Modélisation de la croissance et la production du liège en Tunisie

Abstract

The lack of necessary tools to estimate cork production and assess the management of cork oak forests (Quercus suber L.) in Tunisia is handicapping their development and conservation. The aims of this study were: (i) to specify the impact of first-layer bark removal on tree growth and cork production, (ii) to develop models for estimating cork oak growth and biomass on the scale of individual trees, (iii) to check the bark removal coefficients applied in Tunisia and their impact on the country's cork production. The data were collected from bark removal experiments on several sites and from two inventories conducted at different sites during two successive cork harvesting campaigns. The same experiment was conducted at three trial sites that were representative of productive cork oak forests in Tunisia, with three bark removal coefficients applied to trees of three different diameter classes. Measurements of cork thickness at breast height were taken yearly over a 12-year rotation, at the end of which the cork produced by each tree was harvested and weighed. The results obtained show that the effects of the bark removal coefficients on cork growth and thickness were non-significant, while the effects of diameter class were highly significant. The weight of the harvested cork was significantly affected both by the bark removal coefficients and the diameter class. Two models were developed for the individual tree scale for cork oak growth and biomass, with an accuracy of 96% and 93% respectively. The bark removal coefficients actually applied in Tunisia vary from 0.6 to 3.6 with an average of 1.7. Losses of cork quantities shown by the two inventories were estimated at 14%, 32% and 50% respectively for the three bark removal coefficients applied and analysed (2, 2.5 and 3).