Dålig beredskap för stormar

I vanliga fall är man som svensk och verksam inom det skogstekniska området van att kunskapscentrum rörande avverkningsteknik är just i Sverige, eller Finland. Den stora storm som koncentrerat drabbade delar av södra Sveriges skogar var dock inget vanligt fall. De erfarenheter som vi fick i samband med stormfällningarna på slutet av 60-talet är antingen till stor del glömda eller av mindre värde då både teknik och organisation är förändrad. Men det finns i närbelägna länder en färsk, stor, och dyrköpt kunskapsbank rörande stormfälld skog. I december 1999 blåste stormarna Martin och Lothar ner 180 millioner m3 skog i Europa, varav minst 115 millioner m3 i Frankrike (nästan 3 årsavverkningar). Liksom i Sverige nu inträffade i Frankrike då att en del fick psykologiska problem och depressioner till följd av förödelsen. Tyskland, Schweiz och Danmark drabbades också. Uppskattningsvis 5 millioner m3 blåste även ner i södra Sverige. Som en följd av dessa stormskador genomfördes ett EU-finansierat 3-årigt forsknings- och informationsprojekt ”Storm damaged forests – STODAFOR”, med deltagare från 10 länder och 16 organisationer, dock ingen från Sverige eller Finland. STODAFORs avslutande konferens gick av stapeln 27-28 oktober 2004 i Frieburg, Tyskland. Av de 62 registrerade deltagarna kom ingen från Sverige, men 2 från Finland. I Danmark, liksom i många andra av de drabbade länderna, bedrevs nationell forskning. Denna artikel bygger i huvudsak på information från projektet STODAFOR, samt Danska sammanställningar av erfarenheter. För mer detaljerade kunskaper hänvisas till STODAFORs fritt tillgängliga hemsida (http://www.ctba.fr/stodafor/index.htm) och ”Videntjänsten” på Skov & Lanskab ([email protected])

Productivity of a prototype truck-mounted logging residue bundler and a road-side bundling system

When recovering logging residues (LR) for bioenergy its density should be increased before road transport, otherwise a low proportion of the trucks’ load capacity will be used. One way this can be currently done is to compress LR into bundles that are forwarded to roadside landing. A less well-developed alternative is to forward loose LR and bundle it at landing. In the presented study, a prototype specifically developed for road-side bundling was found to produce larger, heavier bundles than bundling machinery intended for in-field use (mean length, diameter and raw bulk density 4.7 m, 0.8 m and 285 kg m–3, respectively, with 299–445 kg oven dry matter per bundle). The machine was a so at least 30% more productive than previously described in-field bundling systems, producing 14–19 bundles per productive work hour (PWh), equivalent to 5.2–7.8 oven-dry tonnes PWh–1. Bundles were estimated to use 67–86% of an LR truck’s 30 tonnes load capacity, similar to proportions used when transporting loose LR. However, a continuous feeding and compressing process would probably almost double productivity, while longer bundles would enable full use of truck load capacity. With such improvements bundling at road-side could provide a viable alternative to current LR-recovering systems

Operational Aspects of Row and Selective Thinning in the Establishing of a Shelterwood in a 50-Year-Old Norway Spruce Stand

The aim of this study is to investigate the productivity, thinning quotient, reduction in basal area, damage rate, and costs of operation of row and selective thinning in the establishment of a shelterwood in a medium-aged Norway spruce stand. The cutting was performed with a single-grip harvester operating from existing striproads (spacing 15 m) parallel to the tree-rows. Extraction with a forwarder was studied in the same stand. The two thinnings were more alike than expected. The thinning quotient was 0.9 and the reduction in basal area round 40% in both treatments. The time consumption for harvesting was larger in row than in selective thinning because row thinning was more difficult to perform when the harvester worked from striproads parallel to the tree-rows. No difference in forwarding productivity was found. The damage rate was higher in row than in selective thinning. It is concluded that row thinning from striproads parallel to the tree-rows has a negative influence on both productivity and quality of the work. This type of row thinning is difficult to perform because the tree-rows are difficult to identify and because the trees are more difficult to reach. The operational aspects should be considered before a thinning method is chosen. Row thinning should preferably be carried out either by driving on removed rows or from striproads perpendicular to the tree-rows

Comparison of energy-wood and pulpwood thinning systems in young birch stands

In early thinnings, a profitable alternative to pulpwood could be to harvest whole trees as energy-wood. In theoretical analyses, we compared the extractible volumes of energy-wood and pulpwood, and their respective gross values in differently aged stands of early birch thinnings at varying intensities of removal. In a parallel field experiment, we compared the productivity at harvest of either pulpwood or energy-wood, and the profitability when the costs of harvesting and forwarding were included. The theoretical analyses showed that the proportion of the total tree biomass removed as pulpwood increased with increasing thinning intensity and stem size. The biomass volume was 1.5–1.7 times larger than the pulpwood volume for a 13.9 diameter at breast height stand and 2.0–3.5 times larger for a 10.4 diameter at breast height stand. In the field experiment, the harvested volume per hectare of energy-wood was almost twice as high as the harvest of pulpwood. The harvesting productivity (trees Productive harvesting Work Time-hour−1) was 205 in the energy-wood and 120 in the pulpwood treatment. The pulpwood treatment generated a net loss, whereas the energy-wood treatment generated a net income, the average difference being €595 ha−1. We conclude that in birch-dominated early thinning stands, at current market prices, harvesting energy-wood is more profitable than harvesting pulpwood

Compression Processing and Load Compression of Young Scots Pine and Birch Trees in Thinnings for Bioenergy

In many boreal countries forest biomass from dense young stands has great potential to meet growing demands for bioenergy. However, there is currently no costeffective operational system for harvesting such stands. When harvesting, it would be desirable to compress trees and leave some of the foliage and fine branches in the stand in order to reduce extraction of nutrients and improve the harvested material's fuel properties from a reduced ash content point of view. The objectives were to evaluate experimental systems (a boomtip mounted unit for processing bunches, and a small prototype forwarder for compressing loads) in terms of their utility for compressing and partially debranching fresh and stored bunches of Scots pine trees and compressing forwarder loads of fresh Scots pine and birch trees. Processing of fresh bunches resulted in mass losses of about 10% (dbhclass 58 cm; not significant) to 15% (dbhclass 1215 cm; significant) with 35 to 50% reductions in ash contents and increases in bulk and net energy density of about 80 to 160%. Instand storage of bunches before processing generally yielded no significant advantages except for a 10%unit reduction in moisture content. Compression of forwarder loads resulted in 16 (pine) to 32% (birch) increases in load densities, with a significant increase for birch trees. The described techniques facilitate productivity increases of offroad and road transport of tree parts, and a substantial proportion of the ashrich materials such as needles and fine branches are left in the stand. If both tested techniques are applied during the harvesting of young trees the benefits would be substantial

Evaluating the effect of DEM resolution on performance of cartographic depth-to-water maps, for planning logging operations

Reliable and accurate soil moisture maps are needed to minimise the risk of soil disturbance during logging operations. Depth-to-water (DTW) maps extracted from digital elevation models have shown potential for identifying water flow paths and associated wet and moist areas, based on surface topography. We have examined whether DEMs from airborne LiDAR data with varying point density can improve performance of DTW maps in planning logging operations. Soil moisture content was estimated on eight sites after logging operations and compared to DTW maps created from DEMs with resolutions of 2 m, 1 m, and 0.5 m. Different threshold values for wet soil (1 m and 1.5 m depth to water) were also tested. The map performances, measured by accuracy (ACC) and Matthews Correlation Coefficient (MCC), changed slightly (79%, 81% and 82% and 0.33, 0.26 and 0.30 respectively) when DEM resolutions varied from 2 m to 1 m, and 0.5 m. The corresponding values when the DTW threshold value for wet/dry soil changed from 1 m to 1.5 m were 70%, 72%, 71% and 0.38, 0.41 and 0.39. LiDAR-based DEM resolutions of 1–2 m were found to be sufficient for extraction of DTW maps during planning of logging operations, when knowledge about soil hydrological features, associated wet and moist areas, and their connectivity is beneficial

Global analysis of the slope of forest land

Forests of the world constitute one-third of the total land area and are critical for e.g. carbon balance, biodiversity, water supply and as source for bio-based products. Although the terrain within forest land has a great impact on accessibility, there is a lack of knowledge about the distribution of its variation in slope. The aim was to address that knowledge gap and create a globally consistent dataset of the distribution and area of forest land within different slope classes. A Geographic Information System (GIS) analysis was performed using the open-source QGIS, GDAL and R software. The core of the analysis was a digital elevation model and a forest cover mask, both with a final resolution of 90 m. The total forest area according to the forest mask was 4.15 billion hectares whereof 82 per cent was on slope < 15°. The remaining 18 per cent was distributed over the following slope classes, with 6 per cent on a 15–20° slope, 8 per cent on a 20–30° slope and 4 per cent on a slope > 30°. Out of the major forestry countries, China had the largest proportion of forest steeper than 15° followed by Chile and India. A sensitivity analysis with 20 m resolution resulted in increased steep areas by 1 per cent point in flat Sweden and by 11 per cent points in steep Austria. In addition to country-specific and aggregated results of slope distribution and forest area, a global raster dataset is also made freely available to cover user-specific areas that are not necessarily demarcated by country borders. Apart from predicting the regional possibilities for different harvesting equipment, which was the original idea behind this study, the results can be used to relate geographical forest variables to slope. The results could also be used in strategic forest fire fighting and large-scale planning of forest conservation and management

Autonomous Forest Vehicles: Historic, envisioned, and state-of-the-art

The feasibility of using autonomous forest vehicles (which can be regarded as logical developments in the ongoing automation of forest machines), the systems that could be applied in them, their potential advantages and limitations (in the foreseeable future) are considered in this paper. The goals were to analyze: 1) the factors influencing the degree of automation in logging; 2) the technical principles that can be applied to autonomous forest machines, and 3) the feasibility of developing an autonomous path-tracking forest vehicle. A type of vehicle that is believed to have considerable commercial potential is an autonomous forwarder. The degree of automation is influenced by increased productivity, the machine operator as a bottle-neck, cost reduction, and environmental aspects. Technical principles that can be applied to autonomous forest vehicles are satellite navigation, wheel odometry, laser scanner, and radar. A new path-tracking algorithm has been developed to reduce deviations from the desired path by utilizing the driver’s steering commands. The presented system has demonstrated both possibilities and difficulties associated with autonomous forest machines. A field study has shown that it is quite possible for them to learn and track a path previously demonstrated by an operator with an accuracy of 0.1 m on flat ground and also to detect and avoid unexpected obstacles. Although the forest machine safely avoids obstacles, the study shows that further research in the field of obstacle avoidance is needed to optimize performance and ensure safe operation in a real forest environment