单木造材优化嵌入传统林分经营优化中的红松人工林精准经营模式

以黑龙江省红松(Pinus koraiensis Siebold et Zuccarini)人工林主要分布区域的标准幼龄林(初植密度2500、3300株/hm~2,地位指数12、14、16 m)为研究对象,利用韦布尔(Weibull)函数预测株数保存率为85%时不同立地指数的红松人工林在10 a时的直径分布;依据红松人工林幼龄标准林分数据,利用人工红松单木-林分基础模型和球果模型构建的林分模拟器对标准林分进行生长模拟,在传统经营优化模式中嵌套单木造材优化,构建单木造材优化嵌入传统林分经营优化中的红松人工林精准经营模式(简称“精准林分经营优化模式”);以木材和球果总净现值最大为目标,对比精准林分经营优化模式、传统林分经营优化模式的差异,分析造材优化对林分经营优化结果、林分经营措施的影响。结果表明:在约束间伐强度和固定下层伐的条件时,与传统经营优化模式相比,精准林分经营优化模式使总经济效益提升6.5%~9.1%。立地条件越好,精准林分经营优化模式对木材净现值增长率、年均木材产量、主伐时林分平均胸径的增量影响越显著,而对年均球果产量、球果净现值增长率的增量影响较小。在同一立地条件时,与传统林分经营优化模式相比,精准林分经营优化模式提升木材净现值增长率对林分初植密度更敏感。

应用优化建模法构建红松人工林单木直径生长模型

为了提高不完备数据集下红松人工林直径生长模型的预测精度,以1980—2022年黑龙江省75块红松林不同复测间隔期的样地数据(林木胸径、竞争因子和立地等),利用优化建模法构建红松人工林单木直径生长模型,采用单纯形优化算法寻求模拟和实测直径分布差异最小下的模型参数,并利用自举法对模型进行检验。结果表明:优化建模法损失函数的初始参数a=1、b=0.003、c1=c2=1.5时,预测期末林分断面积偏差为0.02 m^(2)·hm^(-2),显著优于由传统归回建模法的精度(林分断面积偏差为0.44 m^(2)·hm^(-2));结合实测数据与视图分析,验证了优化建模法的优势和可靠性,揭示了优化法损失函数与传统回归法构建的直径生长模型之间的差异。因此,优化法损失函数构建的红松人工林生长模型在模拟自然生长中表现优越,为制定科学的森林经营方案提供了技术支持。

Developing kNN forest data imputation for Catalonia

The combined use of LiDAR(Light Detection And Ranging)scanning and field inventories can provide spatially continuous wall-to-wall information on forest characteristics.This information can be used in many ways in forest mapping,scenario analyses,and forest manage-ment planning.This study aimed to find the optimal way to obtain continuous forest data for Catalonia when using kNN imputation(kNN stands for“k nearest neighbors”).In this method,data are imputed to a certain location from k field-measured sample plots,which are the most similar to the location in terms of LiDAR metrics and topographic variables.Weighted multidimensional Euclidean distance was used as the similarity measure.The study tested two different methods to optimize the distance measure.The first method optimized,in the first step,the set of LiDAR and topographic variables used in the measure,as well as the transformations of these variables.The weights of the selected variables were optimized in the second step.The other method optimized the variable set as well as their transformations and weights in one single step.The two-step method that first finds the variables and their transfor-mations and subsequently optimizes their weights resulted in the best imputation results.In the study area,the use of three to five nearest neighbors was recommended.Altitude and latitude turned out to be the most important variables when assessing the similarity of two locations of Catalan forests in the context of kNN data imputation.The optimal distance measure always included both LiDAR metrics and topographic variables.The study showed that the optimal similarity measure may be different for different regions.Therefore,it was suggested that kNN data imputation should always be started with the optimization of the measure that is used to select the k nearest neighbors.

Effect of species composition on ecosystem services in European boreal forest

Forest management in several boreal countries is strongly focused on conifers because they are more productive,the technical quality of their stems is better,and their wood fibers are longer as compared to broadleaves.Favoring conifers in forest management leads to simple forest structures with low resilience and diversity.Such forests are risky in the face of climate change and fluctuating timber prices.Climate change increases the vitality of many forest pests and pathogens such as Heterobasidion spp.and Ips typographus L.which attack mainly spruce.Wind damages are also increasing because of a shorter period of frozen soil to provide a firm anchorage against storms.Wind-thrown trees serve as starting points for bark beetle outbreaks.Increasing the proportion of broadleaved species might alleviate some of these problems.This study predicts the long-term(150 years) consequences of current conifer-oriented forest management in two forest areas,and compared this management with silvicultural strategies that promote mixed forests and broadleaved species.The results show that,in the absence of damages,conifer-oriented forestry would lead to 5–10% higher timber yields and carbon sequestration.The somewhat lower carbon sequestration of broadleaved forests was counteracted by their higher albedo(reflectance).Mixed and broadleafforests were better providers of recreational amenities.Species diversity was much higher in mixed stand and broadleaf-oriented silviculture at stand and forest levels.The analysis indicates that conifer-oriented forest management produces rather small and uncertain economic benefits at a high cost in resilience and diversity.

Optimal management of Korean pine plantations in multifunctional forestry

Korean pine is one of the most important plantation species in northeast China. Besides timber, it produces edible nuts and plantations sequester carbon dioxide from the atmosphere. This study optimized the management of Korean pine plantations for timber production, seed production, carbon sequestration and for the joint production of multiple benefits. As the first step, models were developed for stand dynamics and seed production. These models were used in a simulation-optimization system to find optimal timing and type of thinning treatments and optimal rotation lengths. It was found that three thinnings during the rotation period were optimal. When the amount or profitability of timber production is maximized, suitable rotation lengths are 65-70 years and wood production is 5.5-6.0 m(3) ha(-1) a(-1). The optimal thinning regime is thinning from above. In seed production, optimal rotation lengths are over 100 years. When carbon sequestration in living biomass is maximized, stands should not be clear-cut until trees start to die due to senescence. In the joint production of multiple benefits, the optimal rotation length is 86 years if all benefits (wood, economic profits, seed, carbon sequestration) are equally important. In this management schedule, mean annual wood production is 5.5 m(2) ha(-1) and mean annual seed yield 141 kg ha(-1). It was concluded that it is better to produce timber and seeds in the same stands rather than assign stands to either timber production or seed production.

Optimizing continuous cover management of boreal forest when timber prices and tree growth are stochastic

Background： Decisions on forest management are made under risk and uncertainty because the stand development cannot be predicted exactly and future timber prices are unknown. Deterministic calculations may lead to biased advice on optimal forest management. The study optimized continuous cover management of boreal forest in a situation where tree growth, regeneration, and timber prices include uncertainty. Methods： Both anticipatory and adaptive optimization approaches were used. The adaptive approach optimized the reservation price function instead of fixed cutting years. The future prices of different timber assortments were described by cross-correlated auto-regressive models. The high variation around ingrowth model was simulated using a model that describes the cross- and autocorrelations of the regeneration results of different species and years. Tree growth was predicted with individual tree models, the predictions of which were adjusted on the basis of a climate-induced growth trend, which was stochastic. Residuals of the deterministic diameter growth model were also simulated. They consisted of random tree factors and cross- and autocorrelated temporal terms. Results： Of the analyzed factors, timber price caused most uncertainty in the calculation of the net present value of a certain management schedule. Ingrowth and climate trend were less significant sources of risk and uncertainty than tree growth. Stochastic anticipatory optimization led to more diverse post-cutting stand structures than obtained in deterministic optimization. Cutting interval was shorter when risk and uncertainty were included in the analyses. Conclusions： Adaptive optimization and management led to 6%-14% higher net present values than obtained in management that was based on anticipatory optimization. Increasing risk aversion of the forest landowner led to earlier cuttings in a mature stand. The effect of risk attitude on optimization results was small.

Predicting scenic beauty of forest stands in Catalonia （North-east Spain）

Relative preferences of 90 images of forest stands, photos and virtual reality images were investigated by the intemet to develop a quantitative model for estimating scenic beauty preferences at the stand level, The relative priority values obtained from the questionnaire of a total of 259 judges were analyzed using regression methods for pairwise comparisons. Two models were developed based on two different groups of stands. Both models indicate that the priority of a forest stand increases with an augment in the number of bushes and trees, and also with the mean diameter of trees. On the other hand, the priority is low with large number of pines and small trees. Stands represented by photos receive better priority values than those represented by virtual reality images. When the background of the judges （gender, country or occupation） was included into the model as additional predictors, no significant improvements are achieved.

Optimizing any-aged management of mixed boreal forest under residual basal area constraints

The current trend of forest management in many countries is reduced use of clear-felling and planting, and increased use of continuous cover management. In Finland, the new forest act of 2014 made all types of cuttings equally allowable on the condition that if the post-cutting residual stand basal area is too low, the stand must be regenerated within certain time frame. Forest landowner can freely choose between even-and uneven-aged management. This study developed a method for opti-mizing the timing and type of cuttings without the need to categorize the management system as either even-aged or uneven-aged. A management system that does not set any requirements on the sequence of post-cutting diameter distributions is called any-aged management. Planting or sow-ing was used when stand basal area fell below the required minimum basal area and the amount of advance regeneration was less than required in the regulations. When the cuttings of 200 stands managed earlier with even-aged silviculture were optimized with the developed system, final felling followed by artificial regeneration was selected for almost 50%of stands. Reduction of the minimum basal area limit greatly decreased the use of artificial regeneration but improved profitability, suggesting that the truly optimal management would be to use natural regeneration in financially mature stands. The optimal type of thinning was high thinning in 97-99%of cases. It was calculated that the minimum basal area re-quirement reduced the mean net present value of the stands by 12-16%when discount rate was 3-5%.

Optimized cellular automaton for stand delineation

Forest inventories based on remote sensing often interpret stand characteristics for small raster cells instead of traditional stand compartments. This is the case for instance in the Lidar-based and multi-source forest inventories of Finland where the interpretation units are 16 m 9 16 m grid cells. Using these cells as simulation units in forest planning would lead to very large planning problems. This difficulty could be alleviated by aggregating the grid cells into larger homogeneous segments before planning calculations. This study developed a cellular automaton(CA) for aggregating grid cells into larger calculation units, which in this study were called stands. The criteria used in stand delineation were the shape and size of the stands, and homogeneity of stand attributes within the stand. The stand attributes were: main site type(upland or peatland forest), site fertility, mean tree diameter, mean tree height and stand basal area. In the CA, each cell was joined to one of its adjacent stands for several iterations,until the cells formed a compact layout of homogeneous stands. The CA had several parameters. Due to high number possible parameter combinations, particle swarm optimization was used to find the optimal set of parameter values. Parameter optimization aimed at minimizing within-stand variation and maximizing between-stand variation in stand attributes. When the CA was optimized without any restrictions for its parameters, the resulting stand delineation consisted of small and irregular stands. A clean layout of larger and compact stands was obtained when the CA parameters were optimized with constrained parameter values and so that the layout was penalized as a function of the number of small stands(<0.1 ha). However, there was within-stand variation in fertility class due to small-scale variation in the data. The stands delineated by the CA explained 66–87% of variation in stand basal area, mean tree height and mean diameter, and 41–92% of variation in the fertility class of the site. It was concluded that the CA developed in this study is a flexible new tool,which could be immediately used in forest planning.

Integrated use of GIS, remote sensing and multi-criteria decision analysis to assess ecological land suitability in multi-functional forestry

The Zagros forests are a treasure of valuable oak forests, but they have been severely degraded from long-term misuse. Geographic information systems （GIS） and multi-criteria decision analysis （MCDA） have been increasingly used to improve the management of vulnerable ecosystems to prevent further degradation and increase the sustainability of land use. This study presents a methodology to assess land suitability using remote sensing （RS） to obtain wall-to-wall data for the calculations, GIS to analyze the data, and MCDA to rank alternative land uses. The criteria and subcriteria affecting the suitability of land for different uses were identified and weighted using an analytic hierarchy process. Variables used as subcriteria were assessed using satellite data and other sources of information such as existing maps and field surveys. Numerical values for the subcriteria were classified, and each class was given a priority rating according to expert judgments. Based on the ratings and weights of the subcriteria, a priority map was created for each land use using the weighted linear combination method. The priority maps for different land uses were overlaid to obtain a preliminary land use map, which often indicated several simultaneous land uses for the same location. The preliminary map was further edited by removing unrealistic, mutually exclusive land-use combinations. The study tested and demonstrated the potential of integrating RS, G1S and MCDA techniques for solving complicated land allocation problems in forested regions using a scientifically sound and practical approach for efficient and sustainable allocation of forestland for different uses.

Using ALS raster data in forest planning

Raster type of forest inventory data with site and growing stock variables interpreted for small squareshaped grid cells are increasingly available for forest planning.In Finland,there are two sources of this type of lattice data:the multisource national forest inventory and the inventory that is based on airborne laser scanning(ALS).In both cases,stand variables are interpreted for 16 m×16 m cells.Both data sources cover all private forests of Finland and are freely available for forest planning.This study analyzed different ways to use the ALS raster data in forest planning.The analyses were conducted for a grid of 375×375 cells(140,625 cells,of which 97,893 were productive forest).The basic alternatives were to use the cells as calculation units throughout the planning process,or aggregate the cells into segments before planning calculations.The use of cells made it necessary to use spatial optimization to aggregate cuttings and other treatments into blocks that were large enough for the practical implementation of the plan.In addition,allowing premature cuttings in a part of the cells was a prerequisite for compact treatment areas.The use of segments led to 5–9%higher growth predictions than calculations based on cells.In addition,the areas of the most common fertility classes were overestimated and the areas of rare site classes were underestimated when segments were used.The shape of the treatment blocks was more irregular in cell-based planning.Using cells as calculation units instead of segments led to 20 times longer computing time of the whole planning process than the use of segments when the number of grid cells was approximately 100,000.

Effect of wind damage on the habitat suitability of saproxylic species in a boreal forest landscape

Many forest-dwelling species are dependent on deadwood. Sources of deadwood include competition- and senescence-related mortality of trees, and various damages. This study described a methodology for predicting the effect of wind damage on the amount of deadwood and suitability of the forest for saproxylic species. The methodology was used in a forested boreal landscape of 360 ha to analyze the effects of wind damage on the habitat quality for 27 groups of saproxylic species differing in their requirements for the species, size and decay stage of deadwood objects. A reference plan maximized net present value (MaxNPV) while others either minimized or maximized height differences between adjacent stands. Maximization of height differences resulted in high amount of wind damage and deadwood while minimizing height differences minimized wind damage and the amount of damage-related deadwood. The fourth plan maximized the average habitat suitability index (HSI) of the 27 groups of saproxylic species. The plans were compiled with and without even-flow harvesting constraints for three 10-year periods. Maximization of height differences between adjacent stands resulted in higher HSI values than obtained in the MaxNPV plan or in the plan than minimized height differences between adjacent stands. The average HSI of shade-demanding species correlated negatively with the amount of harvested timber. No strong correlations were found for light-demanding and indifferent species.

At what carbon price forest cutting should stop

T he carbon sink of boreal forests can be increased by paying forest landowners for carbon sequestration and taxing carbon releases. The aim of the study was to analyze the eff ect of carbon pricing on optimal forest management when forests are managed for maximal discounted benefi ts from timber production and carbon payments. A0.5% random sample of all private forest stands of Finland was used in the analyses(48,842 stands). Calculations were performed for a 100-year time horizon. It was assumed that the carbon balance(diff erence between sequestrated carbon and released carbon) in the forest(trees and soil) or the carbon balance of forestry(trees, soil and wood-based products)was subsidized(positive balance) or taxed(negative balance)by 0, 50, 100 or 150 € t-1, corresponding to CO2 prices of 0,13.6, 27.3 or 40.9 € t-1, respectively. The results showed that paying forest landowners 150 € t-1 of carbon sequestrated in forests would lead to the cessation of all cuttings everywhere in Finland for at least 100 years. In the northern part of the country, a carbon price of 100 € t-1 would be enough to make the no-cutting management economically optimal.A low carbon price had the highest relative impact(value ofincreased sequestration divided by the cost of carbon payments). The benefi t/cost ratio of carbon subsidies was higher in the northern part of boreal zone than in the southern parts. Subsidizing within-forest carbon sequestration by 50 € t-1 would increase the carbon sequestration of Finnish forestry by 50%, ranging from 36%(south Finland) to 116%(north Finland). A payment of 100 € t-1 or more would increase carbon sequestration by 70%, which is nearly the maximum possible increase that can be obtained by carbon subsidies.

Height increment of understorey Norway spruces under different tree canopies

Background:Stands having advance regeneration of spruce are logical places to start continuous cover forestry(CCF) in fertile and mesic boreal forests.However,the development of advance regeneration is poorly known.Methods:This study used regression analysis to model the height increment of spruce understorey as a function of seedling height,site characteristics and canopy structure.Results:An admixture of pine and birch in the main canopy improves the height increment of understorey.When the stand basal area is 20 m2ha-1 height increment is twice as fast under pine and birch canopies,as compared to spruce.Height increment of understorey spruce increases with increasing seedling height.Between-stand and within-stand residual variation in the height increment of understorey spruces is high.The increment of 1/6 fastest-growing seedlings is at least 50%greater than the average.Conclusions:The results of this study help forest managers to regulate the density and species composition of the stand,so as to obtain a sufficient height development of the understorey.In pure and almost pure spruce stands,the stand basal area should be low for a good height increment of the understorey.

Carbon forestry is surprising

Background： Forestry offers possibilities to sequestrate carbon in living biomass, deadwood and forest soil, as we as in products prepared of wood. In addition, the use of wood may reduce carbon emissions from fossil fuels. However, harvesting decreases the carbon stocks of forests and increases emissions from decomposing harvest residues. Methods： This study used simulation and optimization to maximize carbon sequestration in a boreal forest estate consisting of nearly 600 stands. A reference management plan maximized net present value and the other plans maximized the total carbon balance of a 100-, 200- or 300-year planning horizon, taking into account the carbon balances of living forest biomass, dead organic matter, and wood-based products Results： Maximizing carbon balance led to low cutting level with all three planning horizons. Depending on the time span, the carbon balance of these schedules was 2 to 3.5 times higher than in the plan that maximized net present value. It was not optimal to commence cuttings when the carbon pool of living biomass and dead organic matter stopped increasing after 150-200 years. Conclusions： Letting many mature trees to die was a better strategy than harvesting them when the aim was to maximize the long-term carbon balance of boreal Fennoscandian forest. The reason for this conclusion was that large dead trees are better carbon stores than harvested trees. To alter this outcome, a higher proportion of harvested trees should be used for products in which carbon is stored for long time.

Delineating forest stands from grid data

Background: Forest inventories are increasingly based on airborne laser scanning(ALS). In Finland, the results of these inventories are calculated for small grid cells, 16 m by 16 m in size. Use of grid data in forest planning results in the additional requirement of aggregating management prescriptions into large enough continuous treatment units. This can be done before the planning calculations, using various segmentation techniques, or during the planning calculations, using spatial optimization. Forestry practice usually prefers reasonably permanent segments created before planning. These segments are expected to be homogeneous in terms of site properties, growing stock characteristics and treatments. Recent research has developed methods for partitioning grids of ALS inventory results into segments that are homogeneous in terms of site and growing stock characteristics. The current study extended previous methods so that also the similarity of treatments was considered in the segmentation process.The study also proposed methods to deal with biases that are likely to appear in the results when grid data are aggregated into large segments.Methods: The analyses were conducted for two datasets, one from southern and the other from northern Finland.Cellular automaton(CA) was used to aggregate the grid cells into segments using site characteristics with(1)growing stock attributes interpreted from ALS data,(2) predicted cutting prescriptions and(3) both stand attributes cutting prescriptions. The CA was optimized for each segmentation task. A method based on virtual stands was used to correct systematic errors in variable estimates calculated for segments.Results: The segmentation was rather similar in all cases. The result is not surprising since treatment prescriptions depend on stand attributes. The use of virtual stands decreased biases in growth prediction and in the areas of different fertility classes.Conclusions: Automated stand delineation was not sensitive to the type of variables that were used in the process.Virtual stands are an easy method to decrease systematic errors in calculations.

Which type of forest management provides most ecosystem services？

Background： Forest ecosystems are increasingly seen as multi-functional production systems, which should provide, besides timber and economic benefits, also other ecosystem services related to biological diversity, recreational uses and environmental functions of forests. This study analyzed the performance of even-aged rotation forest management （RFM）, continuous cover forestry （CCF） and any-aged forestry （AAF） in the production of ecosystem services. AAF allows both even-aged and uneven-aged management schedules. The ecosystem services included in the analyses were net present value, volume of harvested timber, cowberry and bilberry yields, scenic value of the forest, carbon balance and suitability of the forest to Siberian jay. Methods： Data envelopment analysis was used to derive numerical efficiency ratios for the three management systems. Efficiency ratio is the sum of weighted outputs （ecosystem services） divided by the sum of weighted inputs. The linear programing model proposed by Charnes, Cooper and Rhodes was used to derive the weights for calculating efficiency scores for the silvicultural systems. Results and conclusions： CCF provided more ecosystem services than RFM, and CCF was more efficient than RFM and AAF in the production of ecosystem services. Multi-objective management provided more ecosystem services （except harvested timber） than single-objective management that maximized economic profitability. The use of low discount rate （resulting in low cutting level and high growing stock volume） led to better supply of most ecosystems services than the use of high discount rate. RFM where NPV was maximized with high discount rate led to particularly poor provision of most ecosystem services. In CCF the provision of ecosystem services was less sensitive to changes in discount rate and management objective than in RFM.

Evaluation of different approaches to individual tree growth and survival modelling using data collected at irregular intervals-a case study for Pinus patula in Kenya

Background： The minimum set of sub-models for simulating stand dynamics on an individual-tree basis consists of tree-level models for diameter increment and survival. Ingrowth model is a necessary third component in uneven-aged management. The development of this type of model set needs data from permanent plots, in which all trees have been numbered and measured at regular intervals for diameter and survival. New trees passing the ingrowth limit should also be numbered and measured. Unfortunately, few datasets meet all these requirements. The trees may not have numbers or the length of the measurement interval varies. Ingrowth trees may not have been measured, or the number tags may have disappeared causing errors in tree identification. Methods： This article discussed and demonstrated the use of an optimization-based approach to individual-tree growth modelling, which makes it possible to utilize data sets having one or several of the above deficiencies. The idea is to estimate all parameters of the sub-models of a growth simulator simultaneously in such a way that, when simulation begins from the diameter distribution at the first measurement occasion, it yields a similar ending diameter distribution as measured in the second measurement occasion. The method was applied to Pinus patula permanent sample plot data from Kenya. In this dataset, trees were correctly numbered and identified but measurement interval varied from 1 to 13 years. Two simple regression approaches were used and compared to the optimization-based model recovery approach. Results： The optimization-based approach resulted in far more accurate simulations of stand basal area and number of surviving trees than the equations fitted through regression analysis. Conclusions： The optimization-based modelling approach can be recommended for growth modelling when the modelling data have been collected at irregular measurement intervals.

Developing Weibull-based diameter distributions for the major coniferous species in Heilongjiang Province,China

Diameter distribution models play an important role in forest inventories,growth prediction,and management.The Weibull probability density function is widely used in forestry.Although a number of methods have been proposed to predict or recover the Weibull distribution,their applicability and predictive performance for the major tree species of China remain to be determined.Trees in sample plots of three even-aged coniferous species(Larix olgensis,Pinus sylvestris and Pinus koraiensis)were measured both in un-thinned and thinned stands to develop parameter prediction models for the Weibull probability density function.Ordinary least squares(OLS)and maximum likelihood regression(MLER),as well as cumulative distribution function regression(CDFR)were used,and their performance compared.The results show that MLER and CDFR were better than OLS in predicting diameter distributions of tree plantations.CDFR produced the best results in terms of fitting statistics.Based on the error statistics calculated for different age groups,CDFR was considered the most suitable method for developing prediction models for Weibull parameters in coniferous plantations.

Stand management optimization——the role of simplifications

Background:Studies on optimal stand management often make simplifications or restrict the choice of treatments,Examples of simplifications are neglecting natural regeneration that appears on a plantation site,omitting advance regeneration in simulations,or restricting thinning treatments to low thinning(thinning from below).Methods:This study analyzed the imparts of simplifications on the optimization results for Fennoscandian boreal forests.Management of pine and spruce plantations was optimized by gradually reducing the number of simplifying assumptions.Results:Forced low thinning,cleaning the plantation from the natural regeneration of mixed species and ignoring advance regeneration all had a major impact on optimization results.High thinning(thinning from above) resulted in higher NPV and longer rotation length than thinning from below.It was profitable to leave a mixed stand in the tending treatment of young plantation.When advance regeneration was taken into account,it was profitable to increase the number of thinnings and postpone final felling.In the optimal management,both pine and spruce plantation was gradually converted into uneven-aged mixture of spruce and birch.Conclusions:The results suggest that,with the current management costs and timber price level,it may be profitable to switch to continuous cover management on medium growing sites of Fennoscandian boreal forests.