Volume 12, numéro 2, july 2001

EN :

Unguyed spar-trees are commonly used as a part of skyline cable logging systems. Finite Element Analysis is a robust method for determining spar-tree design load that can include virtually any field condition likely to be encountered. The results of Finite Element Analysis over a range of spar-trees similar in size to those typically found in second-growth Douglas-fir stands indicates that (1) some existing guidelines for use of unguyed spar-trees do not correspond to expected field behavior, and (2) lateral loads of a magnitude found in skyline cable yarding systems dominate the structural behavior of unguyed spar-trees. However, the Euler Buckling load which has been used as a guide to spar-tree capacity, may serve to normalize the results of Finite Element Analysis in such a way that simple linear relationships can be used to estimate spar-tree capacity.

EN :

In the past ten years in North America there has been much attention focussed on a so-called "new" forestry paradigm, placing emphasis on what some have described as a more holistic approach to forest management. Will the debate contribute to changes in the conduct of forest operations, particularly clearcutting? How will forest policies that will define the role of forest operations in the region be formulated?

A survey of both public and private sector foresters in the northeastern US was conducted that was designed to solicit their opinions on the future of forest practices in the region. Multiple survey mailings revealed that forestry in the region is entering a period of increasing regulation and that environmental groups will play a more important role in defining these regulations. Although most respondents did not favor banning the practice of clearcutting, there were significant differences in responses from USFS foresters and private sector foresters on issues related to whether fewer foresters will be involved in the management of forests and whether the size of clearcuts should be limited. Implications of these results for the forest engineering/operations community are explored.

EN :

Dehydration and its milder form hypohydration have both short term and long term health effects. In the short term poor, body hydration impairs cognitive performance, physical strength and aerobic power, rendering the worker prone to injury and heat illness. In the long term the potential consequences of hypohydration are kidney stones and bladder cancer. The aim of this study was to evaluate hydration status of forest workers in New Zealand and their preferred fluid replacement. The specific gravity (sg) of urine was used as an indicator of body fluid status. In addition daily fluid loss was compared with a tested algorithm of sweat rate to better understand if workers are hydrating at the desired rate. The results of this preliminary study clearly demonstrate that loggers are working at sub-optimal hydration levels and are consuming inappropriate fluids to replace sweat losses. The hypohydrated state of these workers may pose both an immediate and long term health and safety risk.

EN :

The purpose of this study was to develop and test the application of non-parametric Most Similar Neighbor Inference (MSN) for wood procurement planning. An application developed using this method would be a part of a stem database in Finnish forest enterprises and could predict characteristics of a marked stand with accuracy demanded by bucking simulation. A stem database includes representative samples of stands and stems, applications to control and update data and applications to utilize the database. The study materials used consist of two different kinds of data: data collected by harvesters and historical forest inventory data. The harvester collected stem data came from stands in central Finland, whereas forest inventory data was obtained from all over Finland. The accuracy of the MSN method was analyzed by estimating characteristics of tree stocks and by comparing simulated spruce, pine and birch log length-diameter distributions with the information from actual stands.

The application presented was found to be a useful and flexible tool for predicting characteristics of marked stands based on the stem data collected by a harvester. The forest inventory data was found less suitable for reference data. The most efficient way to create a length-diameter distribution was to calculate length-diameter class estimates from reference stands as weighted averages of the corresponding length-diameter class. The proposed method appears robust against measurement errors of search variables.

EN :

Logging on islands differs considerably from logging carried out on the mainland. The transportation of machines to the islands and between islands calls for special equipment. Furthermore, the long distance transport must be done simultaneously with logging, because the buffer raft between ground forwarding and vessel transport is very small and used also for the transport of logging machines and crews between islands. There are several options to arrange long distance waterway transport by using boats and various kinds of barges. In this study different vessel transport systems carrying wood from islands were studied by using discrete-event simulation. A new push barge system suitable for transport of wood from islands was compared to the current powered barge system. A three barges' setting system gave the lowest harvesting costs when the transport distance exceeded 100 km. At shorter transport distances the current system was most competitive. Direct loading of barges by forwarders was cheaper than the use of a separater loader. Direct loading, however, requires new driving ramps and is not applicable everywhere.

EN :

This paper describes the development of a quantitative method of classifying forest canopy that can be related to degradation in Differential GPS (DGPS) performance. Using digital images taken vertically skywards at 20 sites within a forest on the east coast of Ireland, canopy cover was described using percentage sky obstruction (Op), largest hole (DTmax), and the fragmentation of sky view (DTp) using pixel count and distance transform data. Statistical methods were used to produce three clusters which related to canopy cover in stands of Picea sitkensis and Picea contorta. DGPS data were then collected on 10 separate dates at the 20 sites, every two seconds for five minutes, and the two-dimensional standard deviation of the position fix was used to represent DGPS precision. The standard deviations ranged from 0.5 m to 9.7 m (compared to the manufacturer's specification of approximately 1 m in the horizontal). Precision was found to be related to the total obstruction, the size of the largest hole in the canopy, and the fragmentation of the sky view. Where there was little obstruction (less than 20%) or fragmentation, the DGPS performance was effectively the same as outside the forest, open canopy caused a 2-3 fold degradation in precision, and closed canopy a 5-7 fold degradation. It is suggested that the methods presented could be used to rapidly relate DGPS performance to forest canopy, and therefore may be useful in pre-planning inventory mapping and future machine operations using guidance systems.

EN :

Scientists and managers are increasingly turning to computer modeling and visualization tools to enable them to evaluate the effects of harvest practices better, depict various characteristics and variation existing in the forest, and communicate the impact of environmental changes. This paper examines the suitability of virtual reality (VR) technology in supporting forest managers or forest owners in their decisions.

VR is particularly useful for helping to deal with the following issues in forest management planning: time dependence, irreversibility of decisions, spatial-quantitative variation of features and multiple objectives. It helps managers and stakeholders understand the relationship between underlying data and landscape planning. Some of the key challenges faced in making VR work are: insufficient resolution in forest inventory data, need to re-delineate stands to allow for multiple use planning, adjusting realism of features in the images and linking data currently held by a variety of disparate agencies and owners. Existing mean-based inventories will, for the short to medium term, limit the extent to which VR technologies are used in actual forest management planning.

EN :

Hazards occurring to the fallers and chokersetters (breaker-outs) within cable yarder (hauler) crews working in windthr/ow salvage conditions were recorded. Fallers were exposed to considerably more and potentially more serious hazards than fallers working under normal conditions. The most hazardous parts of the faller's job were those of felling, clearing around the tree to be felled and clearing a path to the tree to be felled. The two most dangerous tree types to deal with were "hung-up" and "rootball trees". The choker setters were exposed to a similar number of hazards per cycle as choker setting in normal conditions, but a number of previously undocumented hazards were recorded. The majority of choking hazards (70%) occurred during the "wait" phase of choking with the most frequent hazard being "standing within one tree length of the turn". The information contained in this article may assist other contractors and forest companies faced with the difficult task of harvesting windthr/own trees.