Study on the influence of environmental factors on tree growth and cork production in the cork oak forests of theniet el had national park (Tissemsilt, Algeria)

Abstract

Variations in cork production capacities according to environmental factors were assessed in 53 temporary survey plots (763 trees) in the montane cork oak forests of Teniet El Had National Park (Algeria). Three production parameters were assessed: thickness (mm/ year), yield (kg) from an average tree and productivity (kg/ha) of a stand. Our study presents the effects of the main environmental factors on cork thickness and production, as identified from generalised linear models. The results show that cork grows slowly (2.38 mm/ year) and that growth rates are affected more by tree-specific variables (state of health, barking diameter and height) than by site factors (exposure). On the other hand, yields are influenced by the conditions of tree growth, as expressed by their total height but also by their state of health. In terms of stand quality, the sites fall into two types depending on the dominant height expressed by the model: (i) high-quality sites (Hd > 10 m; 2,900 kg/ha) characterised by trees with high growth rates in diameter, and (ii) poor quality sites where productivity is less than half of the former (Hd < 10 m; 1,700 kg/ha). These results provide management guidelines to help foresters plan cork harvests from their forests according to rotations and to the desired cork quality.