Category: Research article
article id 9947, category Research article
Creation of value through a harvester on-board bucking optimization system operated in a spruce stand. Silva Fennica vol. 52 no. 3 article id 9947. https://doi.org/10.14214/sf.9947
Highlights: Use of harvester on-board computer bucking optimization remains highly under-utilized in German forestry; Revenue per tree and harvesting productivity were both statistically higher with automatic bucking as compared to quality bucking during a thinning operation in a spruce dominated stand.
Tree bucking, defined as the process in which a stem is segmented into shorter logs of varying lengths, has a significant effect on the value adding potential of a forest enterprise. Because of its importance in terms of correct product and length combinations, improper bucking can lead to financial losses. In this study, two treatments (OFF: quality bucking performed by the operator while using hot keys and ON: automatic bucking using the optimized suggestions from the harvester on-board computer; OBC) were tested in a Norway spruce (Picea abies [L.] Karst.) dominated stand located in Germany. Both treatments had the aim to maximize the value of a stem. The research took place in an 80-year old spruce and beech stand under a regenerative cutting. Fully-mechanized harvesting was performed with an 8-wheel Ponsse Bear single-grip harvester equipped with a H8 harvesting head. Results indicated that the product recovery of the two treatments differed by 4% in undamaged trees (no broken tree-tops or stems) to the benefit of manual bucking. However, the revenue of trees subjected to optimized bucking were up to 4% higher (in average 3%) than those of the manual bucking once expressed on a per cubic meter basis. Moreover, the harvesting productivity of the ON treatment was at the maximum 17% higher compared to the OFF treatment. Based on the results from this case study, the use of an optimization software in Norway spruce dominated stands with the aim to maximize the value of single stems showed promising results.
article id 7728, category Research article
Inter- and intra-annual wood property variation in juvenile wood between six Sitka spruce clones. Silva Fennica vol. 51 no. 4 article id 7728. https://doi.org/10.14214/sf.7728
Highlights: Wood property differences resulted primarily from variation in the proportions of early- and latewood in each annual ring; Width of early- and latewood bands in each ring was found to be a more important determinant of juvenile wood quality than the characteristics of the cells within each band; Wood properties differed greatly between clones, suggesting that there is potential to improve juvenile wood properties through selective breeding.
Increased growth rates have reduced rotation lengths, increasing the proportion of juvenile wood relative to mature wood, which may negatively affect mechanical performance of sawn timber. However, there is limited information available on the potential impact of breeding for vigour on juvenile wood in Sitka spruce (Picea sitchensis (Bong.) Carrière). In this study, the relationship between vigour (based on total height) and wood properties was investigated in six-year-old Sitka spruce clones grown in two replicated field trials in Ireland. Six clones were evaluated, two clones from each of three vigour (high, intermediate and low) classes. Discs were cut from the base of one ramet per replication for each clone to assess wood quality attributes. Radial tracheid width was significantly and positively correlated with ring width and height, and was negatively correlated with density. The wood of the most vigorous clone had significantly larger ring width with thinner cell walls and wider tracheids than all clones in the two other vigour classes, resulting in lower mean wood density. Latewood properties for all wood attributes measured differed significantly between the two sites. Wood property differences resulted primarily from variation in the proportions of early- and latewood in each annual ring. Additionally, the width of early- and latewood bands in each ring was found to be a more important determinant of juvenile wood quality than the characteristics of the cells within each band. Wood properties differed greatly between clones, suggesting that there is potential to improve juvenile wood properties through selective breeding.
article id 1714, category Research article
Effect of deployment-type on stem growth, biomass partitioning and crown characteristics of juvenile Sitka spruce clones. Silva Fennica vol. 51 no. 1 article id 1714. https://doi.org/10.14214/sf.1714
Highlights: Deployment x clone interactions reduced tree height and diameter growth in mixed plots for one clone; Height and diameter heterogeneity was significantly greater in mixed plots; Deployment-type significantly altered relationships between crown variables and competition was more asymmetric in mixed plots compared to monoclonal.
Competitive interactions in clonal forestry are not well understood and this needs to be addressed to develop better deployment strategies. Eight juvenile Sitka spruce (Picea sitchensis (Bong.) Carriére) clones were grown in monoclonal and clonal mixtures in a field experiment for three years to assess the effects of genetic diversity on shoot growth, above- and below-ground biomass partitioning and crown characteristics. Shoot elongation was measured throughout the growing season, while diameter was measured twice annually in May and December. After the third year, crown silhouette area was estimated from digitised images for one ramet per plot and ramets were then destructively harvested. Deployment × clone interactions were observed for tree height and diameter with reductions observed in mixed plots. Mixed plots had significantly greater height and diameter heterogeneity and more asymmetrical competition than monoclonal plots. Results from this study demonstrate that stem growth can be significantly altered when clones are planted in multi-clonal mixtures but for most clones, deployment-type will not significantly reduce their productivity.
article id 1514, category Research article
Cleaning Scots pine seedling stands with mechanical uprooters – a work quality comparison of two related devices. Silva Fennica vol. 50 no. 3 article id 1514. https://doi.org/10.14214/sf.1514
Highlights: The productivity of the narrower modified device was significantly better than the wider original device; Work quality did not differ significantly between devices when stand characteristics, regeneration success and pre-existing damage were taken into account; Results indicate that mechanical uprooting devices may be further developed to a cost-effective alternative to motor-manual techniques for the early cleaning of direct seeded commercial Scots pine stands.
Commercial forests require early cleaning to ensure the unhindered and uniform growth of crop trees. In order to be cost effective, non-crop vegetation should be uprooted to prevent their recovery. Performing this work manually is a labour-intensive task but it can be done mechanically. We evaluated the efficiency of two uprooting devices in direct seeded Scots pine (Pinus sylvestris L.) stands ca. 1 m tall. Productivity and quality of the uprooting work was investigated across eight stands and ca. 160 sample plots in northern Karelia, eastern Finland. Time consumption of the uprooters was analyzed through a linear regression model and the work quality through a multilevel multivariate model in terms of the number of individual Scots pine seedlings, processing units (i.e., a bunch of seedlings to be harvested in the future) and broadleaves. The productivity of the narrower modified device was significantly better in terms of time consumption than the wider original device. Work quality did not differ significantly between devices when stand characteristics, regeneration success and pre-existing damage were taken into account. Results indicate that mechanical uprooting devices may be further developed to a cost-effective alternative to motor-manual techniques for the early cleaning of direct seeded commercial Scots pine stands.
article id 1428, category Research article
Effect of multi-tree handling and tree-size on harvester performance in small-diameter hardwood thinnings. Silva Fennica vol. 50 no. 1 article id 1428. https://doi.org/10.14214/sf.1428
Highlights: Harvesting with the accumulating energy wood head EF28 was studied under small tree dimension (8 dm3) in hardwood thinnings; Reasonable productivity was achieved; Maximum achieved cutting diameter in hornbeam stand was 23 cm and 15% lower than in softwood stands; Head has potential under such conditions.
Early thinnings are laborious and costly. Thus forest companies are searching for cost and time efficient ways to carry out this task. The study’s purpose was to determine the productivity of the EF28 accumulating energy wood harvesting head in harvesting small-diameter hornbeam (Carpinus betulus L.) undergrowth trees and evaluate the effect of its multi-tree handling (MTH) capacity on time consumption. The harvester was a wheeled, three-axle Komatsu 911. A time study of 7.1 hours on 19 plots, with a total area of 0.76 ha was conducted. On average, the harvested tree volume was 8 dm³ and the stand density was 2666 trees/ha. The productivity was modelled with MTH conduction, mean diameter at breast height and the number of trees handled per cycle as independent variables. On average, MTH took 27% longer per cycle, increased extracted volume per cycle by 33% and consequently increased productivity with 5.0%. In 71.9% of the cycles more than one tree was handled and if so, dimensions were smaller than in single-tree handling (5.8 cm vs. 12.0 cm). Maximum felling diameter of 23 cm was about 15% smaller than in softwood (according to the manufacturer’s specifications) and the driver didn’t exploit the EF28’s theoretical potential in terms of trees handled per cycle. It can be concluded that the head could significantly improve productivity in small-diameter wood procurement.
article id 1382, category Research article
Performance of a small and a medium sized professional chippers and the impact of storage time on Scots pine (Pinus sylvestris) stem wood chips characteristics. Silva Fennica vol. 49 no. 5 article id 1382. https://doi.org/10.14214/sf.1382
Highlights: The storage time of pulpwood had no significant effect on particle size distribution in any chip size classes; The study confirms the knowledge that chipping time consumption is inversely proportional to engine power and grapple load size in feeding; The use of an narrower 80 mm × 80 mm sieve on Scots pine material does not seem to offer any benefit compared to a 100 mm × 100 mm sieve from the perspective of chip quality.
The primary aim of this study was to clarify the chipping productivity and fuel consumption of tractor-powered and truck-mounted drum chippers when chipping pine pulpwood at a terminal. The secondary aim was to evaluate the impact of wood storage time on the chemical and physical technical specifications of wood chips by chipping pulpwood from eight different storage time groups, using Scots pine (Pinus sylvestris) pulpwood stems logged between 2 and 21 months previously at the terminal with the above-mentioned chippers. Thirdly, the impact of sieve mesh size on the particle size distribution of wood chips from different age groups was compared by using an 80 mm × 80 mm sieve for a tractor-powered chipper and a 100 mm × 100 mm sieve for a truck-mounted chipper. With both chippers, the chipping productivity grew as a function of grapple load weight. The average chipping productivity of the tractor-powered chipper unit was 19 508 kg (dry mass) per effective hour (E0h), and for the truck-mounted chipper the average productivity was 31 184 kg E0h–1. The tractor-powered drum chipper’s fuel consumption was 3.1 litres and for the truck-mounted chipper 3.3 litres per chipped 1000 kg (dry mass). The amount of extractives or volatiles did not demonstrate any statistically significant differences between storage time groups. The particle size distributions with both chippers were quite uniform, and the storage time of pulpwood did not have a significant effect on the particle size distribution in any chip size classes. One reason for this might be that the basic density of chipped wood was homogenous and there was no statistical difference between different storage times. The use of new sharp knives is likely to have affected chip quality, as witnessed by the absence of oversized particles and the moderate presence of fines. The use of narrower 80 mm × 80 mm sieves on Scots pine material does not seem to offer any benefit compared to 100 mm × 100 mm from the chip quality point of view.
article id 1161, category Research article
Comparative study of the Risutec Automatic Plant Container (APC) and Bracke planting devices. Silva Fennica vol. 48 no. 3 article id 1161. https://doi.org/10.14214/sf.1161
Highlights: As currently designed, the prototype Risutec APC fitted with an automatic feeding system offers no significant advantage over the Bracke planting device in terms of planting productivity or quality; Cost estimates suggest that an idealized automated feeding system could increase productivity and decrease unit costs.
The productivity of mechanized planting could be increased by minimizing the time spent manually reloading seedling cassettes. This study compared the work-time distribution, productivity and quality of the prototype Risutec APC fitted with an automatic feeding system and the commonly-used and manually-loaded Bracke P11.a. An approach of comparative time study was employed that compared performance of two operators using both machines in four sites where slash and stumps had been removed. Operating costs were estimated and compared for these two machines and an idealized machine with automatic feeding system (referred as AUT). AUT was assumed to be similar to the Bracke planting machine with the only difference being in automatic feeding. Productivity of the Risutec APC (196 seedlings per productive work hour [pl PWh0–1]) was lower than that of Bracke (244 pl PWh0–1), making the unit cost 35.7% higher. A large portion (17.6%) of the productive work time of Risutec APC was interrupted by malfunctions, so it cannot be considered robust and reliable yet. Quality of the planting work was reasonable for both machines. The results suggest that an idealized AUT could increase planting capacity (hectares per year [ha yr–1]) by 15.4% and lower the unit cost (Euro per seedling [€ pl–1]) by 4.7% compared to today’s machines. The importance of an automated feeding system increases with planting efficiency because relatively more time is spent reloading seedlings. Proper automatic feeding system could offer a cost-effective solution and could enhance productivity, but the Risutec APC has yet to meet the technical and economic standards required to be competitive.
article id 1064, category Research article
Reloading mechanized tree planting devices faster using a seedling tray carousel. Silva Fennica vol. 48 no. 2 article id 1064. https://doi.org/10.14214/sf.1064
Highlights: Seedling reloading onto the Bracke Planter crane-mounted planting device was twice as fast with the MagMat tray-wise-loaded carousel as today’s seedling-wise-loaded carousel; Tray-wise reloading combined with deplugging seedlings from suitable cultivation trays has the potential to be an efficient and robust way to feed seedlings on any type of tree planting machine.
On Nordic clearcuts, today’s tree planting machines produce high-quality but costly regenerations. Much of this high cost is attributable to the planting machines’ low productivity. One promising way of raising productivity is to lessen the time spent manually reloading seedlings onto the carousels of crane-mounted planting devices. Using MagMat, a carousel test-rig designed by engineering students, we studied how much faster tray-wise seedling reloading is on the Bracke Planter compared to reloading with today’s seedling-wise-loaded carousel. The MagMat test-rig held eight Hiko cultivation trays from which seedlings were deplugged individually and dropped into the planting tube. The time study confirmed that seedling reloading was on average twice as fast with MagMat compared to today’s seedling carousel, thereby increasing assumed planting machine productivity by 8–9% depending on the planting device used. MagMat’s cost-efficiency was analysed to be particularly reliant on its added investment cost, mechanical availability and how quickly trays can be switched automatically. Nevertheless, MagMat’s field performance illustrated the overall potential of tray-wise loading compared to piecewise seedling loading for increasing the productivity of crane-mounted planting devices. Also, deplugging proved to be a reliable method of extracting seedlings from the rigid, copper-painted Hiko cultivation trays even when performed at the excavator’s boom-tip during mounding work. We conclude that, rather than piecewise seedling loading, tray-wise loading combined with deplugging seedlings from suitable cultivation trays is a reliable and much more time-efficient method to feed seedlings on probably any type of tree planting machine.
article id 982, category Research article
Labour consumption models applied to motor-manual pre-commercial thinning in Finland. Silva Fennica vol. 48 no. 2 article id 982. https://doi.org/10.14214/sf.982
Highlights: When a young stand grows and gets older, the work time needed to make pre-commercial thinning increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hardwoods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively.
Labour models were developed to estimate the time required to Pre-Commercially Thin (PCT) with a clearing saw 4- to 20-year-old stands of the main commercial tree species in Finland. Labour (i.e., work-time consumption) was estimated from the density and stem diameter of the removal of 448 stands via an existing work productivity function. The removal based estimator attained was used as the basis for a priori mixed linear regression models. The main finding was that when a young stand grows and gets older, the work time needed to make a PCT increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hardwoods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively. Site fertility also played a role in that the most fertile site (mesic OMT) had an estimated labour requirement 114% higher than that for dryish VT. We also note that, per unit area, small stands require less labour than large ones and soil preparation method had a minor effect on the labour estimate. The stands which had previously gone through PCT were separately analysed. In those stands, the only significant variable concerning the labour estimate was age. The a priori models described here can help foresters to develop economic management programmes and issue quotes for forestry services.
article id 1030, category Research article
Effects of the number of assortments and log concentration on time consumption for forwarding. Silva Fennica vol. 47 no. 4 article id 1030. https://doi.org/10.14214/sf.1030
Highlights: We analysed the effects of total and forwarded log concentrations (m3 (100 m)–1) and the number of loaded assortments on forwarding; The combination of the number of loaded assortments and their abundance (i.e. forwarded log concentration) affected time consumption most; This knowledge enables improved efficiency by optimizing number and assortment proportions in the various loads required to forward a stand.
Forwarding has been carried out for 50 years, but much is still unknown about this work. Its complexity comes from both stand features and essential decision-making. Forwarding time consumption is influenced by e.g. log concentrations and number of assortments. Traditionally, focus has been on the total log concentration (TLC), referring to all logs at the harvesting site. However, we focused on forwarded log concentration (FLC), the load-specific log concentration which depends on the assortment distribution at harvesting site and the load-specific number of assortments. To evaluate the effects of TLC, number of assortments in a load and FLC on the loading and unloading times, a standardized field experiment was carried out. Pile and load sizes were constant, while TLC and FLC were manipulated by varying the pile distribution on the test path. For all work elements, the time consumption per m3 was significantly affected by the number of assortments that were loaded, but only the “driving while loading” work element was also significantly influenced by TLC. However, when untangling the intercorrelation between tested factors, it was found that the time consumption for driving while loading significantly decreased as a function of FLC and was unaffected by the number of assortments in a load. That FLC influences the forwarding time consumption highlights the need to study the effects of combining various assortment proportions in a load. Such knowledge will enable analysis of the most efficient number and assortment proportions to combine in the various loads required to forward a given stand.
article id 930, category Research article
Comparing the efficiency of drum and disc chippers. Silva Fennica vol. 47 no. 2 article id 930. https://doi.org/10.14214/sf.930
The study compared the effect of chipper type on productivity, power demand, fuel consumption and product quality. Tests were conducted on two commercial chipper models, a disc and a drum chipper. Both chippers had the same diameter capacity, were applied to the same tractor and fed with the same feedstock types. Fifteen replications were conducted per machine and for each of four different feedstock types, reaching a total of 120 tests. The disc chipper had a higher energy efficiency and used 19% less fuel per unit product, possibly due to its simpler design, integrating comminuting and discharge system in one synergic device. In contrast, the drum chipper was 8% more productive, since it cut with the same energy all along the length of its knives. The drum chipper produced smaller chips, with a higher incidence of fines. Feedstock type had a strong effect on productivity, energy efficiency and product quality. The effect of feedstock type was mainly related to piece size, and may be stronger than the effect of chipper type. Further studies should determine the effect of blade wear on the relative performance of the two chipper types.
article id 57, category Research article
Performance modelling in forest operations through partial least square regression. Silva Fennica vol. 46 no. 2 article id 57. https://doi.org/10.14214/sf.57
Partial Least Square (PLS) regression is a recent soft-modelling technique that generalizes and combines features from principal component analysis (PCA) and multiple regression. It is particularly useful when predicting one or more dependent variables from a large set of independent variables, often collinear. The authors compared the potential of PLS regression and ordinary linear regression for accurate modelling of forest work, with special reference to wood chipping, wood extraction and the continuous harvesting of short rotation coppice. Compared to linear regression, PLS regression allowed producing models that better fit the original data. What is more, it allowed handling collinear variables, facilitating the extraction of sound models from large amounts of field data obtained from commercial forest operations. On the other hand, PLS regression analysis is not as easy to conduct, and produces models that are less user-friendly. By producing alternative models, PLS regression may provide additional – and not alternative – ways of reading the data. Ideally, a comprehensive data analysis could include both ordinary and PLS regression and proceed from their results in order to get a better understanding of the phenomenon under examination. Furthermore, the computational complexity of PLS regression may stimulate interdisciplinary team-building, to the greater benefit of scientific research within the field of forest operations.
article id 33, category Research article
Determining the impact of some wood characteristics on the performance of a mobile chipper. Silva Fennica vol. 45 no. 1 article id 33. https://doi.org/10.14214/sf.33
A study was conducted to determine the effect of some wood characteristics such as species, moisture content and tree part on the performance and product quality offered by a mobile industrial chipper, of the type commonly used for roadside chipping. Two main species, two tree parts and two moisture content levels were combined in a factorial design yielding 8 treatments, each replicated 5 or 6 times. A flow meter was installed on the chipper engine, and all chips produced were weighed and sampled for moisture content and particle size distribution. The results indicated that some wood characteristics such as species and moisture content have a secondary effect on chipper productivity and fuel consumption, which are primarily controlled by piece size. In particular, fuel consumption per unit dry mass seem to be rather constant and in the range of 3.2 l per oven dry ton. Moisture content and tree part may have a significant effect on the particle size distribution of chips. Of course, these results were only verified for the species used in the test and for industrial chippers, and may change if substantially different species or machines are used.
article id 122, category Research article
Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada. Silva Fennica vol. 44 no. 5 article id 122. https://doi.org/10.14214/sf.122
It has been suggested that without sufficient soil disturbance, harvest in boreal forested peatlands may accelerate paludification and reduce forest productivity. The objectives of this study were to compare the effects of harvest methods (clearcutting vs. careful logging) and season (summer vs. winter harvest) on black spruce regeneration and growth in boreal forested peatlands of eastern Canada, and to identify the soil variables that favour tree growth following harvest. Moreover, we sought to determine how stand growth following harvest compared with that observed following fire. The average tree height of summer clearcuts was greater than that of summer carefully logged stands and that of all winter harvested sites. Summer clearcutting also resulted in a higher density of trees > 3 m and > 4 m tall and in a 50% reduction in Rhododendron groenlandicum cover, a species associated with reduced black spruce growth. Height growth of sample trees was related to foliar N and P concentrations, and to soil total N, pH and available Ca and Mg but not to harvest method or season. Our results also indicate that summer clearcutting could produce stand productivity levels comparable to those observed after high-severity soil burns. These results suggest that summer clearcutting could be used to restore forest productivity following harvest in forested peatlands, and offer further support to the idea that sufficient levels of soil disturbance may be required to restore productivity in ecosystems undergoing paludification.
article id 165, category Research article
Operational efficiency and damage to sawlogs by feed rollers of the harvester head. Silva Fennica vol. 44 no. 1 article id 165. https://doi.org/10.14214/sf.165
In mechanical cutting, deep damage caused by feed rollers can reduce the yield of good quality timber for the sawmill and plywood industries. Additionally the feeding and energy efficiency of feed rollers are important for the profitability of harvester cutting. The objectives of this study were to compare the damages to sawlogs, as well as the time and fuel consumption of stem feeding with six different steel feed rollers during the processing of stems using a single grip harvester. This study tested two rollers with big spikes, two rollers with small spikes, one roller with studs in v-angle and one roller with adaptable steel plates in the ring of the roller. A highly detailed, and accurate processing and fuel consumption projection was recorded using the harvester’s automated data collector on a log and stem level. The roller adaptable plate averaged, for unbarked sawlogs, the lowest damages of 3.7 mm. While the damages of the roller with big spikes were the deepest with an average of 7.8 mm. For medium stems, volume of 0.35 m3, the range of differences between the maximum and minimum effective feeding time per roller was 6–19%, which would increase the effective time consumption of cutting by 1–3%. Corresponding differences in fuel consumption during total stem processing were in the range of 7–15%. According to this study it can be concluded that the traditional rollers with spikes were most effective in processing and fuel consumption, but at the same time they caused the deepest damages to the sawlogs. The roller type with adaptable steel plates was the most effective for small stems, additionally it also caused the least damage to the sawlogs.
article id 186, category Research article
A techno-economic evaluation of Bracke and M-planter tree planting devices. Silva Fennica vol. 43 no. 4 article id 186. https://doi.org/10.14214/sf.186
Techno-economically reasonable mechanization of tree planting has proved to be a difficult task in the Nordic working conditions. Although planting machines and combinations of base machine and planting device have been developed since the 1970s, mechanized planting has not been cost-competitive to manual planting. The aim of this study was to find out work time distributions, productivities, costs and effects of different work difficulty factors on productivities and costs of the state-of-the-art Nordic planting devices, Swedish Bracke and Finnish M-Planter, and to compare the devices with each other. The theory of comparative time studies was the base for the experimental design of this study. In the average working conditions, productivity (E15) of M-Planter (236 seedlings/hour) was 36.0% higher than that of Bracke (174 seedlings/hour). Here, M-Planter performed planting work 23.4% cheaper than Bracke. However, the difference depended greatly on the working conditions; the more stones or stumps the smaller the difference, and the more slash the bigger the difference.
article id 256, category Research article
Harvesting technology and the cost of fuel chips from early thinnings. Silva Fennica vol. 42 no. 2 article id 256. https://doi.org/10.14214/sf.256
This study compared and analyzed the procurement cost of whole tree chips when using supply chains based on comminution at the roadside landing or at the terminal. It also identified the bottlenecks of the most common logging systems used in Finland. The study was done by using existing and published productivity parameters and models. The procurement cost calculations were made for a stand where the forwarding distance was 200 metres, removal of whole trees was 60 m per hectare and the area of the stand was 2.0 hectares. The average size of the removed whole trees was 30 litres. The direct transport distance from the stand to the terminal or to the end use facility was 40 km while the secondary distance from the terminal to the end use facility was 10 km. A stumpage price for the harvested raw material was not included in this study. According to the study the cost of whole trees chips were 31.9–41.6 euros/m at the plant, or 14.9–19.4 euros/MWh when the moisture content of chips was estimated to be 40%. The two-machine system was found to be the most cost competitive logging system in pre-commercial thinnings thanks to both efficient cutting and, especially, forwarding work. In the manual worker based logging, the costs of felling bunching were the same as the mechanised system, whereas in forwarding the costs were almost double. Using the harwarder system the logging costs were found to be the highest, but in the larger tree volumes and removals the costs were almost equal to the manual worker based logging. The supply chain based on chipping at the roadside landing was more cost efficient compared to the chipping at the terminal system. The lower comminution cost at the terminal was not enough to cover the higher transportation cost of unprocessed material to the terminal, handling cost of chips at the terminal or the delivery cost to the end use facility.
article id 365, category Research article
Harvesting and transport of root biomass from fast-growing poplar plantations. Silva Fennica vol. 39 no. 4 article id 365. https://doi.org/10.14214/sf.365
Recovery of tree root biomass can be attractive, since the stump-root system represents a substantial portion of the tree mass and its removal may prove instrumental to re-cultivation. Most available studies concern Nordic technologies, particularly suited to mature conifer stands. Unlike spruce, plantation poplar develops a deep taproot, whose extraction requires completely different methods. The aim of the study was to investigate poplar root recovery operations in plantations with time studies, and to determine the productivity and delivery costs of the operations. Seven operation systems developed to work with poplar plantations in Italian conditions were studied. Extraction and cleaning units were based on general-purpose prime movers. Under favourable conditions extraction and cleaning units achieved a very high productivity: 150 stumps per hour for the extraction unit and 170 for the cleaning unit. Delivered cost varied widely, ranging from 28 to 66 Euros Mg–1. Transportation was the most expensive single work task. It accounted for about 40% of the total recovery cost. Extraction and cleaning contributed approximately 25% each to the total cost, and loading 9%. Guidelines to recovery system improvement and efficient operation are provided.
article id 668, category Research article
Modelling the dynamics of wood productivity on drained peatland sites in Finland. Silva Fennica vol. 33 no. 1 article id 668. https://doi.org/10.14214/sf.668
The dynamics of wood productivity on drained peatland sites was analyzed from the covariance structure generated by stand yield data of repeatedly measured permanent sample plots in 81 Scots pine (Pinus sylvestris L.) or Norway spruce (Picea abies Karst. (L.)) stands with admixtures of birch (Betula pubescens Ehrh.). The site production potential, considered a latent variable, was assumed to follow an autoregressive process over time elapsed since drainage. As a measure of the latent variable, a relative growth rate (RGR) index was determined for all stands at the time of drainage and at four successive measurement time points following drainage (on average 16, 23, 30, and 41 years). The index was calculated as the site index of an upland conifer stand with the ratio of periodic volume growth and standing volume and adjusted by changes in stand stocking and thinning. The observed covariance structure was described by fitting a structural equation model to the data of RGR indices. When only the post-drainage measurement times were included, a quasi-simplex model with equal error variances and equal structural parameters at different measurement times fit the data well indicating a permanent covariance structure among the different measurements. Including the measurement at the time of drainage resulted in a non-permanent structure. The stand parameters at the time of drainage were poorly correlated with post-drainage growth. A considerable increase in the wood productivity of the sites was observed, being greatest during twenty years after drainage and continuing up to 40 years since drainage. This was concluded to be due to changes in site properties rather than stand structure although the effects of the single factors could not be analytically separated from one another. Our modelling approach appeared to improve long-term site productivity estimates based merely on botanical site indices.
Category: Research note
article id 1717, category Research note
Forwarder crane’s boom tip control system and beginner-level operators. Silva Fennica vol. 51 no. 2 article id 1717. https://doi.org/10.14214/sf.1717
Boom tip control (BTC) allows the operator to control boom tip movements directly, instead of controlling each movement separately to achieve the desired boom tip movement; BTC eased boom control, so beginner-level operators using BTC achieved higher productivity than beginner-level operators using a conventional (reference) system; There were no significant differences in the slopes of learning curves between the systems.
The forwarder loads processed wood and transports it to a landing. Productivity of forwarding could be improved by increasing driving speed, but difficult forest terrain limits this. According to current literature, crane work is the most time-consuming work element of forwarding, so improving crane work productivity is essential for improving forwarding productivity. One way to do this is through automation of recurrent boom movement patterns, or alternatively automation can be used to ease crane work. When using conventional boom control (CBC), the operator manually controls each of the independent boom joint movements and combines them to achieve a desired boom tip movement, but boom tip control (BTC) allows the operator to control boom tip movements directly. The objective of the present study was to examine whether BTC facilitates crane work and affects the slopes of learning curves for beginner-level forwarder operators. The study was carried out using a standardised test routine to evaluate effects of two fixed factors, system (levels: CBC, BTC) and point of time (four levels), on five dependent variables. Four of the five dependent variables measured ease of boom control and the fifth measured crane work productivity. The results showed that there were no significant differences in the slopes of learning curves between the systems but the BTC did increase crane work productivity and made boom control easier.
article id 915, category Research note
Comparison of two stump-lifting heads in final felling Norway spruce stand. Silva Fennica vol. 46 no. 4 article id 915. https://doi.org/10.14214/sf.915
The use of stump and root wood chips has increased very rapidly in the 21st century in Finland: in the year 2000, the total consumption of stump wood chips for energy generation was 10 GWh, while in 2010 it was approximately 2 TWh. Metsäteho Oy and TTS Research evaluated two stump-lifting devices for the lifting of Norway spruce (Picea abies) stumps. The productivity and costs of stump lifting were determined. There was one base machine with one operator in the time study. When lifting stumps with a diameter of 30 cm, the effective hour productivity of stump lifting was 11.2 m3 solid over bark (sob)/E0 (4.8 tonD/E0) without site preparation using a Väkevä Stump Processor, and when lifting spruce stumps with a diameter of 40 cm, the productivity was 14.9 m3 sob/E0 (6.5 tonD/E0). When the site preparation (mounding) was integrated into lifting work, the stump-lifting productivity decreased 21–27%. The stump-lifting productivity of the other lifting head (Järvinen) was lower than that of the Väkevä Stump Processor. Some development suggestions for the Järvinen lifting head were presented and discussed. The cost calculations showed that stump-lifting costs are extremely high when stump diameter is less than 20 cm. Therefore, the study recommended a change in the current stump-harvesting guidelines of Finland: The study suggested that all the stumps with a diameter less than 20 cm should be left on the harvesting site.
article id 61, category Research note
Harvesting of short rotation coppice – harvesting trials with a cut and storage system in Germany. Silva Fennica vol. 46 no. 2 article id 61. https://doi.org/10.14214/sf.61
Short rotation coppice (SRC) harvesting techniques are available in Germany, but broad experience and knowledge about machine performance and the related effective costs of harvesting operations are still missing. This information is crucial, as harvesting costs strongly influence the economic performance of the overall supply chain. Therefore, it was the aim of this study to collect and analyze productivity data of different harvesting systems for SRC. The combined cut and chip system on the one hand and the cut and storage system on the other hand were studied by literature review. Several studies analyze the combined cut and chip systems and the reported machine productivities showed great variations. The average was 30 green tons per scheduled machine hour (gt smh–1). Few studies are analysing the cut and storage system. They report that machines still are under development and that further research is needed. Therefore, time studies of harvesting operations using the cut and storage system were carried out. Five trials were performed with the harvesting machine “Stemster MK III” developed by Nordic Biomass. The share of productive working time was 85% and the average productivity was 21 gt smh–1. These results were compared with values from the literature. Resulting harvesting costs were calculated per oven dry ton (euros odt–1). The advantages and disadvantages of both harvesting systems are highlighted.
article id 470, category Research note
Energy wood and pulpwood harvesting from young stands using a prototype whole-tree bundler. Silva Fennica vol. 41 no. 4 article id 470. https://doi.org/10.14214/sf.470
The productivity of cutting and bundling whole trees using the first prototype of a bundle-harvester comprised of a harwarder as the base machine, an accumulating felling head, and a compacting device was studied in three young stands in order to facilitate the further development of the concept. In addition, the removal and its composition were studied as a means of laying the foundations for developing methods for work rating and measurement on delivery. Bundling enables in-depth integration of pulpwood and energy wood procurement. Both energy wood (crown biomass) and pulpwood can be incorporated into the same bundles, and the subsequent separation of these fractions takes place at the debarking phase at the pulpmill. Bundle-harvesting productivities were relatively low (2.8–3.7 m3/E0-h) when compared to current harvesting technology. Improving working techniques, machine structure, and components showed great potential for increasing the efficiency of the concept. The bundles were dimensionally uniform. Their solid volume varied between 0.350 m3 and 0.513 m3, depending on the bundle assortment and stand properties. Integrating energy wood harvesting with pulpwood harvesting increased removal even by 59 per cent.
article id 7132, category Article
Über die Klassifizierung der für Walderziehung entwässerten Moore. Acta Forestalia Fennica vol. 74 no. 5 article id 7132. https://doi.org/10.14214/aff.7132
English title: (1961). On classification of peatlands drained for forestry purposes.
The aim of the study is to find out 1) whether and how the original moor type can be found out based on vegetation regardless the phase of drainage; 2) whether the different phases of draining can be distinguished based on the vegetation; and 3) is it possible to classify the well drained moors into vegetation types that would reflect the productive capacity of the land.
The data consists of samples collected from ditched areas. There are 11 moor types from two climatic ditching zones. The results show that the original moor type can be determined based on vegetation, the phase of drainage can be determined under some limitations, and the classification for productivity can be done for practical purposes.
The PDF contains a summary in Finnish.
article id 7431, category Article
Sahatavaran vientitulon jakaantumisesta vuosina 1913-1953. Acta Forestalia Fennica vol. 61 no. 19 article id 7431. https://doi.org/10.14214/aff.7431
English title: (1954). On the distribution of income from Finnish sawn timber exports in 1913-1953.
The investigation studies the development of a logger’s daily earnings, a sawmill worker’s hourly earnings, saw timber stumpage prices and saw timber export prices, expressed in marks in Finland in 1913-1953, concentrating upon the trends of real value.
Although worker’s earnings in forestry and sawmilling have developed differently especially in the 1920s, the late 1930s and the early 1940s, their general long-time development has been very similar. On the other hand, the stumpage prices increased in real value much sharply than wages before the World War II. The real value of stumpage prices dropped because of economic regulation measures in the 1940s until regulation was abolished and the Korean War boom raised them in 1951, to fall after that. The development depends partly of the development of export prices for sawn timber.
Without changing the distribution of income from exports the real value of labour earnings, measured by export prices, may rise at most at a pace corresponding to the productivity of work. In logging there has been no actual increase in the productivity in the 20th century. As the increase in the productivity in timber transportation has probably been absorbed in increased wages and capital costs in the branch, a rise in forest labour’s real earnings and stumpage is possible only by means of a rise in the productivity of sawmilling or a change in the distribution of export income. It seems that from the end of World War I up to the middle of 1920s this increase of productivity and in export prices of sawn timber was shared only by capital and possibly mill labour. After that up to World War II stumpage prices rose so steeply that they swallowed the entire increase in productivity and reduced capital’s share of the export price. In the 40s the level of earnings followed the trend of productivity in industry, made possible by a sharp reduction in stumpage.
The Acta Forestalia Fennica issue 61 was published in honour of professor Eino Saari’s 60th birthday.
The PDF includes a summary in English.
article id 7240, category Article
English title: (1929). Common alder forest in Kontusaari.
The aim of the study was to determine the value of common alder (Alnus glutinosa (L.) Gaertn.) in forestry by studying an unusually large alder forest in Kontusaari, an island of the size of 75 hectares in the Southern Finland. The forest is grass-herb forest site type. The coastline of the island is partly flooded. Wood has been harvested mainly for fuel wood. The stands have regenerated easily from stump shoots. The annual volume growth is slightly higher than what would be in Norway spruce (Picae abies (L.) Karst.) or Betula sp. stands, estimated based on growth and yield tables made by Ilvessalo. The site is well suited for common alder, and it is difficult to judge what the yield would be for other species on the site.
The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander. The PDF includes a summary in German.
article id 7236, category Article
Können die südfinnischen Seen vermittels der umgebenden Vegetation und Flora bonitiert werden. Acta Forestalia Fennica vol. 34 no. 23 article id 7236. https://doi.org/10.14214/aff.7236
English title: (1929). Can the seas in southern Finland be classified according the productivity by means of surrounding vegetation and flora.
The aim of the study is to define to which extent the productivity of seas in south Finland, and especially the production of animals in sea bottom, can be determined according the forest site classification given to the land areas around the sea, meaning that the productivity class is the same for the forest and the sea. The data for the study has been collected in state owned forests in Evo in middle Finland, in Karelia around the Finnish and Russian border and in southern parts of Karelia.
Where the forests are more barren, VT or Ct types, also the seas have lower productivity, they are oligotrophic or mesotrophic. However, the less barren surrounding forests are not a clear sign of the productivity of the sea. As a result the productivity level of a sea can be estimated relatively good by the fertility of the surrounding areas, though not in all cases.
The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.
The PDF contains a summary in German.
article id 5515, category Article
Metsien käytön muutospaineet. Silva Fennica vol. 27 no. 3 article id 5515. https://doi.org/10.14214/sf.a15676
English title: (1993). Pressures for changes in the use of forests.
The paper discusses how the general trend towards increasing growth and productivity in the European societies is expressed also in forestry. It is reflected, for instance, in the increasing production and productivity of forest industries. Technological progress and call for economic growth require great flexibility from all resources. These pressures for effectiveness and production also concern Finnish forestry and forest management. Industrialization, urbanization and development of forestry have increased the pressure to use forests in recreation, preserving human environment and nature conservation in addition to production of timber. Through the development the definition of sustainability has become wider.
article id 5349, category Article
Time study on different techniques for nursery pot filling operation. Silva Fennica vol. 22 no. 2 article id 5349. https://doi.org/10.14214/sf.a15506
Time study on different techniques in nursery pot filling operations at SUA Training Forest in Northern Tanzania was conducted. The results showed that improved tools and work place design significantly decreased the operation time, hence increased productivity. In addition, worker’s comfort was generally increased.
The PDF includes a summary in Finnish.
article id 5315, category Article
Simulations on the effects of timber harvesting and forest management on the nutrient cycle and productivity of Scots pine stands. Silva Fennica vol. 21 no. 2 article id 5315. https://doi.org/10.14214/sf.a15472
Effects of varying rotation, thinning, fertilization and harvest intensity on the productivity and nitrogen cycle of Scots pine (Pinus sylvestris L.) stand were studied on the basis of computer simulation. The increasing intensity of management increased the loss of nitrogen in the cycle. Short rotation, associated with early thinning by means of the whole tree harvest, proved to be especially detrimental regarding the productivity of the forest ecosystem. Fertilization associated with thinnings is of great importance in maintaining the productivity of a forest ecosystem during an intensive timber harvest.
The PDF includes an abstract in Finnish.
article id 5304, category Article
A method to evaluate productivity of logging machines. Silva Fennica vol. 21 no. 1 article id 5304. https://doi.org/10.14214/sf.a15461
This study deals with the evaluation of logging machines. The analyses were based on the results of a productivity study with special reference to a PIKA 35 processor, a delimber-bucker, working in Kyröskoski forest area in Finland. Factors affecting the productivity of the machine were surveyed. Mathematical models for determining the productivity were developed and their practical applications to the particular problem under study was demonstrated.
The PDF includes an abstract in Finnish.
article id 7510, category Article
Wood procurement in the pressure of change. Acta Forestalia Fennica no. 248 article id 7510. https://doi.org/10.14214/aff.7510
Linear optimization model was used to calculate seven wood procurement scenarios for years 1990, 2000 and 2010. Productivity and cost functions for seven cutting, five terrain transport, three long distance transport and various work supervision and scaling methods were calculated from available work study reports. All methods are based on Nordic cut to length conditions. Finland was divided in three parts for description on harvesting conditions. Twenty imaginary wood processing points and their wood procurement areas were created for these areas. The procurement systems, which consists of the harvesting conditions and work productivity function, were described as a simulation model. In the LP-model the wood procurement system has to fulfil the volume and wood assortment requirements of processing points by minimizing the procurement cost. The model consists of 862 variables and 560 restrictions.
Results show that it is economical to increase the mechanical work in harvesting. Cost increment alternatives effect only little on profitability of manual work. The areas of later thinnings and seed tree- and shelterwood cuttings increase on cost of first thinnings. In mechanized work one method, 10-tonne one grip harvester and forwarder, is gaining advantage among other methods. Working hours of forwarder are decreasing opposite to the harverster. There is only little need to increase the number of harvesters and trucks or their drivers from today’s level. Quite large fluctuations in level of procurement and cost can be handled by constant number of machines, by alternating the number of season workers and by driving machines in two shifts. It is possible, if some environmental problems of large-scale summer time harvesting can be solved.
article id 7627, category Article
Productivity differentials in the Finnish forest industries. Acta Forestalia Fennica no. 180 article id 7627. https://doi.org/10.14214/aff.7627
Improvement of Finnish forest industries’ competitiveness in the world markets through productivity increase as branch and plant level requires the search for appropriate comprehensive productivity indicators and the analysis of factors underlying productivity variations. These were the main objectives of the study. The data was based on the information on individual plants in 1974, obtained from the files of Industrial Statistics in the Central Statistical Office in Finland.
The study uses neoclassical average production functions as the starting point and the theory is expanded to cover factors underlying productivity variation when measured with regard to labour, capital, material input, and total factor input. For the measurement of the latter an index formula is suggested which would not necessarily incorporate neoclassical assumptions as they cannot be assumed valid in the Finnish forest industries. The estimation results of average production functions suggest increasing rate of returns in sawmilling but in pulp and paper production evidence remains inconclusive. The elasticity of substitution is unlikely to be constant and the non-homotheticity assumption cannot be rejected.
The productivity variation is, in general, best explained by a relatively simple model with capital-labour ratio, plant size and output quality as explanatory factors. Further trials with input quality, input price ratio, process characteristics, and the rate of capacity utilization improved the models only marginally in most cases, which may have been partly due to the failure to measure the variables successfully.
The cross-section results are compared with those of an earlier time-series study. The estimation results of average production functions yield somewhat different information in the long and short run. Both cross-section and time-series productivity models illustrate the importance of output level in total productivity.
The PDF includes a summary in Finnish.
article id 7556, category Article
Optimization of stand treatment based on the marginal productivity of land and growing stock. Acta Forestalia Fennica no. 122 article id 7556. https://doi.org/10.14214/aff.7556
Production of timber in forest stands is described by a production function. The variable inputs of the function are land and growing stock and the output is the annual value growth. The partial derivatives of this production function express the marginal productivity of the land and of auction function express the marginal productivity of the land and of the growing stock. These marginal productivities can be utilized for determination of the need of regeneration and thinning. The stand should be regenerated when the marginal productivity of the land falls below the annual rent of a unit area of open land and thinned when the marginal productivity of the growing stock falls below the annual rent of one unit of growing stock.
The PDF includes a summary in Finnish.
article id 7185, category Article
Puunkorjuun tuottavuuteen vaikuttavat tekijät maatilametsätaloudessa. Acta Forestalia Fennica no. 85 article id 7185. https://doi.org/10.14214/aff.7185
English title: (1968). Factors affecting logging productivity in farm forestry.
This is a fourth paper in a series of studies concerning logging in farm forests. The objective was to construct a model representing the productivity per farm of logging for delivery cuts. The first objective was to find out how the productivity of logging should be measured. In the study, combined labour and capital are regarded as the input.
Second object was to consider what variables to use in theory to determine the productivity of logging for delivery cuts. The factors affecting productivity depend on the concept of productivity employed. The productivity per farm of logging in delivery cuts can be determined both by regional and by farm variables. Still considering solely the effect of the quality of labour and capital input, the variables representing the person in charge of the delivery cuts are important explanatory farm variables. Others represent the farm totality (size, lines of production etc.).
Third aim was to develop a statistical-mathematical method suitable for constructing the model. Possible methods include regression analysis, which is, however, not the best method when there is large number of different levels to explain, or factor analysis. The suitable method to use in constructing a model depicting the productivity of a farm, was considered to be to condense the explanatory variables into rotated orthogonal factors. After preliminary correlation analysis, estimates of the factors interpreted as rational were employed as the explanatory variables for selective regression analysis.
Last, the model was tried out against actual material collected per farm, and the hypotheses were tested.
The PDF includes a summary in English.
article id 4577, category Article
Metsäverotuksen uudistamissuunnitelma. Silva Fennica no. 57 article id 4577. https://doi.org/10.14214/sf.a9081
English title: (1942). Reform of forest taxation.
A committee was appointed in 1940 to prepare a proposal for reform of forest taxation. The taxation based on net income of forestry was considered to have limitations, and the actual net income had been observed to be markedly higher than the income that was used in taxation.
The report describes in detail the principles and shortcomings of taxation used since 1922. These include inaccuracies in the forest areas of a woodland estate, and weaknesses in classification of forest land and demand zones. The committee suggests several improvements in calculating the taxable income, which in the new calculations is based on yield on terms of value.
The article includes an abstract in German.
article id 4470, category Article
Päivittäisistä paperipuiden valmistusmääristä eri vuoden aikoina Perä-Pohjolassa. Silva Fennica no. 29 article id 4470. https://doi.org/10.14214/sf.a9042
English title: (1933). Seasonal variations of pulpwood harvesting in the northernmost Finland.
The fellings of small timber have been expanded from seasonal to full-year operation in many areas. A time and motion study was conducted on the felling of pulpwood in different times of the year in seven felling sites in the northernmost Finland. The work was payed per one pulpwood bolt. The output of a one-man teams was larger than 2-6-man teams. Teams of even numbers were more effective than teams of uneven numbers. One-man teams were more popular during summer. The output was largest during the summer. In the late summer the results decrease, because barking of trees becomes more difficult. Shortening of daylight hours begin to shorten the workdays in the autumn. In December, the average working days are about 6 hours. Snow and low temperatures make logging and barking more difficult during the winter. The output was lowest in January, despite that work days are 1 ½ hours longer than in December. It is concluded that pulpwood fellings should be avoided from December to March 15. If the fellings are necessary, the wage system should be changed more flexible than at present. The size of cutter’s lots should be adjusted so, that work periods are not too short. Sufficiently big lots save time spent on travelling between the sites and villages.
The PDF includes a summary in German.