Natural regeneration of Pinus pinea L. in Tunisia as influenced by canopy cover, litter biomass and understorey vegetation

Pinus pinea is one of the most valuable species used in Tunisia in the reforestation program. This species is shade-intolerant and hence needs light to correctly regenerate. It is also influenced by the understorey vegetation and the litter biomass, both also correlated to light availability. To quantify the importance of these different factors, the natural regeneration and evolution of the biomass of understorey vegetation and litter were studied in artificial forests of Pinus pinea located in the coastal dunes of Nefza-Tabarka, and thinned to reach different levels of light. Overstorey cover was measured on 37 plots (500 m2 each) and the biomass of the different species of the understorey and the needle litter was recorded in 8 subplots (0,25m2). The number and age of Pinus pinea seedlings were also determined in each plot. Results showed that the biomass of the understorey vegetation, as well as the number of pine seedlings increased with light availability and concomitantly a decrease of the litter biomass. We will discuss the interactions between the different factors and give practical recommendations to better manage pine stands in the area.