volume: 39, issue: 1
In the study, the relationship between operators’ age, experience and mechanized cut-to-length
(CTL) harvesting productivity was examined. The data were five-year follow-up data from 28
operators and 38 CTL harvesters collected from southern Finland. Productivities were converted
to relative productivities and average productivity models were created. Case specific
productivities were compared to modelled values, and productivity ratio models including
separate lower and upper quartile models were produced.
The relative productivity of operators at the age of 45 years in clear cuttings was 17.8%
higher and in thinnings 14.9% higher than that of operators at the age of 25 years. The relative
lower quartile productivity increased from operators aged 25 to operators aged 45 years by
38.6% in clear cuttings and 29.4% in thinnings. The relative productivity of operators having
experience of 20 years was 23.6% higher in clear cuttings and 16.2% higher in thinnings than
that of operators having experience of 3 years. Operators’ experience of 20 years produced
43.1% better lower quartile relative productivity in clear cuttings and 29.1% in thinnings
compared to 3 years’ experience. The relative upper quartile productivity was 5.7% higher in
clear cuttings for operators aged 45 years than for operators aged 25 years, but otherwise, there
was no statistical correlation between upper quartile productivity and age or experience.
As a conclusion, CTL harvester operators’ average productivity increases slowly after the
initial learning phase up to 15 years of experience. The peak productivity was uncorrelated to
age or experience, but the experience raised the bottom productivity values.
volume: 39, issue: 1
Within the fuel wood supply chain, comminution and transport have been identified as processes
with the highest costs, energy consumption and emissions. The coordination of comminution
and transport aimed at avoiding operational delays is also complex. Nevertheless,
the use of forest biomass helps to reduce the effects of climate change and produces an additional
income, especially in rural areas. About 20 years ago, at the beginning of the industrial
forest fuel utilisation, the focus of the research was on developing and analysing adequate
supply chains and machines. Nowadays, as state-of-the-art systems have been established, the
focus is on improving the efficiency of the processes and the quality of the products. This paper
provides a review of research trends of the last ten years focusing on comminution and transport
of forest biomass in Europe.
Comminution should become more efficient by analysing the effects of wood characteristics on
chipper performance and product quality, by tailoring chipper configuration according to those
findings and by introducing mechanical devices for improving the quality of chips. Transport
processes have the potential to become more efficient if the configuration of trucks is adapted
according to operational and legal requirements, and when considering moisture content
management. Finally, economic and environmental assessment of supply chains was made by
several studies. Future research is expected to focus on customizing the product quality according
to user’s requirements and on optimising the coordination of chipper and truck by
simulation and automatization tools.
volume: 39, issue: 2
This paper discusses the key issues of forestry workers training in Croatia, especially dealing
with the providers of vocational training, their profile, training procedures and measures
necessary for training improvement. A combined approach of literature review, internet search
and questionnaire of training providers was applied in order to collect data on training programs
conducted in Croatia. The research was conducted during 2016, and it included 94
legal entities authorized for occupational safety training in the Republic of Croatia, with respect
to safe working practice training and vocational training for operating machinery (chainsaw
and/or skidder). The analysis used basic descriptive statistics.
Research results showed that 30.85% of the analyzed legal entities provide only training for
safe working practice, 15.96% provide both trainings – safe work practice and vocational
training for operating machinery, 5.32% of the analyzed entities provide only vocational
training for operating machinery, 31.91% do not carry out any form of training in forestry,
while 15.96% refused to answer questions. On the other hand, 15.56% of the legal entities,
which do not carry out any training or did not answer these questions, have on their official
website services posted for vocational training in operating machinery (chainsaw and/or skidder).
The key findings of the conducted research have pointed out the great heterogeneity
amongst providers of forestry workers training, and certain reductions or limitations in the
current training programs, both from the aspect of duration of the theoretical and practical
training, and the use of non-transparent criteria and standards in the assessment of training.
As an example of successful solution in forestry workers training, European Chainsaw Standard
model (ECS) is shortly presented in the paper. Discussion and conclusion sections provide
an overview of legislative and organizational requirements for the application of previously
developed European model (ECS) in developing the certification system for training of forestry
workers in Croatia.
volume: 39, issue: 2
Economic analysis of even-aged fir stand management was illustrated using the example of the
forests of the Croatian Dinaric region, as well as their transformation into more stable unevenaged
structures. Two scenarios (even-aged, uneven-aged) were simulated against the backdrop
of the existing forest stand structure of future forest stand management during a 140-year
period using forest growth modeling software MOSES version 3.0 in order to identify economic
differences amongst different scenarios both at stand level and at forest level. The research
included forest management analysis throughout the transformation period and subsequently
the continuation of balanced state forest management. Moreover, the research also
provided the opportunity of forest purchase within the price range from 1000 to 12,500 EUR/ha,
amid assumed fluctuation of selling prices of timber assortments throughout the simulation
period. Discount rates from 1% to 5% were used during the economic analysis. The research
findings showed that, according to harvesting costs, Net Present Value and Internal Rate of
Return, uneven-aged forest management system, including the transformation period, achieved
superior economic results, albeit at discount rates that exceeded 1.24%. The conclusion was
reached that, according to all economic criteria, uneven-aged mixed silver fir-beech management
system is preferred compared with the pure even-aged silver fir management.
volume: 40, issue: 1
The purpose of this paper is to assess the delivered cost of pulpwood from natural hardwood
stands in the State of Tennessee using forest operations supply chain analysis. The study is
based on primary production and equipment data collected from logging firms using a statewide
in-depth harvesting and transportation survey. Survey results were used to develop estimates
for the delivery cost of hardwood pulpwood removed per green tonne unit hour. Findings
revealed not only the variability of inputs attached to costing harvesting operations, but
also the difficulty in identifying one typical harvest system for the state. This may be explained
by the very diverse operating conditions and systems, as well as the low stumpage prices and
high cost of harvesting and delivery that are predominantly managed by small scale operations.
Results have shown that the cost of harvesting a tonne of wood for a distance of up to 50 km
ranges from an average minimum of $43 per tonne to an average maximum of $51 per tonne.
After this distance, the cost increases exponentially. The fact that this study is the first for the
state that looks at the operations logistics indicates the lack of available knowledge of the true
cost incurred by operators that may have a lasting impact not only on the continuity of logging
operations but also the sustainability and availability of forest products and workforce.
volume: 40, issue: 1
Private forests in Croatia, Bosnia and Herzegovina and Serbia are highly fragmented into
small plots of land with low productivity level and a large number of owners. Nevertheless,
they are recognized in the strategic plans and programs concerning renewable energy as having
a significant potential for woody biomass production. A regional research was conducted
among 350 private forest owners in each of the three South-East European countries, Bosnia
and Herzegovina, Croatia, and Serbia. It analyzed management activities and readiness of
private forest owners to produce additional quantities of woody biomass. Smart regulation
principles were selected as analytical framework in order to understand how the design of
forest policy instruments, based on specific characteristics of the target groups, can contribute
to the improvement of private forest owners’ readiness to mobilize additional quantities of
woody biomass from their forests. The results of this research indicated that although the
majority of private forest owners use their forests for producing firewood to meet their own
needs – 91.2% of private forest owners in Croatia, 85.0% in Bosnia and Herzegovina and
89.7% in Serbia, there is economic interest of private forest owners to produce additional
quantities of woody biomass beyond their own fuelwood household consumption – 43.9% in
Croatia, 45.8% in Bosnia and Herzegovina and 54.8% in Serbia. Moreover, private forest
owners’ socio-demographic characteristics, forest property characteristics and management
objectives significantly impacted the owners’ readiness to produce additional quantities of
woody biomass. The readiness for woody biomass mobilization could be increased by providing
different policy instruments, since this is deemed important by private forest owners. Hence,
forest policy recommendations were proposed that may support the private forest owners’
readiness to produce additional quantities of woody biomass.
volume: 41, issue: 1
The improvement of harvesting methodologies plays an important role in the optimization of wood production in a context of sustainable forest management. Different harvesting methods can be applied according to forest site-specific condition and the appropriate mechanization level depends on a number of factors. Therefore, efficiency and functionality of wood harvesting operations depend on several factors. The aim of this study is to analyze how the different harvesting processes affect operational costs and labor productivity in typical small-scale Italian harvesting companies. A multiple linear regression model (MLR) and artificial neural network (ANN) have been carried out to predict gross time, productivity and costs estimation in a series of qualitative and quantitative variables. The results have created a correct statistical model able to accurately estimate the technical parameters (work time and productivity) and economic parameters (costs per unit of product and per hectare) useful to the forestry entrepreneur to predict the results of the work in advance, considering only the values detectable of some characteristic elements of the worksite.
volume: 41, issue: 1
Upon carrying out logging, residues remain in the cutting area. Logging residues are an additional source of wood raw material for the production of fuel chips to be used in bioenergetics. In order to plan the logging residues collection and processing technology, it is necessary to gather information on the amount of this type of waste and its distribution within the cutting area.
The article deals with the line intersect (LIS) method.
The aim of this article was to assess the accuracy of the LIS method for quantifying logging residues after cut-to-length logging (CTL), uniformly distributed within the technology traffic lanes (strips) of width b on the cutting area of arbitrary shape S.
The studies were conducted using computer simulations. In the models, logging residues are represented as clusters in the form of circles. The laws of distribution of the radius of the clusters and their position in the plot were determined by field measurements.
In the simulations, clusters uniformly distributed along the X-axis and stripes on the Y-axis were considered. The samples of lines were the set of lines of different length and mutually perpendicular and parallel to the coordinate axes X, Y.
In the simulations, four types of stripes were considered with a different angle to the Y-axis. Type 1 – angle = 0°, type 2 – angle = 15°, type 3 angle = 30°, type 4 – angle = 45°.
It was determined through simulation that the estimated mean radius of the clusters is greater by 24% than the true mean radius.
The LIS method formula is appropriate for estimating the amount of forest residues after CTL logging provided the true mean radius is taken. According to the results of simulation experiments, it was found that the results are in good agreement with the theoretical formulas if the location of the sample lines is mutually perpendicular and parallel to the coordinate axes X, Y of the area. Differences remain within the limits of 20% error
volume: 41, issue: 1
Forwarding can be divided into separate work elements. These are affected by several factors: forwarding distance, load volume, and types of assortments harvested. For a detailed planning of thinning, productivity models should include these factors. This study analysed the time consumption of forwarder thinning operations in five pine plantations in the north-east of Argentina, determining how the log size and log concentration affect each work element. Time-and-motion studies were carried out, recording the activities with digital video cameras, and tracking the forwarder movements with global navigation satellite system (GNSS) receivers. Different linear mixed models were fitted to estimate the time consumption of each work element in relation to different predictive factors. When driving on the road, the forwarders had an average speed of 71.6 m min-1 empty and 75.7 m min-1 loaded. When driving in the stand, the average speed was 56.9 m min-1 empty and 52.2 m min-1 loaded. These speeds did not correlate with the forwarder size or load volume. For the loading and unloading elements, the linear mixed model explained 56% and 49% of the variability considering only the fixed effect of the logs size and the load volume. For driving while loading, the total volume loaded, and the log concentration of the assortment loaded explained 50% of the time consumption variability, with 17% being explained by random effects. The general time and productivity model developed can be applied to support accurate decisions in the process of thinning planning.
volume: 41, issue: 1
The great complexity of the operation of wood harvesting machines and unpredictable differences of performance between operators must be reflected in the industry recruitment techniques. This work aimed to carry out an evaluation of the bimanual motor skill in candidates for the position of harvester operators using a virtual reality simulator to generate information that can contribute to and improve the selection process. The work was developed at the Forest Operators Training Center (CENFOR), at the State University of the Center–West, in Irati, PR. A sample of 12 individuals was studied and distributed into three levels of performance. The motor ability of the individuals was evaluated through the variables: »run time«, »fall direction«, and »cutting height«, assessed at different points during a 4-hour practice – 0.5; 1.0; 1.5; 2.0; 3.0 and 4.0 hours – practice in a virtual harvester simulator. The data were analyzed by variance and means, as well as compared to a Tukey test at the 5% level of significance. The individuals had a significant difference in the variables »run time« and »cutting height«, and could be accurately used to predict bimanual motor skill/performance. There was a significant gain in the performance of the operators up to 1.5 hours after the beginning of the skill test, and all those who demonstrated greater and lesser ability in the first half hour of the test maintained this behavior until the end of the training period. The virtual reality simulator can be used as a tool to assess bimanual motor skills during the selection of harvester operators.
volume: 41, issue:
Biomass collection could contribute to the reduction of wildfire prevention costs by obtaining solid biofuels from shrublands that pose a high fire risk, using mechanical harvesting methods that have not been sufficiently tested in shrub formations. The objective of this study is to evaluate the performance of a harvester-baler system (Biobaler WB55) for collecting rockrose (Cistus laurifolius L.) shrublands biomass, to asses the influence of the cutting rotor tool (blades or hammers) on weight and surface productivities and operating costs, as well as to determine the influence of the standing shrub biomass load on productivity and biomass collection efficiency.
A 31-hour test was conducted on 21 ha of a typical Mediterranean shrubland in the centre of Spain. Data collection included time study, daily collected area, fuel consumption and bale measurements. Samples of fresh biomass from bales were collected for the determination of moisture content. The average collected biomass was 2.3 tDM·ha-1 (tonnes of dry matter per hectare), with an average productivity of 1.6 tDM·PMH-1 and an average yield of 0.7 ha·PMH-1. Better results were obtained with blades than with hammers in the cutting rotor tool (35% more collected biomass, 42% higher weight productivity, 61% higher collection efficiency and 14% greater surface productivity). The average harvest-baling costs with blades were estimated at 99.5 €∙PMH-1, 142.1 €∙ha-1 and 53.9 €∙tDM-1 (34.0 €∙tWM-1, € per tonne of wet matter), and with hammers 91.5 €∙PMH-1, 152.5 €∙ha-1 and 81.4 €∙tDM-1 (51.1 €∙tWM-1).
The analysed harvester-baler was operated without difficulty in this type of vegetation and was able to collect up to 31% of the shrub biomass load in the study area. The amount of uncollected biomass and the decrease in biomass collection efficiency, as shrub biomass load increases, suggest that possible mechanical improvements are needed to improve biomass collection efficiency.
volume: 41, issue:
In tactical forest management planning, the decisions required to meet the strategic plan are made, and these include: i) scheduling of spatially explicit harvest-blocks; ii) construction of a road-network required to access these blocks; and iii) transportation costs within the tactical forest planning area (hereafter only referred to as transportation costs) that emerge from the first two decisions. These three decisions are interdependent and should therefore be integrated in any optimization model. At present, this integration is not fully made. This is because: i) the integrated model is NP-hard, and exact solutions are not feasible for large and medium-sized forests; and ii) metaheuristic search algorithms, which can be used on larger forests, have not integrated transportation costs realistically.
The economic consequences of not integrating transportation costs into tactical planning models has not been quantified and evaluated by researchers; and the objective of this paper is to fill this gap in knowledge. To this end, an exact solution approach is used to solve and compare two integrated models: i) a model in which transportation costs are included in the objective function, and b) a model in which transportation costs are excluded from the objective function. The models were applied to three forests ranging in area from 6628 to 19,677 ha.
Results show that: i) the model which included transportation costs yielded solutions with major reductions in both transportation and total costs; and ii) that, as the forests to which the model was applied tripled in area (from 6628 ha to 19,677 ha), the percent reduction in total costs increased disproportionately – more than fivefold (from 3.9% to 21%). These results are important, for they indicate that the integration of transportation costs into a tactical planning model is of major economic consequence.