The Fungi of the Azores

Abstract

The Azores form an archipelago 480 km long, of volcanic islands rising from a submarine ridge. The nearest island to Europe is about 1500 km from Gibraltar, 1250 from Cabo da Roca in Portugal and about 1900 from the English Channel; from the westernmost island it is about 1750 km to Newfoundland. These are truly oceanic islands, of tertiary origin, which have never been in contact with any major land mass and all organisms found on them must have reached them across a wide expanse of ocean.* They have, however, been colonized by Europeans since the I5th century; most of the present woody vegetation consists of introduced trees and shrubs and there has obviously been ample opportunity over a very long period for the accidental introduction of fungi by human activity. The islands fall into three groups, an eastern composed of Sio Miguel and Santa Maria, a central composed of Terceira, SAo Jorge, Graciosa, Pico and Faial and a western of Flores and Corvo. From Santa Maria to Madeira is 740 km, from Sao Miguel to Terceira 12o km. Santa Maria and Graciosa are low lying but most of the islands rise steeply to about 900 m while Pico has an impressive conical peak 2373 m high. The climate resembles that of the Hebrides, with frequent gales, copious rain and a high relative humidity. The mean annual rainfall near the sea at Ponta Delgada is 635 mm and rainfall is considered to increase by 20 per cent every 90 m above sea level. Frost occurs occasionally at 500 m and over, though never on the coast, and owing to frequent mist and low cloud, land above 300 m is always more or less wet, with mean relative humidity seldom falling below 88 per cent. Hence, though the islands are densely inhabited, with housing almost continuous wherever the coastal belt is level enough, permanent habitation above 300 m is regarded as impracticable because of the mist. Though the lavas are alkaline, the high rainfall and extensive leaching of bases renders the soils naturally acid and thin development of Sphagnum occurs in places on the high ground. Some hill pasture, however, has been improved by stripping, fertilizing and reseeding with Lolium and Trifolium repens. The principal industry is cattle raising and the scenery away from the villages is strongly reminiscent of west Wales or north Cornwall, with small green grass fields enclosed by dry stone walls. The native woodland contained few species, notably Myrica faya, Laurus azorica, Juniperus brevifolia and Erica azorica. It has now largely disappeared except from comparatively recent lava flows with a surface too rugged for exploitation. Pittosporum undulatum is now naturalized throughout the archipelago and forms a dominant low