Lichens as indicators of a perturbation/stability gradient in the Asperillo dunes, SW Spain

In the Asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is eliminated, and (3) pine forest resulting from afforestation with Pinus pinea since the end of the 1940s where the composition and abundance of the lichen flora has been drastically changed. Our hypothesis was that the lichen species composition and distribution are influenced by the type and period of human intervention. To test this hypothesis a 1.2 km × 1.1 km area, which includes zones with different degrees of conservation and perturbation, consisting of five different habitats, was selected: well preserved Juniperus woodland, Pinus pinea plantations with dense scrub, dense scrub, P. pinea plantations cleared from scrub, and pioneer scrub in recent pine afforestation. In each area, randomly located 5 m × 5 m homogeneous plots were sampled. In each plot the cover of shrub and lichen species was recorded. The first results show that lichen cover is higher in the most preserved areas, Cladonia mediterranea being the dominant species under the Juniperus phoenicea canopy. The lichen community changes in composition and abundance depending on the time elapsed since the last perturbation.