Current issue: 56(4)
According to the literature, the mechanical strength of the green reaction wood of softwood species (compression wood) is greater than that of normal wood. Drying increases the mechanical strength but less in reaction wood than in normal wood. In particular, the tensile strength along the grain and the impact strength are lower than in normal wood. The compression strength and possibly bending strength are greater, however.
The properties of the reaction wood of hardwood species (tension wood) differ from those of softwoods. When green, all mechanical properties are weaker than those of normal wood. When dried, the tensile strength and impact strength are better and compression strength lower. There is no great difference in the bending strength.
When the higher density of reaction wood is not taken into account and there are no impact forces, the mechanical strength of reaction wood in sawn goods etc. does not differ so much from that of normal wood. The harmful effect of knots, for example, can in practice be much greater.
The PDF includes a summary in English.
An attempt was made in the study to determine the annual periods available for foliage spraying when cleaning Scots pine (Pinus sylvestris L.) dominated seedling stands. The study was made in nine experimental fields which were established in different parts of Finland. The spraying was applied throughout the growing season by DM, MCPA and Roundup. The results were inventoried one year after the treatments.
The results showed that there were big differences both in the destruction of hardwood sprouts and in the survival of pine seedlings due to the time period of the spraying. Threshold points were observed in the range of effect of DM and MCPA. By means of these it is possible to time the spraying treatments in such a way that there remains only slight damage to pine, but hardwood sprouts are destroyed totally. The results varied with Roundup so much, among other things due to rain, that such threshold points could not be determined. This preparation both had a milder effect on the hardwood seedlings and caused slighter damage to pine than the other preparations.
In Sodankylä in Northern Finland, the pines attained a good resistance to arboricides when the efficient temperature sum of the growing season was 550, but in Punkaharju in Central Finland only when it was 850. The seed provenance of the seedlings had an effect on the resistance. The threshold temperature sums of resistance in pine were on the average 70–74% from the long-term average number of degree days at the origin of the seed. The effect on the hardwood trees grew weaker as the long-term average was filled. Resistance of pine followed with a specific lag the lignification of the shoot and the ceasing of the growth of the needles.
The PDF includes a summary in English.
Although crop tree release (CTR) in hardwood stands is an accepted variant of precommercial thinning (PCT), the lack of an affordable and feasible method hinders its adoption. CTR implies selecting between 150 and 500 trees ha–1 when trees are between 7 and 12 m high and cutting only stems competing with the target crop trees. We performed a field trial of a CTR variant of PCT in a 27.8 ha hardwood stand using a backpack mounted chain saw. A detailed time study was performed to document the trial over 13 days. Compared to conventional PCT performed earlier in the life of a stand, precommercial crop tree release required cutting larger stems, which showed to be feasible and productive using a backpack mounted chain saw. Productivity varied between 0.22 to 0.47 ha h–1 during the trial, Although productivity could vary with stand characteristics and worker, this proof of concept trial demonstrates some of the potential uses that this new saw configuration offers and sets the basis for an eventual larger scale deployment of this treatment.