Flora of the Canary Islands. Vegetation zones. Dry thermocanarian zone. Flora and vegetation of the Canary Islands

Zone termocanario dry

     The dry thermocanarian zone, or thermophilic forest zone, is found throughout the Canary Islands, in an altitudinal band situated at approximately 200–500 m, mainly on north- and east-facing slopes, whilst it is almost entirely absent from the south and south-west-facing slopes.
     Climatically, it is characterised by moderate temperatures averaging between 15–18 °C over the year. Rainfall follows an annual distribution pattern typical of the Mediterranean climate, with peaks in winter and spring, followed by a very dry summer, and an average annual rainfall of between 350–600 mm. The influence of the trade winds and the proximity to areas where sea fog forms leads to a gradual decrease in the amount of sunshine and a slight increase in humidity.
    Other ecological factors, such as soil type, wind patterns, geological age, etc., also influence the floristic composition of this vegetation zone, which is characterised by a fairly open type of woodland comprising just a few tree species: the Canary Island palm (Phoenix canariensis), the dragon tree (Dracaena draco), the mastic tree (Pistacia lentiscus), the Canary Island juniper (Juniperus canariensis), the wild olive (Olea guanchica), the Atlantic pistachio (Pistacia atlantica), the mocán (Visnea mocanera), etc., which occasionally form almost monospecific communities, giving rise to what are known as palm groves, juniper groves, wild olive groves, mastic groves, etc.

The Canary Island palm (Phoenix canariensis) can be found from the coast, on sandy or saline soils, up to altitudes of over 600 m, mainly occupying riverbeds and ravine slopes, as it is a hardy and highly adaptable species that requires only a certain amount of soil moisture. The dragon tree (Dracaena draco) is the most symbolic tree of the Canary Islands, but it is now very rare in the wild, with significant populations remaining only in certain areas of Tenerife and northern La Palma (Buracas, La Tosca). The Canary Island juniper (Juniperus canariensis) is a small tree, but very hardy and with highly prized timber; it was once very abundant, and small groves of exceptional beauty still remain, the most spectacular of which is situated in Sabinosa, on the island of El Hierro, where the wind has sculpted these trees into twisted shapes, whilst the largest and best-preserved grove is in Vallehermoso, on the island of La Gomera.

Alongside these dominant tree species are groups of shrubs and herbaceous plants, almost all of which are endemic to the Canary Islands, and which stand out for their abundance, their scenic value and their striking flowers, such as the granadillo (Hypericum canariense), the guaydil (Convolvulus floridus), the wild jasmine (Jasminum odoratissimum), the cliff mallow (Lavatera acerifolia), the buckthorn (Rhamnus crenulata), the hierbamora (Bosea yervamora), the orobal (Withania aristata), the jorao (Asteriscus sericeus), the buckthorn (Rhamnus crenulata), etc.

Many of the numerous species living in this vegetation zone belong to genera that are widely represented in the Canary Islands, whose evolutionary process has given rise to endemic species found on just a single island. This is the case with various daisies (Argyranthemum spp.), everlastings (Limonium spp.), chahorras (Sideritis spp.), sow thistles (Sonchus spp.), viper’s bugloss (Echium spp.), cabezones (Cheirolophus spp.), corazoncillos (Lotus spp.), and wild thyme (Micromeria spp.).
Some plants of Mediterranean origin also find their preferred habitat in this area, becoming very common in marginal or degraded parts of this vegetation zone, such as rockrose (Cistus monspeliensis) or Daphne gnidium.

Dragos de La Tosca, Barlovento

The long-standing concentration of the human population in these areas, engaged in activities such as agriculture, pastoralism and excessive logging, has greatly reduced the original distribution of these forests, with the result that their current occurrences are scarce, offering very few examples of what this vegetation might have been like in its natural state. Examples include the juniper groves on the island of El Hierro, in the north-west of La Gomera, and some very small remaining patches in the Afur area of Tenerife and on the island of La Palma; the mastic forests of Gran Canaria; the scattered juniper groves in Tenerife, La Palma and Gran Canaria; and the palm groves of La Gomera, Tenerife, La Palma, Fuerteventura and Lanzarote.
As for what we might call ‘dragon groves’ – more or less dense clusters of dragon trees – these have almost completely disappeared from the Canarian landscape. The few natural groups of dragon trees that remain today are found on the island of Tenerife (Roque de Tierra and Roque de las Ánimas, in Anaga; Barranco del Infierno and Barranco de Las Carboneras), and on La Palma (El Palmar, Franceses and Las Tricias, in Garafía; La Tosca, in Barlovento).

Whitania aristata

However, the vigour and extent of the original distribution of this vegetation zone are illustrated by the fact that even islands such as Lanzarote and Fuerteventura – which are now almost desert-like and devoid of tree cover – still retain, in addition to their palm groves, evidence that in times past they were home to populations of adernos, almácigos, lentiscos, mocanes and even marmolanes.