The Development of Stain in Wounded Sitka Spruce Stems

In order to investigate the severity of staining in woundedSitka spruce stems, the vertical extent of two categories ofstain (based on colour and termed ‘light’ and ‘heavy’)was measured in stems at two sites in south Scotland. Data wereobtained from 98 wounds most of which were between 8 and 14years old and most of which had been caused by Red deer. Theupward extent of stain and its rate of upward spread were positivelycorrelated with wound surface area and length. Most stain wasof the light type which, although it was associated with nearlyall wounds, usually constituted an insignificant defect anddid not commonly extend for more than 1 m ahve wounds. Heavystain occurred above less than half of all wounds studied butwas common above wounds exceeding 300 cm² surface area. Forall wounds, the mean value for the upward extent of heavy stainwas 16.1 cm with a mean rate of spread of 1.9 cm y^–1.However, for wounds exceeding 300 cm² surface area, the valueswere 51.7 cm and 5.5 cm y^–1. These results suggest that,although there is an important effect of wound size on the typeand extent of stain, wounds of the type studied are unlikelyto lead to severe stain and decay in Sitka spruce over a periodof 8–14 years. The results are discussed in relation toother studies on wound staining in conifers.