by an inventory is great, it calls for improvements in forest inventory methods and timber utilization statistics.
Balance may reveal possibilities for improving the utilization of forest resources. If natural losses are great, increased thinnings and regeneration cuttings of mature and over-mature tree stands increase the supply of timber. If logging losses are great, the efficiency of harvesting should be improved. An overcutting situation calls forth efforts to increase timber production or to decrease the uses of timber in order to avoid overexploitation. If gross increment is greater than the drain there are possibilities to increase harvesting, forest industrial expansion etc.
Forest balance is a way to check and improve the basic estimates of forestry production, to increase the effective use of timber grown in the forest, to commerce policies and measures concerning increment and to control timber utilization on the basis of sustained yield.
The PDF includes a summary in Finnish.
In the densely populated Central Europe, forestry has always had different functions than in Scandinavia or Canada. Today the increasing pressures on the environment and more numerous demands of the people have put emphasis on environmental management and the demands of recreation in forest management practiced in the area. This paper outlines the trends in the utilization of forests in Central Europe, and especially in the Federal Republic of Germany, due to these changing targets. The regulations concerning forestry in Baden-Würtenber, and the forest plan of the Bavarian state forests are used as an example to clarify the principals of forest management and planning.
Production of timber in forest stands is described by a production function. The variable inputs of the function are land and growing stock and the output is the annual value growth. The partial derivatives of this production function express the marginal productivity of the land and of auction function express the marginal productivity of the land and of the growing stock. These marginal productivities can be utilized for determination of the need of regeneration and thinning. The stand should be regenerated when the marginal productivity of the land falls below the annual rent of a unit area of open land and thinned when the marginal productivity of the growing stock falls below the annual rent of one unit of growing stock.
The PDF includes a summary in Finnish.
The aim of this study was to develop cutting budget methods for a forest undertaking. Cutting budget provides information on the future income from the forest undertaking, and on the development of the forest.
Two cutting budget models have been developed, by the application of simulation and linear programming. Both of the models are deterministic in nature, i.e. there is only one possible outcome once the stated input information has been given. To make the models simpler, it has been assumed that thinning and clear cutting with reforestation are the only activities that can occur in the forest. The models are directly applicable only to forests consisting of even-aged Scots pine stands at three different forest types. However, they can easily be extended to cover forests comprising several tree species and more sites.
In the light of this study, simulation seems today to be more appropriate than linear programming in the preparation of cutting budgets. However, the increasing capacity of computers may even in the near future make linear programming quite competitive, especially as if it is borne in mind that the theoretical basis of linear programming is much firmer than that of simulation. The most advisable cutting budget method might consist of a combination of simulation and linear programming. Simulation could be employed to find a rough cutting schedule, and linear programming to test and improve the solution.
The PDF includes a summary in Finnish.
This paper describes different methods of long-term forecasts in forest management planning with a special attention on intention forecasts for a total forest property or district. Methods for calculating the sustained yield on the basis of the actual increment or the yearly area cut are discussed. It is concluded that a better estimate of the sustained yield is obtainable by the application of a long-term forecast technique. Forecasts for 100 years should not be viewed as plans, but as a background for making short-term decisions. Some of the long-term-type programmes, such as the programme of maximum profit, sustained yield in volume and in money are discussed briefly.
It is pointed out that there is often present a conflict between the various elements of the policy formulated by a forest owner. This leads to the conclusion that the calculations of the profitability of single projects may be misleading.
The precision of a long-term forecast is discussed, and how under certain assumptions the error of the allowable cut is influenced by errors in area, volume, age etc. It is shown that the precision in area and volume is more important in this connection than, say, the precision in increment. In conclusion, existing knowledge, methods and equipment for calculations constitute a basis for long-term forecasts which make them an important instrument in forest management planning.
The PDF includes a summary in English.