Thinning is an essential forest management practice that aims to create better growth conditions, health, vitality, and quality by reducing the density of trees in a stand. It can provide many benefits, such as:
- Creating more revenues in a rotation time through more volume and value
- Improving the quality of the remaining trees by reducing competition for resources such as water, nutrients, and sunlight
- Enhancing biodiversity by promoting the growth of understory vegetation, which provides habitat and food for wildlife
- Reducing the risk of wildfires by decreasing fuel load and creating firebreaks
- Increasing resilience to climate change by promoting the growth of faster-growing trees that absorb more carbon dioxide from the atmosphere
Thinning can be applied in even-aged harvesting and in the form of selective cutting in uneven-aged harvesting, as well as in continuous-cover forestry. Therefore, it is a valuable tool of climate-smart forestry that can help us manage our forests sustainably.
Why should we consider thinning?
Sustainable forest management aims to produce wood and services while maintaining the economic, environmental, cultural, and social values of forests today and in the future. Thinning is an effective forest management practice that offers several benefits:
Increased wood production: Thinning creates more space, sunlight, water, and nutrients for the remaining trees, allowing them to grow faster and produce more wood. This results in higher volumes and better quality of wood in forest stands, increasing the revenue potential in a rotation time.
Reduced forest fire risk: Thinning removes excess biomass from the stand, reducing the intensity of forest fires. However, thinning should not expose the stand to too much sunlight, as this can dry up the forest floor and make it easier to catch fire.
Increased resilience: Thinning creates a healthier forest that is more resilient to diseases and insect attacks. This is particularly important given the effects of climate change on forest ecosystems.
Mitigation of climate change: Thinning results in faster carbon sequestration as the remaining trees grow faster and absorb more carbon dioxide from the atmosphere. This makes it a valuable tool in climate-smart forestry.
In British Columbia, thinning has been introduced to generate more opportunities to harvest pulpwood and prevent severe forest fires. After generations of clear-cutting, recent infestations of bark beetles, and massive forest fires, the logging possibilities have decreased, and there is a shortage of pulpwood. Thinning offers a solution to these challenges while also contributing to sustainable forest management.
Thinning is a common practice in Finnish forest management, typically with 1-3 thinnings per rotation time. The timing and need for thinning depend on the species and growing conditions, and guidelines are based on growth or harvesting models developed through years of research.
There are several thinning methods available, including:
- Low thinning: removes sick and damaged trees first, followed by smaller trees, to optimize tree density for growth.
- High thinning: concentrates on removing the tallest trees and produces more sawlogs than low thinning, allowing for a longer rotation time.
- Quality thinning: aims to leave the best quality trees to grow, removing overshadowed smaller trees and those with quality defects.
- Selective cutting: harvests trees of a certain size, species, or quality. While this method was previously banned in Finland due to the risk of forest degradation, it can be a useful tool when applied correctly and considering the future of the stand.
- Corridor thinning: a newer method where trees are removed only from strips and corridors at a certain angle, without selecting specific trees. This method is simpler and cheaper than traditional thinning and can be managed by operators without much experience.
Overall, thinning can help produce more wood and achieve forest stands with better wood quality. It can also reduce excess biomass and help mitigate the effects of climate change, as faster-growing trees sequester carbon more quickly and forests become more resilient to diseases and insect attacks.
Here is a great article for further reading.
Suitable equipment for thinning
When it comes to thinning, the cut-to-length method using a single grip harvester-forwarder combo is generally considered the best equipment. While there may be differing opinions on the best brand of forest machines, it’s clear that larger, more powerful machines are not always necessary for thinning. Since the volume of the trees is considerably smaller compared to clear-cuttings, smaller and more affordable machinery can be just as productive. The key is finding the right balance between power, reach, and weight. While it’s important to have the ability to move felled trees and reach far, heavier machinery can cause soil compacting, displacement, and rutting, which can be counterproductive to thinning efforts. However, in some cases, more powerful machines can be advantageous, such as in continuous cover forestry or late-stage selective cuttings in British Columbia. In these situations, it’s important to be able to cut some of the largest trees and move them to be processed without damaging neighboring trees or seedlings. While careful handling is necessary for smaller trees and undergrowth, it’s not as critical as it is for the larger trees.
Tractor or excavator?
In the Nordics, wheel-based harvesters are the preferred option due to their higher productivity, suitability for flat terrain, and off-road capabilities. However, excavators are commonly used on peatlands because they can achieve a lower surface pressure with the right equipment and are more effective on this type of terrain.
Modern excavator-based harvesters have become increasingly productive and excel in steeper slopes. They can be equipped with special cable-assisting systems that allow them to operate safely on slopes above 60%, depending on the soil, ground roughness, and operator’s skill level. However, mechanized thinning on the steepest slopes may not be practical due to cost concerns, and the costs per cubic meter of wood may become unacceptable.
If you’re looking to develop a profitable business model for thinning, BCon is here to help. Our expert team can provide customized solutions to help you maximize your profits while improving the health of your forest. By optimizing your thinning operations, you can increase production of sawlogs and pulpwood, while reducing waste and minimizing the impact on the environment.