The Garrison Lowlands Biodiversity Profile

 

In the following account it should be noted that for consistency, the biodiversity section follows a 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

• the percentage of the land occupied by woodland is around that for Northern Ireland as a whole (c. 5.6%); majority is coniferous forest
• important broadleaved woodlands, especially on shore of Lough Melvin, including wet-woodland and oak-birch woods
• centre of the LCA has extensive areas of species-rich meadows and purple moor grass fen-meadow
• little intact peat bog
• Lough Melvin is the least modified of all the large loughs in Northern Ireland with rare species of fish

Woodlands

The percentage of the land occupied by woodland is around that for Northern Ireland as a whole (c. 5.6%). The majority is coniferous forest dominated by Sitka spruce with only a small amount of other species - lodgepole pine, Norway spruce and some mixed hardwoods; it is generally of low biodiversity.

Broadleaved woodland is concentrated around the shores and on the islands of Lough Melvin. Much of this woodland is dominated by birch, but there are also oaks, particularly at the Lakeshore Plantation, and in wetter parts alder and willows (wet woodland). The herb layer is moderately diverse and there are abundant epiphytic mosses and lichens. Elsewhere patches of scrub are common through the LCA, the species content depending on the wetness of the ground - alder, hazel, birch, ash and willows are common. Some of this scrub has colonized cut-over bog, but most has colonized abandoned rushy fields, often from the overgrown hedgerows. Diversity of the herb layer is often poor, partly because of the origins of the scrub, i.e. from abandoned rushy pastures, and because there is still some cattle grazing.

Grassland and Arable

Grassland accounts for about 80% of the land cover, but unlike most LCAs improved pasture is not dominant; it is confined to wider, flatter areas between low ridges and is dependent on management practices of individual farmers. The field drainage, re-seeding and use of fertilizers results in low biodiversity for these improved pastures.

Land use in the centre of the LCA is dominated by small, rush-infested pastures, many of which have been abandoned or are little used and have been colonised by scrub. However, because of the traditional, low intensity farming methods, herb-rich hay meadows are common (lowland meadows) with some of the best examples selected as ASSIs. Drumlisaleen ASSI comprises seven small hay meadows that are outstanding in terms of species richness (99 vascular plant species present). The vegetation is generally dominated by jointed rush, with a low cover of grasses and an abundance of sedges including much carnation sedge, flea sedge and tawny sedge. Marsh hawk's-beard is common in flushes and there is an abundance of orchids, including common twayblade, early purple orchid and greater butterfly orchid. Garvros ASSI is similar, but the most distinctive feature of the grasslands there is the abundance of forbs (herbs other than grasses) such as meadow thistle, tormentil, devil's-bit scabious and bugle. Bog pimpernel (rarely found in hay meadows), and the nationally rare blue-eyed-grass are also present.

Tullysranadeega ASSI represents one of the most extensive concentrations of traditionally managed fields in Northern Ireland with a range of species-rich grassland types present. These pastures are dominated by sharp-flowered rush, carnation sedge and sweet vernal grass with a wide variety of associated species. In some places, flushed, acid soils produce 'Fen Meadow', which is dominated by purple moor-grass, meadow thistle and devil's-bit scabious (purple moor grass and rush pastures). The nationally rare melancholy thistle also occurs. Species rich meadows can also be observed at Moneendogue ASSI and at Aghamuldowney.

In the northern and eastern sections of the LCA soils become more severely waterlogged and humic, and indeed there is much cut-over peatland. Here the rush infested acid pastures are species poor and grade into coarse moorland grasses.

Heaths and Bogs

Despite the low altitude, most of the bogs in this LCA have been classed as blanket bog although some are better viewed as transitional between lowland raised bog and blanket bog. 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. It is also important for over-wintering birds and for breeding birds, including waders. Blanket peat is also important as a store for carbon and as a repository of information on past environments.

Almost all the bog in this LCA has been cut-over and some has been lost to forestry. The largest area of intact bog is at Glen West: the northern end of the intact bog is heavily poached but the western half, with its deeper peat mantle, has a well-defined hummock and hollow structure along with an extensive pool complex. The shallow sloping eastward side, which descends down towards the river, has a more uniform surface topography with the bog asphodel lawn containing a scattering of purple moor grass and deer sedge tussocks, low growing heathers and only occasional low hummocks.

In addition to the effects of grazing and poaching, there has also been recent mechanical peat extraction. Other bogs with a centre classed as intact are located at Cornahaltie and Coollum, but these have suffered from recent mechanical cutting and expansion of forestry.

Where the peat thins on low, rocky hills, and where past cutting has left thin peat, acid grassland dominates but there is also some gorse heath and some upland heathland. Upland heathland is a declining habitat in the UK and Ireland, partly as a result of overgrazing and also because of lack of management, so that any remaining areas are significant not only to the biodiversity of LCAs but also to the countries as a whole.

Wetlands and Lakes

Lough Melvin SAC (also Lough Melvin ASSI) is a large mesotrophic lake, 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.

Lough Melvin is the least disturbed of the large loughs of Northern Ireland and has exceptionally clean water; the flora is indicative of this high water quality and is characterised by quillwort, shoreweed, water lobelia, alternate water-milfoil and a variety of pondweeds. The Lough also supports important native fish populations; Arctic charr occurs here at its only remaining Northern Ireland site, there are three genetically distinct populations of brown trout and there are also stocks of Atlantic salmon.

In addition to the open waters, the SAC/ASSI includes a range of associated wetland and terrestrial communities. Habitats include swamp communities, boulder and rock shore, woodland, species-rich grassland and fen. The last contains diverse examples of purple moor grass-meadow thistle fen-meadow, ranging from purple moor grass-dominated swards with black bog-rush, to very herb-rich swards managed as hay meadows (see grasslands above).

Two other mesotrophic lakes located in this LCA are Lough Anierin and Lattone Lough. Lough Aleater is classed as an upland lake with very low nutrient content (oligotrophic) but with the most diverse macrophyte flora of upland lakes.

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

Actions:

• further study of the history and ecology of 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 woodlands rather than conifer plantations which are of poor biodiversity and landscape value, but ensure that planting does not reduce area of important grassland types
• ensure continued protection of wet woodland and other woodlands along the shore of Lough Melvin

GRASSLAND AND ARABLE

Issue: farmland highly variable in biodiversity; low biodiversity improved pastures, but

traditional, less-intensive agriculture also - with species rich grasslands

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.
• ensure protection of traditionally managed grazed and hay meadows
• ensure that purple moor grass meadow-fen is not lost to drainage
• monitor spread of scrub onto these less-intensively managed and abandoned fields

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
• discourage 'reclamation' to pasture fields around the heathland margins
• discourage afforestation

Issue: blanket bogs are of national and international importance

Actions:

• maintain the integrity of existing bogs by for example, preventing infilling, fly-tipping, fires, new drainage, poaching and grazing, and new peat cutting
• consider restoration of bog habitats, especially ones until recently intact, through appropriate water level management, and phasing out peat cutting
• prevent new forest planting

WETLANDS

Issue: important lakes, mainly mesotrophic but some upland oligotrophic lakes

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
• monitor streams in relation to expansion of rural/urban housing and associated septic tanks/sewage treatment plants
• monitor effects of forestry and peat cutting on pH, nutrient status, and sediment load and deposition
• ensure co-operation with Republic of Ireland authorities to maintain Lough Melvin - its high water quality and rare species and habitats.

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