Current issue: 54(4)
Systematic draining of peatlands begun in the state forests of Finland in 1908. It was considered necessary, because 41.4% of the state forests, 5.6 million hectares, consist of peatlands. Of the peatlands, 1.9 million hectares was estimated to be suitable for draining. Furthermore, paludification still continues in the forest lands. By the year 1926, a total of 52,275 hectares of peatland had been drained in the state lands.
Certain factors decide whether the peatland is suitable for draining: the growth increment capacity after draining, technical difficulties in draining, and difficulties in regeneration. Peatland type indicates the growth capacity of the drained peatland. The peatland should turn at least to Vaccinum forest site type or better type to be worth of draining. If the peat layer is thin, the quality of peat is an important deciding factor. The peatland may also be too expensive to drain due to, for instance, long ditches, main ditches difficult to dig, small inclination, uneven surface, and deep cavities at the bottom. The younger the trees of the stand, the faster the growth of the stand revives. The peatlands usually regenerate naturally provided there is sufficient seed trees, and there is seldom need for artificial regeneration.
The PDF includes a summary in English.
Draining of peatlands requires careful planning because of its costs. Only peatlands that have sufficient growth capacity in future should be drained. The future growth capacity can be estimated based on peatland type, the botanical composition of the peat layers and the quality of the surface peat layer of the swamp.
Also the draining methods should be cost effective. To keep the amount of drains low, the drain network and drain lines should be planned so that each drain has high drain effectivity. Most of the peatlands drained in Finland have been forested. Especially the young trees regain soon their growth when the peat begins to dry. It is recommended to leave the young trees, but most profitable to harvest the older forests in the drained area. Practical experiences have shown that even drained open peatlands can be naturally regenerated. Natural regeneration is almost guaranteed to succeed on peatlands, which have seed trees.
A summary in Finnish is included in the PDF.