Allt Coire Ghaidheil is a 23.5 acre exclosure that we erected on the West Affric Estate in November 1994 for natural regeneration. In the 20 years since it was fenced, a profusion of blaeberry and other shrubs have sprung up, and Scots pine, birch, rowan and willows are flourishing once again, providing a greatly-enhanced habitat for wildlife.
Allt Coire Ghaidheil was the first in a series of ten fenced areas that we established between 1994 and 2000 in partnership with the National Trust for Scotland for forest restoration on their 10,000 acre estate, which encompasses the headwaters of the Affric River. The exclosure protects a section of the Allt Coire Ghaidheil, the burn or watercourse at the eastern-most end of West Affric, and which flows into the Affric River 3 km. to the west of Loch Affric. This area included the largest concentration of trees that were remaining on the otherwise virtually-treeless estate at that time.
Situated on the north side of the glen, the Allt Coire Ghaidheil has a south-facing aspect, and that, together with the shelter from the prevailing westerly winds provided by the steep slopes of the watercourse, enabled trees and other woodland plants to survive there. The relative inaccessibility of some sections would also have limited the access that deer had to the area, thereby facilitating its role as a refugium for the woodland vegetation that had disappeared from the surrounding area in this part of the glen. The presence of ostrich-plume feather-moss (Ptilium crista-castrensis), an ancient forest indicator species, in the gorge of the burn when it was surveyed in 1993, illustrates that forest must have been there previously for an extended period of time.
The trees along the burn consisted mainly of downy birch (Betula pubescens), but also included rowan (Sorbus aucuparia) and eared willow (Salix aurita). In the years since the fence was erected, there has been good regeneration of those species, and some young tea-leaved willows (Salix phylicifolia) and Scots pines (Pinus sylvestris) have also sprung up naturally there. This is particularly significant in the case of the pines, as the nearest mature tree that could provide a seed source is about 3 km. to the east (i.e. down-wind).
The tea-leaved willows (there are at least a dozen of them now) are also important, as that species is very scarce in Glen Affric. In 2013 our staff collected cuttings from them, and those have subsequently been propagated as stock plants in our nursery at Dundreggan. Further cuttings and seed will be taken from those to provide a steady supply of young trees for planting out elsewhere in Glen Affric and at other sites where we work.
Blaeberry bushes (Vaccinium myrtillus) have also flourished in the exclosure, benefitting from the protection from deer that is provided by the fence. There are numerous large patches of this woodland plant, reaching a metre in height and fruiting in profusion each year. Blaeberry is a food plant for the caterpillars of the light knot grass moth (Acronicta menyanthidis), and an adult of this species was found in the exclosure in 2008, mostly likely attracted by the food source for its larvae.
The recovery of the vegetation and the healthy growth of young trees is providing a greatly-enhanced habitat for wildlife like this. For example, during a visit to the exclosure in May 2014, several caterpillars of the northern eggar moth (Lasiocampa quercus callunae) were seen feeding on the eared willow shown in the photographs here. Rosette galls induced by a midge (Rabdophaga rosaria) have also been found on this willow, and invertebrates such as these attract birds that feed on them. The birds bring seeds of trees such as rowan in their gut, and those germinate in the birds’ droppings, adding to the regeneration of the young woodland. Rowan in turn supports its own suite of associated organisms, and one of those species – a mite (Eriophyes sorbi) that induces galls in the leaves of the rowan – was found there in 2008.
During another visit in June 2012, numerous scats of a fox (Vulpes vulpes) were observed inside the exclosure, although it was not clear how the animal was getting in or out of the fence!
The young trees inside the exclosure, and the abundant heather and blaeberries, provide a dramatic contrast with the surrounding open and denuded landscape. They are a small island of healthy recovering forest that illustrates how nature responds when we remove the pressure of overgrazing, and the changes that occur when ecological succession takes place again. They complement the new forest we’ve planted on the south side of the Affric River, on land managed by Forestry Commission Scotland, and form a key element of the forest corridor that we envisage stretching from Glen Affric through to the west coast.
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