Blanket bogs have developed on the Pennine uplands and cover vast areas with peat. Development of plant growth is very much limited by climatic extremes, and by the poorly-drained subsoil. This habitat is widespread in the Dales and makes up nearly 25% of the area. There are extensive tracts running down from Langstrothdale to Fountains Fell, and from Buckden Pike down to Appletreewick Moor – effectively those moors over 300 metres high within the Yoredale and Millstone Grit series. Bogs are also to be found in the Millstone grit moorland areas of mid-Wharfedale.
Species-poor cottongrass bog, overwhelmingly dominated by hare’s-tail cottongrass tussocks, usually has some some bog-moss present, mainly S. capillifolium and S. papillosum. Dwarf shrubs may be entirely absent but usually some heather or bilberry can be found. It is found on the Langstrothdale-Ribblesdale watershed.
A richer community occurs where the hare’s-tail cottongrass is partnered by an ericaceous species, most commonly heather. Sometimes the heather becomes dominant, particularly if the moor is managed for grouse. Where the moor is wetter, the bog-mosses expand and can dominate. On the higher hills this heather-cottongrass bog is an important habitat for cowberry and cloudberry with good amounts of other dwarf shrubs. Cowberry is an Arctic-Alpine plant which is mainly found in Scotland.
Bog-moss-rich bogs are the most diverse of the bog communities, and also the rarest. Dominant bog-mosses form a subtle patterning of ridges, hummocks and hollows and these bogs are usually actively growing. They are a habitat for specialised bog plants, including cranberry, bog asphodel and round-leaved sundew. Bog asphodel can form striking golden groups in limited areas, and round-leaved sundew is a well-known insectivorous plant. Large areas of these bogs have been destroyed by burning and drainage and atmospheric pollution reduces acidity and increases fertility.
Peat hags are found where the bog surface has dried out, with an increase in dwarf shrubs and Cladonia lichens. Higher up cowberry and cloudberry can become a feature of this habitat. Lower down, grouse moor management, with its regular disruption and burning, can produce dessication where heather is encouraged to take hold.
In upper Wharfedale there is some wet blanket bog at Oughtershaw and Beckermonds, in the Moss End enclosure. Hare’s-tail cottongrass, purple moor-grass, cross-leaved heath, bog asphodel and tormentil grow with bog mosses Sphagnum spp., and star moss Polytrichum commune.
Near Pen-y-ghent, by Churn Milk Hole, there is a valley bog system which supports bottle sedge Carex rostrata, white sedge C. curta and the bog moss Sphagnum recurvum.
On the Barden and Blubberhouses moors there are some deep mires on the higher moorland. Hare’s-tail cotton-grass is dominant, with cross-leaved heath, crowberry, common cotton-grass and heather. Cloudberry is locally abundant on Henstone Band Side and Thorpe Fell. The richer vegetation in wetter areas includes cranberry, bog asphodel, cross-leaved heath, round-leaved sundew and bog rosemary.
Moorland dominated by crowberry is particularly extensive on Ilkley Moor, with wet heath containing cross-leaved heath and cranberry which have developed on the blanket mires.
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