|Scientific name||Betula pubescens – Sphagnum palustre woodland|
|Common name||Downy Birch – Blunt-leaved Bog-moss woodland|
Download full pdf synopsis: WL4C
Betula pubescens is the sole constant of the low canopy of this community. Salix cinerea is the only other tree species likely to be encountered, accompanying Betula in the canopy or forming an understorey. The field layer is often strikingly dominated by tussocks of Molinia caerulea, amongst which can also be found Dryopteris dilatata, Rubus fruticosus agg. and Juncus effusus. A key characteristic is the usual abundance of Sphagnum species in the bryophyte layer, chiefly Sphagnum palustre, but also Sphagnum fimbriatum, Sphagnum capillifolium, Sphagnum recurvum agg. and Sphagnum squarrosum. Thuidium tamariscinum, Scleropodium purum and Hypnum cupressiforme are constants within this layer.
This community comprises open stands of birch woodland on soils with a fairly high water table or a high degree of flushing, typically occurring on basin peats or occasionally on peaty gleys. It is often found in peaty hollows at higher altitudes but also included here are stands of intact and degraded raised bog systems in the lowlands. Consequently, it largely occurs on level ground. Soils are very acidic and markedly infertile.
Two sub-communities have been described for this community. In the Calluna vulgaris–Eriophorum vaginatum sub-community (WL4Ci), bogland species are abundant and Pinus sylvestris may occur. The Rubus fruticosus-Potentilla erecta sub-community (WL4Cii) is somewhat less acidic and lacks these indicators, but Molinia caerulea and the titular species are more frequent.
Molinia caerulea is also a prominent plant within the wet birch woodlands of community WL4E. That community, however, is not as highly acidic and oligotrophic as WL4F, so Sphagnum and most of the other indicators of bogs are infrequent.
This is not a particularly species-rich woodland community but it has a fairly diverse bryophyte flora. Many stands have a high Sphagnum cover and qualify as EU Annex I habitat 91D0 Bog woodland*.
These stands are threatened by any impacts that may alter the hydrological regime. Stands on intact raised bog are particularly vulnerable to the impacts on the water table that result from nearby turf-cutting. Other threats include overgrazing by deer or livestock, woodland clearance and invasion by non-native species such as Rhododendron ponticum.