Away from the basalt hills there is lower terrain of harder, more acidic and much older Neoproterozoic metamorphic rocks, partly overlain with acidic peat. The vegetation here is mainly a mixture of heath, bog, purple moor-grass, bracken and woodland, and its structure and species composition is of a strongly western, oceanic character reflecting the influence of the wet, windy and equable climate.
The woodland, with much oak and birch and a great luxuriance and diversity of mosses and liverworts on the ground, rocks and trees, is a form of temperate rainforest – a habitat restricted in Europe to the extreme western oceanic fringe and showing some floristic affinities with rainforests in subtropical parts of the world. The woods on the north side of Loch Arienas and further east in Gleann Dubh are among the best examples of temperate rainforest in Europe because their assemblages of mosses and liverworts are particularly rich, including some rare oceanic species such as the liverworts Acrobolbus wilsonii and Radula voluta which evidently require very humid conditions and mild temperatures. The woods were managed for charcoal burning long ago, but their botanical richness including the presence of the moss Hageniella micans and the liverworts Plagiochila heterophylla, Adelanthus decipiens and Jamesoniella autumnalis – species that in Scotland are strongly associated with ancient woodland – suggests that the tree canopy has never been too heavily thinned or disturbed. The woods are also of interest for their lichens, ferns, butterflies (including the uncommon pearl-bordered fritillary and the rare chequered skipper), dragonflies, damselflies and birds; they are grazed by red and roe deer.
Ben Averis, 25-08-2017