Discoloration and associated fungi in stems of silver birch (Betula pendula Roth.) following logging damage

Study aim was to investigate discoloration and associated fungi in 50‐ to 70‐year‐old stems of Betula pendula damaged by logging. Investigated wounds (on 70 stems) were inflicted 4–18 years previously, and all of them had discoloration with mean radial spread (±SD) 2.9 ± 2.9 cm and longitudinal spread 50.3 ± 24.0 cm. Both wound area and length had a strong impact on a total length of discoloration (r = 0.665 and r = 0.745, respectively; p < 0.001), but had no influence on its spread beyond wound margins (r = ?0.035 and r = ?0.079). There was no correlation between the age of an injury and spread of the discoloration neither in vertical (r = ?0.110) nor in radial (r = ?0.280) direction. Average wound closure rate was 1.2 ± 0.5 cm year ^?1. The difference between discoloration length in stems with open and occluded injuries was insignificant (t‐test, p = 0.769). The principal fungi isolated from the wounds were ascomycetes (Epicoccum, Cadophora, Neonectria, Alternaria spp.) that were able to cause discoloration of wood with little effect on its mechanical properties and capable only for limited spread inside a stem of a living tree. In conclusion, results of the present study demonstrate that the amount of discoloured wood beyond logging wounds in B. pendula is mainly restricted to the damaged portion of a stem and that the associated loss of wood production remains low during about 10 years since the damage.