The Sillees Valley Biodiversity Profile
Key Characteristics
- woodlands cover nearly 5% of the LCA, a little less than the percentage for Northern Ireland as a whole (5.6%); three-fifths of this is coniferous woodland spread through relatively small forests and generally of low biodiversity
- small pockets of upland mixed ashwoods and hazel woods are quite common on drumlins
- wet woodlands around loughs and also on very wet drumlin soils
- grassland occupies over 90% of the land cover, a very high percentage even for Northern Ireland (71% for NI as a whole); of this, two-thirds is improved pasture of generally low biodiversity
- in the northwest quarter of the LCA many of the fields are rushy and of low interest
- but this LCA also contains some unimproved meadows of high biodiversity interest
- no significant heaths or bogs
- significant mesotrophic and eutrophic lakes and good fen and reedbed communities that merge into marshy and wet grasslands
Woodlands
Woodlands cover nearly 5% of the LCA, a little less than the percentage for Northern Ireland as a whole (5.6%); three-fifths of this is coniferous woodland spread through relatively small forests. All are dominated by Sitka spruce with Norway spruce and Japanese larch, but many have fringes and small compartments of broadleaves including alder and willow, oaks and mixed broadleaves. Generally, however, the coniferous forests are of low biodiversity. Several small conifer plantations occur in the LCA, often these have been planted on cut-over bog as in Derryscobe and Granshagh.
Small pockets of upland mixed ashwoods are quite common on drumlins, usually associated with hazel, indeed in some woods hazel is dominant. However, because some drumlin soils are heavy and waterlogged, there is frequent alder and willow, to form wet woodland even on the drumlin slopes. Wet woodland also occurs around some of the loughs, as at Ross Lough, but the most extensive is the appropriately named Carr Wood at Lough Curran. Here willows and alder are common, but there are also ash and hazel. Birch has colonised some cut-over bogs, with willow and alder in wetter parts.
Glenwinny Wood is predominantly of ash and hazel, but also beech is common throughout. The wood appears to have been a plantation wood and there is some present-day clearance. Grazing is preventing regeneration and the development of a diverse herb layer, although the presence of beech may also be affecting this.
Castletown Manor, Monea, is a small park characterized by beech, with ash, sycamore, horse chestnut and some conifers (lowland woodland pasture and parkland). Skea Hall is also characterized by beech with ash, sycamore, birch and willows. Lichens and mosses are abundant or frequent at both sites, but the diversity of herbs is generally poor.
Grassland and Arable
Grassland occupies over 90% of the land cover, a very high percentage even for Northern Ireland (71% for NI as a whole); of this, two-thirds is improved pasture that is dominant everywhere except in the northwest quarter of the LCA. This pattern reflects the soil conditions; in the northwest quarter of the LCA, flat, wet, alluvial valleys surround drumlins with soils of severely impeded drainage whereas elsewhere the drumlins are better drained, particularly around Springfield and Moyglass where there are brown earths. Areas of improved pastures in the northwest quarter of the LCA are patchy and related to drainage and management by individual farmers.
Improved pastures generally have low biodiversity as a result of 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 are generally, dense and treed - commonly ash - in the areas of improved pastures. In the poorer grasslands, where fields are very small and rush infested, hedges are overgrown, gappy and shrubs are invading some of the fields.
Whereas many rush infested fields are of low biodiversity, there are several parts of the LCA where, because of the neutral to alkaline soils, unimproved grasslands are species-rich. For example, along the Sillees River at Caldrum and around Derrygonnelly, there are rush fields with meadow thistle (purple moor grass and rush pastures); species-rich meadows occur also at Moybrone and Skea. In many sites, because they are often alongside rivers or in inter-drumlin hollows, these grasslands grade into marshy grasslands and fens and can be of ornithological interests, for example with records of curlew. Several of these species-rich meadows have survived because they are managed traditionally for hay and do not have high inputs of fertilizers or slurry. Small areas of upland calcareous grassland occur on thin limestone soils to the west of Kilamaddoo (see LCA 6).
Records for bird Priority Species are not as diverse as for some LCAs, but nevertheless include bullfinch, reed bunting, skylark and spotted flycatcher, in addition to curlew.
Heaths and Bogs
There are no significant areas of blanket or lowland raised bog in the LCA. Any patches of bog have been cut-over and parts have been colonised by birch or planted with conifers. Similarly there is no significant heath.
Wetlands and Lakes
Fen occurs around several of the loughs, most notably at Ross Lough FNR where the lake lowering after the Sillees drainage scheme has increased its variety of habitats - there is open water, swamp, fen and wet meadow. Bulrush swamp is found in the deeper water, with common reed and tufted sedge locally dominant (reedbeds). This merges with permanently waterlogged fen with bladder sedge, common sedge and creeping bent, with herbs such as marsh bedstraw, water-mint and silverweed. Continuing into the drier land there are varied wet grasslands predominantly of types related to the more neutral soils, including the fen-meadow (purple moor grass and rush pastures) that although not unique to Fermanagh or Northern Ireland, are concentrated here and tend to be more species-rich than similar grasslands in England.
Ross Lough itself, although a mesotrophic lake, was classed as of low priority for conservation/biological interest; Coolyermer Lough was similar but of greater species diversity. Mesotrophic lakes are 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.
Carran and Lankill Loughs are examples of eutrophic standing waters. Carran belongs to a type that probably has the highest diversity of aquatic macrophytes in a eutrophic water body, whilst Lankill is of a type that is relatively un-enriched compared with other lowland lakes and one that is biased in its distribution to the limestone areas of Fermanagh and South Tyrone.
The Sillees and Screenagh Rivers have white-clawed crayfish populations.
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 native woodland cover of variable 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 to foster regeneration and herb layer and if necessary, encourage replanting of canopy species
- encourage planting of broadleaved plantations rather than the small conifer plantations which are of poor biodiversity and landscape value.
GRASSLAND AND ARABLE
Issue: poor biodiversity of farmland, but significant unimproved wet grasslands and meadows
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 particular the 'fen-meadows' and other species rich wet grasslands; thus prevent drainage, fertilizers etc
WETLANDS
Issue: fens in Northern Ireland are a large proportion of the UK resource
Actions:
- protect fens against loss by drainage and infill, which includes use as official refuse tips as well as sites in which to deposit building rubble and fly-tipping
- leakage of fertilizers and slurry from surrounding agricultural land should be prevented as this increases the nutrient levels and affects species composition.
Issue: important lakes (mesotrophic and eutrophic) and rivers
Actions:
- protect water quality of lakes and rivers through nutrient management and by reducing/monitoring suspended sediments, 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 on pH, nutrients and sediment loads and deposition
