An approach for examining the effects of preferential uncertainty on the contents of forest management plan at stand and holding level

A proper forest planning process includes the assessment of the decision-makers’ preferences concerning the future forest use. For some owners, it may be a difficult task to express their preferences exactly and in the form that is required for planning calculations. This study presents a new kind of approach for analyzing the effects of preferential uncertainty. The approach consists of examination of the differences in the actual decision variables in forest planning, i.e. selected treatments for stands between holding-level forest plans. In example calculations, the preferential uncertainty was examined from three different viewpoints: the uncertainty in the weights of the objective variables; the uncertainty in the partial utility function; and the combination of these two uncertainty sources. One thousand preference realizations were generated for each of these uncertainty sources. More than one treatment schedules are proposed for stands that are affected by preferential uncertainty. These stands were detected from among the resulting set of 1,000 forest plans. With this done, two potential decision-making strategies, an adaptive behavior strategy and a threshold proportion strategy, were applied as guides in decision-making for stands, which have more than one treatment alternative selected in the produced optimal forest plans. The adaptive behavior technique required that the forest owner select one treatment alternative for at least one stand that has more than one proposed treatment alternative. The treatment alternatives having frequencies exceeding the given threshold frequency were all accepted simultaneously in the threshold strategy. The main benefit of the approach is to present the effects of uncertainties in a way that can be easily understood by the actual decision-makers. It is a promising tool for practical decision-making situations because at least Finnish non-industrial private forest owners quite often focus on making stand-level forest management decisions. It is also suitable for examinations of other uncertainty sources such as timber prices or inventory data.     

A silvicultural management tool for the Oriental beech (Fagus orientalis Lipsky) forests

Stand density management tools help forest managers and landowners to more effectively allocate growing space so that specific silvicultural objectives can be met. Due to the economic importance of Oriental beech (Fagus orientalis Lipsky) forests in Turkey, a stand density management tool was developed for this species to optimize regeneration success rate and tree growth. For the development of this tool, named stand density management diagram (SDMD), we utilized forest inventory data from the Kastamonu Regional Forest Directorate in Turkey. Previously published forest management approaches and models were employed during the development of the tool. The SDMD illustrates the relation among four forest indexes: the basal area per hectare, number of trees per hectare, forest stand volume per hectare, and quadratic mean diameter of the beech stands. The stand stocking percent (SSP) can be determined based upon any two of these four measurements. The results suggest that SSP is a better predictor of tree growth than BA in Oriental beech forests. The newly developed SDMD allows for a more effective use of the growing space to achieve specific silvicultural objectives including tree regeneration, timber production, thinning planning, and wildlife protection in Oriental beech forests.     

Consideration of strong winds, their directional distribution and snow loading in wind risk assessment related to landscape level forest planning

Forest planning needs to assess various risks that may cause economic or other losses to forest owners. This study aimed at developing a wind risk assessment method, which considers the occurrence and directional distribution of strong winds, and the effect of snow loads and support by neighbouring trees on the expected wind damage. For this purpose, regression models were developed for predicting the critical wind speeds needed to uproot Scots pine, Norway spruce and birch trees at the downwind stand edges in Finnish conditions under unfrozen soil conditions, based on the characteristics of both downwind and upwind stand, and additional snow load on tree crowns. Furthermore, a risk index was developed for the forest landscape, based on the critical wind speeds of stands, occurrence of strong winds and their directional distribution, and the prevailing snow loading in the region. Thereafter, the mean risk index was used as an objective variable in heuristic optimization in forest planning to demonstrate how the optimal cuttings and the spatial layout of the landscape may change depending on the wind and snow conditions and the support that trees provide to each other. Our results show that the directional distribution of strong winds shape the optimal forest landscape structure markedly. Consideration of snow loading in the calculation of critical wind speeds increased the mean risk clearly and produced slightly more aggregated landscape structures in terms of tree height. The consideration of support that neighbouring trees provide to each other had minor effects. To conclude, the consideration of risk of wind induced damages in forest planning calculations clearly affects the selected cutting strategies and impacts the spatial layout of the landscape.     

Modelling site quality and individual-tree growth in pure and mixed Pinus brutia stands in north-east Greece

? Simulation tools, based on individual tree growth and mortality models can produce the most detailed predictions of forest stand development under different management schedules. These models allow the manager to predict the development of any type of stand (even- and uneven-aged, and pure and mixed stands).

? Different model approaches and predictors are required for pure even-aged or mixed uneven-aged forest stands. This study developed and compared two sets of models which enable tree-level simulation of the development of pure and mixed stands of Pinus brutia in north-east Greece. The first set of models for even-aged forestry consists of site index models, diameter growth models, tree height models, and mortality models. The second set, which is for uneven-aged forestry, uses a past growth index instead of a site index.

? The simulations and overall fitting statistics suggest that the two types of models provide realistic and accurate predictions of forest stand development and allow one to simulate the development of complex Pinus brutia stand structures in Dadia National Park forests.

? The advantages of the two approaches are discussed and it is suggested that the growth index is an effective predictor of site quality and the set of models which used such variable as predictor performed in a similar way as the models using site index, which require more information and a given stand structure (even-aged).

     

Comparison of treewise and standwise forest simulators by means of quantile regression

Predicting forest development under varying treatment schedules forms the basis of forest management planning. The actual growth predictions are made with a forest simulator which includes growth equations and additional models for predicting a number of varying tree, forest and site properties. Forest growth simulators typically include either tree-level or stand-level growth models, but these two approaches have not been thoroughly compared. We set out here to compare these two approaches with the SIMO simulator framework in a small data set from southern Finland based on 60 sample plots in 30 stands, the development of which was known for 20 years. The stands chosen were very dense, so that the simulators could be tested under extreme conditions. The results show that the stand-level model is more accurate in almost all cases and its computational burden is much lower. It could therefore be advisable to use tree-level models for short-term predictions, which would ensure detailed information on forest structure for planning the near-future operations. Stand-level models would be more advisable in longer term predictions, especially when accurate volume estimates are considered more important than the forest structure. The errors observed in these simulators were analysed further by quantile regression, which allows empirical estimates of confidence intervals to be obtained for the simulator.     

Predicting stand damage and tree survival in burned forests in Catalonia (North-East Spain)

The study developed models for predicting the post-fire tree survival in Catalonia. The models are appropriate for forest planning purposes. Two types of models were developed: a stand-level model to predict the degree of damage caused by a forest fire, and tree-level models to predict the probability of a tree to survive a forest fire. The models were based on forest inventory and fire data. The inventory data on forest stands were obtained from the second (1989–1990) and third (2000–2001) Spanish national forest inventories, and the fire data consisted of the perimeters of forest fires larger than 20 ha that occurred in Catalonia between the 2nd and 3rd measurement of the inventory plots. The models were based on easily measurable forest characteristics, and they permit the forest manager to predict the effect of stand structure and species composition on the expected damage. According to the stand level fire damage model, the relative damage decreases when the stand basal area or mean tree diameter increases. Conversely, the relative stand damage increases when there is a large variation in tree size, when the stand is located on a steep slope, and when it is dominated by pine. According to the tree level survival models, trees in stands with a high basal area, a large mean tree size and a small variability in tree diameters have a high survival probability. Large trees in dominant positions have the highest probability of surviving a fire. Another result of the study is the exceptionally good post-fire survival ability of Pinus pinea and Quercus suber.     

Nature conservation and timber production in areas with fragmented ownership patterns

Forestry has transformed the tree species composition and structure of Swedish forests. The fragmented ownership pattern in areas with non-industrial private forest ownership (NIPF), in combination with these forestry practices, have created fragmented forests with relatively low proportions of habitat types important to many species. Ecological landscape planning has been suggested and tested as a mean for integrating nature conservation and timber production in Sweden. However, ecological landscape planning concepts have been developed for areas with homogenous ownership patterns and not for areas with fragmented ownership. In this study, stands that are voluntarily set aside by individual forest owners were examined in terms of nature conservation value, and compared to randomly selected stands obtained by Monte Carlo simulation. In order to obtain rather detailed data about the set-aside stands, semi-standardized interviews were carried out directly with forest owners in three landscape areas dominated by NIPF. The interviews showed that 26 out of 29 forest owners could locate some stands where they did not have high requirements for timber yield. These stands had higher than average local and spatial nature conservation value as a result of stand structure, composition and location in the landscape. The stands did not have a random location or size, being found closer to key habitats as well as forming equally large or larger patches than other stands. These stands are suggested to form a basis for ecological landscape planning as forest owners seem to have some kind of ‘common view’ of which stands to set aside. This common view could be used to coordinate the contribution made by individual forest owners to nature conservation in areas with fragmented ownership patterns.     

用计算机模拟闽粤栲天然林生长模型

通过建立单木生长模型、林木枯死模型和林分生长模型来模拟闽粤栲天然林生长规律,结果表明:用这3个模型对所调查样地内林木蓄积进行预测,作为林木蓄积量理论计算值,以二元材积表查表得到的蓄积量作为林木蓄积量的实际值,其精度可达94.15%。这些模型对于模拟闽粤栲天然林的生长规律具有一定的应用价值。     

Connecting an architectural plant model to a forest stand dynamics model—application to Austrian black pine stand visualization

• Context  

Forest stand dynamics models simulate the growth of trees in stands; based on field measurements and system knowledge, they provide a relatively precise representation of forest growth and are well adapted for forest management purposes. Architectural models describe the structure of plants according to ontogenetic development processes; as a support of biomass production and partitioning at organ scale, they simulate individual tree development.     

Optimising the management of even-aged Pinus sylvestris L. stands in Galicia, north-western Spain

The study developed management instructions for even-aged Pinus sylvestris stands in Galicia (north-western Spain). Although these stands are highly productive, no silvicultural management schedules have been proposed so far for them on the basis of systematic analyses. This study used data from 2160 optimisation runs to develop the management instructions. Land expectation value was used as the objective function. Different prices of timber assortments were considered and the discounting rate was varied from 0.5 to 5%. The method employed to find the optimal management schedules of stands was the combination of a stand simulator and an optimisation algorithm. The simulator uses an earlier growth and yield model for Pinus sylvestris in Galicia to predict the future development of the stand with a given management schedule while the optimisation algorithm seeks the best management schedule among all the possible alternatives. The results show that optimal rotation lengths vary widely between 42 and 170 years, high discounting rates and good site quality resulting in the shortest rotations. Four thinnings were found to be suitable for all sites and discounting rates. With discounting rates higher than 1% the commercial thinnings should gradually decrease the stand basal area towards the end of the rotation.     

基于目标树经营的抚育采伐对云冷杉针阔混交林空间结构的影响

[目的]以长白山林区云冷杉针阔混交林为研究对象,分析目标树抚育采伐前后云冷杉针阔混交林空间结构参数的变化,探索目标树抚育采伐对森林空间结构的影响。[方法]基于6块面积1 hm~2的样地,首先遵循近自然森林经营的原理进行林木分类,选定目标树,伐除干扰树;再结合结构化森林经营的原理,计算并分析抚育采伐前后目标树空间结构参数和林分空间结构评价指数的变化。[结果]表明:经目标树抚育采伐后(1)目标树空间结构单元内的树种隔离程度得到进一步提高;林木透光条件有所改善;目标树的竞争压力得以减小;林木空间分布格局总体上得到优化。(2)林分空间结构评价指数进一步提高,林分空间结构水平稳中有升。[结论]通过采取合理的目标树抚育采伐措施能兼顾改善单木水平和林分水平的空间结构状况,在实现优化目标树空间结构的同时,保证林分整体空间结构的稳定。从目标树抚育采伐对林分整体空间结构的影响来看:所有样地的林分空间结构状况均得到进一步改善。     

系统收获表研究的概念和功能(英文)

传统收获表是指某一树种在特定地区和管理体系下，以立地条件和年龄为变量描述林分平均生长过程的数表．林分密度管理图是根据林分密度效果编制的可预测林分平均收获的图．通过与传统收获表和林分密度管理图的概观比较和探讨，该文系统地阐述了系统收获表的概念和功能．系统收获表的基本特点是为预测现实林分在不同立地条件和管理体系下生长过程的计算机程序．因此，系统收获表能描述在多维变量（如年龄、立地条件、林分密度、胸径和树高）条件下的现实林分和单木的无数生长过程     

Determination of number of stems in coniferous forest stands by means of aerial photo‐interpretation

Two models for determination of the number of stems per hectare in forest stands (N) from attributes derived by aerial photo‐interpretation were developed. The models relied on the assumption that N could be determined by dividing the total stand volume per hectare with the volume of the “average tree”; defined by stand mean height and the diameter corresponding to mean basal area of a stand. Input variables of the models were stand mean height, crown closure and site quality. Additionally, model II required input of average stand volume per hectare and average mean diameter derived from stratified field sample plot inventories. Material for 143 coniferous stands was used for the testing of the models. The stands were recorded by intensive field measurements. Aerial photographs at the approximate scale of 1:15 000 were used for photo‐interpretation. The N value was underestimated in model I by 5.4–47.0%. The standard deviation for the differences was 15.2–26.2% for mature stands and 41.4–44.2% for young thinning phase stands. For model II, the mean difference between the predicted and observed N value was in the range ‐16.1% to 12.2%.     

Promoting old-growth characteristics and long-term wood production in Douglas-fir forests

Trade-offs among wood production, wood quality and ecological characteristics in the management of harvested forest stands are explored through model simulation of various silvicultural regimes. Long-term production of merchantable wood, production of various types of high-quality wood, and the level of certain quantitative ecological indicators are projected for coniferous forests of Pacific Northwestern USA. The set of ecological indicators used is based on the species composition and physical structure of old, unlogged forest stands. Simulations are performed with an ecological model of forest stand dynamics that tracks the fate of live and dead trees. Short rotations (<50 years) produce the least amount of high-quality wood over the multi-century simulation period. They also fail to generate ecological attributes resembling those of old forest stands. Production of high-quality wood is moderate to high under all rotations of 80 years or more; however, most ecological indicators require longer rotations unless alternatives to clearcutting are applied. Alternatives examined include retention of 15% cover of live tree canopy at each harvest in combination with artificial thinning between harvests. Thinning from below can expedite the development of large live and dead trees, and canopy height diversity without greatly diminishing wood quantity or quality. Proportional thinning retains understory stems, thereby expediting the recruitment of shade-tolerant trees. A possible drawback to thinning, particularly proportional thinning, is the diminished production of clean-bole wood at rotations of 150 and 260 years. It is concluded that most wood quantity, wood quality and ecological objectives can be met with long rotations (ca. 260 years). Certain objectives can be met with shorter rotations (80–150 years) when treatments of thinning and canopy tree retention are applied.     

德国北部挪威云杉林可持续经营中期计划的实例分析

可持续森林经营理论为中期林业计划和收获调整提供了丰富的模型选择,其不同的方法可应用于各种特定的场合和不同经营类型.本文简要回顾了传统的森林计划方法,一种称为"多林分发展"的概念可以用于任意的经营系统,这个概念把森林看作由一系列林分组成,在每一个林分中可以预先制定多种经营措施的选项,每种选项都可以通过木材或其它产品以及消耗的资源计算出一个目标值.这种简单的概念可以应用到大量的不同森林经营场合,它为森林经营者制定切实可行的森林措施和评价森林经营计划提供方法.在本研究中,以德国北部一片包括21个小班的挪威云杉林班的一个中期计划为例,说明"多林分发展"这一经营系统在实际生产中的应用.每个小班具有不同的初始状态,每个小班预设了若干经营选项,根据小班的初始状态、生长模型为各种选项计算各时期的木材产出.在林班的水平上,经营目标方程包括两个组成部分:净现值和均衡木材收获值.用模拟退火的方法来优化总体目标方程值.优化的总体解决方案在为每个小班选定合适的经营选项的同时,在全林的水平上获得最优的经济和均衡产出组合.     

Predicted leaf area growth and foliage efficiency of loblolly pine plantations

Foliage dynamics research is helpful for better understanding the process of forest production and improving silvicultural practice. However, the difficulty of measuring foliage amount has slowed down the research progress. Since leaf area of an individual tree can be reliably predicted from its diameter, growth and yield models that provide detailed information for each diameter class can be used to benefit foliage dynamics research. Simulation results from a growth and yield system for unthinned loblolly pine plantations indicated that foliage area increased with stand age, peaked between ages 36 and 51, and decreased after that. Volume growth increased with leaf area for young stands and decreased for older stands, whereas foliage efficiency consistently decreased with age. Better sites supported higher levels of leaf area index, volume growth, and foliage efficiency. Higher planting densities led to higher maximum leaf area indices and shorter time to reach that level. Initial density had no effect on foliage efficiency through time.     

Spatial harvest scheduling approach for areas involving multiple ownership

This study presents a practical harvest scheduling approach for multiple ownership planning. The approach has both spatial and non-spatial goals, namely, a spatial landscape-level goal to cluster ecologically valuable resources is considered simultaneously with timber production goals. Harvest scheduling is based on the location of the stand, on one hand, and on an economic variable depicting the cutting maturity of the stand, on the other hand. Proximity to valuable resources decreases the likelihood that the stand is cut. Therefore, harvests tend to be located outside potential resource clusters with small and isolated economically mature stands being cut first. In the application of the approach the landscape-level spatial objective was to cluster old forest stands (age⩾80) and simultaneously maintain a predefined cutting volume. A stand's economic cutting maturity was measured with value increment percentage. In the top-down application of the approach the timber harvest target was specified only for the whole planning area. In the bottom-up application it was specified separately for individual holdings, aiming at promoting the acceptability of the plan. The presented approach was clearly able to cluster old forest patches. In the case study area, the mean size of old forest patches increased from 3.4 to 5.7 ha in 30 years in the top-down plan, and to 4.6 ha in the bottom-up plan. An application of the current planning practice (referred to as the reference plan) decreased the mean patch size to 2.9 ha. The presented approach is easy to apply in forest planning practice.     

A density management diagram for Norway spruce in the temperate European montane region

Norway spruce is one of the most important conifer tree species in Europe, paramount for timber provision, habitat, recreation, and protection of mountain roads and settlements from natural hazards. Although natural Norway spruce forests exhibit diverse structures, even-aged stands can arise after disturbance or as the result of common silvicultural practice, including off-site afforestation. Many even-aged Norway spruce forests face issues such as senescence, insufficient regeneration, mechanical stability, sensitivity to biotic disturbances, and restoration. We propose the use of Density Management Diagrams (DMD), stand-scale graphical models designed to project growth and yield of even-aged forests, as a heuristic tool for assessing the structure and development of even-aged Norway spruce stands. DMDs are predicated on basic tree allometry and the assumption that self-thinning occurs predictably in forest stands. We designed a DMD for Norway spruce in temperate Europe based on wide-ranging forest inventory data. Quantitative relationships between tree- and stand-level variables that describe resistance to selected natural disturbances were superimposed on the DMD. These susceptibility zones were used to demonstrate assessment and possible management actions related to, for example, windfirmness and effectiveness of the protective function against rockfall or avalanches. The Norway spruce DMD provides forest managers and silviculturists a simple, easy-to-use, tool for evaluating stand dynamics and scheduling needed density management actions.     

Laser scanning of forest resources: the nordic experience

This article reviews the research and application of airborne laser scanning for forest inventory in Finland, Norway and Sweden. The first experiments with scanning lasers for forest inventory were conducted in 1991 using the FLASH system, a full-waveform experimental laser developed by the Swedish Defence Research Institute. In Finland at the same time, the HUTSCAT profiling radar provided experiences that inspired the following laser scanning research. Since 1995, data from commercially operated time-of-flight scanning lasers (e.g. TopEye, Optech ALTM and TopoSys) have been used. Especially in Norway, the main objective has been to develop methods that are directly suited for practical forest inventory at the stand level. Mean tree height, stand volume and basal area have been the most important forest mensurational parameters of interest. Laser data have been related to field training plot measurements using regression techniques, and these relationships have been used to predict corresponding properties in all forest stands in an area. Experiences from Finland, Norway and Sweden show that retrieval of stem volume and mean tree height on a stand level from laser scanner data performs as well as, or better than, photogrammetric methods, and better than other remote sensing methods. Laser scanning is, therefore, now beginning to be used operationally in large-area forest inventories. In Finland and Sweden, research has also been done into the identification of single trees and estimation of single-tree properties, such as tree position, tree height, crown width, stem diameter and tree species. In coniferous stands, up to 90% of the trees represented by stem volume have been correctly identified from canopy height models, and the tree height has been estimated with a root mean square error of around 0.6 m. It is significantly more difficult to identify suppressed trees than dominant trees. Spruce and pine have been discriminated on a single-tree level with 95% accuracy. The application of densely sampled laser scanner data to change detection, such as growth and cutting, has also been demonstrated.