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Case study 6: New data from Macronesia, Teneriffe, Canary Islands



VegClass survey of Tenerife,Canary islands, Spain

Following the XVII IBC Congress, CBM staff ( A. & P. Gillison)  conducted  a brief survey of the extraordinary vegetation of Tenerife. The main reason for this visit was to help fill important gaps in the global database represented by the Canary island (Macaronesian) vegetation that occupies an unusual climatic regime. Our contact and kind host was Prof. José Maria Fernández-Palacios of the University of la Laguna, Tenerife.

The following descriptive notes have been extracted from the World Wildlife Fund for Nature (WWF) website: http://www.worldwildlife.org/wildworld/profiles/terrestrial/pa/pa1203_full.html
The Canary Archipelago is a group of volcanic islands and rock islets found in the Macronesia region, which also includes Salvajes, Madeira, Azores and Cape Verde Islands. The Canaries are located in the Atlantic Ocean, between 27º 20’ and 29º 25’north and between 13º 20’ and 18º 10’ west. This ecoregion includes the five western islands: La Palma, Hierro, Gomera, Tenerife, and Gran Canaria. The western islands are younger than the eastern group and are more mountainous, with well-developed forests. The eastern islands are lower are drier and are included here within the Mediterranean Acacia-Argania Dry Woodland and Succulent Thicket ecoregion.

Despite their proximity to Africa (in latitudes similar to those of the Sahara, Egypt and Saudi Arabia), the Canaries show a wide range of different microclimates apart from sub-desert landscapes. This is caused by several factors such as elevation and orientation, but especially because of the influence of northeast to southwest sea winds, called alisios.These relatively hot winds become cooler and more humid as they pass over the sea surface. Once the alisios reach the northern parts of the higher Canary Islands, this moisture is trapped by the dense laurisilva and fayal-brezal (heath) vegetation on the mountain slopes. Low-lying islands with elevations under 750 m receive no rain from the passing alisios so that habitats and climate here are drier and similar to the southern parts of the higher islands. The Canary Island Archipelago was formed by undersea volcanic activity. There have also been eruptions on emergent islands, with the most recent one occurring in La Palma in 1971. La Palma and El Hierro are the youngest islands, only 2-3 million years old. Because of the islands’ origin, all materials in the Canaries are volcanic and, depending on the substances composing the lava, they can be grouped into the following types: Traquitic-fonolitic, basaltic and traquibasaltic rocks, and Piroclastic and slag materials. Different soil types have been produced due to the effects of vegetation, local weather conditions and topography on these volcanic materials (Bacallado et al. 1984, González et al. 1986).

Each of the habitats recognised in the Canaries grows on a specific kind of soil. The following are soil descriptions for dry woodlands and forests. Canarian endemic pine forests grow on two kinds of fertile soil: ancient red lands. Endemic Macronesian heaths are located in humid zones in young soils composed of hydrated aluminic silicates with a high level of organic material. Laurisilva occurs on recent materials in places with well-defined seasons and medium to low organic

substance levels which lie above older soil types. The Canary Islands lack river systems. In spite of that and owing to the steep topography of the western islands, they are crossed by complex systems of ravines produced by water erosion over thousands of years. These gullies serve as drainage for winter rainfall and, on the higher islands like Tenerife, water from the thawing snow and ice flows year-round. Other islands become dry in summer. Vegetation can be described according to elevation zones. At the lowest elevation, coastal vegetation grows, including types typical of cliffs and sandy regions. Endemic palm groves (Phoenix canariensis), and semiarid vegetation.are present. Generally, these vegetation types occur from sea level to 600 m in the north and up to 1,000 m in the south, and include many endemic taxa. Endemics are mainly found to be from the Euphorbiaceae, for example, Euphorbia canariensis, and E. balsamifera . Other important endemic species are Ceropegia fusca, Plocama pendula, Salvia canariensis, Argyranthemum frutescens, Rumex lunaria, Convolvulus floridus, and Messerschmidia fruticosa (Bramwell and Bramwell 1983, González et al. 1986 , Strasburger et al. 1986).

 

Along the transition zone from 50 to 500m, between the sea level coastal community and giving way to laurisilva vegetation, there are thermophiles and pre-steppe bush The species found here are common to both the lower and higher vegetation formations. This zone has been damaged for decades because of its good potential for crops. Some of the endemic and representative species are Bosea yervamora, Echium strictum, Greenovia aurea, Aeonium sp., Monanthes laxiflora, Campylanthus salsoloides, Forsskaolea angustifolia, and Dracaena draco (Bramwell and Bramwell 1983, González et al. 1986).

Humid and shady laurisilva forest grows between 500 and 1400 m in elevation, with some species reaching more than 20 m in height. Some 20 million years ago, this evergreen forest covered large areas of the world. However, because of the dramatic weather changes experienced in the Quaternary, it has only survived in a few places. This is one of the jewels of vegetation biodiversity in the Canary Islands; the best conserved of all Macronesian laurel forest can be found here. Even though laurisilva is formed by several taxa grouped in different families, there are four representative speciesfrom all of Lauraceae. They are: Ocotea foetens, Apollonias barbujana, Laurus azorica, and Persea indica. Other Macronesian endemic species found in laurisilva are Arbutus canariensis, Ilex canariensis, Visnea mocanera, Picconia excelsa, Heberdenia excelsa, Salix canariensis, and Viburnum tinus (Bramwell and Bramwell 1983, González et al. 1986).
Endemic Macronesian heaths, also known as fayal-brezal, grow from 500 to 1,700 m, as transition vegetation between laurisilva and Canarian endemic pine forests, with which they share some species (Ilex canariensis, I. perado, Larus azorica, and Picconia excelsa). There are three distinctive species Myrica faya, Erica arborea and E. scoparia. Three different patterns of distribution can be seen. The first one is the contact zone with laurisilva, where Myrica spp. are dominant, with some Erica spp.; the second one is the typical fayal-brezal association (Myrica-Erica); and finally the third one is the contact zone with pine forests where Erica spp. are more common than Myrica spp. (González et al.1986).
Canarian endemic pine forests (Pinus canariensis) are found almost at sea level in southern areas but in the northern parts of the islands are found from 1,200 to 2,400 m in elevation. Finally, vegetation grows in the high mountains above 2,000 m on La Palma and Tenerife. Some of the typical species of this vegetation can also be found occasionally on other high islands of the archipelago that hold the following climatic attributes: very low humidity level, scarce rainfalls, very cool winters (-16ºC occasionally registered), warm summers (sometimes more than 46ºC), high isolation year-round, and big contrasts of day/night temperatures. Both endemic species and genera are found and these include Spartocytisus supranubius, Erysimum scoparium, Nepeta teydea, Plantago webbii, Senecio palmensis, Juniperus cedrus, Polycarpaea tenuis, and Echium sp.(Bramwell and Bramwell 1983, González et al.1986, Marzol 1998).
All the Canary Islands are like small isolated continents. They are unique for their high level of endemic taxa. Not only species, but even many genera are exclusive to this ecoregion. Every family of plants found in the Canary Islands has endemic representatives, often including endemic genera. Endemism levels are especially high in invertebrates, vascular plants and vertebrates (100% of native terrestrial reptiles). Over a quarter of the 1,992 vascular plants found on the Canary Islands are endemic to these islands (Machado 1998). Endemicity in non-migratory vertebrates is 17.2%, or 21 out of 122 species (Machado 1998). Among arthropod invertebrates, 44.4% of the 6,378 species are endemic (Machado 1998). For non-arthropod invertebrates, endemism is 28.8% out of 774 species (Machado 1998).
References:

  1. Bacallado, J.J., M. Báez, A. Brito, T. Cruz, F. Domínguez, E. Moreno, and J.M. Pérez. 1984. Fauna (marina y terrestre) del Archipiélago Canario. Ed. EDIRCA S.L.
  2. Bramwell, D. and Z. Bramwell. 1983. Flores silvestres de las Islas Canarias. 2nd Edition. Ed. Rueda. González, M.N., J.D. Rodrigo, and C. Suárez. 1986. Flora y Vegetación del Archipiélago Canario. Ed. EDIRCA S.L.
  3. Machado, A. 1998. Biodiversidad. Un paseo por el concepto y las Islas Canarias. Ed. Cabildo Insular de Tenerife.
  4. Martín, A. 1987. Atlas de las aves nidificantes en la isla de Tenerife. Instituto de Estudios Canarios. Monografía XXXII.Marzol, M.V. 1998. El Clima. Geografía de Canarias. 2nd Edition. Ed. Interinsular Canaria.
  5. Strasburger, E., F. Noll, H. Schenck, and A.F.W. Schimper. 1986. Tratado de Botánica. 7th Edition. Ed.Marin S.A.

Although our survey was limited to a very short period (25 -31 July), we were able to traverse most of the key vegetation types on Tenerife. Of all the vegetation types that range throughout the Canaries, Tenerife offers the widest representation. Due to kind weather and exceptionally good road systems, we were able to photograph a wide range of plant types (examples below) and record detailed VegClass data from 9 transects across 38m – 2223m elevation. These data have made a valuable contribution to the CBM global database and significantly extended both climatic and plant morphological coverage. We are much indebted to Prof. Fernández-Palacios for his valuable assistance both in introducing us to the extraordinary vegetation of Islas Canarias and for subsequent help in identifying plant voucher specimens from the transects.


 




 











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