Castle River Valley ASSI

This area is of special scientific interest because of its complex pattern of species-rich dry and wet grassland and the gradations between these habitats. Species-rich grassland tends to occur only where land management is not intensive, in particular where traditional farming practices have been maintained. As a result, it is not a widespread habitat in Northern Ireland and is often fragmented, consisting of individual fields, parts of fields or banks. Species-rich grasslands, like those found at Castle River Valley, are a particularly scarce resource in Northern Ireland.

The area is composed of seven steeply sloping field parcels with a northerly aspect. There is a small associated area of scrub in one field parcel which is complemented by a network of mature intact hedgerows. The combination of topography and the related soil hydrology has resulted in a relatively complex range of grassland communities within a small area. These vary from dry grassland to wet grassland, with moderate base-rich flushing occurring throughout the area. The drier vegetation communities include lowland meadow, characterised by the presence of crested dog’s-tail and common knapweed, and as they gradually become wetter they grade into rush pasture, which is characterised by sharp-flowered rush and common marsh-bedstraw. This subtle gradation is generally related to soil moisture within the field parcels.

The drier fields are grass dominated with a high coverage of herbs representative of lowland meadow grassland communities. crested dog’s-tail is a constant component of the sward along with red fescue, sheep’s-fescue, common bent and sweet vernal-grass. Sedges are abundant in the sward and include glaucous sedge and carnation sedge. Herbs present are typical of traditionally managed drier grasslands and include common knapweed, meadow vetchling, common bird’s-foot-trefoil, Devil’s-bit scabious, bugle, selfheal, Autumn hawkbit, meadow buttercup and fairy flax.

Where there is increased water movement through the soil and local waterlogging, then species reflecting the wetter conditions predominate. On the upper parts of the valley slopes sharp-flowered rush and purple moor-grass are conspicuous with the continual through flow of water, with soft-rush and compact rush occurring in varying proportions mostly towards the base of the slope and at the edge of the river.

Flushing throughout the site has created an interesting mosaic of vegetation communities on the valley slopes and this is reflected by the many species of sedge present which include pale sedge, flea sedge and yellow-sedge. Throughout the area species-rich rush pasture is a constant feature of the wetter parts, with greater bird’s-foot-trefoil, purple-loosestrife, wild Angelica, ragged-Robin, common marsh-bedstraw, lesser spearwort, Devil’s-bit scabious, and bugle all occurring.

To the east of the site at the base of one of the slopes waterlogging has created an area of standing water where fen vegetation occurs, with bottle sedge, bogbean, marsh cinquefoil, water mint and marsh-marigold.

The variation in topography and related soil hydrology, and the effects of past and present management have resulted in a considerable range of species in a relatively small area.
In addition to the vegetation communities described above the following species of note were recorded - common spotted-orchid, greater butterfly-orchid, common Twayblade and lesser clubmoss.

Castle River Valley is an area of semi-natural grassland managed in a traditional way. As such, it provides valuable feeding and roosting sites for a range of animals, including birds and invertebrates.

Site Related Documents

Site map (.PDF 675Kb), Citation document (.PDF 142Kb) and Views about Management document (.PDF 60Kb).