When the correct site is chosen, the time is right and the equipment is suitable for soft terrain, summer harvesting in peat soil forests can be performed well.
UPM’s forestry account manager Pasi Hakkarainen and harvesting contractor Pertti Lehtomäki encourage people to stop over-booking for the winter months when planning thinning in peat soil forests and pine stands.
Veljekset Lehtomäki Oy is a family business from central Finland, and for the last couple of years they have invested in the load capacity of their machinery. When a forwarder is equipped with long and wide tracks suited for harvesting in peat soil forests, and if it has an additional rear axle with tyres, the weight of the big machine is distributed over a wider area. In this way, the surface pressure is closer to the weight of a person walking in rubber boots.
“I could even go to a swamp to pick cloudberries with this ten-wheeler,” confirms Lehtomäki.
Berry picking is still done on foot, however. As the equipment required for a ten-wheeler is a huge investment for the entrepreneur, the machinery is reserved solely for productive work. The past winter was mild, which meant that load-bearing equipment was needed throughout the year.
Specialist assists in machine selection
Summer harvesting is not possible in all peat soil forests, but many stands marked for winter harvesting can be worked on also when the ground is not frozen.
“If the total stand in the compartment covers more than 170 cubic metres of wood per hectare, it is most likely suitable for summer harvesting,” concludes Hakkarainen.
The more stands the logging site has, the more roots there are to increase the load-bearing capacity of the ground. This also means more logging residue that can then be used to strengthen the haul roads. Even with less total stands, summer harvesting is possible when planned carefully. If the stand consists of 120 cubic metres of wood per hectare or less, it is better to leave the harvesting for winter.
“If you are unsure whether you can harvest your own stand during summer, you should contact UPM’s forest customer representative,” advices Hakkarainen.
Swamp stands require precise expertise
July and August are the best months for harvesting peat soil forests during summer, as they are usually preceded by a few weeks of dry weather, meaning the ground has better load-bearing capacity. Spruce forests can also be harvested during summer if the harvest is performed correctly and with suitably equipped machines. A harvesting entrepreneur’s expertise includes the ability to time the tasks correctly. After that, the quality depends largely on the machine operators.
“In these sites, the operators’ expertise is the key. The harvester operator can tell what can or cannot be done with the stand. He also knows instantly whether a ten-wheeler is required for hauling the wood away,” explains Lehtomäki.
“In practice, this means that if it is possible to fell the site with a Moto, a ten-wheeler can easily haul the trees away,” adds Hakkarainen.
Small machines are out of the question for both Lehtomäki and Hakkarainen when it comes to harvesting in peat soil forests. A bigger machine can be equipped with a suitable track structure to lower the surface pressure. In swamps, the load-bearing capacity is the most important feature of the machine. When larger quantities can be hauled away in one go, the pressure on the soil caused by multiple runs can be reduced.
“In this way, the machines can operate at full capacity, which is good for business,” says Lehtomäki.
Summer harvesting of peat soil forests becomes more popular
For a harvesting contractor, summer harvesting means that both the machines and men can continue working throughout the year, and it also relieves some of the stress from winter. Also the quality of the thinning is better in summer, because the working conditions are excellent.
“Lighting and visibility are completely different than during snowy winters,” explains Lehtomäki.
The forest owner, of course, is most interested in the end result, and the contractor also aims for top quality. Veljekset Lehtomäki Oy has been working in the same area for 40 years, and providing good quality is the best selling point.
Trenching has increased the felling opportunities in peat soil forests, and there is demand for pulpwood throughout the year. Summer harvesting is a fine solution all round.
Example – summertime thinning of a swamp stand
This trenched swamp area of three hectares is typical terrain in Multia, central Finland. Thinning of the stands can be done in summer, when the equipment and timing are right, and the job is planned thoroughly.
UPM’s specialist can evaluate in advance whether the stand is eligible for summer harvesting. This is done, for example, based on the number of stands, peat thickness and the depth of groundwater. The longer the dry period has been, the better the load-bearing capacity of the ground.
Planning for haul roads is the key for successful operation. The roads that are used the most (i.e. collector roads) are placed in an area where the ground has the best possible load-bearing capacity. Load-bearing capacities are increased by adding logging residue to the haul roads.
If necessary, multiple collector roads can be built on softer ground so that the stress on the ground surface is distributed more evenly, fewer slumps are generated and the quality of work compares favourably to work done in winter. In principle, the softer the ground for the haul road, the fewer the runs planned for it. The collector roads can also be built outside the actual stand if the ground is more stable there.
Text by: Päivi Stenroos