75 research outputs found
DÄlig beredskap för stormar
I vanliga fall Ă€r man som svensk och verksam inom det skogstekniska omrĂ„det van att kunskapscentrum rörande avverkningsteknik Ă€r 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 stormfĂ€llningarna pĂ„ slutet av 60-talet Ă€r antingen till stor del glömda eller av mindre vĂ€rde dĂ„ bĂ„de teknik och organisation Ă€r förĂ€ndrad. Men det finns i nĂ€rbelĂ€gna lĂ€nder en fĂ€rsk, stor, och dyrköpt kunskapsbank rörande stormfĂ€lld skog. I december 1999 blĂ„ste stormarna Martin och Lothar ner 180 millioner m3 skog i Europa, varav minst 115 millioner m3 i Frankrike (nĂ€stan 3 Ă„rsavverkningar). Liksom i Sverige nu intrĂ€ffade i Frankrike dĂ„ att en del fick psykologiska problem och depressioner till följd av förödelsen. Tyskland, Schweiz och Danmark drabbades ocksĂ„. Uppskattningsvis 5 millioner m3 blĂ„ste Ă€ven ner i södra Sverige. Som en följd av dessa stormskador genomfördes ett EU-finansierat 3-Ă„rigt forsknings- och informationsprojekt âStorm damaged forests â STODAFORâ, med deltagare frĂ„n 10 lĂ€nder och 16 organisationer, dock ingen frĂ„n Sverige eller Finland. STODAFORs avslutande konferens gick av stapeln 27-28 oktober 2004 i Frieburg, Tyskland. Av de 62 registrerade deltagarna kom ingen frĂ„n Sverige, men 2 frĂ„n Finland. I Danmark, liksom i mĂ„nga andra av de drabbade lĂ€nderna, bedrevs nationell forskning. Denna artikel bygger i huvudsak pĂ„ information frĂ„n projektet STODAFOR, samt Danska sammanstĂ€llningar av erfarenheter. För mer detaljerade kunskaper hĂ€nvisas till STODAFORs fritt tillgĂ€ngliga hemsida (http://www.ctba.fr/stodafor/index.htm) och âVidentjĂ€nstenâ pĂ„ 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 trucksâ 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 mâ3, respectively, with 299â445 kg oven dry matter per bundle). The machine was a so at least 30% more productive than
previously described in-field bundling systems, producing 14â19 bundles per productive work hour (PWh), equivalent to 5.2â7.8 oven-dry tonnes PWhâ1. Bundles were estimated to use 67â86% of an LR truckâs 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
Effects of Boom-Corridor and Selective Thinnings on Harvester Productivity in Dense Small Diameter Pyrenean Oak (Quercus pyrenaica Willd.) Coppices in Spain
Due to socioeconomic transformations in the 20th century, Quercus pyrenaica Willd. coppices in Spain, as well as other European coppices, have experimented an abandonment and lack of intervention leading to stagnant high density stands with fragile health due to competition. Thinnings are often required to ensure their stability and health, producing forest products such as firewood or biomass, which are key energy sources in a carbon-neutral economy. However, thinnings are seldom performed because they lack economic sustainability due to a low productivity, high costs and low biomass prices. In this study, two thin-ning methods, selective thinning (ST) and boom-corridor thinning (BCT), were tested car-rying out a time study in a high-density small-diameter Q. pyrenaica stand in the Leon province (Castilla y Leon, Spain) with a forest harvester base machine, on which an accumulating felling head Bracke C16c was mounted. The residual stands were significantly different regarding the final density (greater in BCT) and the final average DBH (bigger in ST), while thinning intensity (odt center dot ha-1) was the same. In most work elements, time per tree was not significantly different. BCT showed a significant 48.6% increase in harvester productivity when compared to ST, with averaging 4.43 and 2.99 odt center dot pmh-1, respectively, due mainly to the average weight per extracted tree, 42% greater in BCT. When considering the common range of unit tree weight, the productivity was 16-23% greater for BCT, far less than observed in the trials. These results show the potential of BCT over ST in the studied conditions, although there is room for improvement. Further studies could include the future evolution of the treated stands and perform a cost analysis
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 1.5â1.7 times larger than the pulpwood volume for a 13.9 diameter at breast height stand and 2.0â3.5 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-hourâ1) 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 âŹ595 haâ1. We conclude that in birch-dominated early thinning stands, at current market prices, harvesting energy-wood is more profitable than harvesting pulpwood
Comparing biomass and nutrient removals of stems and fresh and predried whole trees in thinnings in two Norway spruce experiments
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 1â2 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 15â20° slope, 8 per cent on a 20â30° 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
- âŠ