Laurisilva
On
north-facing slopes, the thermophilic forest gives way to the laurel forest,
a type of subtropical forest characterised climatologically by high humidity
and a moderate, very stable temperature.
The laurel forest is a predominantly tree-dominated, evergreen forest formation, whose vast mass of leathery, glossy leaves promotes the condensation of moisture contained in the mists that almost constantly shroud the area, producing a slow, fine and almost constant local rainfall at the foot of each tree, known as ‘horizontal rain’.
During the Tertiary period (around 20 million years ago), this type of forest was widespread throughout the Mediterranean basin, North Africa and southern Europe, as evidenced by the numerous plant fossils found in these areas. However, the climatic changes that have occurred since then – including ice ages and arid periods that gave rise to the desert barrier of North Africa – led to the disappearance of this vegetation from the continents, with it finding refuge in the Macaronesian archipelagos (the Azores, Madeira and the Canary Islands), as the influence of the ocean acts as a thermostat regulating environmental conditions; consequently, the present-day Canarian laurel forest formations are nothing more than relics of those ancient Mediterranean forests. In the archipelagos of Madeira and the Azores, a more favourable climate allows these forests to cover a larger potential area and to be found at lower altitudes, even almost at sea level, whilst also exhibiting a different floristic composition to that of the Canary Islands.
During the winter, the Canary Islands experience north-westerly winds, which generally bring rain, but in summer the north-easterly trade winds are the prevailing winds. The trade winds do not cause rainfall, but as the moist air rises up the slopes, it condenses and forms a large cloud mass known as a ‘sea of clouds’, which affects altitudes between 400 and 1,200 metres above sea level. Sunlight is thus greatly reduced, tempering the temperatures, and the moisture is trapped by the dense vegetation, which acts as a sort of ‘sponge forest’, providing a water supply that can be up to three times the annual rainfall and is vital for the survival of the laurel forest. This phenomenon, with its extra supply of moisture, does not occur on the islands of Lanzarote and Fuerteventura, as their low altitude prevents the trade winds from having an effect; consequently, there are no laurel forests on these islands.
Thus, the combination of climate and topography determines the distribution of the laurel forest in the Canary Islands, which is found in north-facing areas at altitudes of between 400 and 1,200 metres, with mild temperatures throughout the year (average 12–14 °C) and annual rainfall of between 800 and 1,400 mm. The dry season is largely mitigated by the presence of the aforementioned sea of clouds.
The soils, owing to their age and the effects of the climate and vegetation, are generally well-developed, with considerable depth and a well-defined organic topsoil layer. The environmental conditions of high humidity and temperate temperatures lead to rapid humification and mineralisation of organic matter (fallen leaves and other plant debris), releasing abundant nutrients which are rapidly absorbed by the roots.
The laurel forest plays a vital role in the islands’ water cycle; its ability to capture and retain moisture ensures a continuous supply of water to river valleys and ravine beds, as well as to underground aquifers. It also helps to prevent soil erosion, particularly on the steepest slopes, as the roots act as a kind of mesh that holds the soil in place.
Originally, the laurel forest covered a vast area of woodland in the central and western Canary Islands, but intensive exploitation of its resources from the early days of the conquest of the islands (timber, charcoal, etc.), which continued almost uninterrupted until a few decades ago, has almost completely depleted the pure stands of this forest. As for its original distribution, almost nothing remains in Gran Canaria; barely 10 per cent remains in Tenerife; it is confined to a few ravines and very specific areas in the north of La Palma; and the best-preserved laurel forest in the world is found on La Gomera, within the area currently defined by the Garajonay National Park.
Flora
The laurel forest is the most complex ecosystem found in the Canary Islands. In its purest form, it consists of some 18 species of large, evergreen, shade-loving and thermophilic trees, beneath which a great variety of ferns, mosses, fungi and other organisms typical of shady environments thrive. In many cases, the tree layer forms a closed canopy, creating a roof that barely allows any sunlight to pass through. As the environmental conditions required by this habitat change, the forest gradually opens up and allows more light to penetrate, resulting in a significantly richer and more diverse undergrowth.
The most characteristic tree species of the laurel forest belong to the Lauraceae family, such as the loro (Laurus novocanariensis), the tilo (Ocotea foetens), the viñátigo (Persea indica) and the barbusano (Apollonias barbujana). Other large tree species are also common, such as the acebiño (Ilex canariensis), the wild orange tree (Ilex perado, spp. platyphylla), the aderno (Heberdenia excelsa), the delfino (Pleiomeris canariensis), the mocán (Visnea mocanera), the hija (Prunus lusitanica), the sanguino (Rhamnus glandulosa), the palo blanco (Picconia excelsa), the madroño (Arbutus canariensis), the heather (Erica arborea) and the faya (Morella faya).
Despite their diversity, almost all these species display very marked morphological similarities resulting from adaptation to the same environment. The leaves are evergreen, as in this relatively uniform and favourable climate there is no point in shedding them during a particular season. The leaf surface is of the Lauraceae type: leathery and glossy, allowing water to run off easily and preventing excess moisture; it eventually falls to the ground via the pointed tip, which acts as a drip edge. These mechanisms demonstrate that the laurel forest, despite its latitude, shares certain affinities with tropical rainforests.
The species in the tree layer of the laurel forest are distributed according to their environmental requirements. Areas with higher ambient and soil moisture, such as the bottoms of ravines and shaded river valleys, are occupied by the lime tree and the viñátigo, with the latter becoming dominant as one ascends in altitude.
On the hillsides, the laurel or ‘loro’ predominates, accompanied by the wild orange tree, the holly, the ‘hija’ and the ‘sanguino’. The holly, due to its wider ecological range, is also common in more open areas, growing alongside heather and beech.
In areas where there is greater sunshine, more thermophilic species begin to become more prominent, such as the barbusano, the palo blanco, the aderno and the delfino. The palo blanco is common in areas with rocky outcrops, where it grows alongside strawberry trees and mocanes.
On the trunks and branches of trees, particularly in the damp, shady interior, epiphytic plants are common; these live on the tree, using it merely as a support, without being parasites in any way, as is the case with the golden star (Aichryson laxum), the Christmas fern (Polypodium macaronesicum), etc.
In the more open and sunny areas, as well as along the edges of paths and forest tracks, there is an abundance of subshrubs and herbaceous plants, such as cock’s comb (Isoplexis canariensis), bicácaro (Canarina canariensis), follao (Viburnum rigidum), tree starwort (Gesnouinia arborea), algaritofe (Cedronella canariensis), Canary Islands bindweed (Convolvulus canariensis), white bush (Pericallis appendiculata), mountain queen (Ixanthus viscosus), mountain chahorra (Sideritis macrostachys), the Morgallana (Ranunculus cortusifolius), the ‘pata de gallo’ (Geranium reuteri), the mountain pennyroyal (Bystropogon canariensis), the ivy (Hedera canariensis), the gibalbera (Semele androgyna), the sarsaparilla (Smilax canariensis), etc. The genus Euphorbia, typical of xerophilous and semi-xerophilous areas, is represented in the laurel forest by a single species: the mountain oleander (Euphorbia mellifera), a true rarity that is seriously threatened with extinction.
Notable ferns include large species such as the woodwardia (Woodwardia radicans), the mattress fern (Culcita macrocarpa), the hairy fern (Polystichum setiferum), and the woodland ferns (Dryopteris oligodonta and Diplazium caudatum), etc.
Mosses and lichens, with countless species, cover the entire surface of tree trunks and rocks in the wettest areas, and only the sides exposed to the wind and mist in the driest areas. Among them we can find species such as Parmelia parlata, Usnea articulata, Bryoria fuscencens, Frullaria teneriffae, Porella canariensis, Neckera intermedia, Leucodon canariensis, etc.
A large number of fungi grow in the Canarian laurel forest, particularly during the autumn and winter months. Most of them grow on the forest floor, but many others grow directly on tree trunks. Some of those that can be easily found and identified include Fistulina hepatica, Hygrocybe conica, Mycena galericulata, Ganoderma applanatum, Daldinia concentrica, Auricularia auricula-judae, Lepista nuda, Tricholomopsis rutilans, Phellodon niger, Astraeus hygrometricus, and the unusual Laurobaxidium lauri, which, with its deer-antler-like shape, grows exclusively on the grey trunks of laurel trees.
Fauna
The animal groups best represented in these forests are birds, amongst the vertebrates, and insects and molluscs, amongst the invertebrates.
B irds such as the blackbird (Turdus merula), the chaffinch (Fringilla coelebs), the robin (Erithacus rubecula), the goldcrest (Regulus regulus) and the chiffchaff (Phylloscopus collybita) nest in the forest’s trees and shrubs. The Eurasian woodcock (Scolopax rusticola) builds its nest by digging small hollows in the ground, and is very rarely seen due to its crepuscular habits and the perfect camouflage of its plumage. The most common predators are the sparrowhawk (Accipiter nisus) and the long-eared owl (Asio otus).
However, the most iconic birds of the laurel forest are two rare and beautiful pigeons: the Junonia’s Pigeon (Columba junoniae) and the Bollii’s Pigeon (Columba bollii), both endemic to the Canary Islands. Their feeding habits are similar, with their diet consisting mainly of drupes and berries from the trees, and they lay a single egg.
Most of the birds in the laurel forest contribute significantly to the forest’s expansion by feeding on the fruits of the trees: the seeds are indigestible and are excreted in the birds’ droppings, possibly in a location where competition for light, water and nutrients is less intense than at the base of the parent plant. This method of seed dispersal is known as ornithochory.
The leaf litter on the forest floor is home to an abundance of beetles, particularly carabid beetles, with numerous endemic species, as well as molluscs such as Craspedopoma costata and Insulvitrina oromii. The Cleopatra butterfly (Gonepterix cleoule), endemic to the Canary Islands, is closely associated with the laurel forest, its larvae feeding on the shoots and leaves of the sanguino.
The laurel forest is a predominantly tree-dominated, evergreen forest formation, whose vast mass of leathery, glossy leaves promotes the condensation of moisture contained in the mists that almost constantly shroud the area, producing a slow, fine and almost constant local rainfall at the foot of each tree, known as ‘horizontal rain’.
During the Tertiary period (around 20 million years ago), this type of forest was widespread throughout the Mediterranean basin, North Africa and southern Europe, as evidenced by the numerous plant fossils found in these areas. However, the climatic changes that have occurred since then – including ice ages and arid periods that gave rise to the desert barrier of North Africa – led to the disappearance of this vegetation from the continents, with it finding refuge in the Macaronesian archipelagos (the Azores, Madeira and the Canary Islands), as the influence of the ocean acts as a thermostat regulating environmental conditions; consequently, the present-day Canarian laurel forest formations are nothing more than relics of those ancient Mediterranean forests. In the archipelagos of Madeira and the Azores, a more favourable climate allows these forests to cover a larger potential area and to be found at lower altitudes, even almost at sea level, whilst also exhibiting a different floristic composition to that of the Canary Islands.
During the winter, the Canary Islands experience north-westerly winds, which generally bring rain, but in summer the north-easterly trade winds are the prevailing winds. The trade winds do not cause rainfall, but as the moist air rises up the slopes, it condenses and forms a large cloud mass known as a ‘sea of clouds’, which affects altitudes between 400 and 1,200 metres above sea level. Sunlight is thus greatly reduced, tempering the temperatures, and the moisture is trapped by the dense vegetation, which acts as a sort of ‘sponge forest’, providing a water supply that can be up to three times the annual rainfall and is vital for the survival of the laurel forest. This phenomenon, with its extra supply of moisture, does not occur on the islands of Lanzarote and Fuerteventura, as their low altitude prevents the trade winds from having an effect; consequently, there are no laurel forests on these islands.
Thus, the combination of climate and topography determines the distribution of the laurel forest in the Canary Islands, which is found in north-facing areas at altitudes of between 400 and 1,200 metres, with mild temperatures throughout the year (average 12–14 °C) and annual rainfall of between 800 and 1,400 mm. The dry season is largely mitigated by the presence of the aforementioned sea of clouds.
The soils, owing to their age and the effects of the climate and vegetation, are generally well-developed, with considerable depth and a well-defined organic topsoil layer. The environmental conditions of high humidity and temperate temperatures lead to rapid humification and mineralisation of organic matter (fallen leaves and other plant debris), releasing abundant nutrients which are rapidly absorbed by the roots.
The laurel forest plays a vital role in the islands’ water cycle; its ability to capture and retain moisture ensures a continuous supply of water to river valleys and ravine beds, as well as to underground aquifers. It also helps to prevent soil erosion, particularly on the steepest slopes, as the roots act as a kind of mesh that holds the soil in place.
Originally, the laurel forest covered a vast area of woodland in the central and western Canary Islands, but intensive exploitation of its resources from the early days of the conquest of the islands (timber, charcoal, etc.), which continued almost uninterrupted until a few decades ago, has almost completely depleted the pure stands of this forest. As for its original distribution, almost nothing remains in Gran Canaria; barely 10 per cent remains in Tenerife; it is confined to a few ravines and very specific areas in the north of La Palma; and the best-preserved laurel forest in the world is found on La Gomera, within the area currently defined by the Garajonay National Park.
Flora
The laurel forest is the most complex ecosystem found in the Canary Islands. In its purest form, it consists of some 18 species of large, evergreen, shade-loving and thermophilic trees, beneath which a great variety of ferns, mosses, fungi and other organisms typical of shady environments thrive. In many cases, the tree layer forms a closed canopy, creating a roof that barely allows any sunlight to pass through. As the environmental conditions required by this habitat change, the forest gradually opens up and allows more light to penetrate, resulting in a significantly richer and more diverse undergrowth.
The most characteristic tree species of the laurel forest belong to the Lauraceae family, such as the loro (Laurus novocanariensis), the tilo (Ocotea foetens), the viñátigo (Persea indica) and the barbusano (Apollonias barbujana). Other large tree species are also common, such as the acebiño (Ilex canariensis), the wild orange tree (Ilex perado, spp. platyphylla), the aderno (Heberdenia excelsa), the delfino (Pleiomeris canariensis), the mocán (Visnea mocanera), the hija (Prunus lusitanica), the sanguino (Rhamnus glandulosa), the palo blanco (Picconia excelsa), the madroño (Arbutus canariensis), the heather (Erica arborea) and the faya (Morella faya).
Despite their diversity, almost all these species display very marked morphological similarities resulting from adaptation to the same environment. The leaves are evergreen, as in this relatively uniform and favourable climate there is no point in shedding them during a particular season. The leaf surface is of the Lauraceae type: leathery and glossy, allowing water to run off easily and preventing excess moisture; it eventually falls to the ground via the pointed tip, which acts as a drip edge. These mechanisms demonstrate that the laurel forest, despite its latitude, shares certain affinities with tropical rainforests.
The species in the tree layer of the laurel forest are distributed according to their environmental requirements. Areas with higher ambient and soil moisture, such as the bottoms of ravines and shaded river valleys, are occupied by the lime tree and the viñátigo, with the latter becoming dominant as one ascends in altitude.
On the hillsides, the laurel or ‘loro’ predominates, accompanied by the wild orange tree, the holly, the ‘hija’ and the ‘sanguino’. The holly, due to its wider ecological range, is also common in more open areas, growing alongside heather and beech.
In areas where there is greater sunshine, more thermophilic species begin to become more prominent, such as the barbusano, the palo blanco, the aderno and the delfino. The palo blanco is common in areas with rocky outcrops, where it grows alongside strawberry trees and mocanes.
On the trunks and branches of trees, particularly in the damp, shady interior, epiphytic plants are common; these live on the tree, using it merely as a support, without being parasites in any way, as is the case with the golden star (Aichryson laxum), the Christmas fern (Polypodium macaronesicum), etc.
In the more open and sunny areas, as well as along the edges of paths and forest tracks, there is an abundance of subshrubs and herbaceous plants, such as cock’s comb (Isoplexis canariensis), bicácaro (Canarina canariensis), follao (Viburnum rigidum), tree starwort (Gesnouinia arborea), algaritofe (Cedronella canariensis), Canary Islands bindweed (Convolvulus canariensis), white bush (Pericallis appendiculata), mountain queen (Ixanthus viscosus), mountain chahorra (Sideritis macrostachys), the Morgallana (Ranunculus cortusifolius), the ‘pata de gallo’ (Geranium reuteri), the mountain pennyroyal (Bystropogon canariensis), the ivy (Hedera canariensis), the gibalbera (Semele androgyna), the sarsaparilla (Smilax canariensis), etc. The genus Euphorbia, typical of xerophilous and semi-xerophilous areas, is represented in the laurel forest by a single species: the mountain oleander (Euphorbia mellifera), a true rarity that is seriously threatened with extinction.
Notable ferns include large species such as the woodwardia (Woodwardia radicans), the mattress fern (Culcita macrocarpa), the hairy fern (Polystichum setiferum), and the woodland ferns (Dryopteris oligodonta and Diplazium caudatum), etc.
Mosses and lichens, with countless species, cover the entire surface of tree trunks and rocks in the wettest areas, and only the sides exposed to the wind and mist in the driest areas. Among them we can find species such as Parmelia parlata, Usnea articulata, Bryoria fuscencens, Frullaria teneriffae, Porella canariensis, Neckera intermedia, Leucodon canariensis, etc.
A large number of fungi grow in the Canarian laurel forest, particularly during the autumn and winter months. Most of them grow on the forest floor, but many others grow directly on tree trunks. Some of those that can be easily found and identified include Fistulina hepatica, Hygrocybe conica, Mycena galericulata, Ganoderma applanatum, Daldinia concentrica, Auricularia auricula-judae, Lepista nuda, Tricholomopsis rutilans, Phellodon niger, Astraeus hygrometricus, and the unusual Laurobaxidium lauri, which, with its deer-antler-like shape, grows exclusively on the grey trunks of laurel trees.
Fauna
The animal groups best represented in these forests are birds, amongst the vertebrates, and insects and molluscs, amongst the invertebrates.
B irds such as the blackbird (Turdus merula), the chaffinch (Fringilla coelebs), the robin (Erithacus rubecula), the goldcrest (Regulus regulus) and the chiffchaff (Phylloscopus collybita) nest in the forest’s trees and shrubs. The Eurasian woodcock (Scolopax rusticola) builds its nest by digging small hollows in the ground, and is very rarely seen due to its crepuscular habits and the perfect camouflage of its plumage. The most common predators are the sparrowhawk (Accipiter nisus) and the long-eared owl (Asio otus).
However, the most iconic birds of the laurel forest are two rare and beautiful pigeons: the Junonia’s Pigeon (Columba junoniae) and the Bollii’s Pigeon (Columba bollii), both endemic to the Canary Islands. Their feeding habits are similar, with their diet consisting mainly of drupes and berries from the trees, and they lay a single egg.
Most of the birds in the laurel forest contribute significantly to the forest’s expansion by feeding on the fruits of the trees: the seeds are indigestible and are excreted in the birds’ droppings, possibly in a location where competition for light, water and nutrients is less intense than at the base of the parent plant. This method of seed dispersal is known as ornithochory.
The leaf litter on the forest floor is home to an abundance of beetles, particularly carabid beetles, with numerous endemic species, as well as molluscs such as Craspedopoma costata and Insulvitrina oromii. The Cleopatra butterfly (Gonepterix cleoule), endemic to the Canary Islands, is closely associated with the laurel forest, its larvae feeding on the shoots and leaves of the sanguino.
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