Effect of stem bending and soil moisture on the incidence of resin pockets in radiata pine
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RESEARCH ARTICLE
Open Access
Effect of stem bending and soil moisture on the incidence of resin pockets in radiata pine Trevor G Jones1*, Geoffrey M Downes2, Michael S Watt3, Mark O Kimberley4, Darius S Culvenor5, Maria Ottenschlaeger6, George Estcourt4 and Jianming Xue3
Abstract Background: Mechanical bending stress due to tree sway in strong winds and water stress during drought are thought to contribute to the formation of resin pockets, but it is unclear if these are linked and whether the initiation of resin pockets is influenced by the water status of the trees at the time of stem bending. Methods: The effect of stem bending on the formation of resin pockets was evaluated under various soil moisture conditions. The stems of 12-year-old radiata pine (Pinus radiata D.Don) trees were bent mechanically in spring or summer when the soil was water deficient, and in summer after rehydration. After the completion of the growth season, a selected sample of trees was felled and stem discs were assessed for the presence of resin pockets, using disc photos and image analysis. All stem bending treatments were compared with control trees. Results: Stem bending in spring or summer was found to increase the number of Type 1 resin pockets, but had no effect on the number of Type 2 resin pockets. The soil moisture conditions at the time of stem bending had no effect on the number of Type 1 or 2 resin pockets. Conclusions: The Type 1 resin pockets occurred in the inner part of the early wood, adjacent to the growth ring boundary. This suggests the Type 1 resin pockets were initiated in the mature wood, behind the cambium and zone of differentiation, and were not influenced by the water status of the tree stems at the time of stem bending. Keywords: Resin pockets; Pinus radiata; Stem bending; Water stress; Winching
Background Resin pockets are a major cause of degrade in the appearance grade timber of radiata pine (Pinus radiata D. Don). When present at moderate to severe levels in the logs of radiata pine, they can lead to significant reductions in the value of the timber (McConchie & Turner, 2002; Cown et al., 2011). Resin pockets occur as Type 1 and 2 forms in the logs of radiata pine (Sommerville, 1980; McConchie et al., 2008; Ottenschlaeger et al., 2012). Type 1 resin pockets are described as lens-shaped accumulations of resin and callus tissue within a growth-ring that cause no damage to the cambium, while Type 2 resin pockets are similar except the cambium is ruptured and healing results in an occlusion scar that can occur over several growth rings. Resin pockets occur at some level in * Correspondence: [email protected] 1 The New Zealand Institute for Plant & Food Research Ltd, Private Bag 11600, Palmerston North 4442, New Zealand Full list of author information is available at the end of the article
all stands of radiata pine in New Zealand (Park, 2004), but reach epidemic levels in regions that are windy and/or dry. The formation of resin pockets in trees is thought to occur as a result of the stress
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