Biological, Chemical, and Physical Properties of Scots Pine from Sweden Under Special Consideration of Crown Defoliation

1990

312 S.

zahlr. Abb., Tab., Lit. Ang.

Unselbständiges Werk

200034029

The report of the 1988 forest damage survey in Europe indicated that 1.8% of the younger Swedish pine stands had lost more than 25% of their needles (Global Environment Monitoring System 1989). Defoliation in Swedish pine forests older than 60 years, the stand age with highest felled timber volume, amount to 8.9%. The amount of moderately and severely defoliated pine trees in Sweden is distinctly smaller than in Central Europe and the recently observed crown defoliation in southernmost Sweden is most likely triggered by a drought condition, but it cannot be excluded that the changed soil conditions, due to pollution impact, result in an additional stress (Andersson 1985). The forest industry, and especially pine wood, is of high importance for the national Swedish economy and for the forest products supply tothe other European countries. Swedish timber is well known for its high quality due to constant increment growth combined with well shaped merchantable boles found exclusively in old trees and providing highest technological and decorative properties. Considering the irritations about the quality of coniferous wood from pollution affected forests, serious efforts are required to secure the excellent reputation of Swedish wood and wood products. Earlier investigations in Germany proved that Scots pine is less affected by air pollution than Norway spruce and Silver fir (CMA 1986, Fruehwald et al. 1986, Glos and Schulz 1986, Kufner and Schulz 1986, Hapla and Kottwitz 1987, Hapla, Knigge and Rommerskirchen 1987, Hapla and Lewark 1988, Hapla 1988, Bues and Schulz 1988, Schulz et al. 1988). Growth ring width and sapwood percentage of diseased pine trees are generally reduced but these deviations are smaller than in spruce and fir. The moisture content pattern from the outer to the inner sapwood does not reveal considerable differences in water supply between healthy and damaged trees. Despite growth depression, no significant deviation of the sapwood density of healthy pine trees from that of diseased ones was found. Modulus of elasticity, bending, compression, shear, impact bending and torsional strength as well as maximum swelling and shringage of pollution-affected German pine trees did not deviate neither from the results of former studies nor from healthy trees grown in the same stands. So far, restrictions for the utilization of German pine wood from polluted areas immediately after felling need not be taken into account. The chemical composition of green pine wood from defoliated trees has not yet been studied. Analysis of main components and heartwood extractives under special consideration of natural wood durability are needed. Due to the experience that pine sapwod is most susceptible to fungal attack, two years wet-stored German pine logs healthy and defoliated pine trees were compared with green logs of the same trees ...........