BG1B Rhynchospora alba – Narthecium ossifragum bog
Vegetation
The main species in this rather open community are Rhynchospora alba, Molinia caerulea and Schoenus nigricans, accompanied by patches of Erica tetralix, Narthecium ossifragum and the wine-tipped leaves of Eriophorum angustifolium. The bryophyte layer is mostly composed of sphagna with Sphagnum papillosum constant and both Sphagnum cuspidatum and Sphagnum subsecundum agg. frequent, but dark conspicuous patches of Campylopus atrovirens will also be often seen. The sticky rosettes of Drosera spp. are also characteristic of this community with Drosera rotundifolia and Drosera intermedia constant species, while Drosera anglica is a frequent find. Menyanthes trifoliata is also frequent, occurring in particularly wet areas, while Myrica gale may be found where there is a little groundwater flushing.
Ecology
This is mainly a community of wet depressions in lowland blanket bogs but has also been recorded from raised bogs in the midlands (mean altitude = 88 m, n = 65; mean slope = 0.8°, n = 59). It occurs on acidic, oligotrophic, ombrogenous deep peats (mean extent of bare peat = 15.8%, n = 71).
Sub-communities
There are two sub-communities described. The Sphagnum subsecundum agg. – Potamogeton polygonifolius sub-community (BG1Bi) represents wetter examples of this vegetation possibly with some flushing and in which one will find species such Menyanthes trifoliata, Potamogeton polygonifolius, Carex limosa, which are not encountered in the typical Calluna vulgaris – Campylopus atrovirens sub-community (BG1Bii).
Similar communities
The vegetation here is close to that of BG1A Sphagnum cuspidatum – Sphagnum subsecundum agg. bog but the cover of sphagna is not so high, Rhynchospora alba is more frequently present and Molinia caerulea and Schoenus nigricans are more prominent.
Conservation value
Almost all examples of this community qualify as EU HD Annex I habitat 7150 Rhynchosporion depressions. This is on average a moderately species-rich community (species/4 m2 = 17.5, n = 130) that supports several specialists.
Management
The main threat to the bogs supporting this vegetation is turf-cutting, either by hand or machine, and associated drainage. Some sites have also suffered from afforestation. Locally, action has been taken to address these impacts and some sites are managed strictly for conservation.