Included here are the Azores a group of nine volcanic islands situated in the North Atlantic. The three largest islands, São Miguel, Terceira and Pico represent about 69% of the total area of the archipelago.

Azorean Rocky Coastal Vegetation

The most common coastal habitat in the Azores is exposed lava (mainly andesitic cliffs and sharp basaltic rocks) with some of the older areas now subject to considerable coastal erosion. In places the exposure is extremely intense. On the north-facing Cachorro coastline on Pico Island, for example, storms with strong winds and high waves can occur all year round with waves often reaching 7 m in height and washing upslope for 20 m or more. Such places are often devoid of vegetation. Also at Cachorro the geological structure of the pahoehoe basaltic lavas often give rise to almost flat coastal platforms that are difficult for plants to colonize, but in fissures the endemic Spergularia azorica (Caryophyllaceae) often forms the pioneer zone of maritime vascular plants together with Asplenium marinum and species of Atriplex - a second zone is often characterized by the endemic grass Festuca petraea (Poaceae). Even in less exposed situations the vegetation is usually sparse with percentage cover often below 30% but species diversity increases. Aspenium marinum, Crithmum maritimum and Solidago sempervirens are usually the most conspicuous species but endemic taxa in addition to the ones mentioned above such as Azorina vidalii (Campanulaceae), Corema album subsp. azorica (Empetraceae) and Euphorbia azorica (Euphorbiaceae) may also be present. Where the coastal belt is quite wide there can be a degree of structural diversity with shrubs and various sized herbaceous species. Very steep coastal, rocky slopes are difficult to survey but are known to be important for a number of rare endemic species. On Terceira Island, for example, these may support the Azorean endemics Euphorbia stygiana (Euphorbiaceae) and Lactuca watsoniana (Asteraceae) and the Macaronesian endemics Diphasium madeirense (Lycopodiaceae) and Smilax canariensis (Smilacaceae). Landward of the coastal fringe, maritime grassland dominated by either Cynodon dactylon or the endemic Agrostis azorica (Poaceae) is often one of the main vegetation types.

Azorean Coastal Shrublands

These formations represent the most landward belt of coastal zonation and represent a transition to non-maritime vegetation. Three types are recognized in the central islands - Erica azorica shrubland, Myrica faya shrubland and mixed shrubland. In the first of these the endemic Erica azorica (Ericaceae) can, in places, form almost monospecific stands especially in areas subject to strong ocean winds. In these situations this sparse community can reach heights of up to 1.5 m and is typically without stratification. Myrica faya formations are also typically poor in both floristic and structural diversity. They occur in less exposed situations, usually on poor substrata such as recent lava and where freshwater availability is low during summer periods. In more favourable areas, in terms of shelter and hydrology more complex, mixed communities occur. This are characterized by species such as Myrica faya, Myrsine africana, Pittorsporum undulatum and the endemic Erica azorica (Ericaceae) and Juniperus brevifolia (Cupressaceae). The bushy undergrowth may include Crithmum maritimum, Silene vulgaris ssp. marina and the endemic Coreme album subsp. azoricum (Empetraceae), while herbaceous elements may comprise the endemic Carex hochstetteriana (Cyperaceae), Daucus carota ssp. azorica (Apiaceae) and Festuca petraea (Poaceae). However, these rich coastal shrublands are becoming increasingly rare.

References

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Dias, E., Mendes, C., Melio, C., Pereira, D. & Elias, R. 2005. Azores central Islands vegetation and flora guide. Quercetea, 7: 123-173.

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Humphries, C. J. 1979. Endemism and Evolution in Macaronesia. In: Plants and Islands. Ed. D, Bramwell. Academic Press.

Schäfer, H. 2005. Flora of the Azores. A Field Guide. Margraf Publishers.

Sjogren, E. 1993. Dry coastal ecosystems of Madeira and the Azores. In: Ecosystems of the World 2B  Dry Coastal Ecosystems  Africa, America, Asia and Oceania. Ed. Eddy van der Marel. Elsevier.

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Tutin, T. G. 1953. The vegetation of the Azores. Journal of Ecology, 41: 53-61.

Tutin, T. G. & Warburg, E. F. 1932. Contributions from the University Herbarium Cambridge - notes on the flora of the Azores. The Journal of Botany, 70: 38-46.