Development of epicormic sprouts on Sitka spruce stems in response to windthrown gap formation

Summary Sprouting as a response to injury or changed environmental conditions is uncommon in conifers, but it is a feature of Sitka spruce (Picea sitchensis (Bong.) Carr.). This study provides observations from two surveys of epicormic sprouts on standing and fallen trees in windthrown gaps within planted Sitka spruce forests of upland Britain. In a survey in Kielder Forest, epicormic sprouts were found on standing trees in closed stands and on trees at the edge of small gaps (area 4‐96 m 2 ). However, the branches were smaller, younger and had lower annual increment than those from trees on the edge of large gaps (area 215‐1494 m 2 ) and along a roadline within the same stand. In a survey at five sites in upland Britain, fallen trees were found to be alive in half of the 109 windthrown gaps, and there were epicormic branches showing excurrent vertical growth in a quarter of the gaps. The presence of epicormic branches on fallen trees, and their size was related to gap size as expressed by mean skyview. Sprouting on standing trees may affect timber quality by increasing the number and size of knots, and this has implications for the trend in management towards increased thinning and group felling. Sprouting on fallen trees may assist the perpetuation of the former canopy species in gap filling and this has implications for stand dynamics in retentions and natural reserves of spruce.

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