Estimation of the Gentan probability using the price of logs in private plantation forests

The Gentan probability is defined as the probability that a newly planted forest stand will be harvested at a certain age. In this study, the Gentan probability was estimated using the price of logs, in accordance with the notion that the probability is influenced by economic factors. In order to estimate the Gentan probability, we adopted a probability density function based on the forest owners’ decision-making process, which consisted of a decision criterion, a decision criterion function and a criterion threshold. The price of logs was employed for the criterion, and the decision criterion function was defined as the value of the forest stand based on the price of logs. Moreover, the mechanism of changes in the threshold was formulated based on the random walk concept. The parameters of the suggested Gentan probability were calibrated to fit the harvesting tendencies observed in the past. Finally, the Gentan probability distributions estimated using the prices of logs over the past 20 years were compared with those estimated using felling age means and variances. The two distributions were closely correlated during most years. The proposed Gentan probability model takes advantage of short-term yield predictions such as an analysis of forest owners’ reactions to the current price changes.     

Gentan probability analysis with a state-dependent discrete forest growth model

The previous stochastic models applied for Gentan probability estimation utilized either a stationary or nonstationary Poisson process to describe the forest owners’ harvesting behavior by means of the counting process. A nonstationary Poisson process has the advantage over a stationary Poisson process of capturing a time-dependent change of harvesting events. However, a nonstationary Poisson process can lack one preferred characteristic of the probability theory when utilizing an average growth function with an asymptotic nature of growth. That is, the sum of the derived Gentan probabilities over time does not always become unity. In this paper, we introduce a state-dependent discrete forest growth model with an asymptotic nature of growth to overcome the problem, then propose a stochastic model applied for Gentan probability estimation. The Mitscherlich type growth function is utilized. The derived probability law to capture the harvesting behavior is shown to be the binomial probability law. The derived probabilities prove to sum up to unity over time.     

Calculation of yields on a national level by combining yields of each prefecture using the Gentan probability

The purpose of this study was to calculate the harvesting volumes on a national level by combining yields of each prefecture using the Gentan probability. The calculation was conducted as follows. First, the Gentan probabilities were estimated for the 22 prefectures that had reliable harvesting data by the maximum likelihood method. Second, these prefectures were clustered into 3 groups by the agglomerative hierarchical clustering method based on the estimated Gentan probability patterns, and then the synthesized Gentan probabilities were estimated for each cluster from the aggregated stand areas and harvested areas of prefectures which belonged to the same cluster. Third, the other 25 prefectures without reliable harvesting data were classified into the preceding 3 clusters by discriminant analysis with socioeconomic explanatory variables. Finally, harvesting area and volume were calculated for each prefecture based on the estimated Gentan probabilities: The former 22 prefectures employed the Gentan probabilities derived from their own harvesting data while the latter 25 prefectures employed the synthesized Gentan probabilities corresponding to their cluster number classified. The validation results showed that the supposed method caused the percentage error of 2.11% in total of all 47 prefectures towards the corresponding forestry statistics in a log volume. It was sufficiently precise compared with the previous prediction results of around 20% percentage error on a national level.     

Application of the logistic, gompertz, and richards growth functions to gentan probability analysis

In a previous paper, a stochastic model complying with a state-dependent growth rate function was proposed for Gentan probability estimation. The growth function applied was the so-called Mitscherlich type of growth function. In this paper, application of other growth functions,i.e., the logistic, Gompertz and Richards growth functions, is addressed. Assuming growth dynamics as a function of time and state, an alternative stochastic model is derived with the above three growth dynamics. In the proposed model, the time is assumed to be continuous and the state to be discrete. Like in the previous paper, the sum of the Gentan probabilities derived from the proposed model with three growth functions over time is proved to be always unity. This is because the state-dependent part of the growth dynamics is a linear function of the state, which is the same as in the Mitscherlich growth function. This leads to the binomial probability law for a stochastic process, satisfying the unity requirement of the sum of the Gentan probabilities. This research was supported by a Grant-in-Aid for Scientific Research (No.11660155) from the Ministry of Education, Culture, Science, Sports, and Technology of Japan.     

林龄空间理论与减反率法应用初探——湖南省会同集体林区森林采伐量预估研究

本文以会同县过去5年森林采伐情况为例,论证了应用林龄空间理论——减反率法预估集体林采伐量的可能性,并提供一个线性规划经营方案作为对照。通过比较,认为在规划期较长的条件下,减反率法预估采伐量与线性规划方案所得收获量一致。     

Management tools for optimal allocation of wood fibre to conventional log and bio-energy markets in Ireland: a case study

A set of tools are described for optimal allocation of wood fibre at an operational planning level. These were applied to a case study in Ireland. Allocation was based on optimising net value recovery (delivered price minus harvesting and transportation costs) while meeting market demands and operational constraints (mainly crew capability and productivity limits). Two new models were developed to predict harvesting costs and transportation costs for Irish forest conditions. A new model was developed to link Sitka spruce biomass expansion factors to optimal log-making algorithms so that log and bio-energy product yields could be estimated for individual harvest areas. An existing operational allocation model based on a tabu search heuristic procedure was used. The case study included 16 forest harvest areas and 12 processing plants (saw logs, pallet logs, stakes, pulp, bio-energy slash bundles, etc.). New terrestrial lidar scanning procedures were used to obtain representative stem profiles from over 4,000 trees for the 16 forests. We demonstrated that optimal allocation of bio-energy and log products, while complex, can be achieved through the use of appropriate management tools.     

Stochastic control modeling for forest stand management under uncertain price dynamics through geometric brownian motion

In this paper, a stochastic control model is constructed by incorporating geometric Brownian motion to capture uncertain price dynamics into a one-stage and two-state stochastic dynamic programming model. The proposed model is designed to search for optimal harvest timing under price uncertainty without considering other forestry operations,e.g., thinning. We consider the option of abandoning forest management for an alternative use of forest land besides replantation. Our experimental analysis shows that the optimal harvest timing under stochastic log prices is delayed when a price level is crucially low for maintaining the management. It is also shown that when the current log price is sufficiently high, the optimal harvest timing derived from both the stochastic and deterministic approach becomes the same. With a downward trend of stochastic price dynamics, the optimal harvest timing tends to be hastened overall. This is because of the depreciation effect on the future return, which stimulates harvesting in an earlier period. This research was supported by a Grant-in-Aid for Scientific Research (No.11660155) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.     

Responses of polypore fungi following disturbance-emulating harvesting treatments and deadwood creation in boreal Norway spruce dominated forests

ABSTRACT

The emulation of natural disturbances in harvesting has become a widely accepted approach to reach ecologically sustainable forest management. The purpose of this study was to examine the responses of polypore fungi (species richness and composition) on four different cutting methods (selection, gap, patch, and clear-cutting) plus uncut controls, and the creation of high stumps and cut logs in combination with harvesting. Polypores were inventoried one year before, and two and seven years after cutting. A total of 71 polypore species were found, but no red-listed species were recorded seven years after cutting. Irrespective of the treatment, the variation in polypore richness was best explained by the number of deadwood objects in the stands. Species richness per deadwood object was the highest on natural logs. Species richness per volume of spruce deadwood was the highest on small-diameter deadwood and stumps, intermediate on natural logs and lower on cut logs and high stumps. These results indicate that cut logs created in harvesting cannot compensate the loss of deadwood in cutting and energy wood harvesting. Our results demonstrate the difficulty in rapidly creating habitats for red-listed polypores in commercially managed forests.     

Productivity and cost of whole‑tree harvesting without debarking in a Eucalyptus nitens plantation in Tasmania,Australia

There is increasing interest worldwide in using tree harvesting biomass as an energy source. Bark retained on logs is commonly used as an energy source, but is generally removed from eucalypt logs during harvest. In order to evaluate the potential use of eucalypt bark as fuel, there is a need for information on the productivity and cost implications of retaining eucalypt bark during harvest operations. The study examined the impact of retaining bark on logs on the productivity and costs of a whole?tree to roadside harvesting system in a short?rotation Eucalyptus nitens plantation in Australia being harvested for pulp logs. Trees were felled and bunched with a feller?buncher in spring, then left infield for four weeks to promote bark adhesion and reduce bark loss. A skidder extracted the trees to roadside where a processor processed them to predominantly 10?m logs. Machine productivities were calculated from estimated tree and log volumes and cycle times recorded from video recordings. The feller?buncher's productivity (65 m3 PMH₀^?1) was less than expected as it appeared to be underpowered to handle the larger trees on the study site. The skidder's productivity (56 m3 PMH₀^?1) was comparable to those reported in studies under similar conditions and with bark retained. The roadside processor's productivity (25 m3 PMH₀^?1) was lower than expected. This was believed to result from the operator separately stacking 10?m and 5?m logs, and the lower feed speed resulting from slippage due to the reduced feed roller pressure used in the study to reduce bark loss. Future research could identify feed rollers that increase feed speed while retaining bark. Harvest system costs (AUD18 GMt^?1) were similar to those reported for a eucalypt roadside processing trial where bark was removed. These results suggest that retaining bark on the logs at roadside did not affect the harvesting system's productivity or costs.     

Comparison of two harvesting systems for the production of forest biomass from the thinning of Picea abies plantations

Abstract

This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed [euro]25 t^?1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds [euro]40 t^?1. If the delivered price of sawlogs increases to [euro]50 t^?1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds [euro]35 t^?1. The CTL system is less sensitive to long extraction and transport distances than the WTH system.     

Estimation of taper rates and volume of smaller-sized logs in spotted gum saw timber plantations in Southeast Queensland,Australia

Spotted gum (Corymbia citriodora subsp. variegata) is a popular tree species for hardwood saw timber plantations in Southeast Queensland (SEQ), Australia. In many parts of the world, logs up to 10cm top diameter are considered to be merchantable logs and acceptable at sawmills. However, due to the higher handling costs of smaller-sized logs, sawmills in SEQ are only buying logs with a top diameter of 25cm and larger. This necessitates the determination of the volume of logs with top diameters between 10 and 25cm. This paper compares the taper rates of different sizes of spotted gum logs and estimates the stem volume of spotted gum logs between 10 and 24.94cm diameter. Analysis showed that there is a statistically significant difference between the mean taper rates of bottom (30.5–64.2cm diameter) and top parts of stems (10–24.94cm diameter) at harvesting age. Using only the average taper rate of large diameter logs would underestimate the log volume of smaller-diameter logs. The average length of spotted gum logs between 10 and 24.94cm was found to be 19.27 m. Therefore, by the sawmill declining to use 10–24.94cm diameter logs, approximately 0.55m³ of log volume per tree at harvesting age would be lost.     

Economic analysis on log damage during logging operation in Caspian Forests

Waste wood was studied in an economic enterprise by logging, function, tree species and log size in four Caspian hardwood sites. Damaged logs were recorded with additional information obtained for the location, dimensions and type of damage. The data were analyzed statistically to determine significant differences of damage during logging process. The results indicated that animal harvesting systems cause more volume (40.5% of log volume) and value loss (89.5 $·m^?3) to logs than mechanized harvesting systems (13.9% and 6.0 $·m^?3), also bucking resulted in significantly more volume (9.9% of log volume) and value loss (5.5 $·m^?3) when compared to skidding (0.2% of log volume and 0.2 $·m^?3), decking (0.4% of log volume and 0.2 $·m^?3) and loading (0.2% of log’s volume and 0.3 $·m^?3) operations. Study showed that the processes of skidding, decking and loading of logs have very little impact on damage levels. Volume and value losses of damaged logs are not sensitive to tree species and log size. The information from the field study is important in creating new guidelines or training to help minimize hardwood log damage during the timber harvesting process.     

Roundwood supply in Norway: micro-level analysis of self-employed forest owners

This paper presents a short-run roundwood supply analysis of self-employed Norwegian forest owners, based on a two-period utility maximising consumption-savings model. The supply function was estimated by applying the Tobit model on an unbalanced panel of approximately 160 Norwegian farmers, from 1976 to 1997, representing a total of 3413 observations. Simultaneity between the single forest owner's harvesting level and his individual tax rate was allowed by estimating simultaneous equations Tobit models. The current roundwood price and standing stock per hectare had significant positive impacts on the supply, while harvesting costs, age of the owner, tax rate and lagged roundwood price (representing expected price) had negative impacts. Price and cost elasticities were relatively sensitive to the prices forecasted for the owners who did not supply roundwood in a given period. These results suggest that price subsidies and operating subsidies, as well as tax relieves, could increase the harvest level, which is considerably lower than the sustainable harvest level. An operating subsidy seems at least as efficient as a price subsidy, while tax reliefs are the least efficient of the three policy means.     

The impact of mechanical log surface damage on chip size uniformity during debranching and debarking Eucalyptus pulpwood logs using a single-grip harvester

Mechanised harvesting operations are becoming more prevalent in South Africa with the realisation that motormanual and manual harvesting operations pose significant health and safety risks to workers. The damage inflicted by single-grip harvester feed rollers and delimbing knives on log surfaces during debranching and debarking eucalypts, may affect eventual chip quality. Chip quality influences pulp quality and recovery in the kraft pulping process. This study investigates the influence of two mechanised debranching and debarking treatments on Eucalyptus pulp logs (threeand five-feed roller passes along the stem surface) by feed rollers and delimbing knives on chip uniformity, size and purity. The two mechanised treatments to three log classes (base, middle and top logs) were compared with chips produced from manually debarked logs. Manually debarked logs produced significantly less undesirable-sized chips than both three and five-pass processed logs. The volume of undesirablesized chips produced during chipping also increased with decreasing log size. Manually debarked logs produced chips with significantly less bark than three-pass-processed logs (0.008% vs 0.062%), and five-pass-processed logs produced chips with significantly less bark than three-pass-processed logs (0.018% vs 0.062%). Middle logs also produced chips with significantly less bark than base logs (0.016% vs 0.056%), and top logs produced chips with significantly less bark than base logs (0.017% vs 0.056%). In all cases the bark content on logs was considerably less than the maximum of 1.0% generally specified by kraft pulp mills.     

The impact of log surface damage caused by harvester Eucalyptus debarking on pulp value recovery

Mechanised harvesting operations are growing in popularity in South Africa, as motor-manual and manual harvesting operations pose significant health and safety risks to workers. Potential damage inflicted by single-grip harvester feed rollers and delimbing knives on the log surface during debranching and debarking of eucalypts may affect chip size distributions during chip production. Chip size is important as it influences pulp quality and recovery in the kraft pulping process. The study investigated the influence of two mechanised debarking treatments in eucalypts (three feed roller passes and five feed roller passes along the stem surface) with feed-roller-induced log surface damage on pulp value recovery. The two mechanised treatments were compared against chips produced from manually debarked logs with no surface damage. In addition, the effect of two log drying periods (one week and two weeks) and three log classes (base, middle and top logs) on chip quality were also analysed. An economic evaluation was conducted to quantify potential recoverable pulp value losses associated with debarking treatments and log drying periods. Logs subject to manual debarking produced significantly less undesired sized chips than both three-pass and five-pass mechanically debarked logs and therefore had significantly greater pulp value recovery. Mechanically debarked logs had a projected pulp value recovery of R62, R86 and R123 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a one-week log drying period. Mechanically debarked logs also had a projected pulp value recovery of R77, R40 and R59 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a two-week log drying period. Logs dried for two weeks also produced significantly less under-sized chips than chips produced from one-week-dried logs and therefore had greater pulp value recovery. However, two-week-dried logs produced wood chips with significantly more over-thick chips than logs dried for one week. The volume of undesirable-sized chips produced during chipping increased with decreasing log size.     

An investigation of the influence of harvesting practice on the development of blue-stain in Corsican pine logs

In September 1991, at Thetford, East Anglia and at Inverness,north-east Scotland, a comparison was initiated between blue-staindevelopment in Corsican pine logs from trees felled and processedby harvesting machine and similar logs from trees felled andtrimmed out by chain-saw. Blue-stain was assessed in discs from batches of logs destructivelysampled at 2-week intervals after felling. At the more southerlysite of Thetford, stain was first observed after 4 weeks. Themaximum recorded area was 10 per cent of the wood surface ina sample analysed after 10weeks. In contrast, stain never exceeded,1.1 per cent of the wood surface at Inverness. Amounts of stainwere significantly greater with machine-harvested logs thanwith chainsaw-harvested logs and were correlated with the amountof bark removed or loosened during harvesting. The use of spikedrollers resulted in more stain than did the use of rubber rollers. The fungi isolated from stained wood included Sphaeropsis sapinea,Potebniamyces coniferarum and Ceratocystis coerulescens. Theseare species adapted to the colonization of wood exposed throughdamage to the overlying bark     

Impact of stochastic price and growth processes on optimal rotation age

This paper analyses timber harvesting in the Finnish economic and wood production environment. Empirical evidence including stumpage prices, silvicultural costs, etc., since 1949 covers all non-industrial private forestry. Stumpage price and volume growth processes are proxied by GBMs. Optimal harvesting age solutions and numerical results recognising price drift, price and growth volatility, volume growth, value growth and stand establishment costs, as well as thinning benefits, are provided for Scots pine. Moreover, comparative static and sensitivity solutions, including numerical results, show the impact of the discount rate, price drift, and price and growth volatilities on optimal harvesting age. Price volatility prolonged harvesting age by some 5–9 years, and growth volatility by about 1–2, but negative price drift for discount rates from 5 to 2% fell by roughly 6–10 years. Ignoring the future thinning benefits prolonged the harvesting age only by 1–2 years, but ignoring future stand establishment costs reduced it by 2–4 years. Including the price drift and volatility violated the 70 year age limit in the Forest Act for discount rates exceeding 3.5%. The recommended harvesting age of 80 years could be established only by ignoring the price drift. In all, this study produces solutions and programs that can be incorporated into a forest management planning software product widely used in Finland (Hynynen et al. in For Ecol Manage 207(1–2):5–18, 2005).

Immediate Effects of Logging,Mounding, and Removal of Logging Residues on Epixylic Species in Managed Boreal Norway Spruce Stands in Southern Finland

The immediate effects of bioenergy harvesting methods on epixylic species were studied in mature managed Norway spruce dominated forests in southern Finland. The treatments included logging, residue harvesting, and soil preparation as either mounding or mounding combined with stump harvesting. Altogether, 110 logs and 440 species sample plots on logs were inventoried before and after logging, and after soil preparation treatments. Logging decreased the cover and species richness in all epixylic species groups. The soil preparation decreased the cover of macrolichens, while stump harvesting was significantly most devastating both for cover and richness in bryophytes. We suggest that bioenergy harvesting critically affects the epixylic species, and therefore the use of less devastating methods and compensation for the loss of coarse woody debris is recommended on a landscape level.     

An Economic Analysis to Aid the Marginal Decision on Rotation Length: II Development of the Technique

The economic principle, which was presented in an earlier paper(Forestry, 37, 161), is developed into a flexible techniqueof economic analysis for use in forest management. The techniqueprovides a rapid method for analysis of the marginal decisionon financial rotation length; whether to fell now, or in fiveyears or so. The developments include incorporation of a price-sizegradient, different product prices, various costs of operation,reductions in volume yield, and various establishment and maintenancecosts. Now in its final form, it can incorporate these changesin stand conditions without any laborious calculation. The techniqueis used to analyse the effect of financial factors on the marginaldecision, i.e. prices, costs, and productivity. It is suggestedthat financial rotations are fundamentally dependent on therelation between physical production and the interest rate.Second, establishment and annual maintenance costs have no effecton the decision. Third, prices, or more specifically the ratioof pulpwood price:sawtimber price, are not of major importance,because they influence the decision within the limits alreadyimposed by production and interest rates. The justificationfor pulpwood rotations is also examined. This paper has developeda basic technique for projects of forest economics. It is partof the research work into the economics of timber production,which is being undertaken by the author at the Forestry Department,University College of North Wales, Bangor.     

“一带一路”沿线国家对华原木出口贸易效率与潜力

利用"一带一路"沿线主要国家与中国双边原木贸易数据,文中实证分析影响沿线国家对华原木出口主要因素,并进一步测算出其原木出口贸易效率与潜力。结果表明:中国人造板和木家具出口量、沿线国家人均GDP、国土面积、与中国是否有共同边界、距离和经济规模相对差异等指标是影响对华原木出口的主要因素;2007年以后,沿线国家对华原木出口贸易效率逐年降低,年平均效率低于0.5,而原木出口贸易潜力则逐年提升。从保障我国原木贸易安全、降低原木进口成本以及加大对"一带一路"沿线国家林业投资等方面提出相应建议。