Constant species

Lythrum portula, Ranunculus flammula.

Rare species

Alopecurus aequalis, Pilularia globulifera.

Physiognomy

The Lythrum portula-Ranunculus flammula community comprises generally open vegetation in which L. portula and R. flammula are the only constants, the former sometimes occurring with abundance, occasionally in locally monodominant stands. Apart from Eleocharis palustris, other associates are recorded rather sporadically and only rarely with high cover values, but can be quite varied: Agrostis stolonifera, Juncus bufonius, J. effusus, J. articulatus, Galium palustre, Callitriche stagnalis, Littorella uniflora, Mentha aquatica, Alisma plantago-aquatica, Myosotis scorpioides and Apium inundatum have all been found here. The community also provides a locus for the nationally rare Pilularia globulifera, a perennial plant but one quick to colonise the damp open muds characteristic of this vegetation (Jermy in Stewart et al. 1994), Limosella aquatica, an ephemeral herb, and Alopecurus aequalis, an annual grass which invades here as water levels drop (Hubbard 1984, Twist in Stewart et al. 1994).

Habitat

The Lythrum-Ranunculus community is typical of silty or peaty soils, wetted and exposed by fluctuating or temporary waters around pool, lake and reservoir margins and in flooded gravel and brick-earth workings.

Compared with the habitats of Bidention assemblages, the situations colonised by this vegetation are not nutrient-rich and, though the cover of the sward can be extensive, the herbage does not have the lush character of those nitrophilous ephemeral communities.

Synonymy

Obionetum and Halimionetum auct. angl.

Constant species

Halimione portulacoides, Puccinellia maritima.

Rare species

Arthrocnemum perenne, Frankenia laevis, Inula crithmoides, Limonium bellidifolium, Suaeda vera.

Physiognomy

This is a closed, species-poor association in which Halimione portulacoides is constant and physiognomically conspicuous as a bushy canopy up to 50 cm high or as a virtually prostrate carpet. Puccinellia maritima is also constant and there is frequently a little Suaeda maritima and sparse records for a variety of species from both low and upper marsh. Epiphytic algae are often abundant on the lower stems of the H. portulacoides and at some sites small patches of fucoids are present beneath canopy gaps.

Sub-communities

Géhu & Delzenne (1975) allocated samples of Halimione portulacoides vegetation with the red alga Bostrychia scorpioides to the separate association Bostrychio-Halimionetum portulacoidis (Corillion 1953) R.Tx. 1963. Although B. scorpioides was recorded occasionally here, there is no substantial floristic reason for distinguishing samples containing this species as even a sub-community within the Halimionetum. The three following subcommunities are, however, quite distinct.

Sub-community with Halimione portulacoides dominant.

In this most species-poor sub-community, H. portulacoides always has high cover values (usually >90%) and there is usually a sparse undercover of Puccinellia maritima and some Suaeda maritima. The H. portulacoides may be present as a low or tall even-topped canopy or as discrete hemispherical bushes 1–2 m diameter and up to 50 cm high.

Synonymy

Armeria maritima-Aster tripolium provisional nodum Ivimey-Cook & Proctor 1966 p.p.; Crithmum maritimum rock-crevice community Proctor 1975; Crithmion communities Shimwell 1976 ms.

Constant species

Crithmum maritimum, Spergularia rupicola, Festuca rubra, Armeria maritima.

Rare species

Parapholis incurva, Limonium recurvum (and probably other apomicts of the L. binervosum group, e.g. L. paradoxum, L. transwallianum; see also Ingrouille 1981).

Physiognomy

The Crithmo-Spergularietum has a low-growing, very open cover of scattered vascular perennials rooted in rock crevices. The distribution of the plants and the overall appearance of the vegetation are strongly influenced by the nature of the substrate and, in general, none of the association constants can be said to be truly dominant, though all but Spergularia rupicola may be particularly abundant in individual stands. Plantago maritima is the most frequent associate throughout the association. Bryophytes are rarely conspicuous with only Schistidium maritimum and Tortella flavovirens recorded very occasionally. The only lichens are epilithic.

Sub-communities

Typical sub-community: Crithmo-Spergularietum rupicolae typicum Géhu 1964. The four association constants here account for the bulk of the vegetation cover and, of the associates, only Plantago maritima and P. coronopus attain a constancy above I.

Iula crithmoides sub-community: Crithmo-Spergularietum rupicolae plantaginetosum coronopi Géhu 1964 p.p. Spergularia rupicola is rather less frequent in this sub-community but Inula crithmoides and Plantago coronopus are both constant and the former may be abundant. Limonium binervosum (including its apomicts), Parapholis incurva and Desmazeria marina are all preferentially frequent.

Synonymy

Asplenium trichomanes-Fissidens cristatus Association Birks 1913 p.p.

Constant species

Asplenium ruta-muraria, Asplenium trichomanes, Homalothecium sericeum, Porella platyphylla.

Rare species

Hornungia petraea, Silene nutans.

Physiognomy

The Asplenietum trichomano-rutae-murariae comprises generally very open and often fragmentary stands of crevice vegetation in which diminutive ferns and bryophytes are the most distinctive components. The commonest ferns here are Asplenium ruta-muraria and A. trichomanes, the latter almost always the tetraploid ssp. quadrivalens according to Page (1982) although, on Skye, most of the plants examined have proved morphologically intermediate between this and the diploid ssp. trichomanes (Wood 1969). Both A. trichomanes and A. ruta-muraria are more or less evergreen plants whose small rosettes are very frequent here but of low total cover. The bulkier A. adiantum-nigrum occurs very rarely in the community but A. viride is typically absent. Ceterach officinarum is a good preferential but it is only really common in this vegetation towards the south and west of Britain.

Among other perennial vascular plants, only Festuca ovina, Koeleria macrantha, Thymus praecox, Sedum acre and Helianthemum nummularium occur with any frequency, with Arenaria serpyllifolia and Saxifaga tridactylites figuring as ephemerals, but all of these species are strongly preferential to one sub-community which is transitional to rocky turf where the cover of plants is greater. Through the community as a whole, the other prominent element in the vegetation comprises bryophytes whose cushions and mats can cram the crevices and spread out a little way over the rock surfaces.

Synonymy

Carex arenaria community West 1936, 1937; Corynephorus canescens localities Marshall 1967 p.p.; Carex arenaria vegetation Noble 1982 p.p.

Constant species

Carex arenaria.

Rare species

Astragalus danicus, Corynephorus canescens.

Physiognomy

The Carex arenaria community includes very open to more or less closed swards in which the sand-sedge is the most abundant plant, where vascular associates are few in number and usually sparsely distributed and where there is hardly any contribution from mosses or lichens on what is often still a somewhat mobile sand surface. Where the sedge is invading freshly-deposited material, its initial cover may be very low, the shoots emerging, spaced out and generally single, in striking straight lines from the far-creeping rhizomes. If accretion continues at a fairly modest rate, well-established plants can keep pace but, as the sand starts to become stabilised, clones can thicken up very considerably with densely-packed shoots growing tiller-like from short, closely-spaced branches. Up to several hundred shoots per m2 have been recorded in this vegetation, but vigour is affected by soil conditions in a particular stand and by grazing which can reduce the sedge to very squat proportions (Tidmarsh 1939, Noble 1982).

In younger stands, or where C. arenaria has preempted a site and remained strongly dominant, there may be very little else growing among it.

Constant species

Galium aparine, Urtica dioica.

Rare species

Allium triquetrum.

Physiognomy

The Urtica dioica-Galium aparine community comprises generally species-poor tall-herb vegetation dominated by often densely abundant U. dioica, frequently growing over 1 m high by mid-summer. G. aparine is the only other constant throughout and it typically forms sprawls among the nettles. Poa trivialis is also common and locally quite extensive as a thin carpet of shoots over the ground and among the nettle stools. Through the community as a whole, no other species occurs with any frequency and, by late autumn, the bulk of the herbage collapses and is rapidly incorporated through the winter to leave ground that can be virtually bare.

Sub-communities

Typical sub-community. Here, the usual very dense nettle and goosegrass cover has scattered plants of Cirsium arvense and occasional Bromus sterilis. Seaside stands often have Smyrnium olusatrum, sometimes in local abundance.

Arrhenatherum elatius-Rubus fruticosus agg. sub-community. In this vegetation, the cover of nettle is not usually so thick and there are scattered tussocks of Arrhenatherum elatius, patches of Rubus fruticosus agg. and, by early summer, emergent flowering shoots of first, Anthriscus sylvestris, and then Heracleum sphondylium. In somewhat more open places, there can be seen Taraxacum officinale agg., Lolium perenne, Dactylis glomerata, Bromus mollis, Achillea millefolium and Potentilla reptans while Hedera helix can form a patchy ground carpet.

Synonymy

Airo multiculmis-Arnoseridetum minimae (Allorge 1922) R.Tx. 1950 sensu Silverside 1977.

Constant species

Anagallis arvensis, Briza minor, Rumex acetosella, Silene gallica, Trifolium dubium.

Rare species

Briza minor, Silene gallica, Trifolium suffocatum.

Physiognomy

In the Briza minor-Silene gallica community, common annuals like Anagallis arvensis, Trifolium dubium, Aphanes microcarpa and Vicia sativa ssp. nigra, together with Rumex acetosella, are very common constituents of the open cover. However, the more striking feature here is the constancy of the two nationally scarce annuals Silene gallica and Briza minor.

Other diminutive ephemeral grasses also figure with some frequency: Bromus hordeaceus ssp. thominei, Vulpia bromoides, the scarcer V. myuros, Aira caryophyllea (including plants sometimes distinguished as ssp. multiculmis) and A. praecox. There are also typically sporadic elements of the swards within which this assemblage develops, like sparse fronds of Pteridium aquilinum pushing up into open ground, and occasional Anthoxanthum odoratum, Hypochoeris radicata and Plantago lanceolata.

Other occasionals of the community include Geraniummolle, Chrysanthemum segetum, Sherardia arvensis, Veronica arvensis, Myosotis ramosissima, Ornithopus perpusillus and sometimes naturalised representatives of the bulb crops among which this vegetation often occurs, like Allium triquetrum and Gladiolus byzantinus. The nationally rare Trifolium suffocatum has been recorded here and three naturalised introductions that can occur are Briza maxima, Phalaris minor and Bromus diandrus.

Habitat

The Briza-Silene community is confined to disturbed sandy soils in the extreme oceanic climate of the far south-west of Britain where it now occurs most characteristically among the bulb fields of The Scillies.

Synonymy

Rorippa islandica-Gnaphalium uliginosum community Birse 1984.

Constant species

Filaginella uliginosa, Rorippa palustris.

Rare species

Limosella aquatica.

Physiognomy

The Rorippa palustris-Filaginella community comprises open or closed vegetation in which R. palustris and Filaginella uliginosa are the most consistent feature and where either can be abundant over patches of damp mud, but which may also be variously dominated by the occasional to frequent annual knotweeds, Polygonum persicaria, P. hydropiper and P. aviculare. Bidens tripartita also occurs commonly but not usually with any abundance and there is usually some Juncus bufonius. Other plants recorded occasionally are Plantago major, Lythrum portula, Littorella uniflora and the grasses Agrostis stolonifera, Alopecurus geniculatus, Poa annua and Phalaris arundinacea. Scattered individuals of Rumex crispus, R. obtusifolius, Chenopodium rubrum, Cirsium arvense and Epilobium obscurum may catch the eye but such species are never common. This community can provide a locus for the nationally rare Limosella aquatica.

Habitat

The Rorippa-Filaginella community is characteristically found in periodically-flooded, eutrophic muds and sands around the margins of fluctuating pools, lakes and reservoirs, on islands and banksides in mature river systems and in ruts along paths and trackways.

The community depends upon the exposure of bare, damp substrates by lowering of water-tables in rivers and lakes after the winter or by evaporation from smaller pools and flooded ruts with the warmth of spring.

Synonymy

Ammophiletum arenariae Moss 1906, Tansley 1911, 1939, all p.p.; Elymo-Ammophiletum arenariae Br.-Bl. & De Leeuw 1936; Ammophila arenaria stands Gimingham 1964a p.p.

Constant species

Ammophila arenaria.

Rare species

Allium ampeloprasum ssp. babingtonii, Corynephorus canescens, Euphorbia paralias, E. portlandica, Scrophularia scorodonia.

Physiognomy

The Ammophila arenaria community includes virtually all the vegetation of more mobile coastal sands in which the robust perennial grass Ammophila arenaria plays a dominant role in the dune-building process. In young stands, or where newly eroded surfaces among established dunes are being recolonised, the cover of the plant is often low, with just a few sparse shoots emerging from freshly-blown sand that may be otherwise quite bare. Growth can become very vigorous, however, in activelyaccreting material where Ammophila can spread its horizontal rhizomes far and keep pace with burial of up to 1 m a year, the expanding clones putting up denselybranching tillers that become aggregated into the characteristic tussocks (Gemmell et al. 1953, Greig-Smith 1961, Ranwell 1972). The shoots enhance accretion even more, continuing to proliferate among the upbuilding sand, until they can be packed at 150–200 m−2. Adjacent tussocks, with their spreading foliage reaching 1 m or more in height, can thus enlarge to form an extensive cover of the grass over stretches of still shifting sand that is being built into often substantial dunes.

Synonymy

Armeria maritima-Grimmia maritima rock crevice community Ostenfeld 1908; Armeria maritima-Ligusticum scoticum low cliff vegetation Petch 1933; Armeria maritima-Grimmia maritima and Asplenium marinum-Grimmia maritima Associations Birks 1973; Habitat Groups II & III Goldsmith 1975; Armeria maritima-Grimmia maritima association Malloch & Okusanya 1979.

Constant species

Armeria maritima, Festuca rubra, Ligusticum scoticum, Schistidium maritimum.

Physiognomy

As in the Crithmo-Spergularietum, the vegetation comprises a low-growing, very open cover, mainly of vascular perennials whose precise arrangement is strongly influenced by the availability and pattern of rockcrevices. There is no single dominant but Armeria maritima, Festuca rubra and Ligusticum scoticum may each be abundant in particular stands. Plantago maritima, Rhodiola rosea and Silene vulgaris ssp. maritima are frequent. Although Schistidium maritimum is occasionally present in the Crithmo-Spergularietum, it is here constant, though always in small amounts. Other bryophytes are rare. Birks (1973) recorded Anaptychia fusca and Ramalina siliquosa as frequently occurring lichens exclusive to this vegetation on Skye.

Asplenium marinum is an occasional in the community but it may become locally abundant in sheltered rockcrevices with Trichostomum brachydontium (Birks 1973).

Habitat

The Armeria-Ligusticum community replaces Crithmo-Spergularietum as the most maritime vascular plant community north of Galloway. It occurs on all rock types, being limited mainly by the physical structure of the deposits. On softer sandstones, such as parts of the Old Red Sandstone which comprises much of the Caithness cliffs, the vegetation cover tends to be greater than usual.

Synonymy

Echinochloo-Setarietum (Kruseman & Vlieger 1939) emend. Kruseman & Vlieger apud Sissingh, Vlieger & Westhoff 1940 sensu Silverdale 1977

Constant species

Crepis capillaris, Digitaria ischaemum, Elymus repens, Erodium cicutarium, Geranium molle, Poa annua, Senecio vulgaris, Spergula arvensis, Stellaria media.

Rare species.

Apera spica-venti.

Physiognomy

The rare annual introduced grass Digitaria ischaemum, together with Erodium cicutarium and Spergula arvensis, provide a distinctive group of constants in this Digitaria Erodium annual weed community. Also very frequent are Stellaria media, Poa annua, Senecio vulgaris, Geranium molle, Crepis capillaris and Elymus repens.

Other common associates are Bilderdykia convolvulus, Capsella bursa-pastoris, Rumex acetosella, Papaver dubium, Chenopodium album and Taraxacum officinale agg. Occasionals of the community include Polygonum aviculare, Medicago sativa, Ornithopus perpusillus, Scleranthus annuus, Raphanus raphanistrum and Urtica urens with Holcus mollis and Achillea millefolium sometimes figuring. Bryophytes are occasionally found with Bryum rubens and Pleuridium subulatum most common.

Habitat

The Digitaria-Erodium community is confined to fertilised sandy soils disturbed by the cultivation of root crops and cereals in a very localised part of south-east England.

D. ischaemum is a native of warm-temperate parts of Europe and Asia first recorded in East Anglia in about 1805 and since then locally established among arable crops in sandy fields in southern and south-east England (Hubbard 1984), having probably spread in contaminated seed (Salisbury 1964). It has declined markedly in its occurrences with the shift to more intensive kinds of arable agriculture, although it can persist in situations with quite considerable soil enrichment.

Constant species

Eleocharis uniglumis, Agrostis stolonifera.

Physiognomy

Although Eleocharis uniglumis is a widespread minor constituent of a variety of damp transitional communities along the upper marsh fringes (Birks 1973, Adam 1976), it is here dominant in a species-poor association, similar in floristics and appearance to the Blysmetum rufi. There is often an extensive undercarpet of Agrostis stolonifera and Juncus gerardii, Glaux maritima, Festuca rubra, Triglochin maritima, Potentilia anserina and Alopecurus geniculatus all occur frequently and may be abundant in particular stands. As in the Blysmetum, cover is variable and algae and bryophytes may form a patchy carpet over the substrate surface.

Habitat

In Britain, the Eleocharitetum occurs most frequently in depressions in the upper marsh. Some of the most extensive stands occur in brackish marshes by the River Gilpin, Cumbria. Rarely, it occurs in what is a widespread habitat in Scandinavia, as a fringe of emergent vegetation, as around the brackish and atidal Loch an Amadain in Skye.

Zonation and succession

The Eleocharitetum occurs patchily within other uppermarsh associations such as the Juncetum gerardi and it does not play a major role in salt-marsh succession.

Distribution

The association is a rare community on British saltmarshes occurring locally along the west coast from the Dovey estuary northwards.

Affinities

British vegetation dominated by E. uniglumis is clearly closely related to that described from Scandinavia (Gillner 1960, Tyler 1969b, Siira 1970) although the emergent stands in Britain lack the aquatic species characteristic of the Eleocharetum of, for example, the Baltic.

Constant species

Elymus repens, Matricaria perforata, Poa annua.

Physiognomy

The Poa annua-Matricaria perforata community includes coarse weedy vegetation with a variety of more ephemeral herbs, some small, others more bulky, and some perennial grasses. Poa annua is the commonest grass but Elymus repens and Agrostis stolonifera are frequent in many of the sub-communities and Lolium perenne is also often prominent. Matricaria perforata and, somewhat less commonly, Chamomilla suaveolens, are characteristic, too, with Polygonum aviculare. No other associates of the community as a whole are frequent throughout but Capsella bursa-pastoris, Holcus lanatus, Chenopodium album, Rumex obtusifolius and R. crispus occur commonly in several subcommunities. Plantago lanceolata, Taraxacum officinale agg., Stellaria media, Sinapis arvensis and Anagallis arvensis are scarce throughout. Bryophytes are sparse but Pottia truncata, Funaria hugrometrica, Brvum argenteum, B. caespiticium and B. microerythrocarpon can occasionally be seen, sometimes in great abundance.

Sub-communities

Senecio squalidus-Epilobium angustifolium sub-community. Perennial grasses are very sparse here and mixtures of Poa annua and Matricaria perforata with Chamomilla suaveolens and Polygonum aviculare form the bulk of the cover with Senecio squalidus and Epilobium angustifolium frequent preferentials. Scattered plants of Tussilago farfara and Reseda lutea can sometimes be seen and carpets of Funaria hygrometrica and Bryum spp. are occasionally very extensive.

Lolium perenne-Capsella bursa-pastoris sub-community.

Lolium perenne, Holcus lanatus and Poa trivialis are all frequent in this sub-community along with Capsella bursa-pastoris and Polygonum persicaria. Papaver rhoeas, Lapsana communis, Chenopodium album, Plantago major, Atriplex prostrata, Rumex obtusifolius and Cirsium arvense occur occasionally.

Synonymy

Mertensia maritima localities Scott 1963c; Atriplex glabriuscula-Rumex crispus Association Birks 1973.

Constant species

Galium aparine, Matricaria maritima.

Rare species

Mertensia maritima, Polygonum oxyspermum spp. raii.

Physiognomy

The Matricaria maritima-Galium aparine community consists of generally open and often patchy strandline vegetation in which Matricaria maritima, various Atriplex spp. and the annual weeds Galium aparine and Stellaria media are the most frequent and prominent elements. Among the oraches, A. glabriuscula is especially common here, but A. prostrata and A. patula also occur occasionally, and each of these can be found in some abundance. The more local A. laciniata is sometimes recorded, too, though usually as sparse scattered individuals, and the rare A. praecox can be seen in close association with this vegetation at some of its few localities around sea lochs in western Scotland (Taschereau 1985).

Beta vulgaris ssp. maritima, a very characteristic plant of shingle strandlines in southern Britain, is hardly ever found here, and Honkenya peploides and Cakile maritima, which are a constant feature of sandy foreshore vegetation around our coasts, tend to be only infrequent. Rumex crispus var. littoreus, however, remains fairly common and it can be conspicuous with its tall flowering shoots, and there may be occasional patches of Sonchus asper, S. arvensis, Cochlearia officinalis, Chamomilla suaveolens and Silene vulgaris ssp. maritima.

Constant species

Poa annua, Polygonum aviculare, Polygonum lapathifolium, Polygonum persicaria.

Physiognomy

The Polygonum-Poa community includes open or closed stands of vegetation in which various knotweeds are the most characteristic feature. P. persicaria, P. lapathifolium and P. aviculare are all very common here and each can be abundant, often in locally dense, even more or less monodominant patches. Poa annua is also constant but not usually of extensive cover and there is often some Stellaria media, Chenopodium album, Plantago major and Chamomilla suaveolens. More bulky occasionals include Elymus repens, Lolium perenne, Urtica dioica and Cirsium arvense but none of these is more than locally prominent. Smaller herbaceous associates found at low frequency are Viola arvensis, Anagallis arvensis, Ranunculus repens, Trifolium repens, Spergula arvensis and Veronica persica, and there can be occasional scattered individuals of Rumex crispus, R. obtusifolius, Sonchus asper and Euphorbia helioscopa.

Habitat

This Polygonum-Poa community is characteristic of damp eutrophic soils in disturbed places such as gateways, tracks, farmyards and ill-managed leys, on dumped topsoil and made ground around building sites.

Compared with the Rorippa-Filaginella community, this vegetation is less dependent on long winter flooding to maintain extensive areas of ground then laid bare by a drop in the water table. Indeed, local impedence of drainage of rainwater, as on heavy or trampled ground, is sufficient to create suitable conditions for the rapid appearance of the annual knotweeds, Poa annua and weeds like Stellaria media, Chenopodium album and Chamomilla suaveolens.

The appearance of this fifth volume of British Plant Communities brings to a close the publication of the National Vegetation Classification and, as Coordinator of the project, it is my privilege to put on record the gratitude of the whole research team and my own personal thanks to all who have been instrumental in the completion of the work.

For this volume, we were extremely fortunate in having access from the outset to the data which Dr Paul Adam had energetically assembled for his postgraduate research at Cambridge University into British saltmarsh vegetation. Extensive in its coverage and already developed into a classification scheme with highly informative vegetation descriptions, this work obviated the need for any further detailed survey on our part and more than laid a foundation for our own scheme. Such additional data as we did collect to fill any gaps was also supplemented by local surveys by Dr Pat Doody and Margaret Hill of the then NCC, Dr Malcolm Carter and Dr Judith Roper-Lindsay. In integrating this into the NVC framework and reviewing the progress of our synthesis Paul Adam continued to give of his time and expertise without demur.

For sea-cliffs we were equally blessed in inheriting large quantities of data from Andrew Malloch whose geographical and floristic coverage of this difficult and neglected habitat was adventurously wide and whose knowledge of the plant communities and their environmental relationships was second to none.

Synonymy

Atriplicetum Gillham 1953; Ornithocoprophilous vegetation Gillham 1956b p.p.; Lavateretum arboreae J.-M. & J. Géhu 1961; Beta maritima – sociatie Beeftink 1962; Atriplici-Betetum perennis J.-M. & J. Géhu 1969; Beto-Tripleurospermetum maritimi Malloch 1970; Herring gull colony vegetation Sobey & Ken worthy 1979 p.p.

Constant species

Atriplex prostrata agg., Beta vulgaris ssp. maritima, Festuca rubra, Matricaria maritima.

Physiognomy

The Atriplici-Betetum is very variable in its floristics and appearance. Usually one or more of Atriplex prostata agg. (including A. glabriuscula and A. babingtonii: Aellen 1964), Beta vulgar is ssp. maritima and Lavatera arborea dominate in an open or closed, often scruffy, cover with sometimes abundant Matricaria maritima. Festuca rubra, Spergularia rupicola, Armeria maritima and Dactylis glomerata occur frequently in isolated but often vigorous fragments of crevice vegetation or maritime sward. Various species characteristic of open disturbed places, such as Polygonum aviculare agg. and Rumex crispus, may be prominent on the sometimes extensive areas of bare ground. There may be a marked seasonal variation in the vegetation with a dramatic spring growth of overwintered Cochlearia officinalis (or C. danica: Gillham 1953) being succeeded by A. prostrata.

Habitat

The community is most characteristic of rocky coastal sites where there is a combination of high maritime influence and intense disturbance by sea-birds, notably gulls (Larus spp.), razorbill (Alca torda) and guillemot (Uria aalge). Essentially similar mixtures of Atriplex spp. and Beta can also be found on strandline debris in sandy and shingle foreshores.

Synonymy

Setario-Veronicetum politae Oberdorfer 1957 sensu Silverside 1977; Tripleurospermum maritimum stands Kay 1994 p.p.

Constant species

Bilderdykia convolvulus, Chenopodium album, Matricaria perforata, Polygonum aviculare, Stellaria media, Veronica persica, Veronica polita.

Physiognomy

In the Veronico-Lamietum, both Veronica persica and the more geographically restricted V. polita are constant, the former often in some abundance by summer. Polygonum aviculare also frequently has high cover and Stellaria media and Bilderdykia convolvulus are constant contributors among the smaller herbs. Often more conspicuous, however, are the mealy shoots of Chenopodium album and the big daisy-like inflorescences of Matricaria perforata, especially where this shows a second flush of flowering in unploughed stubble remaining after harvest into the autumn.

Lamium hybridum is a particularly diagnostic associate of the above constants but it is not universally present in this community. More frequent are Poa annua, Elymus repens, Senecio vulgaris, Capsella bursa-pastoris and Chamomilla suaveolens with Euphorbia helioscopia, Sonchus oleraceus, Solanum nigrum and Urtica urens among the occasionals.

Habitat

The Veronico-Lamietum is characteristically a weed community of cereals and other annual field crops on lighter, well-drained, highly fertile circumneutral soils in the warmer and drier lowlands of southern and eastern Britain.

Suitable soil conditions for most of the common species of this assemblage are very widespread through the lowland agricultural landscape of this country but both Veronica polita and, more strikingly, Lamium hybridum are more restricted to areas with a Continental climate (Perring & Walters 1962).