Forest soil is prepared for next tree generation.
Soil preparation is the first link in the chain of silvicultural operations during a commercial forest’s rotation cycle. It is done after final felling as a part of forest regeneration activities. Purpose of soil preparation is to improve the germination of seeds and to secure growing conditions for seedlings. The right soil preparation is very important for giving a new generation of trees a good start.
The chosen forest regeneration method – cultivation by planting or sowing, or natural regeneration – determines how the soil needs to be prepared. Tree species, soil type and water conditions on the site affect soil preparation as well. Because there often is variation among these factors even inside one regeneration area, the best method can be a combination of different techniques.
Soil preparation techniques fall into two different categories: mound forming and mineral soil exposure. The rule of thumb is that mound forming techniques work better for moist soils while mineral soil exposure techniques can be used in drier forest sites.
For Spruce planting, the most commonly used soil preparation method is mounding. A patch of forest soil is extracted by excavator and turned upside down to its original place or next to it. Spruce seedling is then planted on top of the created mound. Mineral soil exposure is used to regenerate Pine stands, which are also established by sowing and natural regeneration in addition to planting. With a harrow attached to a forwarder, the soil’s organic surface layer is broken and mineral soil, which offer seeds suitable conditions for sprouting, is exposed. If sown, seeds are distributed simultaneously.
To prevent negative environmental impacts, soil preparation is always done with the lowest possible intensity. This prevents excessive soil particle runoff and nutrient leaching. Waterways are protected by leaving untouched buffer zones around them. In sites with steeper slopes, soil preparation is aligned with the slope and most steep areas are left untouched to prevent erosion and runoffs.
It goes without saying that valuable habitats and other such areas are protected from soil preparation operations. Immediate surroundings of retention trees, other living trees and deadwood are also excluded.
Planting is the starting point for new forest growth.