A study of labour productivity was conducted in fully mechanised harvesting technologies. The study revealed that the productivity of harvesters was particularly affected by the average tree volume of the felled trees, and the productivity of forwarders was affected mainly by two factors -haulage distance and machine payload. Dependences of other factors such as natural and site conditions, technical parameters and skills of operators could not be demonstrated. Regression equations of dependences were created for all these three significant criteria and costs per cubic meter of processed timber were calculated for them according to the cost function. A regression function was then developed for the forwarder that takes into account both significant criteria influencing the forwarder productivity. Mechanised cut-to-length (CTL) wood harvesting methods have become widely used in many industrialised European countries such as Sweden (ca. 98%), Ireland (ca. 95%) and Finland (ca. 91%) compared to motor-manual harvesting (Karjalainen et al. 2001). During the last two decades the mechanisation of working processes in forestry has increased rapidly. Due to labour shortage and the need for economical wood production, a lot of developments were made towards rationalisation especially in harvesting (Schaeffer et al. 2001). The CTL system requires less labour, less road construction, and fewer landing areas than the other ground-based systems (Bettinger, Kellogg 1993).Productivity of the CTL system depends on the forest stand, site and operational factors such as ground conditions, slope, operator's motivation and skill, branch size, operational layout, tree size, tree form, log assortments processed, numbers of unmerchantable and merchantable trees per unit area, hauling distance, undergrowth density and machine design (Brunberg et al. 1989;Spinelli et al. 2002;Stampfer 1999;Makkonen 1991;Richardson 1989). Harvester productivity is closely related to the tree size and stand characteristics (Bulley 1999).The aim of this study was to generalise productivity trends of different machine classes and to show general trends of productivity in relation to the most demanding factors in clear-cutting operations and to determine the operation cost for different harvester and forwarder classes. MATERIAL AND METHODSAltogether 21 field studies for harvester and 8 field studies for forwarder were carried out. Both types of purpose-built and excavator-based machines were investigated. In harvesting operations 15 different machines were studied, out of which 12 were excavator-based and 3 purpose-built harvesters, and in hauling operations 7 different machines were studied, out of which 1 was excavator-based and 6 purpose-built forwarders.The experiments were carried out in standard working conditions typical for Ireland. The average tree size varied between 0.1 m 3 and 1.0 m 3 and the hauling distance varied from 80 to 1,400 m. All the

A study was done using eight different logging machines (harvesters and forwarders) in clear-felling operations to quantify the associated fuel consumption, and to define the inherent relationship between engine output power and fuel consumption. Exhaust emissions were also calculated on the basis of mean fuel consumption values, obtained by measurements, and from the developed regression and correlation model for diesel and rapeseed methyl ester (RME) fuels. The calculation considered exhaust emissions associated with the manufacture, distribution, and combustion of the respective fuels. It was found that carbon dioxide emissions amounted to 9.63 kg/ m 3 of delivered timber for diesel fuel, and to 10.64 kg/m 3 for RME. It was also found that when using RME only 2.82 kg/m 3 of carbon dioxide emissions originated from fossil resources, therefore, it is only this amount that can be deemed an environmental load, confirming RME as a lesser environmental pollutant.

Cable cranes are among the most important means of yarding and transporting timber in many mountainous regions of Europe. In the last decade, all-terrain mobile tower cable cranes have been increasing due to their adaptability to operate both in uphill as well in downhill configuration. This research assesses the efficiency and the costs of a mobile cable crane manufactured in Czech Republic and designed for all-terrain application and specifically mounted on a wheeled agricultural tractor. A total of 100 cycle times were recorded in order to obtain evaluate the performance in the downhill as well uphill extraction configuration. The productivity analysis was based on regression equation as a function lateral distance, skyline slope distance and extracted volume. Increasing in number of lateral distance and extraction distance resulted as significant variables affecting the cycle time. Even if the test highlights a good efficiency of the extraction system for both the configuration (uphill vs downhill) there a still many organisational features that could be improved in order to fully exploit the potentiality of the tested cable crane system.

ABSTRACT:The forests located in the northern areas of Iran are known as Hyrcanian Forests and are distributed across three provinces, namely Gilan, Maznadarn and Golestan. These provinces are situated in the north of Iran near the Caspian Sea. Timber products in the said forests during the last two decades were markedly different so that the total timber harvested in the first decade was 1.6 million m 3 on average, however, in the second decade it nearly amounted to 1 million m 3 . Two major timber products of Iran are studied and compared in this research, namely logs and squared timber. Squared timber products averaged 10.7% during the first decade, but they fell to 7.3% over the second decade. Apropos of log products, they reached 20.9% and 29.2% over the first and the second decade, respectively. Analyses of the data indicate the following converse linear equation between squared timber products and log products during the 20 years of study: Y =-0.359X + 18.065 (Y = log products, X = squared timber, R 2 = 0.768).Accordingly, any increase in log products at a time caused the squared timber products to decrease at the same time.

Abstract:The life cycle operation phase of John Deere 1490D energy wood harvester from the aspect of energy audit and environmentally negative influence caused by emissions were evaluated. Energy audit quantifies energy used in the form of fuels and oils as well as energy expended for manufacture, transport and distribution of these fuels and oils. Emissions produced by operation are determined according to the consumption of fuels and oils based on emission factors. We also made a comparison of the general calculation of costs based on data provided by the manufacturer with costs ascertained in real operating conditions. The costs are divided into purchase, operating and other costs. Total costs are subsequently converted into unit costs according to the assumed productivity of the machine, its estimated lifetime, and the mean real throughput of the machine. The machine throughput, and thus also its operating economics, is greatly dependent on the character of the processed material, its stem volume, moisture, way of dendromass preparation, and operator's skills. Energy use was calculated at 74.4 MJ·FU -1 (functional unit) related to fuel consumption and 13.4 MJ·FU -1 related to the consumption of oils. The total energy use of the life cycle operation phase of the slash bundler was determined as 87.8 MJ per each bundle produced. The real productivity of the machine in the given operating conditions was several times lower than the productivity indicated by the manufacturer.