BG1A Sphagnum cuspidatum – Sphagnum subsecundum agg. hollow
Vegetation
Sphagnum mosses dominate this low-growing community, with Sphagnum cuspidatum and/or Sphagnum subsecundum agg. (typically Sphagnum denticulatum) filling bog pools or forming luxurious quaking mats or carpets. Eriophorum angustifolium is the only other constant species. Rhynchospora alba is sometimes found growing through the Sphagnum layer and can be abundant, and Menyanthes trifoliata is frequent in wetter areas. Drosera spp., Molinia caerulea and Narthecium ossifragum are occasionally encountered, and Schoenus nigricans can be found on blanket bogs, but diversity in terms of species numbers is quite low. Other Sphagnum species, including Sphagnum papillosum, Sphagnum magellanicum (= Sphagnum divinum/medium), Sphagnum capillifolium and Sphagnum palustre each occur only infrequently.
Ecology
This is a frequently inundated community of wet hollows, pools and pool margins of raised bogs and blanket bogs in the lowlands. It primarily occurs on deep, acidic, oligotrophic, ombrogenous peats. Sphagnum-dominated springheads from upland slopes can also be assigned to this community but so far have been poorly sampled. Mean altitude = 151 m, n = 18; mean slope = 0.5°, n = 17; mean extent of bare peat = 0.7%, n = 14.
Sub-communities
Two sub-communities are described for this community. The Sphagnum cuspidatum sub-community (BG1Ai) represents this niche on midland raised bogs on which Sphagnum subsecundum agg. seldom occurs. The Sphagnum subsecundum agg. – Schoenus nigricans sub-community (BG1Aii) represents western raised bogs and blanket bogs, where both of these Sphagnum species are usually found.
Similar communities
In no other community are Sphagnum cuspidatum and Sphagnum subsecundum agg. as dominant as they are here and this serves to differentiate this community from others in which Eriophorum angustifolium or Rhynchospora alba may be abundant (e.g. BG1B or BG1D).
Conservation value
Many examples of this community qualify as EU HD Annex I habitat 7130 Blanket bog (active)* or 7120 Raised bog (active)* although some examples could potentially be from 7120 Degraded raised bog. Wherever Rhynchospora alba is abundant in hollows, however, this type of vegetation is better treated as habitat 7150 Rhynchosporion depressions. This is on average a species-poor community (species/4 m2 = 11.6, n = 27), but 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.