Predicting final thickness of cork planks. Application to sampling cork production

Abstract

105 cork samples (20 cm x 20 cm) have been extracted from seven sites selected as representatives of the main cork oak production areas in Spain. Age, thickness and annual growth of cork have been measured on the transversal section of each piece. Thickness of cork one, two and three years before stripping has been calculated. Lineal regression analysis has been performed to obtain predicting equations for thickness at debarking time, where independent variables were thickness one, two or three years before stripping and growth rate at each moment. A set of equations was obtained, and regression coefficients varied between 0.9918 (the year before stripping) and 0.9182 (three years before stripping). Due to the sampling method, it is considered that these equations can be applied all over the cork oak distribution area in Spain. Best results can be obtained using the following equation: EF = 0.70021 + 1.05232 * Et–1 (EF: final cork thickness; Et–1: cork thickness one year before stripping) The results allow some changes in the current sampling methods, designed for owners assessment, as sampling in the field can be done the year before stripping. Due to the role of thickness in grading of cork planks, more 75 % of the production is not affected by these estimations, when thickness one year before stripping is used.