Habitat account - Raised bogs and mires and fens


7150 Depressions on peat substrates of the Rhynchosporion 

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 7150 Depressions on peat substrates of the Rhynchosporion.  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 7150 Depressions on peat substrates of the Rhynchosporion. Click image for enlarged map.

Description and ecological characteristics

 

Depressions on peat substrates of the Rhynchosporion occur in complex mosaics with lowland wet heath and valley mire vegetation, in transition mires, and on the margins of bog pools and hollows in both raised and blanket bogs. The vegetation is typically very open, usually characterised by an abundance of white beak-sedge Rhynchospora alba, often with well-developed algal mats, the bog moss Sphagnum denticulatum, round-leaved sundew Drosera rotundifolia and, in relatively base-rich sites, brown mosses such as Drepanocladus revolvens and Scorpidium scorpioides. The Nationally scarce species brown beak-sedge Rhynchospora fusca and marsh clubmoss Lycopodiella inundata also occur in this habitat.

 

On lowland heaths in southern and eastern England this habitat occurs on humid, bare or recently exposed peat in three distinct situations:

 

     

  1. in and around the edges of seasonal bog pools, particularly on patterned areas of valley mire,
  2. in flushes on the edges of valley mires in heathlands, and
  3. in areas that are artificially disturbed, such as along footpaths and trackways and in old peat-cuttings and abandoned ditches.

 

In these southern localities, Depressions on peat substrates of the Rhynchosporion are often associated with NVC type M21 Narthecium ossifragum Sphagnum papillosum mire. In the north and west, within 7110 Active raised bogs and 7130 Blanket bogs, this habitat type is usually part of the transition between bog pools (NVC types M1 Sphagnum auriculatum bog pool community and M2 Sphagnum cuspidatum/recurvum bog pool community) and the surounding bog vegetation (mainly M17 Scirpus cespitosus Eriophorum vaginatum blanket mire and M18 Erica tetralix Sphagnum papillosum raised and blanket mire).

European status and distribution

 

This Annex I type appears to be widely distributed in the EU, especially in the Atlantic and Continental biogeographical regions.

UK status and distribution Click to view UK distribution of this habitat

 

Depressions on peat substrates of the Rhynchosporion is a rare habitat type in the UK that exhibits a narrow range of ecological variation and has a restricted geographical distribution. This habitat type has a very discontinuous distribution, being found in largest quantity on heaths in southern England and on blanket and raised bogs in western Britain, with an outlying example in East Anglia.

Site selection rationale

 

The SAC series includes the small number of sites supporting extensive vegetation mosaics in which this habitat type can be found. The sites selected reflect the discontinuous distribution of the habitat, and include examples from lowland valley mires and wet heath in the south and east, and from blanket bogs in the north and west.

 

Small fragmentary stands occur in a range of disturbed contexts, often covering less than 10 m2, and lacking the more notable species such as bog orchid Hammarbya paludosa and great sundew Drosera anglica; these have not been considered for site selection, on account of their poor quality.


Site accounts

Dorset Heaths Dorset and Somerset
The two Dorset Heaths cSACs, together with the New Forest, support a large proportion of the resource of Depressions on peat substrates of the Rhynchosporion within England. The habitat is widespread on the Dorset Heaths, both in bog pools of valley mires and in flushes. There are numerous valley mires within the Dorset Heaths, and the habitat type is most extensively represented here as part of a habitat mosaic. This location shows extensive representation of brown-beak sedge Rhynchospora fusca and is also important for great sundew Drosera anglica and bog orchid Hammarbya paludosa.
Dorset Heaths (Purbeck and Wareham) and Studland Dunes Dorset and Somerset
The two Dorset Heaths cSACs, together with the New Forest, support a large proportion of the resource of Depressions on peat substrates of the Rhynchosporion within England. The habitat is widespread on the Dorset Heaths, both in bog pools of valley mires and in flushes. There are numerous valley mires within the Dorset Heaths, and the habitat type is most extensively represented here as part of a habitat mosaic. This location shows extensive representation of brown-beak sedge Rhynchospora fusca and is also important for great sundew Drosera anglica and bog orchid Hammarbya paludosa.
Inverpolly Highlands and Islands
At this large upland site in north-west Scotland, Depressions on peat substrates of the Rhynchosporion are typically associated with bog pools and other areas of surface patterning within extensive 7130 Blanket bogs and valley mire systems. These areas are typically species-poor and contrast with sites selected in southern Britain.
Roydon Common and Dersingham Bog East Anglia
Dersingham Bog represents Depressions on peat substrates of the Rhynchosporion in eastern England. There are examples of this habitat type present in natural bog pools of patterned valley mire, in flushes on the margins of valley mire and locally in disturbed areas associated with trackways and paths in mire and wet heath. Mosaics containing this habitat type are important for bog orchid Hammarbya paludosa.
The New Forest Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
The New Forest, one of three sites selected in southern England, is considered to hold the largest area in England of Depressions on peat substrates of the Rhynchosporion, in complex habitat mosaics associated primarily with the extensive valley bogs of this site. The habitat type is developed in three situations: in natural bog pools of patterned bog surfaces, in flushes on the margins of valley mires and in areas disturbed by peat-digging, footpaths, tracks, ditches etc. In places the habitat type is rich in brown mosses Cratoneuron spp. and Scorpidium scorpioides, suggesting flushing by mineral-rich waters. The mosaics in which this habitat type occurs are an important location for bog orchid Hammarbya paludosa.
Thursley, Ash, Pirbright and Chobham Surrey, East and West Sussex
This site contains examples of Depressions on peat substrates of the Rhynchosporion in south-east England, where it occurs as part of a mosaic associated with valley bog and wet heath. The vegetation is found in natural bog pools of patterned valley mire and in disturbed peat of trackways and former peat-cuttings.
Woolmer Forest Hampshire and Isle of Wight
In this west Wealden site, seepage mires and other waterlogged areas are a minor feature amongst predominantly wet heath habitat. Seepages are fed from a mix of acidic and calcareous sources, and give rise to a series of pool and hummock structures within the mire. The Rhynchospora alba occurs within NVC type M21 Narthecium ossifragum Sphagnum papillosum mire. It includes a range of bog-mosses Sphagnum spp., cottongrasses Eriophorum angustifolium and E. vaginatum, bog asphodel Narthecium ossifragum, cranberry Vaccinium oxycoccos and the rare marsh clubmoss Lycopodiella inundata.

SACs/SCIs/cSACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection

Caithness and Sutherland Peatlands Highlands and Islands
Claish Moss and Kentra Moss Highlands and Islands
Coladoir Bog Highlands and Islands
Cors Caron West Wales and The Valleys
Cors Fochno West Wales and The Valleys
Eilean na Muice Duibhe Highlands and Islands
Eryri/ Snowdonia West Wales and The Valleys
Feur Lochain Highlands and Islands
Flow of Dergoals South Western Scotland
Foinaven Highlands and Islands
Kilhern Moss South Western Scotland
Kirkcowan Flow South Western Scotland
Lewis Peatlands Highlands and Islands
Loch Maree Complex Highlands and Islands
Merrick Kells South Western Scotland
Mochrum Lochs South Western Scotland
Mointeach nan Lochain Dubha Highlands and Islands
Mointeach Scadabhaigh Highlands and Islands
North Harris Highlands and Islands
Preseli West Wales and The Valleys
Rannoch Moor Eastern Scotland, Highlands and Islands
Rhinog West Wales and The Valleys
Rum Highlands and Islands
Sligachan Peatlands Highlands and Islands
Subberthwaite, Blawith and Torver Low Commons Cumbria
 

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