Wet woodlands are woodlands & scrub found in a variety of environments where the water table is high due to poorly drained or seasonally waterlogged soils. They are associated with characteristic ‘wet’ habitats such as floodplains, flushes, river valleys & plateau woodlands.
- Site: Permanently waterlogged floodplains, river valleys, along streams, flushes, transition zones, between open water & drier grounds. Successional habitats on fens, mires & bogs.
- Soil: Wet mineral soils on base-rich clays to permanently wet nutrient-rich peatlands or nutrient-poor peatlands
- Main species: Alder, downy birch & willow
- Other species: Oak, ash, pine, beech
- UK: 50,000-70,000 ha
- NI: 2,600 ha
- Wet woodlands are typically dominated by alder Alnus glutinosa, downy birch Betula pubescens & willow Salix spp. These species can extract oxygen from the water that saturates the woodland. They also include oak Quercus spp., ash Fraxinus excelsior, pine & beech on drier, riparian areas.
- Wet woodlands occur on a range of soil types, including nutrient-rich mineral, acid soils & nutrient poor ones.
- Wet woodlands occur on floodplains, as successional habitats on cutover bogs, mires & fens, on margins of water bodies along lowland & upland streams, hill-side flushed & in peaty hollows.
- They are often part of a mosaic of other woodland habitats such as oakwoods, mixed ash, wetlands or within coniferous plantations. They may form transitions to open habitats including heath & acid grassland.
- Although wet woodlands are typically water-saturated, they are a successional habitat & naturally dry out.
- Wet woodlands provide habitats for a variety of plant communities that are similar to those recorded in the NVC of Great Britain: W1: Salix cinerea (Grey willow) – Galium palustre (Marsh Bedstraw) woodland, W2: Salix cinerea (Grey willow) – Betula pubescens (Downy birch) – Phragmites australis (common reed) woodland, W3: Salix pentandra (Bay Willow) – Carex rostrata (Bottle sedge) woodland, W4: Betula pubescens (Downy birch) – Molinia caerulea (purple moor-grass) woodland, W5: Alnus glutinosa (Alder) – Carex paniculata (greater tussock sedge) woodland, W6: Alnus glutinosa (Alder) – Urtica dioica (Common nettle) woodland, W7: Alnus glutinosa (Common alder) – Fraxinus excelsior (Ash) – Lysimachia nemorum (Yellow pimpernel) woodland.
- As wet woodlands combine features of several other ecosystems, they are species-rich. They support a range of mosses, including Sphagnum spp., which dominate the ground layer & bog species such as heather, common cottongrass, purple moorgrass, sedges Carex spp., marsh marigold, ferns, bottle sedge, lesser celandine, golden saxifrage & common marsh-bedstraw. The nutrient rich conditions also support plants such as nettle, docks & grasses. Rare species supported by alder wet woodlands include elongated sedge Carex elongata & large bitter-cress Cardamine amara.
Current Status in UK & Northern Ireland
- The total extent of wet woodland in the UK is unknown but is estimated between 50,000 & 70,000 ha (JNCC, 2001).
- In Northern Ireland wet woodland occupies an estimated 2,600ha (EHS unpublished estimates, based upon Graham, 1975), but this is a probable underestimate. The condition of wet woodland in NI is unknown.
- As a result of past large-scale clearance, much of the current wet woodland resource in NI is secondary & less than 100 years old (Paul Corbett, pers. comm.). As they mature, wet woodlands support greater species diversity.
- Wet woodlands tend to be scattered in small stands of 3-5 ha in size (Cabot, 1999; NIEA, 2005).
- Due to the inaccessibility of wet woodlands, they have been generally unmanaged & are often used for grazing & shelter by livestock.
- Wet woodlands are threatened by grazing pressure, habitat loss & fragmentation, air pollution, climate change, nutrient enrichment & changes in water levels due to drainage, peat extraction & agricultural practices. Invasion by species such as sycamore, rhododendron & giant hogweed can alter the woodland structure.
- Aghanloo Wood
- Breen Oakwood
- Cranny Falls
- Tow River Wood