Compression wood was measured by placing thin (3mm), waterlogged, slices of wood on a light box. The compression wood was located by its darker colour. The position of the compression wood was marked on tracing paper, and then digitised into an ARC/INFO coverage. The proportion of the cross-sectional area of the stem occupied by compression wood was calculated using an AML. Weighted compression wood area (where greater emphasis is given to compression wood at near the bark than to similar wood near the pith) was also calculated but the results were generally very similar to those reported here.
Average values for the ten snapped and ten undamaged pine trees from Blackhall forest are shown in the figure below.
Each bar represents data from a different height in the tree. A slightly greater compression wood proportion was found in the snapped trees compared to the undamaged trees at 10m, but the difference was not significant. The very large value for the undamaged trees at 14m is based on data for only one tree, and is therefore unreliable.
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