Sperrin Foothills 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

• low woodland cover (c.2% compared with c.5.6% for Northern Ireland as a whole), but excellent examples of priority woodland types including upland oakwoods, upland mixed ashwoods and wet woodlands
• notable examples of other woodland, particularly hazel and hazel-oak woodland
• grassland is c.81% of the land cover, around 10% greater than for Northern Ireland as a whole
• improved pastures account for nearly three-quarters of the grassland, but rough grassland is widespread both on the foothills beneath the blanket peat and in the broad flat areas between the isolated rounded hills
• rough grasslands, both acid and damp neutral grasslands, important not only for plant species diversity but as habitats for mammals and birds, including breeding waders
• upland heathland, a declining habitat in the UK, common on the rounded hills
• almost no intact blanket or raised bog; most has been cut-over in the past and recent mechanised cutting is widespread
• main rivers are part of the Foyle catchment - of international importance to Atlantic salmon

Woodlands

Woodlands account for only c.2% of the land cover, which is low even for Northern Ireland (c.5.6%). Many of the woodlands are on the steep sides of rivers and streams and contain patches of several different types of woodland. Not only are these patches excellent examples of particular types, but together they enhance the biodiversity value of the woodland as a whole. Not all of these riverside or glen woodlands have been investigated, but the following are representative of the diversity and species richness that may be found.

Corbylin Wood ASSI is an extensive semi-natural woodland where the variety of environmental conditions has resulted in several distinctive woodland plant communities and a richness of woodland plants that is amongst the best in Northern Ireland. The composition of the woodland reflects both management and local soil conditions. Although the bulk of the wood occurs on acidic soils, there are also parts where soils are base-rich and wetter. Downy birch and mature oak generally dominate the canopy (upland oakwood), but where the soils are morebase-rich, ash dominates (upland mixed ashwoods) and on wet soils alder is dominant (wet woodland). The shrub layer is dominated by hazel and in wetter conditions by willows. The herb layer reflects the acidic nature of the majority of the wood and is dominated by great woodrush with bluebell locally abundant. On base-rich soils, there is a notable increase in species richness with primrose, wood avens, sanicle and lesser celandine included and, in wetter parts, wood anemone, golden-saxifrage and remote sedge. The relatively rare bird cherry and wood fescue are also found in this woodland.

Silverbook Wood ASSI, is similar in its diversity of woodland types and species richness that result from different soil conditions - it too has upland oakwood, upland mixed ashwood and wet woodland - but in parts the canopy, in the absence of standard trees, is often of hazel. Ervey Wodd ASSI and Altmover Glen ASSI also show variation from base-rich to acid woodlands.

Woodlands in which hazel forms the dominant canopy species, with some oak and birch and with alder and willow in wetter parts, are common along many of the rivers, including an extensive stretch along the Inver Burn, in the upper Burn Dennet and the Dunnyboe Burn. Some riverside woodlands have also been planted with non-native trees as in Altdarragh Glen where the north side has beech; the south side is a more typical hazel woodland with oak, ash alder and birch.

Woodlands are not confined to riversides, some occur on hillslopes, as at Creaghan Wood where there are stands of oak, of birch and of oak and beech over a dense hazel-birch cover. Whilst some of these hillside woodlands are semi-natural, often occupying short, steep or rocky slopes, others have clearly been planted as part of 'landscaping' of lands belonging to estates, and others are on abandoned wet fields or cut-over bog.

Small estate woodlands are scattered through the LCA, typically with much planted beech and oak; some of the oak is part of semi-natural woodland along streams that was taken into the estates. Scots pine and larch are quite common, particularly in estates of the latter part of the nineteenth century. Ash and sycamore have in some instances become very abundant. Some of the estates already planted by the 1830s, remain surrounded by woodland (lowland woodland pastures and parkland) and are at least 'long-established' woodland and semi-natural parts are probably ancient. Learmount was reported in the 1830s as having been planted 'in the last 30 years, chiefly with fir'; today the parkland is in State Forest and although there is much Sitka spruce, Norway spruce and larch, there is also beech, oak and 'intimate broadleaved mixture'.

Other State forests are found at Knockbrack, where larch and Sitka spruce dominate although there are some planted mixed hardwoods and some semi-natural wood along the stream; that, like most of the streamside woodlands in the LCA, was present in the 1830s. New coniferous plantations are also located on the hillsides above Lisdillon, on the eastern slopes of Mullaghmeash Hill and to the east of Raspberry Hill.

Grassland and Arable

Grassland is c.81% of the land cover, around 10% greater than for Northern Ireland as a whole. Improved pastures account for nearly three-quarters of the grassland, but rough grassland is widespread both on the foothills beneath the blanket peat and in the broad flat areas between the isolated rounded hills. Arable land (including grass re-seeding) covers c.3% of the LCA.

Improved pastures generally have low biodiversity as a result of relatively intensive management. However, the degree of improvement in the LCA is varied. 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 management of the predominantly hawthorn hedgerows is variable; some of the larger fields have dense, well-maintained hedges, but commonly the hedges are gappy and reinforced by wire. Hedgerow trees are common, especially at lower elevations, - most frequently of ash but beech is locally significant. There is some field amalgamation, especially on upper margins where there has been reclamation.

Much of the rough grassland occurs on the upland margins where it may have clumps of rushes separated by grazed grasses, be rush dominated or may merge into more acidic areas on the margins of cut-over blanket bog where wavy hair grass, mat grass or purple moor grass may be frequent. However, there are rough grasslands in the lowlands too; they surround some areas of cut-over lowland bog, occur in field corners or comprise one or two fields in low situations. Depending on situation, these generally damp grasslands may be acidic, with species similar to the upland margins, or neutral with high or dominant rush cover and include other species such as tufted hair grass and meadow sweet.

Rough and damp grasslands are an important element in the biodiversity of the LCA, not only for the increased diversity of plant life, but also because they provide habitats for Priority Species of mammals and birds; thus the Irish hare finds refuge in these less-managed grasslands and waders - including curlew and snipe - have breeding sites.

Although the biodiversity of improved pastures and arable is generally low, farmland, together with the intricate mix of woodlands, damp grasslands and bogs within it, attracts many of the Priority Species of birds - bullfinch, curlew, reed bunting, song thrush, spotted flycatcher, yellowhammer and skylark are widespread.

Heaths and Bogs

Heath, dominated by common heather is frequent on the rounded hills of the LCA; in many places it has come to dominate cut-over blanket bog, but it is also dominant on some slopes that are too steep for deep peat to form. It distribution is also affected by grazing history; sharp boundaries may be found between heather dominated land and acid grassland - the latter a result of a history of heavy grazing that has removed the heather cover. Upland heathland is a declining habitat in Britain and Ireland, partly resulting from forestry and land reclamation but also from overgrazing in recent times. The widespread occurrence of this habitat in the LCA is therefore of local and national significance, and because the habitat is largely restricted in Europe to the northwest seaboard, is also of international importance.

Blanket bog is common in the LCA, but because altitudes are lower and the rounded hills have steep slopes, it is not as widespread as in adjacent LCAs that include the main Sperrin Mountains. Almost all of the blanket bog is cut-over, generally old cutting, and in consequence much is now occupied by acid grassland or heather heath. One area of intact bog in Farkland in the northeast abuts onto the extensive commercial extraction that has taken place at Altahullion (see LCA 34)

Lowland raised bog is difficult to separate from blanket peat in this LCA because of the intermediate altitude; they should probably be regarded as raised bogs within a transitional zone between lowland and upland blanket peat. However, as with blanket bogs almost all have been cut-over and several have been colonised by trees; birch tends to dominate on the drier peat surface whereas around the wetter edges alder and willow may be found. One area of intact raised bog at Aghabrack has been subject to recent machine (compact harvester) extraction. Such extraction has been common in the LCA and because of its prevalence, has been on cut-over bog.

Wetlands and Lakes

Lough Ash is one of the largest of the lakes in this LCA surveyed by the Northern Ireland Lake Survey. It has been classified as mesotrophic; that is, characterised by having a middle level of nutrients between nutrient poor (oligotrophic) and nutrient rich (eutrophic). Mesotrophic lakes potentially have the highest macrophyte diversity of any lake type. Furthermore, relative to other lake types, they contain a higher proportion of nationally scarce and rare aquatic plants. This is an increasingly rare type of lake in Northern Ireland because the nutrient status of many is being increased through input of water from agricultural land that has had applications of fertilizers and slurry. Moor Lough is also mesotrophic and of a type that has the most diverse aquatic macrophyte flora of the upland lakes. Mill Pond is of no priority type. Several other lakes occur in the LCA, but have not been surveyed.

The two main rivers in the LCA are the R. Faughan and the Burn Dennet and both have many steep-sided tributaries. There are no records for Priority Species, but the rivers are part of the Foyle catchment that is of international importance for Atlantic salmon; that part of the system in Northern Ireland is the largest salmon and trout fishery in the country.

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, but some of high biodiversity value

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 along streams to foster regeneration and if necessary, encourage replanting of canopy species
• encourage planting of native 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, particularly lowland damp pastures
• 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: loss of upland heathland and decline in its biodiversity

Actions:

• promote membership of ESA and other environmental schemes through consultation with farmers and thereby
• control grazing intensity on existing heathland to encourage development of heathland and of heather of different ages
• control gazing intensity on some upland grassland to promote return to heathland
• manage heather so that it does not become 'leggy' and has different ages and structures (where grazing is not used consider burning, cutting - but following guidelines)
• discourage 'reclamation' to pasture fields around the heathland margins
• discourage afforestation

Issue: although there are no extensive intact raised bogs or blanket bogs, the cut-over bogs do provide important habitats and species diversity

Actions:

• maintain the integrity of existing raised bogs by for example, preventing infilling, fly-tipping, fires, new drainage and new peat cutting
• restore raised bog habitats through appropriate water level management, tree removal (where only sporadic) and phasing out peat cutting
• allow bogs already colonised by trees to develop into woodland
• prevent new forest planting on raised/blanket bog
• consider impacts on biodiversity of schemes to reclaim marginal blanket bog

WETLANDS

Issue: important examples of upland mesotrophic lakes and rivers of international importance for salmon

Actions:

• protect water quality of lakes and rivers through nutrient management, 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, sand pits etc.
• monitor streams in relation to expansion of rural housing and associated septic tanks/sewage treatment plants
• monitor streams and rivers in relation to sediments from peat cutting so that spawning and nursery beds of salmon are not affected

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