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.     

Wood Extraction with Farm Tractor and Sulky: Estimating Productivity, Cost and Energy Consumption

A winch and a sulky can transform a farm tractor into an effective small-scale logging machine, closely resembling a wheeled cable skidder. The additional cost of these implements is very small, but they offer significant benefits when extracting timber under the conditions of small-scale forestry. The authors developed a productivity model for skidding timber with wheeled farm tractors, equipped with winch and sulky. The origin data pool contained over 300 individual skidding cycles, extracted from 8 separate tests. Statistical analysis of the data allowed calculating a simple mathematical relationship for estimating skidding productivity as a function of significant work conditions, such as: piece size, winching distance, tractor power, skidding distance and crew size. This model can provide useful directions to prospective users, contributing to operation planning, costing and optimization. It can predict a large proportion of the variability in the data and was successfully validated using reserved cycle records, extracted from the same data pool and not used for model development. Depending on tractor power and piece size, the average turn volume and productivity can exceed respectively 2 m³ per cycle and 4 m³ per Scheduled Machine Hour (SMH). Top performance can reach 8 m³ SMH⁻¹, with heavy tractors and large logs.     

A Comparison of Productivity in Five Small-Scale Harvesting Systems

The use of small-scale harvesting equipment continues to grow in forestry in many regions of the world. This equipment includes various devices and methods used to harvesting that generally are smaller, less expensive and less productive than advanced forestry machines. The objective of this study is to compare the efficiency of five alternative extraction methods implemented in a harvesting unit located in a mixed beech and oak forest ecosystem in northwestern Turkey. A continuous time study was conducted during primary transport operations that included skidding with animal power, skidding with farm tractor, hauling with farm tractor, hauling with forest tractor, and extraction by skyline. Timber was skidded uphill on a skid trail, and an average skidding distance of 100 m for all haulage methods was considered. Average slope of the harvesting unit ranged from 20 to 40 %. Average productivities for respective haulage methods were 3.80, 6.25, 2.80, 5.25 and 10.09 m³/h. Significant differences were found between productivity of haulage methods using one-way analysis of variance. The extraction by skyline, skidding with farm tractor, and hauling with forest tractor were determined to be the most statistically different methods, the productivity of these methods was found significantly higher than the other methods. Skid trails are useful for shortening distances during forest operations and skidding with farm tractor is a productive method in small-scale forestry of Turkey.     

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).     

Time Consumption and Production Costs of Two Small-Scale Wood Harvesting Systems in Northern Greece

A field-based study was carried out to determine the productivity and production cost of the tree length (TL) and the wood assortment (WA) systems implemented under small-scale forestry conditions in two Scots pine stands in Northern Greece. Tree felling and processing productivity were estimated at 8.64 m³ per productive machine hour (PMH^?1) and 10.21 m³ PMH^?1, respectively. Wood felling and processing times were strongly dependent on dbh and total tree volume. However, when manual debarking was also considered the productivity rates decreased to 1.96 and 1.43 m³ PMH^?1, respectively. Skidding productivity was calculated to be 3.35 m³ PMH^?1 for TL and 7.17 m³ PMH^?1 for WA, respectively. Strong correlations have been found between the net skidding time and (a) the skidding distance and (b) the load per turn in both wood harvesting systems. Production costs varied greatly, from 19.38 € m^?3 up to 44.81 € m^?3 of roundwood depending on the harvesting system and the inclusion of debarking. The findings suggest that the WA system is more efficient in terms of productivity and production cost than TL, and that there is a substantial optimization potential. The optimization potential can be encoded in four suggestions: (a) opening up of more forest roads to reduce high skidding times, (b) replacement of manual debarking by mechanical debarking at the sawmill, (c) replacement of old pieces of equipment with newer ones and (d) training of the existing workforce.     

Time consumption, productivity, and cost analysis of skidding in the Hyrcanian forest in Iran

The performance of the skidder Timber jack 450 C was presented in timber skidding of non-coniferous trees in hilly and mountainous conditions.An empirical time study was conducted to evaluate the current skidding system in Hyrcanian forest in northern Iran for improving production rate of skidding and finding out the production cost for planning.Based on the identified elements of skidding work phase and 130 recorded cycles,we calculated the models for effective time consumption,total productivity,and unit cost.The validity of the model was tested at 95% confidence interval.The average load volume per cycle was 2.82 m 3,average one way skidding distance was 450 m,and the average slope was 18%.The average travel speed of unloaded skidder was 5.8 km·h-1,and the average speed of loaded skidder was 0.1 km·h-1 higher than the speed of the unloaded ones.The travel speed was predominantly affected by longitudinal slopes and types of strip roads.The average speed of pulling the cable was 1.16 km·h-1,and that of load winching was 0.74 km·h-1.The average outputs in skidding was 10.6 m 3 ·h-1 and the unit cost was 12.1 US$ per hour.The time consumption and productivity of skidding depends on distances and slope,number of logs per cycle,volume,log length,etc.However,the influence of variables is not the same.     

Simulation Study of a Single-grip Harvester in Thinning from Below and Thinning from Above

Abstract

The time consumption and productivity of a single-grip harvester were studied, using a simulation model, when thinning from below and above in eight randomly selected stands. The model estimated the time required for each work element, given machine and tree positions, and tree size. A 2×5 factorial design was used with factors thinning type [from below (T_b) and above (T_a)] and tree size. Trees were subjectively selected for harvest according to thinning type. Total basal area removal was 30% plot^?1. Approximately 50% more trees were harvested in T_b than in T_a Time consumption tree^?1 was higher for T_a than T_b. Time consumption for machine and boom movements decreased with increasing number of harvested trees, and time for felling and processing of trees increased with harvested mean stem volume. Harvester productivity was 36% higher for T_a, since the increase in harvested mean stem volume was higher than the increase in time consumption tree^?1.     

Analysis of Spacing for Spotted Gum Plantations for Maximizing Merchantable Logs' Volume in Southeast Queensland,Australia

Spotted gum (Corymbia citriodora subspecies Variegata) has the potential to be the major hardwood species for large-scale plantations in Southeast Queensland, Australia, but production research is limited due to the lack of age of research plots. Optimal spacing is a major subject of concern. Based on time series data from a spotted gum experiment site, growth performance was analyzed for five spacing levels: 11.3 m?×?11.3 m (78 stems ha^?1), 7.4 m?×?7.4 m (182 stems ha^?1), 5.4 m?×?5.4 m (343 stems ha^?1), 3.6 m?×?3.6 m (771 stems ha^?1), and 2.9 m?×?2.9 m (1189 stems ha^?1). The major objective was assumed to be to maximize total merchantable log volume. A growth model was produced, and the mean diameter at breast height (DBH) and total merchantable log volume for each spacing level at a range of harvesting ages were estimated. From the analysis, the spacing level of 5.4 m?×?5.4 m was found to be optimal for maximizing merchantable log volume to a 10-cm small-end diameter. Further analysis of mean DBH, height, and volume of the largest 200 and 250 trees from this spacing level indicates that merchantable log volume could be maximized by retaining the 250 largest trees ha^?1. The total financial revenue from the best spacing level in 25 and 30 yr are predicted to be Australian dollars (A$) 13,637 and A$17,779 ha^?1, respectively. If full rotation data could be obtained, more reliable models could be produced, and a more accurate financial estimate could be made.     

兴安落叶松人工林抚育机械作业效率的研究

通过对沾河林业局现有的兴安落叶松人工林抚育机械即割灌机、油锯、集材机械进行分析和研究,结果表明：国产机型与国外先进机型相比,还存在着很大的改进空间。短距离集材,畜力集材具有优势;随集材距离加大,拖拉机集材效率明显高于畜力集材。影响集材效率的关键因素是回空和重载时间。     

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.     

Machine productivity and residual harvesting residues associated with a cut-to-length harvest system in southern Tasmania

The cut-to-length method is a preferred method for harvest of pine plantations in Australia. The cut-to-length method studied in southern Tasmania consists of a feller-buncher, processor, forwarder, grapple loader and tractortrailers that were producing only pulp logs for the plantation owner Norske Skog. An elemental time study method was applied to evaluate the productivity of the machines within the flat terrain, Pinus radiata plantation. Multiple regression was used in SPSS to develop the productivity prediction models. The productivity of the feller-buncher and processor averaged 122.20 m³ per productive machine hours excluding all delays (PMH₀) and 84.32 m³ PMH₀ ^?1, respectively. The average productivity for the forwarder, grapple loader and truck were 80.90 m³ PMH₀ ^?1, 100.80 m³ PMH₀ ^?1 and 27.40 m³ PMH₀ ^?1, respectively. The average fuel consumption of the feller-buncher, forwarder and processor were also documented. The trial assessed harvest residue left on the site and found 238.7 GMt ha^?1 (31% of total biomass above the stump) was left of which 46% was stemwood. These research findings can be used for harvesting planning and improving logging efficiency.     

A comparison between excavator-based harvester productivity in coppiced and planted Eucalyptus grandis compartments in KwaZulu-Natal,South Africa

Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions – such as coppiced Eucalyptus compartments – where they have not operated before. For this reason, harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or harvesters are not used in these compartments due to a lack of productivity knowledge. This research aimed to determine the influence of tree volume and tree form on the productivity of an excavator-based harvester in coppiced regrowth – with either double or single stems, or planted single stems – in Eucalyptus grandis pulpwood compartments. In addition, the stem felled first and the distance between stems were investigated for coppiced double stems. The stem felled first is whichever stem between the two coppiced double stems the harvester grabbed, felled and processed first. The tree volume was determined; thereafter the trees were classified into different form classes. The tree volume and the cycle time were used to determine productivity. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single stems and then coppiced double stems. When harvesting a 0.2 m³ tree, the mean harvester productivity was 8.7 m³ per productive machine hour (PMH₀) in coppiced double stems, 13.8 m³ per PMH₀ in coppiced single stems and 16.1 m³ per PMH₀ in planted trees. In coppiced double stems the productivity was significantly influenced by the size of the stem felled first. In coppiced double stems the productivity was not significantly influenced by the distance between stems. The productivity for both coppiced single stems and coppiced double stems was significantly influenced by stem form. The poorly formed trees had lower productivity compared to the trees with good form.     

福建省国有林场手扶拖拉机标准参数的研究

本文针对福建省国有木场伐区木材生产状况。分析修建手扶拖拉机集材道的可行性。并根据东风12型手扶拖拉机机械性能。研究手扶拖拉机林道设计行车速度、最大纵坡、最小弯道半径等主要技术标准参数。     

Productivity of single-grip harvesters in clear-cutting operations in the northern European part of Russia

A field-based study was carried out to broaden our knowledge of fully mechanized cut-to-length harvesting productivity in naturally grown forests in the northern European part of Russia (NEPR). The recorded data comprised 38 midsized single-grip harvesters (JD 1270D) in clear-cutting operations in the Karelia, Komi, Vologda, Leningrad, Tver, and Kirov regions in NEPR, 4.3 million felled trees, and 1.4 million m³ u.b. (under bark) of processed timber. Harvesting operations were conducted in forest stands composed of spruce (48% on average), pine (19%), birch (22%), and aspen (11%), with an average stem volume 0.31 m³ u.b. The cut-to-length harvesters produced from 4.3 to 14.9 m³ u.b./productive machine hour (PMH) and 16.0–49.5 m³ u.b./stem processing machine hour (S _proc MH). A machine evaluation analysis and a regression analysis were used to formulate models for predicting cutting productivity of modern single-grip harvester. The regression models were developed to estimate the productivity of the harvesters in the regions taking into account two significant factors influencing the productivity: the stem volume and tree species of the felled trees. Productivity/cubic meter u.b. of processed timber/PMH was calculated according to stem volume and tree species distributions in most forest-covered NEPR regions. Further research is suggested to improve the developed productivity models and to allow prediction of system performance over a broad range of stand and site conditions.     

Carbon sequestration of modern Quercus suber L. silvoarable agroforestry systems in Portugal: a YieldSAFE-based estimation

Modern alley cropping designs, with trees aligned in rows and adapted to operating farming machinery, have been suggested for Europe. This paper explores the potential for adoption of cork oak (Quercus suber L.) agroforestry in Portugal and estimates the potential carbon sequestration. Spatial modeling and Portuguese datasets were used to estimate target areas where cork oak could grow on farmland. Different implementation scenarios were then modeled for this area assuming a modern silvoarable agroforestry system (113 trees ha^?1 thinned at year 20 for establishing 50 trees ha^?1). The YieldSAFE process-based model was used to predict the biomass and carbon yield of cork oak under low and high soil water holding capacity levels. Approximately 353,000 ha are available in Portugal for new cork oak alley cropping. Assuming implementation rates between 10 % of the area with low soil water capacity (60 mm: 15 cm depth, coarse texture) and 70 % of the area with high soil water holding capacity (1,228 mm: 200 cm depth, very fine texture), then carbon sequestration could be 5 × 10⁶ and 123 × 10⁶ Mg CO₂ respectively. Due to higher yields on more productive land, scenarios of limited implementation in high productivity locations can sequester similar amounts of carbon as wide implementation on low productivity land, suggesting that a priori land classification assessments can improve the targeting of land and financial incentives for carbon sequestration.     

Impact of number of stems per stool on mechanical harvesting of a Eucalyptus globulus coppiced plantation in south-west Western Australia

Coppice regeneration of eucalypt plantations is increasingly being used in Australia to reduce re-establishment costs. However, little is known about the impact of early coppice reduction regimes on harvester performance during clearfelling. The trial compared the productivity, time consumption, cost and fuel use of a single-grip harvester (Hyundai 210LC-9 base and SP 591LX harvesting head) clearfelling a 10.5-year-old, second-rotation coppiced Eucalyptus globulus stand in south-west Western Australia for chip logs. Coppice stems had been reduced to one stem or two stems per stool or left untreated. Time and piece counts were used to determine harvester productivity. Harvester cycle and elemental times and the number of logs and harvester head passes per stem were obtained from video recordings. Harvester fuel use was determined by refilling the fuel tank to the same point each day. Stem size was the major factor influencing harvester productivity (20.8 m3 per productive machine hour without delays [PMH₀], 11.8 m³ PMH₀^?1 and 8.6 m³ PMH₀^?1 in the single-stem (mean stem volume [MSV] 0.21 m³), two-stem (MSV 0.09 m³) and untreated trial areas (MSV 0.06 m³), respectively. Estimated harvester cost (AU$ m^–3) was considerably greater for the two-stem and untreated trial areas, which reflected the lower harvester productivity in these areas. Processing time represented over 60% of the total cycle time for all trial areas. Coppice characteristics resulted in significantly different moving/positioning times between trial areas. However, this difference had no impact on cycle times. Number of logs per stem was a significant variable in cycle and processing time regressions for all trial areas and felling time for the single-stem trial area. Number of harvester head passes was a significant variable in cycle and processing time regressions for the single-stem trial area and processing times for the two-stem trial area, although its effect was less than that of the number of logs per stem. Fuel consumption (L PMH₀^?1) was relatively constant between the trial areas, hence harvester energy intensity (L m^?3) reflected the harvester productivity in each trial area.     

Soil organic matter in European forest floors in relation to stand characteristics and environmental factors

Published data on the quantities of organic matter in the forest floor (SOM_fl) of European forest stands were collated. Studies of SOM_fl were included if the total sampled surface was at least 0.15 m², the surface of a single sample was at least 100 cm², live material was sorted out, and ash or carbon content was determined. Data from 59 forest stands were compared with regard to stand characteristics and environment. Using a single variable, tree genus was most important for the amount of SOM_fl (R ² _adj = 0.34). The amounts in spruce stands (41 × 10³ kg ha^?1) were significantly higher than those in larch, Douglas fir, oak and birch stands (4–11 × 10³ kg ha^?1). The best significant multiple model was genus combined with stand age and basal area (R ² _adj. = 0.72). The importance of litter quantity and quality for differentiating the tree genera is discussed.     

Predicting site productivity of the timber tree Pterocarpus angolensis§

Pterocarpus angolensis is an important timber tree of the miombo woodlands of sub-Saharan Africa. The species only grows in natural mixed forests and little is known about is productivity potential. This study aimed at investigating productivity of P. angolensis on a local scale in Namibia and Angola and on a regional scale in southern Africa. The most commonly accepted productivity indicator is stem diameter increment and this was used to study productivity at a regional scale. Indicators of productivity used at the local scale were basal area, proportional basal area and site form, which were derived from 217 forest inventory plots in Namibia and Angola. The productivity measures were modelled with abiotic site factors; biotic factors were added for the local scale. Results indicated that the most consistent site factors at local and regional scale were not related to climate but to forest cover, with the species having a competitive advantage in more open forests. Mean annual diameter increment in the open forests of Namibia was 0.51 cm after 50 years. Boosted regression tree models at a local scale showed that species presence can be modelled more successfully than species basal area, proportional basal area (correlation of 0.72 vs 0.56 and 0.45, respectively) and site form. The sites with the highest productivity of P. angolensis at the local scale had a temperature seasonality below 34.5 °C, a slope of less than 1.5°, tree cover less than 20% and stand basal area higher than 9 m² ha^?1. The results can assist in establishing a site-dependent growth model for the species and direct forest and fire management towards the most productive areas.     

Biomass harvesting in Eucalyptus plantations in Western Australia

Australia is at an early stage of exploring the use of forest biomass to generate energy. This study evaluated the biomass yield and the productivity rates of equipment for harvesting biomass in a poor-quality eucalypt plantation. The operation consisted of a tracked feller-buncher, grapple skidder and mobile chipper. Time study methods were used to measure the harvesting operation. A multiple regression model was constructed to predict skidding productivity. Biomass production was 63.9 t ha^?1 based on the recorded load weight of eight trucks. Delays were documented and analysed. The average delay for all equipment was about 30% of working time. The study results will help guide biomass harvesting managers to estimate productivity and cost of similar operation sites.     

宁夏六盘山香水河小流域华北落叶松人工林乔木层生物量的坡面变化和尺度效应

生物量受坡面环境条件变化影响而有坡面变化与尺度效应。本文在六盘山半湿润区的香水河小流域选择了33 a生华北落叶松人工林的一个斜坡长480 m,水平长398 m的典型坡面,在整个坡面上建立了宽30 m的调查样带,均匀分为空间连续的16个样地,在2014年生长季中期调查不同坡位的样地生物量,分析其坡面变化规律。结果表明:生物量存在明显的坡位差异。坡面生物量t·hm^-2平均值为118.59,其变化范围为96.19 139.18,变幅为42.99,变异系数为0.12;随着离坡顶距离的增加,生物量总体上呈现先升高后降低的变化趋势,在坡面的中上部(水平坡长为87.71 m)达到最大。生物量存在坡面空间尺度效应,即随着相对坡长(X₁)的增加,生物量的顺坡滑动平均值(Y₁)先增大后减小,其回归关系式为:Y₁=23.004X₁³-60.834X₁²+31.786X₁+123.43(R²=0.84),坡面尺度效应表现为每100 m水平坡长生物量变化的数值为6.12 t·hm^-2;各样地生物量与整个坡面平均值的比值(Y₂,小数)随相对坡长有很好的非线性关系,基本上呈先增加后下降、后趋于稳定的变化趋势,其关系式为Y₂=1.722 6X₁³-2.844 5X₁²+1.033 8X₁+1.000 1(R²=0.57),可基于此将特定坡位样地的生物量换算成整个坡面的估算值。造成生物量坡面变化的主要原因是太阳辐射和光照时间随海拔的变化等多种因素造成的。