Fungal colonization of coastal Douglas-fir following mechanical commercial thinning damage

Commercial-aged Douglas-fir trees mechanically damaged during commercial thinning activities were investigated to quantify fungal taxa present 14years after thinning. A total of 235 wood cores from 18 damaged and 18 non-damaged control trees were obtained. Fungi were isolated on malt extract agar and molecular methods were used to identify 48 taxa. Damaged Douglas-fir trees were more than twice as likely to contain wood-inhabiting fungi as undamaged trees (p=0.07) and contained more than 2.5 times more fungi (p=0.006). However, typical Douglas-fir stem-decay fungi were not isolated. Fungi present were mostly endophytes and no significant differences were found in frequencies of decay/non-decay soft-rot fungi between damaged and control trees (p=0.67). Likewise, no significant differences were found for the trend in number of fungi isolates over radial depth into the stem between damaged and control trees (p=0.29). Frequency of fungal isolates was non-linearly related to depth in the tree bole. Significant differences between damaged and control trees (p=0.03) was influenced by the data in the outermost 3mm. With the exception of these data, there were no significant differences between damaged and control trees in the radial trend in fungal frequency (p=0.37). Results of this study suggest that wounding in commercial-aged Douglas-fir may not contribute significantly to occurrence and species composition of wood inhabiting fungi over the period of a short-rotation final harvest. However, damage mitigation is recommended supported by a related study showing vertical discolouration affecting all wounded stems. © 2010 Blackwell Verlag GmbH.