Quality grading of cork planks with image analysis based on sanitary state of trees:the case of oak forests of M’Sila and Zarieffet (North-West of Algeria)

Abstract: The classification of the quality of cork by image analysis was studied in summer2009 in two production areas, one coastal (M’Sila) and one mountainous (Zarieffet). The corksampling was randomly performed in each area from 40 trees belonging to three healthcategories: healthy (defoliation 60%).The results show that the thickness of boards and their average annual increases (all state ofhealth combined) were respectively about 25mm (2.3mm/yr) in coastal versus 21mm (1.9mm/yr)in mountain forests. The average coefficients of porosity (all health status combined) calculatedfrom image analysis techniques vary between 4.90% and 4.50% in tangential section. In the oakforests of M’Sila, prone to an advanced decline, superimposed on a large genetic variation oftrees, variable porosity (total area of pores, pore density, % CP) vary significantly across thethree health situations. In Zarieffet, limited decline and slow growth of cork seem to have noeffect. The classification of cork planks according to their increasing quality, and thus to thedecreasing abundance of defects, does not seem to be dependent on the health status of the trees.The physiological changes of the tree do not necessarily induce a complete eradication of thecork of good quality but rather provoke a gradual reduction of its surface in relation to decayintensity. This phenomenon is much more pronounced in coastal stands than in mountain stands.