UPLAND HEATHLAND

Upland heathland occurs on mineral soils and thin peats throughout the uplands of the UK, above the upper limit of agricultural enclosure. It includes both ‘wet’ and ‘dry’ heath. Dry heath is characterised by a high cover of species such as heather, bell heather, bilberry, crowberry and western gorse. Wet heath is dominated by mixtures of heather, cross-leaved heath, purple moor-grass and deer grass, alongside carpets of mosses (notably Sphagnum species). Good-quality heathland has patches of heather at different stages of growth (i.e. is structurally diverse). Unfortunately the extent of heather moorland has declined significantly in Wales, mainly as a result of heavy grazing (and subsequent conversion to grassland) and afforestation.

Upland heathlands in Wales can support a range of uncommon birds including merlin, hen harrier and red and black grouse; the habitat may also contain important invertebrate and lower plant assemblages (mosses and lichens).

Upland heathland often forms a mosaic with other habitats such as blanket bog, mires, grassland, bracken, scree, scrub and woodland. Blanket bog can also be dominated by dwarf shrub vegetation, but this habitat typically occurs over deep peat and is the subject of a separate action plan. Similarly montane heath which is restricted to high altitudes, and lowland heathland which lies below the upper limit of enclosure, are also covered by separate plans.

Current Status in Carmarthenshire

The total extent of upland heathland in Carmarthenshire is relatively small. Much of the upland heathland resource is concentrated in the north and east. Cwm Doethie–Mynydd Mallaen SSSI supports an extensive area of upland heathland and is designated a SAC for its dry heath vegetation. Mynydd Llanllwni, north of Brechfa, is another important area, although it is somewhat over-grazed.

• Current Factors Affecting the Habitat
• Overgrazing, particularly by sheep, has led to the replacement of much upland heathland by grassland; overgrazing can also result in poor structural diversity with few transitions from open heath to scrub and woodland.
• Conversion to grassland by ploughing, reseeding, liming and fertilizer application, particularly at lower elevations; drainage also results in the degradation of wet heath vegetation.
• Inappropriate burning regimes.
• Afforestation.
• Bracken encroachment.
• Acidification and nitrogen enrichment through atmospheric deposition, leading to vegetation changes and a loss in bryophyte and lichen interest.
• Loss of habitat through developments such as wind farms and communication masts.
• Damage through recreational pressure.
• Climate change could potentially impact upon the habitat in future.

BLANKET BOG

Blanket bog is a globally rare habitat, approximately 10–15% of which occurs in Britain and Ireland. In the UK it covers large expanses of the uplands in the north and west, where the climate is typically cool and wet. Peat depth generally exceeds 0.5 m, having accumulated through the slow decomposition of plant material under waterlogged conditions. Studies indicate that most blanket peat in the UK began to develop between 5000 and 6000 years ago.

Bog mosses (Sphagnum species) are a prominent component of blanket bog vegetation, alongside dwarf shrubs such as heather, bilberry, crowberry and cross-leaved heath. Other common plants include cotton grasses and deer grass. Blanket bogs can support a rich invertebrate fauna and they are often of ornithological importance.

The carbon trapped in the peat makes this, along with other peat habitats, vital in the challenge to address climate change.

Current Status in Carmarthenshire

Much of the blanket bog in Carmarthenshire is modified and no longer peat forming. Survey data shows areas of intact blanket bog but much more wet and dry modified bog habitat. Much of this vegetation is concentrated in the upland areas of north Carmarthenshire.

Two SSSIs in Carmarthenshire contain blanket bog vegetation, including the extensive Cwm Doethie–Mynydd Mallaen SSSI. Many areas of blanket bog occur on common land.

Current Factors Affecting the Habitat

• Agricultural intensification, including overgrazing by sheep, burning and drainage.
• Afforestation – resulting in direct loss of habitat and drying out of adjacent blanket bog.
• Recreation pressure, particularly from 4WD vehicles.
• Developments such as wind farms and communication masts.
• Erosion of peat - some of this may be due to natural processes, but some is also linked to drainage.
• Commercial moss collecting is considered to be a significant factor in some areas.
• Climatic change is a potential future threat and atmospheric pollution is also thought to be a factor.