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.     

Carbon sequestration in Spanish Mediterranean forests under two management alternatives: a modeling approach

Management implications associated with two different silvicultural strategies in two Spanish pine forests (Scots pine stands in northern Spain and Mediterranean Maritime pine stands in Central Spain) were explored. Whole-stand yield, growth models and individual tree equations were used to estimate carbon stock in forests under different silvicultural alternatives and site indexes. Each alternative was evaluated on the basis of the land expectation value (LEV). Results reveal the appropriateness of implementing carbon payments, because it can clearly complement traditional management objectives in economic terms. Longer rotations on the poorest sites result in a positive economic return by introducing carbon output. The proportion of carbon stock in the final harvest relative to total fixed carbon is always higher in long rotation scenarios. However, short rotation systems produce the highest values of carbon MAI regardless of site index. The impact of carbon price is higher on the Maritime pine stands than on Scots pine stands. For both the species, changes in the discount rate have a minor impact on Carbon LEV. Notwithstanding, the proportion of total LEV due to carbon is greater when the discount rate increases.     

Forest management effects on in situ and ex situ slash pine forest carbon balance

In this study we analyzed the effect of silviculture on carbon (C) budgets in Pinus elliottii (slash pine) plantations on the southeastern U.S. Coastal Plain. We developed a hybrid model that integrates a widely used growth and yield model for slash pine with allometric and biometric equations determined for long-term C exchange studies to simulate in situ C pools. The model used current values of forest product conversion efficiencies and forest product decay rates to calculate ex situ C pool. The model was validated from a variety of sources, accurately simulating C estimates based on multiple measurement techniques and sites. Site productivity was the major factor driving C sequestration in slash pine stands. On high productivity sites, silvicultural schemes that promote sawtimber-type products are more suitable for increasing C storage (even not taking in account the consequent economical revenues associated with sawtimber production). When rotation length was increased from 22 to 35 years on unthinned and thinned stands, respectively, we estimated net increments of 26 and 20 MgC ha⁻¹ in average C stock of the first five rotations. Even though in situ C pool in slash pine accounts for most of this net increment, C in sawtimber products increased from 8 and 14 to 23 and 24 MgC ha⁻¹, on unthinned and thinned stands, respectively. Thinning effects on net C stock depended on intensity and timing of intervention, mainly due to changes in diameter classes that promote higher proportion of long-lived products. Emissions associated with silvicultural activities, including transportation of logs to the mill, are small compared to the magnitude of net C sequestration, accounting for between 2.2 and 2.3% of gross C stock. This slash pine plantation C sequestration model, based on empirical and biological relationships, is appropriate for use in regional C stock assessments or for C credit verification.     

An Economic Analysis to Aid the Marginal Decision on Rotation Length: I. Presentation of the Principle

This economic analysis of the rotation problem is based on theactual decision which the forest manager must make for everystand, i.e. whether to fell now or in five years or so. Thismarginal decision becomes important, and need only be carefullyconsidered, when the stand nears financial maturity. The marginalapproach is perhaps the most realistic approach to the problemof financial rotations. The financial decision is based uponthe recognized criterion of maximum net discounted revenue (N.D.R.)per unit total invested capital. Certain theories of productioneconomics are combined with the practical methods of forestvaluation. These principles are used to present the economicanalysis as a graphical choice of the rotation at which thecombined yield of pulpwood and sawtimber maximizes N.D.R. Finally,current product prices are introduced and the optimum rotationis found. These current prices may genuinely be assumed to beconstant for any particular five-year period. A subsequent paperwill develop the basic principle into a multi-product technique.The principle is presented essentially as a fundamental techniquefor the projects of forest economics: its application and useare considered here in general terms, and for a specific Sitkaspruce (Picea sitchensis) stand type. An instrument for therapid determination of financial rotation and N.D.R. has beendeveloped from this principle of rotation determination.     

3-level MCGP: an efficient algorithm for MCGP in solving multi-forest management problems

The efficiency gains when harvests are determined using the Faustmann approach instead of Maximum Sustained Yield (MSY), Forest Rent or some silvicultural rules were studies. The analysis was based on a variable-density stand growth model and computations over all admissible combinations of initial stand age and basal area for Finnish Norway spruce and Scots pine sites. Following MSY or Forest Rent led to a major reduction in the economic value of especially highly stocked stands. Finnish silvicultural recommendations (an example of silvicultural rules) encouraged production of higher than optimal quality timber. Applying Forest Rent, MSY or silvicultural recommendations led to respective reductions of 63%, 30% and 13% in the value of a typical conifer forest at a 4% rate of interest. The results also showed that an increase in the rate of interest may lengthen the ongoing rotation if the initial state falls outside the optimal path initiated at bare land.     

六个杨树无性系苗木生长、生物量和光合作用的研究*

六个杨树无性系苗木（２年生根１年生于）叶面积、苗高和地径的季生长用Ｒｉｃｈａｒｄｓ方程模拟，根据模拟参数分别计算最大绝对生长速率，平均绝对生长速率，生长期和拐点。结果为：六个无性系之间在生长速率、拐点和生长期方面均有明显的差异；最好的欧美杨６４号生长季末的总生物量是赤峰杨３４号的六倍多；六个无性系的总生物量与它们的总叶面积、平均单个叶片的面积、叶面积的平均生长速率和每株树的日净光合总量等呈正相关，而与单位叶面积的日净光合总量呈负相关；总生物量生产依赖于叶面积、苗高、直径的生长速率及其生长期。     

On the effect of volatile stumpage prices on the economic attractiveness of a silvicultural transformation strategy

This paper evaluates the economic attractiveness of a silvicultural transformation strategy, focussing on risk, as a result of the volatility of stumpage prices. Based on a situation of a 58-year-old spruce stand [Picea abies (L.) Karst.], which can be found near Freising (Upper Bavaria, Germany), a growth model (silva 2.2) was used to project the stand development. Growth simulations were conducted for a specific transformation strategy, from regular to irregular age structure on the one hand, and for a conservative silvicultural strategy (thinning, clear-cut, reforestation), on the other hand. The transformation strategy was aimed at achieving an uneven-aged stand structure. It was based on early initiation, small-scale regeneration cuts carried out frequently and periodically. The harvests were, therefore, more evenly distributed over the time period analysed. Unlike transformation, even-aged silviculture consisted of relatively strong thinning up to age 68, followed by weak or no interventions up to age 98, the rotation age, aiming to maximise mean value increment. Both strategies were modelled over a time period of 198 years. Based on the growth data, a Monte Carlo model was used to estimate the financial results of both strategies. The stumpage price was assumed as a random variable with a probability density which follows a normal distribution. From the results of 1000 simulations for each strategy, distributions of the net present value (NPV) were calculated. Due to the complexity of the growth model silva, the calculations, being valid not for a forest enterprise but for one single stand, were restricted so that the time for every intervention was fixed, regardless of the stumpage price. Since the revenues produced by transformation were more evenly distributed over time than those achieved by the conservative even-aged strategy, the latter was far more influenced by very low or very high prices at the time of the clear-cuts. This fact caused a much smaller variation in NPV of the transformation. Parallel to this result, the probability of producing a deficit (that is to achieve a negative NPV) was lower for the transformation. The financial effect shown in this study in favour of transformation certainly compensates for a potentially higher risk of storm damage during the transformation treatment.     

Profitability of alternative management regimes in Scots pine stands on drained peatlands

In drained, forested peatlands, ditch network maintenance (DNM) is often considered necessary for tree growth, but it also constitutes additional management costs. Commercial thinnings, in turn, in addition to their silvicultural benefits, are generally applied to enhance the financial performance of stand management but results from peatland stands are scarce. In this study, our aim was to find financially feasible management practices for Scots pine-dominated stands on drained peatland sites in Finland. Using mainly inventory data sets, we compiled altogether 29 typical model-stands for four climatic areas, four site types, and two stand conditions according to need for silvicultural care. We used MOTTI stand simulator to predict the development of the model-stands according to different management regimes consisting of various combinations of 0–2 DNM and 0–2 thinnings with different timings and thinning intensities. We then calculated and compared the financial feasibility of the regimes using net present value (NPV; discount rate 3%) analysis. The separate effect of DNM on the profitability was marginal, but the positive effect of thinnings was clear. The harvesting removals varied within a wide range, depending on the timing and intensity of thinnings, but on average, the NPV doubled due to the thinnings. In the stands of initially good silvicultural condition, regimes including only one thinning and a DNM operation generally displayed a good financial result. In the stands of initially poor silvicultural condition due to neglected early care, regimes with two thinnings produced the best NPV regardless of the often low-yielding first thinning.     

Canopy fuel characteristics in relation to crown fire potential in pine stands: analysis, modelling and classification

Crown fire occurrence and subsequent crown fire behaviour are strongly dependent on canopy fuel characteristics, especially canopy fuel load (CFL), canopy bulk density (CBD) and canopy base height (CBH). Therefore, quantification of such variables is required for the appropriate selection of silvicultural treatments aimed at reducing susceptibility to crown fire. Data from the IV Spanish National Forest Inventory and individual tree biomass dry weight equations were used to estimate the canopy fuel characteristics of four representative types of pine stands in north-western Spain. Probability of crown fire initiation and crown fire rate of spread were simulated by using the mean surface fuel load observed for each type of pine in this area and assuming different burning conditions. The results indicate that a 22.13 % of the sample plots analysed showed a rather high potential for active crown fire spread under moderate burning conditions, and this value increases to 69.27 % under extreme burning conditions. Equations relating the canopy fuel characteristics to common stand variables (stand density, basal area and dominant height) were fitted simultaneously for each pine, and weighting factors for heteroscedasticity were included. The models explained more than 93.90, 74.70 and 69.42 % of the observed variability in CFL, CBD and CBH, respectively. Basal area was the most important variable for estimating CFL and CBD while dominant height explained most of the observed variability in CBH. The use of the fitted equations together with existing dynamic growth models and fire management decision support systems will enable assessment of the crown fire potential associated with different silvicultural alternatives used in these types of pine stands.     

Development strategies for privately owned forestry in the mountainous region of Sweden

Forestry in Sweden as well as in other European countries is characterised by intense and increasing international competition resulting in decreasing roundwood prices in real terms. This is especially the situation in the mountainous region of Sweden with long transportation distances between the felling site and the processing industries located at the coast. The question arises whether forestry must be run more extensively than at present to achieve the optimal rate of silvicultural activities compared with the amount of timber cut. With this in mind, optimising economic analyses have been performed at the stand level as well as at the level of forest estates. Results of the analyses reveal that more intensive thinning (more frequent operations) and shorter rotation periods would increase profit and offset continuously decreasing roundwood prices. Intensive pre-commercial thinning (cleaning) is especially important for profitability of the subsequent thinnings and the final cut. The large number of cuts during the rotation will increase logging costs. However, this will be more than offset by the increasing production of economically matured dimensions of timber, an effect that will be still more pronounced when using new harvesting technology. Moreover, frequent high thinning operations (thinning ‘from above’ or removal of dominant trees) will result in more dense wood close to the pith, more evenly distributed year rings, and fewer and smaller knots in the lower part of the stem — in other words more valuable roundwood which will justify high transportation costs. Several biological and technical aspects of these treatment programs are discussed in the paper.     

A financial evaluation of two contrasting silvicultural systems applicable to Pinus taeda grown in north-east Uruguay

The Loblolly pine (Pinus taeda L.) plantation area in north-east Uruguay was 108 000 ha in 2008. Recent industrial capacity developments have resulted in major structural changes. Silvicultural system selection depends on site productivity, costs, timber prices and public policies. This study aimed to assess economic returns for two silvicultural systems in north-east Uruguay, in scenarios with and without a plantation subsidy: System I, with a short, 12-year rotation, primarily for small logs; and System II, with a longer, 24-year rotation. For System I, the underbark volume was 198 m³ ha^?1 (mean annual increment16.5 m³ ha^?1 y?¹) and land expectation value (LEV) at a 9.7% discount rate was US$561 ha^?1 and US$442 ha^?1, with and without subsidy, respectively. System II resulted in 318 m³ ha^?1 underbark volume (13.2 m³ ha^?1 y^?1) and the LEV was US$860 ha^?1 and US$771 ha^?1, with and without subsidy, respectively. System I was more profitable than extensive cattle husbandry only when the distance to mill was equal to or less than 60 km and wood millyard prices were equal to or higher than US$27.8 m^?3 and US$28.8 m^?3 with and without subsidy, respectively. Values for System II, in which the main product was a mix of sawlog diameters, were positive and higher than those for System I, both with and without subsidy. If a company invested in forest plantations without due provision for early silvicultural treatments, such as pruning and precommercial thinning, a high risk of financial loss would ensue. Long-rotation sawtimber regimes similar to System II would be more profitable and offer a lower risk of financial losses. The results suggest subsidy withdrawal in Uruguay should not lead to changes in silvicultural systems; in fact, it rendered regimes designed for low-value wood, such as System I, even less advisable.     

Dynamics of ecosystem services in <Emphasis Type="Italic">Pinus sylvestris</Emphasis> stands under different managements and site quality classes

Timber and biodiversity are considered two antagonistic ecosystem services (ES), largely influenced by silviculture and site ecological conditions. In order to address the trade-offs between these two ES over time, we performed a retrospective study at compartment level in the Pinus sylvestris forests of the Spanish Central Mountain System. Archival data from Management Plans for eight forests with contrasting silvicultural systems (uniform shelterwood system, group shelterwood system, irregular shelterwood system,) and three different site quality classes were analysed. Timber production was assessed through stand volume, harvested timber volume and a stand volume index. Biodiversity was examined through structural diversity (Gini index, Shannon tree size diversity index, Simpson’s reciprocal index and evenness index, all applied to diameter classes) and the abundance of large living trees. For all silvicultural systems investigated, stand volume and harvested timber volume have grown since the beginning of the management plans (beginning of the twentieth century in some forests). The largest yields of timber corresponded to the best quality sites with more intensive silvicultural treatments (uniform and group shelterwood systems). The uniform shelterwood system showed lower figures for structural diversity, though not always significant. The best site qualities maintained notable structural diversity values, even under the most intensive management system. The application of the different management systems over decades has revealed a synergy between timber production and structural diversity, particularly in those systems maintaining more than one age class, although results are conditioned by forest harvesting history. The interaction between historical silvicultural treatment and site quality has been identified as an important source of information to understand forest dynamics and functioning of ES provision.     

Modelling near-natural silvicultural regimes for beech – an economic sensitivity analysis

Near-natural silvicultural regimes for beech (Fagus sylvatica L.), in the form of uneven-aged selective felling, receive increasing interest in Denmark. This is partly due to the ability of this system to preserve the forest climate and maintain important ecological functions such as bio-geochemical cycling and biodiversity conservation. The optimal age to convert from even-aged management to uneven-aged selective felling seems to be as early as possible, about 55 years, when sufficient natural seeding can be expected. A fixed conversion period of 100 years is assumed. This regime, here analysed by the use of a so-called chessboard model, appears to be economically superior to clear felling if the regime is initiated in medium-aged stands down to the age of 55 years, assuming a high site quality and a real discount rate of 3% per annum. Uneven-aged selective felling seems to be economically superior to even-aged natural regeneration, assuming that: (i) the stumpage prices of regeneration harvests are increased by 10%, or (ii) the diameters of regeneration harvests exceed those of even-aged management by about 17% simultaneous with an identical increase of the maximum stumpage price. Clear felling seems to be the more profitable regime only if: (i) the stand is close to the economic optimal rotation age for clear felling, and (ii) when the stumpage prices of regeneration harvests achieved by use of the uneven-aged selective management regime are reduced by 10% or more due to quality defects caused by prolonged rotation ages. The above results are sensitive to variation of stumpage prices, but less so to variation of regeneration costs associated with near-natural management systems. However, the near-natural silvicultural regimes may be unable to fulfill the liquidity objectives following from the application of traditional management systems.     

Establishing forest tree species on peatland in a reflooded area of the Huleh Valley, Israel

The study evaluates the establishment performance of four treespecies (Ficus carica, Fraxinus syriaca, Salix acmophylla, Platanusorientalis) 3 years after planting in the peatland in the HulehValley. To develop good tree establishment and avoid uprooting,two types of soils were tested as alternatives for the rhizosphere.For each tree 6 m³ of soil (2 x 2 x 1.5 m) were replaced withriver bed alluvium or terra-rossa, in which the tree was planted.Control trees were planted directly in the peat. Changing therhizosphere soil type to river bed alluvium significantly improvedthe establishment and performance of Salix acmophylla and Fraxinussyriaca (survival, height, diameter and canopy shade area).Ficus carica was not affected by changing the soil in the rhizosphere,while Platanus orientalis was affected mainly in canopy shadearea. Terra-rossa improved establishment only of Salix acmophylla;it did not affect the other species.     

Impact of site and provenance on economic return in Nordmann fir Christmas tree production

Abstract

The economic potential of 35 seed lots from Danish landraces of Nordmann fir [Abies nordmanniana (Stev.) Spach.] and seven imported provenances were evaluated for high-value Christmas tree production over a full rotation at six locations in Denmark. Naturally grown Christmas trees were evaluated and no leader length control or trimming of the side branches was allowed, but only simple cutting of double terminal leaders. Seed source as well as site strongly affected the economic revenue. Average net sales price per planted tree ranged over sites from €2.43 to €6.64, and among provenances from €1.38 to €7.06 with an average of €4.95. Changes in prices and grading as seen under cycling market conditions seemed not to affect the economic ranking of the better part of the provenances, whereas discounting the net sales income caused moderate rank changes, reflecting differences in rotation time. Limited seed source by site interactions were present and mainly caused by the slowest growing sources. Among the Danish domesticated seed sources of mostly unknown origin several were as suitable as the tested imported sources. In general, the Danish sources were faster growing than imports, although very large variation was present.     

From a strategic to a tactical forest management plan using a hierarchic optimization approach

The Finnish state forest enterprise, Metsähallitus, defines the regional harvest levels for a 10-year period in a strategic-level natural resources plan. Although this plan defines stand-level harvest schedules for all stands, in practice, it cannot be used, as the harvests need to be clustered in time and in space. It is applied by giving each subregion goals they need to fulfill in a tactical level planning process, and the harvests are manually clustered into predefined groups of adjacent stands (departments). In this study, we developed a hierarchical optimization process making use of departments for clustering the harvests. For each of the departments, 91 different stand-level harvest schedules (plans) were determined using incomes from one period and the forest value at the end as objectives. The department-level plans were then used as alternatives in a region-level goal optimization problem. The resulting hierarchic plan was compared to the stand-level solution of the strategic-level plan which served as a benchmark plan. The hierarchical plan clustered the harvests and achieved the goals set better than the benchmark plan, but the net present income was 3.3% lower. The approach turned out usable, but further developing of the approach is needed to reduce the costs of clustering.     

Modelling mortality of Scots pine (Pinus sylvestris L.) plantations in the northwest of Spain

Mortality is an important element of growth and yield models, especially if only low intensity silvicultural treatments are carried out. The objective of the present study was to develop a model for predicting tree number decline in planted even-aged stands of Scots pine (Pinus sylvestris L.) in Galicia (northwestern Spain). The model was constructed using data from two inventories of a trial network involving 68 permanent plots located in unthinned stands, or stands thinned lightly from below. Two alternatives were tested. In one alternative, a two-step modelling strategy was applied. First, a binary response function predicting the survival probability of all the trees in the stand was constructed, and an equation for reduction in tree number was developed, using only data where death had occurred over the period analyzed. Three different approaches were then used to compare the application of the above-mentioned functions together. In the other alternative, a mortality function for directly predicting the reduction in tree number was fitted, including all plots (with and without occurrence of mortality). Both alternatives provided similar results, showed logical behavior, and performed satisfactorily in evaluation tests. However, in choosing the best strategy for inclusion in a stand-level simulator, the use of the second alternative is recommended because it possesses the path invariance property required in a mortality model.     

Determination of specific gravity of green Pinus taeda samples by near infrared spectroscopy: comparison of pre-processing methods using multivariate figures of merit

Near infrared diffuse reflectance was used for the determination of specific gravity in green Pinus taeda L. wood samples representing simulated increment cores obtained at breast height and merchantable green logs. The effects of using three pre-processing methods (second derivative, multiplicative scatter correction, and orthogonal signal correction) to reduce the scatter observed in the original spectra were evaluated. The effectiveness of each method was assessed in terms of the average predictive ability of the models and in terms of multivariate figures of merit derived from net analyte signal theory. Specific gravity was successfully modeled using green wood samples. No differences in predictive ability among models were found, although more parsimonious regressions were obtained using transformed spectra. The incorporation of figures of merit for the characterization of calibration models proved to be a valuable tool for understanding the effects of the pre-processing alternatives on the final results.     

Pedunculate oak (Quercus robur L.) silviculture in natural stands of NW Spain: Environmental conditioners

Forest management is often carried out in different ways, without any appropriate environmental restrictions. Stands of pedunculate oak (Quercus robur L.) in Galicia (NW Spain) have been harvested by alternating high forest and, mainly, coppice forest. However, some totally inappropriate silvicultural treatments have been used, such as thinning of the best trees and inadequate pruning. The objective of the present study was to analyse how environmental characteristics affect the management of oak forests in Galicia. For this, a botanical inventory was carried out in 39 selected stands of Q. robur and a total of 42 parameters were measured, 4 of which were physiographical, 12 climatic, 19 edaphic and 7 silvicultural. In order to analyse the possible relationships among these variables, the silvicultural data were compared with the other data, by canonical correlation analysis. All parameters were correlated with the silvicultural regime, although the correlation was weak for the floristic data. It is therefore evident that the environmental conditions affect how forest stands should be managed, although this does not imply that more profitable use of the stands cannot be achieved than at present, and alternative silvicultural methods must be found to enable appropriate management and conservation of oak stands.     

Financial performance of using genetically improved regeneration material of Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) in Finland

The financial viability of using improved seed material of Scots pine was assessed in Finnish conditions. Based on a few dozen field trials, a range of genetic gains for height growth was incorporated into a stand simulator. Technically genetic gain was modelled into individual growth models by applying the Chapman-Richards type function and using genetic gain estimates as asymptotic scaling parameters. Stand projections, including the effect of genetic gain, were further converted into monetary terms by calculating bare land values, i.e. BLVs according to the Faustman rotation model. Following this, the financial attractiveness of using improved seed material from Scots pine was determined by comparing the BLVs between stands with and without genetic gain. The study focused on the private forest owner’s point of view, reflecting the primary demand conditions for improved seed material. Comparisons between BLVs indicated that using improved seed material of Scots pine would be financially viable for private forest owners in most parts of Finland, the discount rate being 3%. The main results were robust, with pertinent changes in silvicultural costs and stumpage prices. This study demonstrates the need for financial analysis in decision-making in the context of regeneration material.