Leaf Area Index estimation and lifespan of Quercus suber L. leaves in the Ain Snoussi, Bellif and Khroufa forests in northwestern Tunisia

Abstract: The study focuses on the estimation of the Leaf Area Index (LAI) by two methods:
litter traps (direct method) and hemispherical photographs (indirect method) in three stands of Quercus suber chosen according to an altitudinal gradient. These are the Ain Snoussi, Bellif and Khroufa forests. In each forest, one a plot of 1 ha was placed. Square litter traps with an area of 1 m² were installed every 15 m. This device makes it possible to recover all the aerial parts lost by the trees. From each collector, after separation of the different fractions collected, thirty cork oak leaves per date were sampled to measure their elementary leaf area (SLA). The leaf area index is then determined by multiplying the dry leaf biomass by the SLA. Collection was irregular. For the tree stratum, digital hemispherical photographs were taken every 10 m, aiming upwards, in irregular time steps, during the same year 2011. These photographs were analyzed with the GLA software. The lifespan of the leaves was determined from the hemispherical LAI and the total litter LAI. The study of the structure of the canopy by means of its leaf area index estimated by litter collection showed that the total cumulative LAI of the tree stratum was 1.25 m²/m², 3.48 m²/m² and 1.24 m²/m² for Quercus suber L., respectively, in Ain Snoussi, Bellif and Khroufa and around 1.6 m²/m² estimated by hemispherical photography in the three study sites. The lifespan of Quercus suber leaves is 11 months, 4.5 months, 10.3 months, respectively, in Ain Snoussi, Bellif, Khroufa stands.