Integrated harvesting for conventional log and energy wood assortments: a case study in a pine plantation in Western Australia

Biomass or energy wood harvesting can be integrated with conventional log harvesting (saw log or pulpwood production) to allow more cost-effective energy wood supply. The efficiency of an integrated energy wood harvesting system was evaluated and compared with conventional log harvesting in a 32-year-old Pinus radiata plantation (radiata pine) located in south-west Western Australia. The harvesting system consisted of a harvester and a forwarder. The study included two treatments: a conventional log-harvesting operation where merchantable sawlogs and pulp logs were produced at the stump by the harvester and extracted by the forwarder; and an integrated energy wood operation where the harvester produced sawlogs, pulp logs and energy wood at the stump that were extracted by the forwarder. In the integrated energy wood harvesting plot, 37 m3 ha?1 of energy wood was extracted in addition to the sawlog and pulp log volumes. Extracting the additional energy wood reduced the productivity of the forwarder and increased the cost of extraction (AU$2.7?m?3) compared with the control plot (AU$2.2?m?3). Harvesting system cost was not significantly impacted, with a cost of AU$3.18?m?3 in the control plot and AU$3.23?m?3 in the integrated energy wood harvesting plot. Diameter at breast height (DBH) was a significant factor influencing the working time of the harvester, whereas load volume, extraction distance and extraction type (sawlog, pulp logs, and pulp log/energy wood) significantly impacted forwarding time. Increasing DBH resulted in longer working cycles for the harvester. Heavier loads and longer forwarding distances increased forwarding cycle time, while extracting sawlogs was least expensive and energy wood extraction was the most expensive. The marginal cost of the energy wood was approximately AU$10.2?m?3 (AU$7.0 extraction and AU$3.2 harvesting), which is about double the cost of the sawlogs. Additional material recovered in the integrated energy wood plot resulted in less residual residues on the plot (103.2 green metric tonnes per hectare [GMt ha?1]) than the control plot (144.2 GMt ha?1).     

Examining the Optimal Method to Extract Logging Residues from Small-Scale Forestry in the Nasunogahara Area,Tochigi Prefecture,Japan

This study examines the optimal method to extract logging residues from small, fragmented and scattered forests separately from the mechanized operational systems used on aggregated forestry operation sites. First, small-scale logging systems operated by a private logging contractor and an individual forest owner were investigated. Regression equations for estimating felling and processing cycle times were established as a function of stem and log volumes, respectively. Equations to estimate the forwarding and transporting cycle times were established as a function of the forwarding and transporting distances using the forwarding and transporting velocities, respectively. Then, equations to estimate productivities and costs were established with the cycle times, volumes and hourly operational expenses consisting of labour and machinery expenses. Finally, costs of the small-scale systems—mini-forwarder and 4 t truck operated by a private logging contractor, and manual logging and light truck operated by an individual forest owner—were estimated and compared with the mechanized operation system operated by the Forest Owners’ Association. The mechanized operation system was found to have the highest cost and could not compete for small forestry operational sites and small stem volumes. The small-scale systems could be effective for harvesting small areas. This was especially true when conducting extracting operations without machines, as done by the individual forest owner, and transporting operations by a private logging contractor, in which the hourly income of the individual forest owner was higher than the hourly labour expenses.     

Path tracking in forest terrain by an autonomous forwarder

Abstract

Autonomous navigation in forest terrain, where operation paths are rarely straight or flat and obstacles are common, is challenging. This paper evaluates a system designed to autonomously follow previously demonstrated paths in a forest environment without loading/unloading timber, a pre-step in the development of fully autonomous forwarders. The system consisted of a forwarder equipped with a high-precision global positioning system to measure the vehicle's heading and position. A gyro was used to compensate for the influence of the vehicle's roll and pitch. On an ordinary clear-cut forest area with numerous stumps, the vehicle was able to follow two different tracks, three times each at a speed of 1 m s^?1, with a mean path tracking error of 6 and 7 cm, respectively. The error never exceeded 35 cm, and in 90% of the observations it was less than 14 and 15 cm, respectively. This accuracy is well within the necessary tolerance for forestry operations. In fact, a human operator would probably have a hard time following the track more accurately. Hence, the developed systems function satisfactorily when using previously demonstrated paths. However, further research on planning new paths in unknown unstructured terrain and on loading/unloading is required before timber transports can be fully automated.     

Effects of aggregating forests, establishing forest road networks, and mechanization on operational efficiency and costs in a mountainous region in Japan

We investigated forest road networks and forestry operations before and after mechanization on aggregated forestry operation sites. We developed equations to estimate densities of road networks with av...     

Comparative analyses on the cycle time,productivity, and cost between commercial thinning and clear-cutting operations in Nasu-machi Forest Owners’ Co-operative,Tochigi Prefecture,Japan

This study investigates clear-cutting operations on moderately and gently sloping sites. Cycle times, productivities, and costs of those operations are analyzed and compared with those of commercial thinning operations, to enable logging contractors to easily find trends of those three variables. Felling cycle times of clear-cutting were lower than those of commercial thinning operations. Processing cycle times of clear-cutting on the gently sloping site were lower than those of clear-cutting on the moderately sloping site and commercial thinning. However, processing cycle times of clear-cutting on the moderately sloping site were similar to those of commercial thinning. Forwarding cycle times of clear-cutting on the moderately sloping site were the lowest among the estimated forwarding cycle times. Costs of operation systems were the lowest with clear-cutting on the gently sloping site, followed by clear-cutting on the moderately sloping site, and then commercial thinning with mechanized and current operation systems according to forwarding distance, with extracted volume 0.5 m³/stem. Costs of the current thinning operation system were less than those with a mechanized thinning system below extracted volume 0.3 m³/stem, because of smaller machinery expenses.     

A comparison of six parallel levers and two joysticks for the maneuverability of forwarders

In order to clarify the operational features of two types of controllers, which were six parallel levers and two joysticks, a comparative investigation was conducted for three different forwarders. From the results of a detailed time and operational analysis, operations of a grapple crane which were related to slewing, boom and arm functions were proved to be the main functions in loading and unloading. In regard to the six parallel levers, the following four defects were pointed out. The positions assigned for the functions, slewing, arm and rotator were not in natural relations to those movements. A lever for extension is difficult to operate. Very difficult operations occurred simultaneously controlling more than three functions. Movements of hands and fingers were very complex. In regard to the two joysticks, there was no serious problem in operations, then again, movements of the joysticks were simple. Operating with the two joysticks seemed not to be difficult even if a few extra functions were added. Thus it was advisable to equip a forwarder with the two joysticks as a controller.     

Cost-productivity analysis of South African pine sawtimber mechanised cut-to-length harvesting

The South African forestry industry is experiencing an increase in the number of fully mechanised timber-harvesting systems. Understanding the productivity of these systems, for which data is currently limited for South Africa, is an important step to maximise the utilisation of machines being used. A time study of a mechanised cut-to-length system was conducted in Pinus elliottii sawtimber plantations in the Southern Cape forestry region of South Africa. A harvester and a forwarder were studied with the intention of analysing the division of work time amongst work elements, modelling each machine’s productivity and cost, and estimate fuel consumption. For the harvester’s productivity, a multiple regression model was developed using diameter at breast height (DBH), average distance moved per work cycle and slope class as predictors (adjusted R²? = 0.80). The harvester had a mean productivity of 33.6 m³ per productive machine hour (PMH₀) under the current conditions with most of the productive time being used in the moving element. It consumed 25.5 L PMH₀ ^?1 of diesel on average. The forwarder’s fuel consumption was calculated as 16.8 L PMH₀ ^?1, while productivity was 46.8 m³ PMH₀ ^?1. The forwarder spent the longest portion of the work cycle in the loading and unloading phases. A productivity regression model was created that included load size and distance moved during the driving in the loaded phase (adjusted R?² = 0.78).     

Feasibility of a harvesting system for logging residues as unutilized forest biomass

The concept of a “harvesting system for unutilized forest biomass by a processor and a forwarder” is examined for the purpose of constructing a system to harvest logging residues (or slashes) as a new resource for energy. The rate of slash harvesting, α, and the energy input rate of hauling slashes,p (%), are defined as indices of the possibility of harvesting slashes and the utilization of slashes for energy, respectively. From an analysis of the field experiment, both the volume of logs hauled by the forwarder per day,E _F (m³/day), andp are expressed as functions of the hauling distance,L(m). The productivity of the processor,E _P (m³/day), andL were used to calculate α. Results showed that α was approximately 0.95 for the experiment site, indicating that almost all the slashes could be hauled. It was recognized that the energy utilization of slashes was feasible for this site becausep was less than 1 %. The hauling cost per unit weight of slashes was calculated as 15.4 yen/kg on an oven-dry weight basis. This high cost clarified that the cost must be reduced by taking measures such as enhancing the hauling efficiency of the forwarder. A part of this paper was orally presented at the 5th Annual Meeting of the Japan Forest Engineering Society (1998).     

A Case Study on the Productivity of Forwarder Extraction in Small-Scale Southern Italian Forests

Most timber harvesting operations in the southern Mediterranean area of Italy can be considered to be in an early stage of mechanization. It is mainly based on agricultural tractors that are sometimes equipped with specific forest-related accessories such as winches, hydraulic cranes, or log grapples. In recent years, there has been an increase of specialized forestry machines working in Calabria, southern Italy, including forwarders, skidders and cable yarders. This study assesses the efficiency and costs of extraction using forwarders, as a mechanized alternative to agricultural tractors and horse logging. Time studies were conducted to quantify the productivity and operational cost of log forwarding for two John Deere forwarders in two different coniferous stands: (A) Calabrian pine and (B) silver fir. The empirical time study included 100 forwarding cycles (i.e., 50 for each site) that were broken down into four different work phase elements. Models for cycle time, total productivity and individual work phases were calculated. The average load per cycle was 11.8 m³ in stand A and 9.97 m³ in stand B and the average one-way forwarding distance was 306 m in A and 597 m in B. The average productivity per scheduled machine hour (SMH) was 14.4 m³ in A and 15.7 m³ in B, while the costs, calculated to be 3.60 €/m³ in A and 4.90 €/m³ in B, were considered lower respect traditional methods.     

森林采运系统动力学模型研究

为了分析森林采运系统的效率和成本,本文选择系统中关键的采—集过程,利用系统动力学的方法建立模型,进行计算机仿真模拟。结果显示,以特定时间范围内完成一定工作量为前提,系统运行的效率和成本与初始设备的投入量关系不大,与设备条件、外部条件、林木条件等关系很大。但初始采造设备的投入量会影响集材设备的运行效率和成本。在实际生产中,首先应根据林木条件和外部条件选择合适的设备,这样才能使得运行效率最高而成本最低;其次在设备的安排上,应充分保障采造设备,但也不应使其生产力与集材设备的生产力相差过大,否则会造成后期集材设备需求激增等问题。     

油松蜂窝状容器育苗技术

培育1-2年生油松苗木,采用蜂窝连体容器育苗,可提高装袋效率5~6倍,降低生产成本,并能培育出合格的油松苗木,适宜在林区推广。     

Damage to saplings in mechanized selection cutting in uneven-aged Norway spruce stands

Abstract

Damage to 0.5–2.5 m saplings in selection cuttings in uneven-aged Norway spruce stands was studied in three stands in Finland. Harvest removals were 96–122 m³ha^?1 or 32–41% of initial basal area. Harvesting was carried out with one-grip harvester and forwarder in March–April 2007. The strip road network had been established in previous cuttings. Before harvesting, trees higher than 2.5 m were measured and mapped with coordinates. Saplings 0.5–2.5 m were measured on circular sample plots of 10 m² on a square grid, where line and plot intervals were 7.07 m. Trees to remove were selected with a computerized tree selection procedure and marked before cutting. Factors affecting the probability and severity of injury to an individual sapling were studied with logistic regression models. Percentage of injured saplings was 17.6, 29.8, and 61.0%, depending on study stand. Stem breakage was the most common type of injury. Distance of the sapling from the nearest strip road, sapling height, harvested basal area within 25 m of the sapling, and the distance to the nearest remaining tree were statistically significant factors in the model of the probability of injury. In the model for the severity of injury, only the distance from the nearest strip road and the sapling height were significant. Saplings near strip roads were vulnerable during both cutting and forwarding, and they often ended up under slash or logs. Development in working methods and machinery are potentially effective in reducing sapling damage in selection cuttings.     

Forestry operations in the European mountains: a study of current practices and efficiency gaps

Timber production is an important ecosystem service of European mountain forests. This paper aimed to assess the current practices in logging operations and to identify the efficiency gaps in timber production. The study was located in 7 case study areas from representative European mountain ranges, where 632 logging operations were analysed. The focus was on road infrastructure, transport systems, harvesting methods and extraction technologies. Often inappropriate technology was used in steep terrain; there was no correlation between the average slope and the selection of harvesting systems (HS). Skidding was the most common extraction method (75%), while cable yarding and forwarding had shares of 15% and 8%. The mean road density was 18.5?m?ha^?1. The mean extraction distance was 501?m. The mean harvesting and extraction productivity were 9.0 and 10.2?m³?h^?1; the mean costs were 11.1 and 11.7?€?m^?³, respectively. Non-mechanized and obsolete HS reported the lowest efficiency and the highest environmental footprint, while fully mechanized systems reported the highest efficiency, the lowest number of accidents and the lowest stand damage. Cable yarders are the appropriate extraction technology in steep terrain, but they require a well-developed road network. Higher mechanization degree, improved quality of the road networks, knowledge transfer to practice and training of forest workers are some of the necessary measures to overcome the efficiency gaps in timber production in European mountain forests.     

A comparison of harvesting productivity and costs in thinning operations with and without midfield

Mechanised thinning operations can be carried out in the forest where skid roads are provided on which harvesters and forwarders can move. In the transition to continuous cover forestry (CCF) it is better to keep a thinner network of skid roads in the forest. Instead of tracks for harvesters and forwarders, these areas can be used for younger generations of trees. Moreover, fewer skid roads in the forest environment make the stand more natural. Fewer skid roads were introduced in this research as an alternative thinning operation with midfield¹ (MF) to the most popular mechanised thinning operation with skid roads² (SR). The aim of this paper is to analyse the productivity and economic aspects of thinning operations based on harvesters and forwarders, where there are different distances between skid roads. In both of the operations, harvesters and forwarders were used, but in the MF operation a chainsaw was additionally used to cut trees beyond the reach of the harvester boom. The distances between skid roads in the MF operation were 35–38 m, while in the other they were 18–20 m. The research was carried out in premature pine stands in a flat terrain in Poland. Bigger productivity and lower costs were found in the MF thinning operations. In the younger 44-year-old stand, the average harvester (Timberjack 770) productivity (in operational time) in the MF operation was 5.87 m³h⁻¹ and in the SR operation 4.52 m³h⁻¹; forwarding provided by the Vimek 606 6WD achieved a productivity of 5.03 and 4.52 m³h⁻¹, respectively. In the older 72-year-old stand, the Timberjack 1270B productivity was 11.53 m³h⁻¹ in MF and 8.70 m³h⁻¹ in SR; the Timberjack 1010B forwarder achieved 11.22 m³h⁻¹ (MF) and 8.84 m³h⁻¹(SR).The costs of harvesting and forwarding 1 m³ of wood were lower in the MF operations. In the younger stand, harvesting costs were 5.78 €/m³ (MF) and 6.72 €/m³ (SR) while forwarding costs were 1.94 and 2.18 €/m³ respectively. In the older stand, harvesting costs were 5.58 €/m³ (MF) and 6.78 €/m³ (SR); the forwarding costs were 2.65 €/m³ (MF) and 3.41 €/m³ (SR).     

基质配比和容器规格对杉木容器苗生长的影响

以1年生杉木裸根苗为试验材料,选用3种基质类型、13种配比、4种容器规格,重复3次,20株小区的析因试验设计,研究基质配比和容器规格对2年生容器苗生长的影响。结果表明：基质配比和容器规格对苗高生长有显著影响,泥炭比例在80%的范围内,随着泥炭比例的增大苗高逐渐增加;容器直径在14 cm范围内,苗高随着容器规格增大而增加,容器直径超过14 cm,苗高差异不显著。综合考虑苗木高度和容器苗生产成本,2年生杉木容器苗培育的最佳基质配比为：18%的黄心土＋73%黑龙江泥炭土＋3%菜枯＋3%糠灰＋3%珍珠岩,最适容器规格为高20 cm,直径14 cm。容器苗生长不仅受基质配比和容器规格主效应的影响,其主效应之间还存在交互效应。因此,要根据容器苗培育年限相应的调整容器规格和基质配比,以达到低成本生产杉木优质容器苗的目标。     

关于山水林田湖草系统运行效率的理论思考

在我国不断深化生态保护修复战略部署的过程中,山水林田湖草生命共同体系统保护修复的重要性越发凸显。基于山水林田湖草生命共同体的科学内涵,文中剖析了山水林田湖草生命共同体的时空演变动态运行机理,构建了其运行效率分析框架;此外,还从山水林田湖草生命共同体的时间演化和空间差异2个维度构建了运行效率评价体系,明确其运行效率提升的实现路径。对山水林田湖草生命共同体运行效率进行理论机理阐释和评价体系构建有助于为我国生态保护修复工程实践提供丰富的理论依据,为推进区域生态与经济协调发展提供参考。     

Wood transportation machine replacement using goal programming

ABSTRACT

Farm tractor?+?trailers play a key role in wood transportation after forests are logged. Despite of the fact that a forwarder is a forestry vehicle that carries felled logs for shorter distances off the ground, tractors are still used in some forest areas of the world, such as the Hyrcanian forest in northern Iran. This study was conducted to investigate the possibility of using both the light forwarder and forestry trailer instead of a farm tractor?+?trailer in wood transportation. The optimal machine option for wood transportation is determined using goal programming model in the study area. In this paper, multi-objective goals (such as economic, operational, environmental and ergonomic) were considered. The results showed that considering only the economic goal, the contractor could save up to 44% in costs by purchasing and replacing a forestry trailer with a 2-wheel trailer attached to the farm tractor. In addition, considering various goals, a light forwarder could be selected as the optimal machine. Currently, the most important objectives of all forest contractors are to establish economic goals and reduce wood transportation costs. Since other goals, such as environmental and ergonomic, are also important; it is suggested that multi-objective approaches should use for planning.     

Nitrogen mineralization along an altitudinal gradient: Interactions of soil temperature, moisture, and substrate quality

Net soil N mineralization was measured in situ for 2 consecutive years along a 2000-m altitudinal gradient encompassing six vegetation types in northern California. Both anaerobic and aerobic field incubations showed that soil temperature and moisture strongly controlled N release. In sealed container studies, N mineralization per unit of total Kjeldahl N ( ) had a Q₁₀ rate of 2 and varied between 5 and 38 g N/kg when moisture was abundant (anaerobic incubation). However, aerobic mineralization rates fell to between 2 and 22 g N/kg because of summer drought. Aerobic rates were greatest at mid-elevations (the mixed-conifer forest), and were reduced by cold temperatures at higher elevations and by soil drought at lower. The lowest rate found for any site was in a pine plantation scalped of topsoil a decade previously, during site preparation. Open-container incubations involving intact, 15-cm soil cores and ion-exchange resins produced mineralization rates correlated with potential growing days, but not with rates from sealed containers. The forest floor accounted for nearly all the net N mobilized on the coldest site, but only one-half to one-third of the N mobilized on warmer sites. Open containers have important advantages in assessing soil N dynamics.     

Cost, energy and carbon dioxide (CO2) effectiveness of a harvesting and transporting system for residual forest biomass

The purpose of this study is to examine the feasibility of a system to harvest logging residues (or slashes) as a new resource for energy in Japan. A harvesting and transporting system for residual forest biomass was constructed with reference to some European countries where the utilization of bioenergy is making steady progress and examined on the basis of field experiments in Japanese forestry. The feasibility of the system is discussed from the standpoints of cost and energy, and the system is compared with those of the European countries. With respect to the system proposed in this study, it is desirable that the process of chipper comminuting is incorporated into the system as early as possible, considering the trends of harvesting cost and fuel consumption per unit weight of residual forest biomass. Such a system is not particularly feasible in Japan from the standpoint of the harvesting cost per MWh of bioenergy. However, no specific problems are found from the point of view of the energy input rate, and it is clarified that it is possible for Japan to reduce domestic carbon dioxide emissions by utilizing biomass as an energy resource. A comparison with the European countries and a preliminary sensitivity analysis of the system demonstrate that the technical development to reduce the harvesting cost,e.g., improving the forwarding and transporting efficiency, and support from the government are essential for realizing bioenergy utilization in Japan. A part of this paper was orally presented at the 111th Annual Meeting of the Japanese Forestry Society (2000). JSPS Research Fellow. This study was supported in part by a Grant-in-Aid for Scientific Research from the Japan Ministry of Education, Science and Culture (No. 10460061).     

Time Prediction Models and Cost Evaluation of Cut-To-Length (CTL) Harvesting Method in a Mountainous Forest

Time equations are derived for felling with chainsaw, skidding with cable wheeled skidder, loading with grapple hydraulic loader and trucking of logs within a cut-to-length harvesting method. The continuous time study method was applied to collect data for felling, skidding, loading and a transportation model. Multiple regression analysis via SPSS software was applied to develop the time models. Felling time was found to be highly dependent on diameter at breast height. Skidding distance, winching distance, slope of the trail and piece volume were significant variables for the skidding time prediction model. The loading time model was developed considering piece volume. Transportation distance and load volume were used as independent variables in modeling the transportation time. The net production of felling was estimated at 12 trees/h (56.65 m³/h). The net production rates for skidding, loading and traveling averaged 18.51, 41.90 and 3.32 m³/h respectively. The total cost of harvesting from stand to mill was estimated 19.70 €/m³. The skidding phase was the most expensive component of the cut-to-length method. The bucking and delimbing components were less costly than the other logging phases. The results of this study can be used for harvesting planning and productivity optimization.