La Palma is one of the youngest and highest islands of the Canaries (only 2 MY and 2400 m a.s.l.). The island is relatively small (729 km2) composed of a big cauldron, which occupies the northern part of the island and has a deep of 2000 m. This island is remarkably conserved, especially the pine forest. There are four main types of habitats. Lowland areas are occupied by sub-desert shrub vegetation adapted to the infra-thermomediterranean arid-semiarid climate. The thermophyllous woodlands represent the type of vegetation more destroyed by human causes in all Canary Islands. The potential area for the endemic laurel forest is located from 300 m to 1500 m a.s.l. This type of vegetation has been systematically destroyed in La Palma, but still some remnants can be found where the forest is mature and has a high species number for this latitudinal position (more than 150 species of bryophytes). From 1500 m to the uplands (2000 m) is an endemic pine forest, which is also very rich in bryophyte species (166 species). Above the timberline (2000 m) the vegetation is formed by shrub vegetation dominated by Adenocarpus foliolosus included in the supra and oro - mediterranean dry belts. The climate is semi arid (infra-thermomediterranean arid-semiarid) with a mean annual precipitation around 500 mm. The proposed field work in La Palma would be to make an elevationnal transect (300 - 2400 m) from the North-East zone (Santa-Cruz-Punta LLana), where there are some coastal shrubs and rocky vegetation to the highest point (Pico de la Nieve), crossing some of the best preserved laurel forest and pine forest areas.