Overall, the area covers almost 5 hectares (or 22 acres), ranging from the uppermost, more open, area at 800’ altitude, down to to the shady gorge below the dam, at around 500’.

The uppermost area (Compartment 1) extends from just below the old Pen y Llyn farm downstream to roughly level with Ynys Isaf, where the public road ends and the footpath begins. The most obvious trees in this section are the Scots Pine, many of which have been struck by lightning and appear to be reaching the end of their life.This area has been lightly grazed by ponies for some time, creating an open, grassy area with scattered trees and scrubby areas of gorse and bramble. The landscape is rather peculiar : grassy hummocks between small streams, solitary boulders (probably glacial erratics) and drier slopes with gorse growing on thin soil over slate. The gorse has traditionally been burnt to maintain open areas for grazing. Without some form of continued management (either cutting or light burning) this area will quickly revert to scrub, and (eventually) to trees.

At the lower end of this grassy area there seems to have been less grazing and there are more trees, mainly Birch, with plenty of regeneration (Compartment 2). The valley becomes narrower and the damp sides are steep and in parts are covered in ferns.

The next section (compartment 3) has much larger trees, many of which were planted by the Penrhyn estate. Many of the species are not what one would expect in ‘natural’ woodland here – they include Sweet Chestnuts, a Hornbeam, Corsican Pine, and a number of tall Scots Pine.

The main part of the woodland (Compartment 4) extends from the bridge over the Galedfrwd near Yr Ocar, down the valley close to the head of the reservoir. Part of this may be ‘ancient woodland’ but there has also been some estate planting as in compartment 3. The majority of trees are Oak, Rowan and Birch but there is plenty of Holly and also Beech and Sycamore. The most striking aspect to this section of woodland is the age structure of the trees. The majority of mature trees have damaged, broken limbs and lots of standing dead wood, but beneath them there are lots of healthy young trees waiting to grow through.

The last section (Compartment 5) encompasses the dam and reservoir and surrounding land . As the reservoir has been filling with silt, vegetation has been extending into the shallower areas at the edges, creating a ‘wet woodland’ of Alder and Willows. Below the dam is a very damp tree-lined gorge extending to the remains of the second dam.

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