Litterfall production and seasonal variations in leaf area index of cork oak stand in the forest Ain Snoussi (Northwestern Tunisia)
Abstract: Although it is used as an index of primary production, studies relating to litter falls from cork oak are scarce in Tunisia. Thus the understanding of its dynamics is a prerequisite for the study of energy flows (through canopy structure, LAI) and the nutrient cycle in a Mediterranean forest ecosystem based on cork oak. The objective of the study is to quantify the litter falls, their monthly variations and compare them with their foliar index (LAI). In a 1 ha plot in the forest of Ain Snoussi, where the three arborescent (cork oak), shrub (Arbutus unedo) and herbaceous (Briza maxima) strata exist, leaf fall has been determined at 35 square traps, of 1 m² of surface, placed systematically every 15 m, under the trees to 10 cm above the ground. Pick-up was monthly from January 2010 to September 2011. The LAI (Leaf area index) of the stand was estimated by hemispheric photography systematically every 10 m in the year 2011, one to two times per season. The results showed that litter fall occurred throughout the year with a spring peak (May). This fall varied from year to year. It was in the order of 389.422 ± 34.7 g/m²/year in 2010, whereas in 2011 it was 300.51 ± 35.041 g/m² over a 9-month period of measurements. The most important fractions were mainly the leaves of cork oak, canary oak, Arbutus unedo and Myrtus communis, the main species of shrub. The foliar contribution was on the order of 83% of the total biomass. The seasonal variation of LAI showed that this functional parameter evolved according to the season. It was low at the end of winter, increased in spring when leaf fall was maximal, reached its maximum value in summer when the fall was minimal and then decreased in autumn.