Synonymy

Juncus acutiflorus-Acrocladium cuspidatum nodum McVean & Ratcliffe 1962 p.p., Eddy et al. 1969; Juncus acutiflorus pasture Birse & Robertson 1967, 1973; Juncus acutiflorus-Acrocladium cuspidatum sociation Edgell 1969; Species-rich Juncetum effusi Eddy et al. 1969; Juncus acutiflorus-Filipendula ulmaria Association Birks 1973; Juncus articulatus-Acrocladium cuspidatum nodum Prentice & Prentice 1975; Potentillo-Juncetum acutiflori Birse & Robertson 1976, Birse 1980, 1984; Juncus acutiflorus-Sphagnum palustre nodum Adam et al. 1977 p.p.; Galium palustre nodum Daniels 1978 p.p.; Fen communities 27 & 28 Meade 1981; Junco acutiflori-Molinietum (O’Sullivan 1968) Ratcliffe & Hattey 1982 p.p:, Fen meadow Ratcliffe & Hattey 1982 p.p.

Constant species

Galium palustre, Holcus lanatus, Juncus effususlacutiflorus, Lotus uliginosus.

Physiognomy

The Juncus effusus!acutiflorus-Galiumpalustre rush-pasture is a rather ill-defined assemblage of vegetation characterised by the abundance of either Juncus effusus or J. acutiflorus, sometimes both, in a ground of mesophytic herbs of wide occurrence in moister agricultural grasslands. Diversity among the dominants is not very great (nothing like so locally varied as in the Juncus-Cirsium fen-meadow, for example), but the structure of the vegetation can show considerable differences according to the treatment history. And, though the flora is rarely strikingly rich, the associates are quite diverse, both across the whole range of the community and, on a local scale, from site to site and even within large stands. Such variation makes the bounds of this vegetation type hard to fix, both against other rushdominated communities, a problem that is greater towards the east of its distribution, and, increasingly to the west, against grasslands in which Molinia caerulea plays a prominent role.

Of the two rushes which usually dominate here, J. effusus is the commoner throughout, extending across the whole range of the community, though being distinctly more frequent and abundant in the more easterly sub-community through which this vegetation grades imperceptibly to the Holco-Juncetum. J. acutiflorus is much more distinctly western in its occurrence, rivalling or exceeding J. effusus in the other of the sub-communities, which is much more distinctive in its floristics and the usual type of this vegetation which has figured in previous accounts (e.g. McVean & Ratcliffe 1962, Birse & Robertson 1967, 1973,1976, Edgell 1969, Birks 1973, Adam et al. 1977, Ratcliffe & Hattey 1982).

Constant species

Montia fontana, Ranunculus flammula, R. omiophyllus, Sphagnum auriculatum.

Physiognomy

Ranunculus omiophyllus-Montia fontana rills typically have a rather crowded, though not always continuous, cover of vascular plants and bryophytes, much of the growth often submerged in the shallow waters, with a floating or shortly-emergent canopy. Ranunculus omiophyllus is often abundant, its delicate white summer flowers set off against the dark green of the floating leaves, and there is very frequently some Montia fontana. Then, the bronze-coloured floating leaves of Potamogeton polygonifolius are commonly prominent and there can be local patches of Agrostis stolonifera, Glyceria fluitans, Juncus bulbosus, J. articulatus and Callitriche stagnalis and scattered plants of Ranunculus flammula, Myosotis secunda and Stellaria alsine with, more occasionally, Ranunculus repens, Equisetum palustre, Hydrocotyle vulgaris, Galium palustre and Lotus uliginosus. Juncus bufonius and Scirpus setaceus can also sometimes be seen on open patches of wet mud. Bryophytes quite commonly make a substantial contribution to the cover, though the frequent species are very few. Often, there are red-brown clumps of Sphagnum auriculatum growing semi-submerged and freshgreen patches of Philonotis fontana but, apart from occasional Polytrichum commune, other species are sparse with just scattered records for such plants as Calliergon cuspidatum, C. stramineum, Drepanocladus exannulatus, D. vernicosus, Scapania irrigua and Rhytidiadelphus squarrosus.

Habitat

This community is typical of spring-heads and rills at moderate altitudes in south-western Britain, where there is irrigation with circumneutral and probably quite oligotrophic waters.

Phytogeographically, the Ranunculus-Montia com munity can be seen as an oceanic replacement for the Philonoto-Saxifragetum. It has been recorded only from south-western England, Wales and from around the Lake District, though further sampling may well reveal that it occurs throughout the British range of R. omiophyllus, an Oceanic West European plant which is found in central southern and south-west England, through much of north-west England and south-west Scotland. All known stands of the community fall within that part of the country with mild winters, where February minima are by and large more than 1 °C above freezing (Climatological Atlas 1952) though, apart from the presence of R. omiophyllus and the generally Atlantic S. auriculatum such conditions make themselves felt here mostly in a negative way, with the very obvious exclusion of species characteristic of montane springs, such as Saxifraga stellaris, Epilobium anagallidifolium, E. alsinifolium, Pohlia ludwigii, P. wahlenbergii var. glacialis and Bryum weigelii.

Synonymy

Sphagneto-Juncetum effusi, Carex rostrata facies Eddy et al. 1969; Carex lasiocarpa-Menyanthes trifoliata Association Birks 1973 p.p.; Carex rostrata-Carex limosa nodum Birks 1973 p.p.; Sphagno-Caricetum curtae Passarge 1964 sensu Birse 1980; Caricetum chordorrhizae Paul & Lutz 1941 sensu Birse 1980; Caricetum rostratae Dierssen 1982 p.p.; Caricetum limosae Dierssen 1982 p.p.; Caricetum lasiocarpae Dierssen 1982 p.p.

Constant species

Carex rostrata, Poly trichum commune, Sphagnum cuspidatum, S. recurvum.

Rare species

Carex chordorrhiza, Lysimachia thyrsiflora.

Physiognomy

The Carex rostrata-Sphagnum recurvum mire typically has a cover of sedges over a carpet of semi-aquatic Sphagna, with generally a very small contribution from vascular associates. Carex rostrata is the commonest sedge throughout, forming a usually rather open cover of shoots a few decimetres tall, but it can be accompanied by C. curta, C. lasiocarpa, C. limosa or C. nigra and the first two especially can be locally prominent, as in some stands in Birks’ (1973) Carex lasiocarpa-Menyanthes Association and the Sphagno-Caricetum curtae (Passarge 1964) of Birse (1980). The kind of vegetation in which the very rare C. chordorrhiza occurs in Sutherland is also probably best considered as part of this community (Birse 1980, who placed it in a distinct Caricetum chordorrhizae Paul & Lutz 1941). Occasionally, this taller element is enriched by Eriophorum angustifolium, though this is typically less frequent here than in the Rhynchosporion bog pools, or by Juncus effusus or J. acutiflorus, though these do not show the regular pattern of dominance that they can exhibit in the Carex echinata-Sphagnum mire.

Beneath this cover, there is a generally extensive soft wet carpet of Sphagna, among which Sphagnum recurvum and S. cuspidatum are the most frequent and usually the most abundant. S. auriculatum (including var. inundatum) occurs quite commonly, too, and there is the suggestion among the available samples that it shows the same increase towards more oceanic regions that can be seen in the Rhynchosporion (e.g. Birks 1973, Birse 1980). S. palustre is occasional and there are sparse records for S. subnitens and S. papillosum, but more base-tolerant S. squarrosum and S. teres are characteristically rare, a good contrast with the Carex rostrata-Sphagnum squarrosum mire. Other bryophytes are few, but Poly trichum commune is very frequent and it can be abundant in the carpet as scattered patches. Aulacomnium palustre and Calliergon stramineum occur very sparsely, a further distinction between this community and the Carex-Sphagnum squarrosum and Carex-Sphagnum warnstorfii mires.

Synonymy

Vaccineto-Callunetum hepaticosum McVean & Ratcliffe 1962, Birks 1973; Vaccinium-Sphagnum-Hymenophyllum wilsonii nodum Prentice & Prentice 1975; H erber ta adunca-Calluna vulgaris Association Birse 1984.

Constant species

Blechnum spicant, Calluna vulgaris, Deschampsia flexuosa, Potentilla erecta, Vaccinium myrtillus, Dicranum scoparium, Hylocomium splendens, Hypnum cupressiforme s.l., Plagiothecium undulatum, Pleurozium schreberi, Rhytidiadelphus loreus, Sphagnum capillifolium.

Rare species

Anas trophy llum donianum, A. joergensenii, Bazzania pearsonii, Campylopus setifolius, Colura calyptrifolia, Mastigophora woodsii, Myurium hochstetteri, Plagiochila carringtonii, Scapania ornithopodioides. Physiognomy The Calluna vulgaris-Vaccinium myrtillus-Sphagnum capillifolium heath has a mixed canopy of sub-shrubs, usually 3-5 dm tall, with a damp layer of luxuriant bryophytes. Calluna vulgaris is usually the dominant ericoid, although Vaccinium myrtillus is also constant and Empetrum nigrum, almost always ssp. hermaphroditum, is present in many stands, and each of these can show modest abundance. Erica cinerea occurs quite frequently, although it becomes distinctly patchy in the most humid situations occupied by this vegetation, and there is occasionally some V. vitis-idaea. In its general composition, then, the canopy is like that of much Calluna-Vaccinium heath, although E. nigrum ssp. nigrum tends to be the predominant crowberry there and, more importantly, regeneration after burning plays a large part in determining the floristics and structure of the sub-shrub element, and the associated flora, at any particular time. With the Calluna-Vaccinium-Sphagnum heath, on the other hand, fire is highly inimical to the distinctive composition of the richest stands and, though this vegetation sometimes experiences light grazing, treatments are not of consequence in maintaining its characteristic features. Other sub-shrubs figure very occasionally, with sometimes a little Arctostaphylos uvaursi, A. alpinus or Juniperus communis ssp. nana, but the general scarcity of these species helps separate the community from the Calluna-Juniperus heath, a vegetation type of rather similar geographical range and particular habitat requirements.

As in the Calluna-Vaccinium heath, Deschampsiaflexuosa and Potentilla erecta are both very common among the associates, although they are usually present here as sparse, scattered individuals. More distinctively in this heath, there is constant Blechnum spicant and frequent records for Solidago virgaurea and Listera cordata, the last Northern Montane plant providing one of the floristic links between this community and our native pine and related juniper and birch woods.

There is a clear contrast, among the Cardamino-Montion springs and flushes of acid to circumneutral habitats, between the upland communities described above, where Montia fontana, Saxifraga stellaris and Philonotis fontana are conspicuous and the vegetation of lowland and often shaded situations, in which Chrysosplenium oppositifolium occurs with such bryophytes as Hookeria lucens, Rhizomnium punctatum, Trichocolea tomentella, Pellia epiphyIla and Conocephalum conicum. Such assemblages were used by Westhoff & den Held (1969) to diagnose distinct sub-alliances within the Cardamino-Montion, the sub-montane and montane Montion and the lowland Cardaminion. The latter kind of vegetatation has not been separately sampled in this survey but it figures in the field and ground layers of various wet woodlands, notably the Alnus-Carex, Alnus-Urtica and Alnus-Fraxinus-Lysimachia types, where it is distinctive of seepage lines and damp stream banks, quite often with Cardamine flexuosa, C. amara and Chrysosplenium alternifolium (see also Oberdörfer 1977). Similar mixtures of plants can also be found widely through lowland Britain, especially in the wetter west and around the upland fringes, along stream sides and wet banks which were probably once wooded but where shade is now provided by tall herbs or by virtue of the aspect of the sites. These need further sampling to see if the kinds of communities identified on the Continent occur here.

Synonymy

Molinietum caeruleae Rankin 1911b, Tansley 1939 p.p.; Molinia consocies Summerhayes & Williams 1926; Submoorland heath Muir & Fraser 1940 p.p.; Gentiana pneumonanthe localities Simmonds 1946; Damp heath Rose 1953; Wet heath Rose 1953, Rutter 1955, Newbould 1960, Ivimey-Cook & Proctor 1967; Three-species heath Williams & Lambert 1959; Calluna-Erica tetralix wet heath Gimingham 1964 p.p., Bannister 1966 p.p.; Ericetum tetralicis boreoatlanticum Ivimey-Cook et al. 1975; Campylopo-Ericetum tetralicis Birse & Robertson 1976 p.p.; Mire noda 1-5 Daniels 1978 p.p.; Narthecio-Ericetum tetralicis Moore (1964) 1968 sensu Birse 1980 p.p.

Constant species

Calluna vulgaris, Erica tetralix, Molinia caerulea, Sphagnum compactum.

Rare species

Erica ciliaris, Gentiana pneumonanthe, Lepidotis inundata, Rhynchospora fusca.

Physiognomy

The Ericetum tetralicis is characteristically dominated by mixtures of Erica tetralix, Calluna vulgaris and Molinia caerulea, but the proportions of these are very variable, being influenced by differences in the water regime and trophic state of the soils, and also by grazing and burning, the last factor being able to transform the appearance of particular stands over short periods of time and producing great structural diversity within a small compass (e.g. Williams & Lambert 1961). E. tetralix often grows very vigorously here, typically on these wetter soils adopting a semi-prostrate habit (Bannister 1966). Calluna, on the other hand, is often subordinate and of somewhat weak growth (Gimingham 1972), though it can become abundant in drier stands or where there has been deliberate encouragement by controlled burning. In other situations, Molinia is very much the dominant, with the ericoids reduced to sparsely-scattered bushes among dense tussocks of the grass, such that some accounts of the community have grouped it within a broadly-defined Molinietum (Rankin 1911b, Summerhayes & Williams 1926, Tansley 1939).

Typically, however, no other sub-shrubs attain high frequency through the community as a whole, though some can be of local importance. Thus, Erica cinerea and Ulex gallii figure occasionally, and sometimes with local abundance, in transitions to drier heaths in southwest England, and E. cinerea and U. minor can occur in similar situations further east. More strikingly, around Poole Harbour and in Cornwall, the Ericetum provides one of the loci for the nationally-rare E. ciliaris and its hybrids with E. tetralix ( = E. × watsonii Benth.: Chapman 1975).

Synonymy

Anthelia julacea-Deschampsia cespitosa provisional nodum McVean & Ratcliffe 1962; Anthelia julacea banks Birks 1973.

Constant species

Deschampsia cespitosa, Anthelia julacea, Marsupella emarginata, Scapania undulata, Sphagnum auriculatum.

Rare species

Anthelia juratzkana, Pohlia ludwigii.

Physiognomy

In the Sphagno auriculati-Anthelietum julaceae, Anthelia julacea more than justifies the claim of McVicar (1912) that it is ‘the most conspicuous hepatic of our highland mountains’. For though its individual shoots are threadlike, they are here massed into extraordinarily robust and dense tufts, cushions or huge swelling masses, up to a metre or more thick and sometimes covering as much as several square metres in total extent. Dull and glaucous when kept wet, as they typically are, or occasionally drying out to a pale grey colour, the larger mats and banks can scarcely be missed, even from a distance.

In terms of its associated flora, however, this is generally a rather species-poor assemblage, with vascular plants being especially sparse. Among other bryophytes, Sphagnum auriculatum, Marsupella emarginata (both var. emarginata and var. aquatica) and Scapania undulata are all constant and, though none rivals A. julacea itself in abundance, the first in particular can be found as patches of moderate size, often prominent by virtue of their coppery hue. Racomitrium lanuginosum and Philonotis fontana are also quite frequent, with Calliergon sarmentosum, Campylopus atrovirens, Polytrichum commune and Racomitrium fasciculare occurring occasionally. Rare bryophytes recorded here include Anthelia juratzkana, which seems totally to replace A. julacea in some stands (McVean & Ratcliffe 1962), and Pohlia ludwigii.

The commonest vascular plant in the community is Deschampsia cespitosa (presumably sometimes ssp. alpina at higher altitudes) and this is typically found as small tufts set in the bryophyte cushions. Scattered plants of Nardus stricta also occur quite often with occasional Narthecium ossifragum, Pinguicula vulgaris, Carex demissa and Saxifraga stellaris. Less frequent are Eriophorum angustifolium, Carex bigelowii, C. nigra, Festuca vivipara, Agrostis canina, A. stolonifera, Juncus bulbosus, Thalictrum alpinum and Viola palustris.

The available data do not indicate any well-marked sub-divisions within the community, though there is a suggestion that Racomitrium lanuginosum, Nardus and Narthecium might define one sub-group, with Philonotis fontana, Calliergon sarmentosum, Carex demissa and Pinguicula vulgaris preferential to another.

Synonymy

Valley moor plashes Rankin 1911 b p.p.; Hyperico-Potamogetonetum sensu Birse 1980, Ratcliffe & Hattey 1982, Dierssen 1982; Flushing Water Community NCC New Forest Bogs Report 1984 p.p.

Constant species

Hypericum elodes, Juncus bulbosuslkochii, Potamogeton polygonifolius, Ranunculus flammula, Sphagnum auriculatum.

Rare species

Galium debile, Pilularia globulifera.

Physiognomy

The Hyperico-Potametum polygonifolii has a very distinctive appearance, typically consisting of low creeping or floating mats of Hypericum elodes and Potamogeton polygonifolius, the former prominent with its soft tomentose shoots, the flowering ones shortly erect, against the olive-green foliage of the latter, lying flat on the surface of the water or the wet soil of the small runnels and pools in which this vegetation characteristically grows. Very often, except where the ground has been badly trampled by grazing animals, a feature of some of the stands included in Ratcliffe & Hattey (1982) and the NCC New Forest Bogs Report (1984), these two constants are set in a carpet of more or less submerged Sphagnum auriculatum, sometimes accompanied by S. cuspidatum, S. palustre or S. recurvum, and very occasionally with small patches of S. papillosum growing on the slightly raised areas. But other bryophytes are typically sparse: some stands show a modest local abundance of Polytrichum commune or Aulacomnium palustre, and Drepanocladus exannulatus, D. revolvens and Calliergon cuspidatum can also be found, but enrichment of this element of the vegetation is rare.

Neither is the associated vascular flora very extensive or consistent, being frequently confined to scattered plants of a variety of bog and poor-fen herbs, growing among the dominants or projecting above them as a very open canopy. Only Juncus bulbosus (very occasionally recorded as J. kochii) and Ranunculus flammula attain constancy among the companions but, of smaller species, Hydrocotyle vulgaris, Anagallis tenella, Drosera rotundifolia, Narthecium ossifragum and Galium palustre, all occur with moderate frequency, together with such sedges as Carex demissa, C. echinata, C. panicea and C. nigra. Then, there can be sparse shoots or small patches of Molinia caerulea, Agrostis canina ssp. canina, Juncus articulatus, J. effusus, J. acutiflorus, Eleocharis multicaulis, Eriophorum angustifolium and Rhynchospora alba.

Synonymy

Litter Godwin & Tansley 1929; Molinietum Godwin 1941, Willis & Jefferies 1959, Ivimey-Cook et al. 1975 p.p.; Molinia-edge Haslam 1965; Cirsio-Molinietum peucedanetosum (Sissingh & De Vries 1942) Wheeler 1978; Cirsio-Molinietum (Sissingh & De Vries 1942) Wheeler 1980c p.p.; Grassy Heath NCC Devon Heathland Report 1980.

Constant species

Carex panicea, Cirsium dissectum, Lotus uliginosus, Molinia caerulea, Potentilla erecta.

Rare species

Hypericum undulatum, Peucedanum palustre, Selinum carvifolia.

Physiognomy

The Cirsio-Molinietum caeruleae includes the bulk of the Molinia caerulea vegetation in the lowland south-east of Britain. Molinia is almost always the dominant plant in the community and it can be very abundant, forming the basis of a rough sward or occurring as a more stronglytussocky cover, a kind of structure well shown in the classic early account of this vegetation from Wicken Fen in Cambridgeshire (Godwin & Tansley 1929). And there are stands in which the abundance of Molinia is so overwhelming that its dense herbage and thick litter reduce the associated flora to scattered individuals of a very few species. Often, however, the number of companions is considerable: although many of the associates are plants of fairly wide distribution among damper meadows and pastures, the most frequent of them comprise a quite distinctive assemblage, and some of the preferentials attain such local prominence as to mask the major contribution which Molinia and the other constants make to the community. Much of this character reflects the origin of this kind of vegetation from rather diverse precursors by the application of particular treatments.

In structural terms, the most important associates of Molinia are other monocotyledons of medium stature, particularly rushes, which can make quite a substantial contribution to the dense layer of herbage characteristic of the community. Typically, this is 20-60 cm tall, though its physiognomy is strongly dependent on the style and incidence of treatment: in grazed stands, for example, the cover can be shorter than this, with stretches of close-cropped sward running among clumps of more resistant plants; where there is no grazing, and where the vegetation has not been mown for some time, the herbage can be taller and ranker. The trophic state of the substrate also influences the structure of the vegetation, with shorter and more open swards developing over more calcareous and impoverished soils.

Synonymy

Limestone heath Hope-Simpson & Willis 1955 p.p.; Agrosto-Ulicetum gallii Shimwell 1968 p.p.; Ulici-Ericetum cinereae Bridgewater 1970; Calluno-S cille turn vernae, Ulex gallii subassociation Malloch 1971 ; Calluna-Ulex gallii heaths Gimingham 1972; Grass-heath Ward et al. 1912a p.p.

Constant species

Calluna vulgaris, Erica cinerea, Ulex gallii.

Rare species

Agrostis curtisii, Viola lactea.

Physiognomy

The Calluna vulgaris-Ulex gallii heath is a floristically rather diverse community with only three constants overall, but its characteristic mixture of Calluna vulgaris, Ulex gallii and Erica cinerea, typically lacking E. tetralix, Molinia caerulea or Agrostis curtisii, is quite diagnostic. Often, the three sub-shrubs are co-dominant, though their proportions are quite variable and locally each can be poorly represented, E. cinerea in particular tending to become patchy where the community extends on to cooler aspects and to higher altitudes. In the latter situations, too, this kind of heath can have small amounts of Vaccinium myrtillus. On disturbed ground, as along pathways or over abandoned fields and settlements, U. europaeus may occur with some abundance.

Typically, the sub-shrub canopy is of high cover, sometimes excluding all but a very sparse herbaceous component but, quite often, the bushes are separated by systems of grassy runnels and, where the vegetation has been open to grazing, the structural contrast between these two components can be sharply accentuated. Where the bushes themselves are nibbled, a common occurrence, the canopy can be reduced in height: it is generally less than 30 cm, and a frequent picture is of dense ‘hedgehogs’ of gorse with short, but rather more untidy, bushes of heather scattered amongst them. In coastal stands, too, exposure to wind helps limit subshrub growth and, in exceptional cases, cliff-top heaths which are also heavily grazed can have a very tight cover of woody growth no more than a few centimetres high. Burning can also affect the structure and composition of the vegetation: controlled fires are rare but accidental burns can open up the ground, providing an opportunity for local dominance of U. gallii which can sprout vigorously from surviving buried stools, or E. cinerea, which can seed prolifically and out-perform Calluna in the early years of recovery, particularly on warmer aspects. Such temporary perturbations of dominance may also allow Pteridium aquilinum to increase its representation in this kind of heath.

The sampling of mire vegetation

In our survey of mires, the primary purpose has been to provide a classification of their vegetation according to its floristic composition, and not to categorise mires on the basis of their ecological development or hydrology, their situation in the landscape, or their gross morphology or fine surface patterning. Each of these other approaches to describing mires can yield benefits of its own, and we have tried to bring their various perspectives to bear in the interpretation of our results. Indeed, it was our hope that we might achieve some greater measure of understanding as to how the vegetation of mires relates to their form and function as perceived from these different standpoints. In the task of data collection, however, we were not concerned to dispose our samples according to any prior judgements about what did or did not constitute a particular kind of mire environment; rather, to ensure an adequate representation somewhere in our scheme of all vegetation types found in and around mires.

Most of that vegetation is described in this section of the work. Essentially, we are dealing here with communities made up of bryophytes, herbaceous plants and sub-shrubs sampled from a wide variety of bogs and wet heaths, fens, flushes, springs and soakways, where the ground is kept permanently or periodically waterlogged by high atmospheric humidity, a high ground watertable or lateral water flow. Many of the vegetation types occur on soils that are organic in character, but some are characteristic of mineral profiles, and the account presented here is thus not simply a classification of samples from peatlands, a category that is sometimes taken as synonymous with mires. On the other hand, there are certain kinds of vegetation which are often encountered in these different sorts of mires, indeed which frequently form an integral part of their mosaic of communities, but which are not included here. We did sample these, applying the same general principles of data collection throughout, but allowed the floristic distinctions among the vegetation types to emerge in the analyses, and have described certain communities in other sections of the work. Sometimes the reasons for this are more obvious, as with the various kinds of woodland that are associated with mires.

Synonymy

Mixed fen Holdgate 1955b p.p.; Carex nigra-Sanguisorba officinalis nodum Proctor 1974 p.p.; Carex nigra-Sanguisorba officinalis community Wheeler 1980c; Crepido-Juncetum Jones 1984.

Constant species Carex nigra, C. panicea, Crépis paludosa, Equisetum palustre, Filipendula ulmaria, Molinia caerulea, Potentilla erecta, Ranunculus acris, Succisa pratensis, Valeriana dioica, Calliergon cuspidatum.

Rare species

Primula farinosa.

Physiognomy

The Molinia caerulea-Crepis paludosa mire is a striking vegetation type, well-defined by a substantial block of constants and frequent companions, but showing quite considerable variation in its associated flora and embracing stands which, at one extreme, resemble swamp and, towards the other, are of a rank grassy character. Molinia caerulea is almost always present and it is often abundant, being the commonest dominant overall and frequently growing in a strongly-tussocky form, creating an irregular canopy up to 50 cm or so tall, and exerting a marked influence on the character and distribution of the associates. Among these are some other plants which can make a substantial contribution to the herbage. Carex nigra, for example, is a constant and it quite frequently occurs as prominent tufts or tussocks (var. subcaespitosa), sometimes rivalling or exceeding Molinia in its cover, particularly in the Sanguisorba sub-community (Proctor 1974). C. panicea can also be fairly abundant and C. pulicaris occurs commonly, too, though not usually as dense tufts. Then, in stands which are transitional to swamp, there can be some C. appropinquata, as at Malham Tarn in North Yorkshire (Proctor 1974), or C. rostrata, as at Sunbiggin Tarn in Cumbria (Holdgate 19556). In the Festuca subcommunity, by contrast, it is taller rushes and grasses which, together with Molinia, provide the bulk of the cover, Juncus acutiflorus forming locally dense patches, J. conglomeratus occurring as scattered tussocks. J. articulatus is also occasional throughout, though it often grows as a semi-decumbent plant and is rarely abundant.

The other important structural element typical of the community as a whole comprises hemicryptophyte dicotyledons which are capable of moderate to tall growth among the Molinia, sedges and rushes, but many of which can also subsist as rosettes in grazed stands. Most frequent among this group are Succisapratensis, Filipendula ulmaria, Valeriana dioica, Cirsium palustre, Caltha palustris and, adding a particularly distinct regional look, the Continental Northern Crépis paludosa and Northern Montane Trollius europaeus.

Synonymy

Oxyphilous fen vegetation Pallis 1911, Godwin & Turner 1933, Tansley 1939p.p.; Carex rostrata-Acrocladium cor difolium I cuspidatum sociation Spence 1964 p.p.; Carex lasiocarpa-Myrica & Myrica-Carex lasiocarpa sociations Spence 1964 p.p.; Carex nigra-Acrocladium sociation Spence 1964 p.p.; Carex rostrata-Aulacomnium palustre Association Birks 1973; Poor fen communities Proctor 1974 p.p.; General fen Adam et al. 1975 p.p.; Carex curta-Carex rostrata community Wheeler 1978; Caricetum lasiocarpae Koch 1926 sensu Birse 1980 p.p.

Constant species

Carex nigra, C. rostrata, Eriophorum angustifolium, Potentilla palustris, Succisa pratensis, Aulacomnium palustre, Sphagnum squarrosum.

Physiognomy

The Carex rostrata-Sphagnum squarrosum mire is a fairly heterogenous vegetation type characterised overall by the dominance of sedges with scattered poor-fen herbs over a patchy carpet of moderately base-tolerant Sphagna. The sedge cover is usually a few decimetres tall but quite variable in its abundance. The commonest species throughout are Carex rostrata and C. nigra, the former generally the more extensive and sometimes with a dense cover, the latter typically less abundant, though locally dominant, as in some stands of the Carex nigra-Acrocladium sociation described from Scottish lochs by Spence (1964) and in some of the Malham Tarn fens in North Yorkshire (Proctor 1974). C. lasiocarpa extends its occurrence among British mires into this kind of vegetation and it too can attain local prominence, so much so that stands which, on general grounds, clearly belong here have sometimes been included in distinct communities characterised by this sedge: e.g. the Carex lasiocarpa sociations of Spence (1964) and the Caricetum lasiocarpae (Koch 1926) of Birse (1980). C. curta, though generally more characteristic of oligotrophic and base-poor Rhynchosporion pools, is occasionally found (Spence 1964, Birks 1973, Wheeler 1978 who diagnosed a Carex curta-Carex rostrata community from the Ant valley in Norfolk) but C. limosa is typically absent. Likewise, towards the other extreme, C. diandra does not penetrate into this community: it is a good diagnostic species for the closely-related Carex rostrata-Calliergon mire. Finally, there may be a little C. echinata, especially where the Car ex-Sphagnum squarrosum mire extends on to firmer flushed peats.

Synonymy

Dune heath auct. angl., Calluna-Erica cinerea heath Gimingham 19646, 1972 p.p.; Calluna-Empetrum nigrum heath Gimingham 19646, 1972 p.p.

Constant species

Calluna vulgaris, Carex arenaria.

Rare species

Euphorbia portlandica, Trifolium suffocatum, Usnea flammea.

Physiognomy

Calluna vulgaris is the only constant sub-shrub throughout the Calluna-Carex arenaria heath, and it is often present in abundance, sometimes as an overwhelming dominant in rather impoverished vegetation. Generally, though, the cover of heather is discontinuous, decidedly patchy in younger or grazed stands, and there is frequently some other sub-shrub present, either intimately mixed with the Calluna or with the bushes of the codominants forming a more distinct mosaic. The most characteristic of these associaties is Erica cinerea, with Empetrum nigrum ssp. nigrum figuring in some places, and each of these can be abundant, locally to the exclusion of Calluna itself. Very occasionally, Ulex gallii can be found and in some stands Rosa pimpinellifolia is plentiful, with Erica tetralix and Salix repens occurring in transitions to wetter heath. Vaccinium myrtillus is typically very rare.

Even when some of these other sub-shrubs are present, the community can be distinguished from similar assemblages by the constancy of Carex arenaria, though this is hardly ever more than moderately abundant and often distinctly senile, except where the sand substrate becomes locally mobile, when renewed vigour and cover in the plant usually presage a transition to patches of Carex dune vegetation. Ammophila arenaria is also frequent through the community, though it is characteristically sparse and usually decidedly moribund, with just scattered shoots.

In more species-poor stands, little else than these plants may be represented, but other tracts of this kind of heath show considerable enrichment. First, among grasses, there is often some Festuca rubra or F. ovina (inadequately distinguished in the available data), with Agrostis capillaris and Anthoxanthum odoratum also occurring frequently in some situations and, less commonly, Poa pratensis (probably P. subcaerulea). The annuals Air a praecox and, more sparsely, A. caryophyllea can sometimes be found too. Apart from C. arenaria, sedges are absent though Luzula campestris occurs quite often.

Synonymy

Festuca ovina-Calluna ‘Rock Heath’ Coombe & Frost 1956ap.p.; Erica vagans-Ulex europaeus ‘Mixed Heath’, Genista pilosa variant Coombe & Frost 1956tz; Calluno-Scilletum vernae Malloch 1971 p.p.; Maritime heath Urquhart & Gimingham 1979p.p.; Genisto maritimae-Ericetum einereae Bridgewater 1970; Anthyllio corbierei-Ericetum cinereae Bridgewater 1970; Festuca ovina-Calluna vulgaris heath Hopkins 1983; Erica vagans-Ulex europaeus heath, Genista pilosa variant Hopkins 1983.

Constant species

Calluna vulgaris, Erica cinerea, Festuca ovina, Holcus lanatus, Hypochoeris radicata, Lotus corniculatus, Plantago lanceolata, P. maritima, Potentilla erecta, Scilla verna, Thymus praecox.

Rare species

Allium schoenoprasum, Astragalus danicus, Erica vagans, Euphorbia portlandica, Genista pilosa, Herniaria ciliolata, Isoetes histrix, Minuartia verna, Primula scotica, Scilla autumnalis, S. verna, Spiranthes spiralis, Trifolium bocconei, T. occidentale.

Physiognomy

In the Calluna vulgaris-Scilla verna heath, sub-shrubs are a consistent feature of the vegetation, though they are not always very obvious at first sight. For one thing, the canopy is typically of very short stature, rarely over 20 cm and usually less than 10 cm, with the bushes often wind-shaped over the unconformities of the ground. Then, the cover of the woody plants is rarely continuous and quite often rather open, particularly in unsheltered or rocky situations where it can be reduced to scattered bushes with stretches of grassy sward or exposures between. Even where the sub-shrubs are more extensive, their branches are commonly inter-penetrated by the herbs and, in grazed sites, which occur throughout the range of the community but which are especially preva Lent to the north, the whole vegetation can be trimmed to a neat, tight mat, just 2 or 3 cm high.

Of the sub-shrubs, Calluna vulgaris is the most frequent throughout and the commonest dominant though, on drier soils, it is characteristically accompanied by Erica cinerea and this, too, can be abundant. Where the community extends on to wetter ground, as it often does in the rainier north of the country, the latter is much reduced in frequency and E. tetralix and/or Empetrum nigrum ssp. nigrum (generally one or the other) are the more usual associates of Calluna and sometimes codominant with it.