Response of young red alder to pruning

Abstract

Red alder (Alnus rubra, Bong.) is the most common hardwood in Washington, Oregon and British Columbia. It is used for a variety of products including firewood, pulp, and solid wood products such as furniture, cabinets and musical instruments. Pruning may be a viable management technique for increasing clear wood and, thus, value in managed stands but little information has been available. To determine the biological effects of pruning red alder, we selected 530 trees in 3-, 6- and 10-year-old plantations. Sample trees were from plots that had different previous silvicultural treatments, providing a range of growth rates. Pruning removed one third of the live crown, was performed on seven dates throughout the year, and included both live and dead branches as well as a sub-sample of intentionally damaged collars around dead branches. The rate of branch occlusion (healing) was well correlated with tree growth at breast height and with distance from the base of the live crown. Live branches occluded more rapidly than dead branches and dead branches occluded more rapidly if the branch collar was intentionally wounded during pruning.The number of epicormic branches induced by pruning was minimal, but increased with tree age and where trees were growing in an open condition. No stem breakage or sunscald was observed as a result of treatment. Six years following pruning, 91% of pruned branches less than 1 cm in diameter and 80% of branches 2–3 cm in diameter had completely occluded. Those that had not occluded by that time were on trees with low growth rates. Time of year of treatment had little effect on tree growth rates, occlusion rate, epicormic branch formation, and damage. Pruning young trees did not result in any damage or loss of growth. To maximize the amount of clear wood it would be best to prune as soon as logistically possible. Thus, if economic incentives are present for clear wood, landowners and managers may want to consider pruning young trees, taking into account the possible need for multiple lifts.

Citation

Brodie, Leslie C.; Harrington, Constance A. 2006. Response of young red alder to pruning. In: Deal, Robert L.; Harrington, Constance A., eds. Red alder: A state of knowledge. Gen. Tech. Rep. PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 95-102.