FACTORS INFLUENCING THE FORMATION OF RESIN POCKETS IN PRUNED RADIATA PINE BUTT LOGS FROM NEW ZEALAND

摘要

Resin pocket incidence is an important variable when assessing the potential appearance-grade quality of wood from Pinus radiata D. Don in New Zealand. High levels diminish value. Several theories have been proposed to explain the origin of resin pockets; in New Zealand researchers have considered silviculture to be an important factor.A comprehensive database derived from stand sampling and sawing Studies has been used to explore the relationship between butt log resin pocket incidence and twenty nine climatic, physical, soil and silvicultural variables. A total of 1055 sites, distributed over 281 stands in four distinct regions, were analysed. The incidence of butt log resin pockets ranged from 0 to 7.65 RP/m(2).Multiple linear regression methods were utilised to build a prediction model. Initially, four significant predictors were isolated, vapour pressure deficit, solar radiation, a measure of wind damage and readily available water. Further analysis showed a fifth variable (tree diameter breast height/size of the defect core), also contributed to the model. The R-2 value of the equation was 0.50 and residual analysis showed the model to be generally unbiased over four locations.Average daily October vapour pressure deficit made the biggest (58) contribution to the regression and the coefficients were all positive except water availability which was negative, as expected. We interpreted these results to infer that stress (associated with moisture and exposure related issues) in conjunction with other factors, including accelerated growth, is a major cause of resin pocket incidence.