Included here are the Azores, a group of nine volcanic islands situated in the North Atlantic. In geological terms these are the youngest of the Macaronesian Islands. The highest, Pico, reaches an altitude of about 2300m (the highest mountain in Portugues territory) and the three largest islands, São Miguel, Terceira and Pico represent about 69% of the total area of the archipelago.

Azorean Laurel Forest

These broad-leaved evergreen forest, are largely dominated by Laurus azorica (a Macaronesian endemic) and Myrica faya and are considered to be the natural climax vegetation up to an altitude of about 600m. Similar laurel forests can be found in Madeira and the Canaries, and all are thought to be the relicts of vegetation that was once widespread in southern Europe before climatic cooling during the Pleistocene. These macaronesian forests are rich in endemics. On the Azores they include Ilex perado subsp. azorica (Aquifoliaceae) and Notelaea azorica (Oleaceae) among the trees, Euphorbia stygiana (Euphorbiaceae), Picconia azorica (Oleaceae), Prunus lusitanics ssp. azorica (Rosaceae), Rubus hochstetterorum (Rosaceae), Vaccinium cylindraceum (Ericaceae), Viburnum tinus var. subcordatum (Adoxaceae) among the shrubs and Hypericum foliosum (Hypericaceae), Rubia peregrina var. azorica (Rubiaceae), Sanicula azorica (Apiaceae), Senecio malvaefolius (Asteraceae), Lactuca watsoniana (Asteraceae) and Selaginalla azorica in the field layer. In the central islands three sub formations are recognized – mesic forest, humid forest and hyper-humid forest. In mesic forest the environmental conditions are characterized by moderate winds, high levels of precipitation and low humidity, and usually have high levels of floristic diversity. Among the trees there is typically a high level of codominance. In addition to Larus azorica include Myrica faya and the endemic Frangula azorica (Rhamnaceae) and Picconia azorica (Oleaceae). The herbaceous layer is usually dominated by pteridophytes like Diplasium caudata and the endemic Dryopteris azorica and D. crispifolia (Dryopteridaceae). Other herbaceous elements may include the endemic Bellis azorica (Asteraceae), Platanthera azorica and P. micrantha (Orchidaceae). Humid laurel forests have elevated levels of both floristic and structural diversity and as implied occur in areas of high atmospheric humidity and rainfall, and usually have a degree of soil saturation at certain parts of the year. In addition the Laurus azorica they are typically dominated by the endemic Erica azorica (Eriaceae), Frangula azorica (Rhamnaceae) and Ilex perado subsp. azorica (Aquifoliaceae). Ferns again dominate the herbaceous layer with species such as Diplazium caudatum, Dryopteris affinis, Pteris incompleta and the endemic Dryopteris azorica (Dryopteridaceae). Hyper-humid laurel forests occur at high altitudes where human intervention has been less pronounced and as a consequence these now represent the commonest form of laurel forest in the Azores. Both strong humid winds and high levels of precipitation characterize the environment of these upland areas. In floristic terms, one of the main differences between these and other laurel forest is the absence of Erica azorica, which is replaced by its upland counterpart the endemic Vaccinium cylindraceum (Ericaceae). They also tend to have a less complex vertical structure but a more complex horizontal structure with many hummocks and hollow. Many of the low-lying areas are permanently saturated making germination difficult. Nevertheless, the herbaceous ground layer is well developed particularly with species such as Culcita macrocarpa and the endemic Dryopteris azorica, but the filmy fern Trichomanes speciosum may also be common.

Azorean Cloud Forest (Ilex Forest)

Forest dominated by the endemic Ilex perado subsp. azorica (Aquifoliaceae), also know as cloud forest is, as implied, confined to areas of almost permanent cloud cover and extremely high humidity. This occurs at altitudes of between 700-900 m usually on north-facing slopes. These forests also tend to be associated with acidic lavas, and as such the forest floor is often composed of peat, which is more or less permanently saturated. At ground level there is also a degree of horizontal structure with various hummocks and hollows with varying degrees of wetness. Ilex perado usually emerges above a canopy dominated by the endemic Juniperus brevifolia (Cupressaceae) and Vaccinium cylindraceum (Ericaceae). The herbaceous ground layer is largely dominated by pteridophytes like Culcita macrocarpa, Dryopteris aemula and Trichomanes speciosum, and as with all cloud forests, the epiphytic flora is well developed with species such as the filmy fern Hymenophyllum tunbrigense and the Macaronesian endemic Elaphoglossum semicylindraceum (Elaphoglossaceae).

Azorean Juniper Forest

Forest dominated by the endemic Juniperus brevifolia (Cupressaceae) is confined to areas of extreme wetness and strong winds and typically occurs on exposed mountaintops. In the central islands two types are recognized – juniper forest and juniper forested peat land. In the former there is usually a continuous and fairly uniform layer of juniper often with a three-tiered structure comprising a canopy up to 4.5 m high, a shrub layer and a herbaceous layer. However, these forests are often so dense that little can grow on the darkened forest floor. The epiphytic flora, on the other hand, is often well developed and includes a distinctive epiphytic bryo-community that can completely envelop juniper branches. In the case of juniper forest on peat bog, the juniper trees form a sparse canopy while Sphagnum and other bog mosses dominate the underlying peat. On Terceira, there is also forest co dominated by Juniperus brevifolia and the endemic Ilex parado ssp. azorica (Aquifoliaceae). Associated species here include Culcita macrocarpa, Laurus azorica, Myrsine africana and the endemic Vaccinium cylindraceum (Ericaceae).

Azorean Erica woodland

Above about 600m the laurel forest peters out and is replaced by woodland mainly composed of the endemic Erica azorica (Ericaceae) which can grows to a height of about 6m. The endemic Juniper brevifolia (Cupressaceae) is also common in this zone. The shrub layer typically includes Hedera canariensis and Myrsine africana, while endemics such as Bellis azorica (Asteraceae) and Lysimachis azorica (Myrsinaceae) can be found in the field layer. In places, these woodlands have been converted to grazing pasture but surprisingly these areas can still support up to 14 endemics including Carex azorica (Cyperaceae) and Doboecia azorica (Ericaceae).

References

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