Crown, stem and wood properties of wind-damaged and undamaged Sitka spruce

The study investigated the differences in slenderness ratio of all the snapped, overturned or undamaged trees within a wind-damaged stand of Sitka spruce containing areas of both, wet and dry soils. In addition, crown size, proportion of compression wood and mechanical properties of wood were investigated on 12 sets of trees of similar diameter that had snapped, overturned or remained undamaged from each of two further wind-damaged stands of Sitka spruce.

No difference in stem diameter, height or slenderness ratio were found between the damaged and undamaged trees sampled from the dry part of the wind-damaged stand. On the wet part of the site, however, the snapped trees were found to be significantly taller and of greater diameter than the undamaged or overturned trees although slenderness ratios were similar for all trees.

The experiment investigating matched sets of trees found that the snapped and overturned trees had significantly smaller crowns than the undamaged trees. Furthermore, the snapped trees had wood in the outer part of the stem that was less stiff, but of bending strength similar to that of similar wood taken from the undamaged and overturned trees. According to the results, high proportions of compression wood may be involved in the occurrence of storm damage.

It is suggested that trees containing compression wood should be preferentially removed from the forest during thinning. Since it is not feasible to measure compression wood in standing trees, the presence of leaning stems or asymmetric crowns should be used to identify the trees to be removed. Furthermore, trees with small crowns should also be preferentially removed during thinning. (C) 2000 Elsevier Science B.V. All rights reserved.