2. Craig Cerrig Gleisiad, Brecon Beacons National Park

[Image courtesy of CCW]

Craig Cerrig-gleisiad National Nature Reserve

Leader: Tim Rich [National Museum of Wales]

Craig Cerrig-gleisiad is a dramatic, ice-carved, north-east facing valley in the central Brecon Beacon mountains, with cliffs to 150 m high, screes, moraines and terraces.

Over 500 higher and lower plant species have been recorded, including a number of arctic-alpines such as Saxifraga oppositifolia which are at about their southern limits in Britain, and at least 16 Hieracium species.

The vegetation history has been studied using pollen in the partial peat-cores. The strata of the Old Red Sandstone vary in structure and composition with some hard, massive beds and some softer, thinner beds. These rocks give rise to a range of soils, some of which are relatively base-rich but most are fairly neutral in pH, and some are leached.

The excursion will look at the vegetation of the mires, slopes and cliffs and it is probable that the entire day will be spent within the reserve.

If the weather is unsuitable for the mountains we will find an alternative lowland site and it may be possible to make a brief visit to the National Park Centre at Libanus.

We will cover some rough ground with a little cliff scrambling.
This is a strenuous excursion. Walking boots and wet weather clothing are essential.