This study looked at small tree harvesting, such as is found with early thinning.
Helmer Belbo of the Norwegian Forest and Landscape Institute (Skogoglandskap) carried out a study titled “A Comparison of Two Working Methods for Small Tree Harvesting with a Multi Tree Felling Head Mounted on a Farm Tractor”. The article was published in Silva Fennica 2010 44(3), pg 453 to 464. The study was carried out in a mixed stand of Norway spruce (Picea abies) and birch (Betula pubescens) with an average size of 0.035 m3/tree.
The study investigated the productivity of a small multi-tree felling head (Nisula 280E), mounted on a farm tractor (Valmet XM) with a 10 tonne timber trailer, while harvesting energy wood in a thinning operation. The two different work methods were as follows:
- Conventional felling and bunching of trees with the tractor. The timber trailer was then loaded afterwards and extracted to roadside. The same tractor was used for felling and extraction.
- Direct loading of the trees onto the trailer straight after felling, with immediate extraction to roadside.
With the average tree size of 0.035 m3, both systems had productivity levels of 3 m3 per hour. However, as more trees were collected in the felling cycle (>0.1 m3), the direct loading system became more productive. The separate loading method had the highest productivity when less than 0.05 m3 was collected in the felling cycle. The system output per hour is still very low and therefore the cost of harvesting energy wood from thinning in this scenario will remain expensive. Work methods and felling head improvements could help make the systems more cost effective. The journal can be consulted for a detailed and more complete account of the research. Source: www.metla.fi/silvafennica/full/sf44/sf443453.pdf