Foyle Valley Biodiversity Profile

In the following account it should be noted that for consistency, the biodiversity section follows the standard order for all LCAs even though some of the communities discussed later may have more importance for biodiversity than those discussed earlier

Key Characteristics

• although woodlands occupy only a small percentage of the LCA, they include some, or parts of some, of the best examples of priority woodland types in Northern Ireland, including some of the more extensive upland oakwoods
• significant amount of estate woodland and 'landscaping' of broadleaved woodlands along the R. Mourne - addition of beech, conifers etc
• improved pastures dominant, but wet grasslands important, especially alongside R Foyle in the north - important for waders and other wetland birds
• some intact lowland raised bog and intact blanket bog - important habitats on a national and European scale
• rivers with significant populations of Priority Species and part of the Foyle system - of international importance for Atlantic salmon.

Woodlands

Although woodlands occupy only a small percentage of the LCA, they include some, or parts of some, of the best examples of priority woodland types in Northern Ireland. For example, in the southeast there is a significant part of woodlands that occur at the confluence of the Glenelly and Owenkillew Rivers. The Owenkillew River SAC (and Owenkillew and Glenelly Woods ASSI) is associated with several woodlands which together represent one of the best examples of old sessile oak wood (upland oakwood) in Northern Ireland. The woods contain a number of associated physical features, including waterfalls, gorges, cliffs and scattered boulder scree, which contribute to the diversity of the woodland communities. However, the canopy is generally dominated by sessile oak with frequent downy birch and some planted beech. The shrub layer consists of rowan and holly, with hazel locally frequent and occasional goat willow. In places, the ground flora is dominated by grasses, including wavy hair-grass, and calcifuge (not tolerant of lime) mosses such as Rhytidiadelphus loreus. Where grazing is absent, bilberry, great wood-rush and bluebell are dominant in the ground flora; species such as bluebell and lesser celandine reach local dominance where the slopes are mineral-enriched.

Along the Mourne River, especially on steeper meander scars, some woodlands are also dominated by oak, frequently with birch and hazel, but there are also species that indicate planting, including beech, Scots pine and other conifers. In other parts, these woodlands are more base-rich and ash becomes the canopy dominant; yet other parts are wet and dominated by alder. The woodlands are generally species-rich, partly because of the changing ground conditions, but there are parts that are grazed and the herb layer is predominantly grasses. These woodlands, as well as those at the Owenkillew-Glenelly confluence, were present in the 1830s and therefore are at least 'long-established'; such woodlands may contain species not present in more recent woodlands.

Upland mixed ashwoods are not frequent in the LCA, but examples include Grange Wood ASSI that partially lies over an isolated outcrop of Dungiven limestone. The wood is largely comprised of a low hazel canopy with occasional ash standards over a diverse base-rich herb flora. Frequent exposed rocky outcrops and boulders are covered by a luxuriant growth of mosses, particularly on the upper slopes. The lower slopes are waterlogged with extensive flushing and in these areas willow and alder predominate in wet woodland. Similarly, Strabane Glen ASSI is a calcicolous (favouring lime) type due to the underlying geology. Hazel and ash are the predominant tree species with rowan and scrub oak, and occasional holly.

Wet woodlands are not extensive in the LCA; apart from forming small patches within other woodland types, they tend to be located at the edges and other wetter parts of cut-over bogs, as at McKean's Bog.

Examples of lowland woodland pasture and parkland are frequent. Although most are small, their influence has extended into the countryside, as exemplified by woodlands alongside the Mourne River (see above), particularly between Strabane and Newtownstewart. Here oak, beech, elm, horse chestnut and Scots pine are common amongst a wide range of species.

The most extensive estate woodlands are those at Holy Hill where beech and oak are the most abundant species, with elm, sycamore, ash and birch common. The herb layer is not diverse and the epiphytic moss and lichen flora is also poor. There are also plantations of Norway spruce.

There are no extensive coniferous forests in the LCA; the plantation at Wood Hills is dominated by Scots pine and Sitka spruce with larch, but there are also ash, alder and other broadleaves.

Grassland and Arable

Grassland covers the vast majority of the LCA and most of that is improved pasture. Undulating land above the Mourne/Strule is composed of sands, gravels and tills on which there are well-drained soils; improved pastures are intensively managed and there are also some arable fields. Improved pastures generally have low biodiversity as a result of the relatively intensive management. Some of the pastures are sown grasslands dominated by ryegrass and few other species - low biodiversity is in-built. Other grasslands have been converted to improved pastures through management. High levels of grazing or repeated cutting for silage, high inputs of fertilizers and slurry, and selective herbicides serve to reduce diversity of both flora and fauna.

Biodiversity in areas of improved pastures and arable is often concentrated in hedgerows. Indeed, they may be the most significant wildlife habitat over much of lowland Northern Ireland, especially where there are few semi-natural habitats. Hedgerows are a refuge for many woodland and farmland plants and animals. In this LCA hedgerows in the lower lands are generally well-managed, although thinning in the few upland parts, and provide the micro-habitats for enhancement of the biodiversity, for example for farmland birds and the semi-shade in which spring-flowering plants can establish - provided that the hedgerow is not too intensively managed.

To the north of the LCA, on the east bank of the R. Foyle, the land is flat and in addition to bog and marsh, there are wet grasslands that are important for breeding waders, including lapwing, snipe and curlew. In uplands to the east of the LCA, for example the lower slopes of Knockavoe, and on the margins of blanket peat to the north of the Owenkillew, there are acid, rushy grasslands that, although of low biodiversity, also provide habitats for waders.

Despite the overall dominance of improved pastures, there are sufficient intermixed habitats (woodland, hedges, arable fields, wet grasslands, bogs) in the farmland to provide habitats for a range of bird Priority Species, including yellowhammer, spotted flycatcher, song thrush, skylark, reed bunting, linnet and bullfinch.

Heaths and Bogs

The LCA has both lowland raised bog and blanket bog, although some of the bogs may be transitional between the two; thus on the north side of the Owenkillew there are some sites on broad ledges that have been classed as lowland (North and South Lislea) whereas others at a similar altitude (Straletterdallan) have been classed as blanket - probably because they were almost continuous with other bog upslope.

Lowland raised bog is a rare habitat in the UK, and Northern Ireland has a large proportion of that remaining; in particular it has much of the intact lowland bog. In the best examples there is a diversity of structural features including hummocks and hollows and pools that give rise to micro-habitats related especially to the height of the water table. The plant species are adapted not only to the generally waterlogged, acid and low nutrient conditions, but also to these small-scale variations in topography and water level. Typical plant species include bog mosses, deer sedge, cotton sedges, bog asphodel, sundews, cross-leaved heath and common heather. In addition, raised bogs (together with blanket bogs) are important repositories of archaeological and environmental information, and significant stores of carbon.

McKean's Moss ASSI is most north-western lowland raised bog in Northern Ireland. The intact dome has characteristic vegetation and structural features, including hummock and lawn complexes and small shallow pools. There is a range of bog mosses associated with these micro-habitats. The periphery of the bog has been extensively cut for turf in the past (McKean's Moss Part II ASSI) and is now dominated by downy birch with frequent willow where the water table is maintained at a higher level. The ground flora is dominated by bog mosses and dense stands of purple moor-grass. These old hand cuttings provide additional habitat diversity to McKean's Moss ASSI and are integral to its hydrology. North and South Lislea is the only other extensive area of 'lowland' bog, but it is completely cut-over.

Blanket bog is confined in Europe to the northwest margins of the continent, so that Northern Ireland contains not only a large proportion of the UK's and of Ireland's total area of blanket bog, but also is of major importance at a European scale. Blanket bog, and particularly intact blanket bog, in any LCA is therefore of national and international significance. It is home to plant species adapted to the acidic, low nutrient conditions - including common heather, cross-leaved heath, cotton sedges, bog asphodel, deer sedge, bog mosses (Sphagnum species) and sundews. Some of the best examples of blanket bog, particularly those in the northwest of Britain and Ireland, have micro-topographic features such as pools and hummocks that provide micro-habitats for flora and fauna. Blanket bog is also important for over-wintering birds and for breeding birds, including waders. It is a significant store for carbon and a repository of information on past environments.

Blanket bog is confined in this LCA to the flat and gentle slopes to the north of the Owenkillew beginning at Lisnafin in the west and extending intermittently to The Black Park in the extreme east. Whereas most of the blanket bog is cut-over, there are intact remnants at Straletterdallan and a more extensive intact area down the centre of the low spur at Tullynadall. However, modern compact-harvester extraction (with drains) has eaten into this bog. Parts of Straletterdallan have been colonized by trees.

Wetlands and Lakes

The Owenkillew River (Owenkillew River SAC, Owenkillew River ASSI) is ultra-oligotrophic (very low in nutrients) in its upland reaches, gradually becoming oligotrophic and oligo-mesotrophic through its middle and lower reaches (only the lower reaches are in this LCA). The river is notable for its physical diversity and the naturalness of banks and channel, and the richness of its plant and animal communities. Beds of stream water-crowfoot occur throughout its middle and lower reaches, typically in association with intermediate water-starwort and pondweeds such as broad-leaved pondweed and shining pondweed. Both salmon and brown trout are present in the river, in addition to species such as brook lamprey. Otter, dipper and kingfishers are present along the length of the river. The Foyle system, which includes the Strule/Mourne and Derg is, along with the Roe and Faughan, the most important salmon fishery in the north of Ireland.

None of the lakes examined by the Northern Ireland Lake Survey were classed as of priority to biodiversity; Lough Neas has a small area of fen, otherwise fen and reedbed are rare. In the north, the R. Foyle grades into its estuary where there are mudflats, patches of saltmarsh and important habitats for wetland birds (see LCA 32 and 35).

Key Issues

General actions for UK and NI Priority Habitats and Priority Species are detailed in the Habitat Action Plans and Species Action Plans.

WOODLANDS

Issue: low woodland cover of variable biodiversity value, but including important examples of Priority types

Actions:

• enhance the biodiversity value of demesne/parkland woodland through control of grazing and felling; by encouraging planting of saplings of the standard trees; by preventing further loss of parkland; by retention of fallen and veteran trees (particularly for bryophytes, ferns, fungi and fauna)
• further study of the history and ecology of demesne and other broadleaved woodlands particularly any ancient and long-established, as a key to future management
• encourage control of grazing in broadleaved woodlands to foster regeneration and if necessary, encourage replanting of canopy species
• encourage planting of broadleaved plantations, through appropriate grant schemes, rather than the small conifer plantations which are of poor biodiversity and landscape value.

GRASSLAND AND ARABLE

Issue: poor biodiversity of farmland

Actions:

• maintain and improve field boundaries especially hedgerows . This may be achieved through adoption of correct cutting cycles; hedge laying and replanting where necessary; leaving saplings uncut to develop into hedgerow trees; avoidance of spraying with fertilizers, slurry, herbicides; provision of wildlife strips and conservation headlands around fields; and limitation of field amalgamation
• encourage (through participation in Environmental Schemes) adoption of less intensive management of pastures to allow reversion to more species-rich grassland and protect unsown areas of species-rich grassland - in this LCA applies mainly to wet grasslands
• maintain and enhance floodplain grassland by restricting field or arterial drainage - of importance to waders and other wetland birds
• leave stubble over winter, rather than autumn ploughing, to increase food resources for farmland birds; spring sown cereals are beneficial to breeding farmland birds.

HEATH AND BOGS

Issue: raised bogs/blanket bogs of national and international importance

Actions:

• maintain the integrity of existing lowland raised bogs and blanket bogs by for example, preventing infilling, fly-tipping, fires, new drainage and new peat cutting - applies particularly to intact bogs, but cut-over bogs can provide important habitats for birds and invertebrates
• consider restoration of raised bog/blanket bog habitats through appropriate water level management, removal of individual colonizing trees and phasing out peat cutting - applies particularly to any areas of recent mechanical cutting
• prevent new forest planting on raised/blanket bog

WETLANDS

Issue: important rivers with populations of rare aquatic plants and fauna; rivers part of the Foyle system - important for salmon

Actions:

• protect water quality of rivers through nutrient management and by ensuring that suspended sediments and deposition are low, thus
• promote and encourage existing good farming practices so that streams are not polluted by run-off from agricultural land or seepage from silage pits
• continued monitoring of streams below industrial plants/quarries
• monitor streams in relation to peat cutting (sediment load and deposition) - important for salmon that nursery and spawning beds are clear
• monitor streams in relation to expansion of rural/urban housing and associated septic tanks/sewage treatment plants
• recognise that monitoring of streams in relation to forestry and other operations upstream of the LCA boundary may be important
• continue cross-border cooperation in relation to salmon population

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