Optimal intensity and age of management in young Aleppo pine stands for post-fire resilience

During the last few decades, the number of forest fires has been increasing in the Mediterranean Basin due to several factors, among others global warming. Large burned areas are promoting a higher number of naturally regenerated stands which are being poorly managed in general, causing the risk of new wildfires to increase. The most important conifer in dry areas is Pinus halepensis Mill., a well-adapted species to fire-prone habitats due to its high post-fire seeding capacity. High seedling density in the regenerated areas produces high inter-specific competition, which could induce low cone production related to an insufficient amount of seeds stored in the canopy for post-fire recolonization (immaturity risk); adequate young pine tree stand management is therefore required, mainly based on thinning and pruning. In this study different thinning intensities, with and without pruning, were tested in two Aleppo pine post-fire regenerated areas at 5 and 10 years after a fire event. Significant relationships between seed and cone characteristics to site, treatment, cone age and cone type were found. Also the relatively little importance of Aleppo pine seeds in the soil seed bank was checked. The optimal management strategies for Aleppo pine forests in good site quality 5 years after fire was a final density of 1600 trees ha(-1) (plus pruning after 5 years) or 800 trees ha(-1) as well as a final density of 800 trees ha(-1) plus pruning after 10 years. In poor site quality, the best method was no treatment or thinning to 1600 trees ha(-1) 5 years after fire plus pruning after another 5 years. This management policy can produce benefits in the reproductive processes of Aleppo pine after fire regeneration, as it shortens the juvenile phase and promotes a higher amount of closed cones stored in the canopy, thus increasing the canopy seed bank and reducing the immaturity risk. (C) 2008 Elsevier B.V. All rights reserved.