Above altitudes of 600 m up to 1200-1500 m is the montane level, where the Monteverde forest develops. This formation, characterised by a huge diversity of arboreal species, can be found on all the islands with the exception of Lanzarote, as that island does not reach a sufficient height above sea level. Its natural distribution is principally defined by the influence of the trade winds on the northern slopes of the most mountainous islands, which give rise to the ‘sea of clouds’. This cloud bank is responsible for the so-called ‘horizontal rain’ or ‘fog precipitation’, that provides humidity and water resources to the vegetation, and which adds to the direct annual precipitation. In some southern basins, occasional overflows from the sea of clouds also enable this plant formation to survive. Monteverde soils are particularly deep, acidic, with abundant humus, and normally nitrogen-rich. They tend to be covered by a thick layer of decomposing organic matter, containing a lot of plant remains (e.g., fallen trunks, dry branches, and leaf litter). The Monteverde forest includes two woodland formations: the laurel forest, known locally as the laurisilva, and the Morella-Eric heath, or fayal-brezal.
The laurel forest is probably one of the most well-known arboreal formations in the Canaries, and is considered a true living fossil. It is characteristic of northern zones and regions influenced by the mists generated by the trade winds. It is a subtropical humid forest composed of many shade trees, i.e., with wide leaves that create cover and allow little light to reach the forest floor (ombrophilic forest). The most common trees are the laurel (Laurus novocanariensis), the Canary laurel (Apollonias barbujana), species of holly (Ilex canariensis and Ilex perado), Persea indica, Rhamnus glandulosa, Picconia excelsa and Viburnum tinus subsp. rigidum. The rarest include Heberdenia excelsa, the stinkwood (Ocotea foetens), the Canary spurge (Euphorbia mellifera), Pleiomeris canariensis, Arbutus canariensis, Sambucus palmensis, and the Portugal laurel (Prunus lusitanica). In general, the laurel forest develops on deep soils.
The Morella-Erica heath is either a laurel forest substitution formation that occurs in areas degraded by repeated logging, or a natural transition to the pine forests. It is a forest characterised by abundant tree heaths (Erica arborea), firetrees (Morella faya), and, to a lesser extent, the heather Erica platycodon subsp. platycodon, which are typical of the most humid summit zones on Tenerife and La Gomera. It can occasionally be accompanied by the small-leaved holly (Ilex canariensis) or laurel (Laurus novocanariensis). For this reason it is a poorer formation than the laurel forest. Some plants in the Morella-Erica heath can become so large and the vegetation so closed that they make it difficult for other species to become established, as happens in some stands on El Hierro.
