The Development of Stain in Wounded Sitka Spruce Stems

In order to investigate the severity of staining in wounded Sitka spruce stems, the vertical extent of two categories of stain (based on colour and termed ‘light’ and ‘heavy’) was measured in stems at two sites in south Scotland. Data were obtained from 98 wounds most of which were between 8 and 14 years old and most of which had been caused by Red deer. The upward extent of stain and its rate of upward spread were positively correlated with wound surface area and length. Most stain was of the light type which, although it was associated with nearly all wounds, usually constituted an insignificant defect and did not commonly extend for more than 1 m ahve wounds. Heavy stain occurred above less than half of all wounds studied but was common above wounds exceeding 300 cm 2 surface area. For all wounds, the mean value for the upward extent of heavy stain was 16.1 cm with a mean rate of spread of 1.9 cm y −1 . However, for wounds exceeding 300 cm 2 surface area, the values were 51.7 cm and 5.5 cm y −1 . These results suggest that, although there is an important effect of wound size on the type and extent of stain, wounds of the type studied are unlikely to lead to severe stain and decay in Sitka spruce over a period of 8–14 years. The results are discussed in relation to other studies on wound staining in conifers.