Synonymy

Halimiono-Frankenietum laevis Adam 1976 p.p; Sussex Frankenia laevis stands Brightmore 1979.

Constant species

Armeria maritima, Frankenia laevis, Halimione portulacoides.

Rare species

Frankenia laevis, Inula crithmoides, Arthrocnemum perenne.

Physiognomy

This community has a short uneven open sward dominated by Halimione portulacoides and Frankenia laevis with scattered plants of Armeria maritima and Puccinellia maritima. Festuca rubra, Limonium vulgare, annual Salicornia spp. and Spergularia media are frequent at low cover values and at some sites Inula crithmoides is conspicuous.

Habitat

The community generally occurs on mixtures of silt, sand and shingle at salt-marsh/sand-dune interfaces. Similar vegetation but lacking H. portulacoides has been recorded from Chalk undercliffs and rubble (Brightmore 1979).

Distribution

The community is confined to the south coast of Sussex where the best stands are developed at East Head, Chichester Harbour. Frankenia laevis has recently been reported from Anglesey (Roberts 1975) where it has become well established (after original planting?) among Festuca rubra, Armeria maritima and Puccinellia maritima to produce vegetation rather similar to this community.

Affinities

The community is distinguished from the Suaeda vera-Limonium binervosum salt-marsh by the absence here of S. vera and the replacement of Limonium bellidifolium and L. binervosum by L. vulgare. Géhu & Géhu-Franck (1975) and Géhu & Delzenne (1975) regard the Sussex stands as representing a species-poor parallel to the Frankenio-Limonietum lychnidifolii of north-west France and have provisionally assigned them (and the Anglesey vegetation) to the Limonio vulgaris-Frankenietum laevis.

Synonymy

Armerieto maritimae-Daucetum gummiferi Géhu 1964 p.p.

Constant species

Festuca rubra, Dactylis glomerata, Daucus carota ssp. gummifer.

Rare species

Brassica oleracea, Scilla verna, Silene nutans.

Physiognomy

The Festuca-Daucus maritime grassland has a fairly short, rather tussocky sward generally dominated by grasses of which F. rubra is usually the most abundant. Dactylis glomerata is constant and, though rarely abundant, may be in the form variously described as var. abbreviata, var. maritima or ssp. hispanica, which Tutin (1980a) considered to be one of the tetraploid populations within the species. Daucus carota ssp. gummifer is also constant in generally small amounts and, when flowering, it gives the vegetation a distinctive stamp. The maritime element in the community is small and the only other frequent species throughout are Plantago lanceolata and Lotus corniculatus. Bryophytes are rare.

Sub-communities

Bromus hordeaceus ssp. ferronii sub-community: Armerieto-Daucetum gummiferi typicum Géhu 1964 p.p. B. hordeaceus ssp. ferronii and Armeria maritima are additional constants here and Plantago coronopus, P. lanceolata and Lotus corniculatus occur frequently. Although F. rubra is often abundant, there is usually no single dominant and the sward is sufficiently open to permit repeated colonisation by B. hordeaceus ssp. ferronii and other therophytes such as Desmazeria marina, Senecio vulgaris and Vicia sativa.

Ononis repens sub-community. O. repens is an additional constant in this sub-community and occasionally it is co-dominant with F. rubra.

Synonymy

Ammophiletum arenariae Moss 1906, Tansley 1911, 1939, all p.p.; Elymo-Ammophiletum arenariae Br.-Bl. & De Leeuw 1936.

Constant species

Ammophila arenaria, Festuca rubra, Hypochoeris radicata, Poa pratensis s. l.

Rare species

Acaena novae-zelandiae, Epipactis dunensis, Euphorbia paralias, Mibora minima, Oenothera stricta, Vulpia fasciculata.

Physiognomy

The Ammophila arenaria-Festuca rubra community is the major vegetation type of less mobile coastal sands where Ammophila arenaria is still usually the dominant, but where conditions are such as to allow the development of a fairly rich and often abundant associated flora over the stabilising dune surface. The marram tussocks may be big, with the shoots generally reaching 60–100 cm in height, but the tillers are not so densely packed or vigorous as in younger plants, and the accretion of bare sand among them much less rapid than in the earlier stages of colonisation. Where the tussocks are growing close together, the canopy of arching foliage can be quite extensive, but beneath this and particularly among more widely spaced marram, a variety of other herbs and also bryophytes can gain a hold, forming a patchy carpet of shorter vegetation that may be of locally high cover.

Constant species

Alopecurus myosuroides, Bilderykia convolvolus, Elymus repens, Polygonum aviculare, Stellaria media, Veronica persica.

Physiognomy

The Alopecuro-Chamomilletum is the most distinctive weed assemblage in which the annual grass Alopecurus myosuroides is found. Its tufts can be very abundant here, along with Elymus repens, Polygonum aviculare and Stellaria media, each of which can also show locally high cover. Veronica persica and Bilderdykia convolvulus are also constant, though generally in smaller amounts.

The characteristic mayweed of this vegetation, Chamomilla recutita, is only occasional overall but Matricaria perforata is frequent, along with Chenopodium album, Capsella bursa-pastoris, Sinapis arvensis, Sonchus asper, Senecio vulgaris, Avena fatua, Poa annua, Plantago major, Polygonum persicaria and Cirsium arvense. Among the more common occasional are Convolvulus arvensis, Euphorbia helioscopa, Solanum nigrum, Urtica urens and the scarce goosefoot Chenopodium hybridum.

Habitat

This assemblage is typical of winter-sown cereals and other field crops on loamy and clayey soils that occur in the warmer and drier south-east of England but which are protected from drought by their heavy texture.

A. myosuroides is native across much of Europe but is only common in Britain in the more Continental parts of the country where the July mean is above 15 °C (Naylor 1972), being especially abundant in the southeast Midlands and East Anglia. It can get a head start among arable crops in this region by autumn germination and survive through the winter as a rosette, flowering from May to August of the following year.

Synonymy

Sandscale Salix repens dunes Pear sall 1934; Campylium stellatum-Salix repens nodum Jones 1992; Carex flacca-Thalloid Liverwort nodum Jones 1992 p.p.

Constant species

Agrostis stolonifera, Carex flacca, Epipactis palustris, Equisetum variegatum, Hydrocotyle vulgaris, Mentha aquatica, Salix repens, Calliergon cuspidatum, Campylium stellatum.

Rare species

Dactylorhiza majalis ssp. praetermissa and ssp. purpurella, Juncus acutus, Liparis loeselii, Pyrola rotundifolia.

Physiognomy

The Salix repens-Campylium stellatum community comprises generally closed vegetation of dune slacks with an often extensive low bushy carpet of S. repens, frequently species-rich assemblages of vascular associates and a usually extensive carpet of bryophytes among which both Campylium stellatum and Calliergon cuspidatum figure very commonly, the former generally especially abundant.

The constant combination of Carex flacca, Equisetum variegatum and, in most sub-communities, Epipactis palustris with more widely occurring dune-slack plants such as Hydrocotyle vulgaris, Agrostis stolonifera and Mentha aquatica, is what gives this vegetation its particular character. Among these species, E. variegatum can be especially abundant and it sometimes assumes a striking tussock growth-form, perhaps because of rapid shoot proliferation in the early stages of colonisation (Jones 1992). Also, as with the Salix-Calliergon community, the only occasional occurrence of Potentilla anserina and Carex nigra here, and the generally low cover of the latter, is an important contrast with the Potentilla-Carex slack vegetation.

Among the other commoner associates, Carex arenaria, Leontodon autumnalis, Ranunculus flammula, Rubus caesius, Lotus corniculatus and Juncus articulatus are the most frequent with more occasional Taraxacum officinale agg. and Equisetum palustre.

Constant species

Dactylis glomerata, Lolium perenne, Plantago lanceolata, Taraxacum officinale agg.

Physiognomy

The Lolium perenne-Dactylis glomerata community comprises coarse weedy grassland vegetation in which Lolium perenne and Dactylis glomerata usually make up the bulk of the more or less closed cover, along with a variety of perennial associates and scattered ephemerals which find a place in locally disturbed places. Plantago lanceolata and Taraxacum officinale agg. are the commonest of these companions but Achillea millefolium, Plantago major, Trifolium pratense, Agrostis stolonifera, Urtica dioica, Hypochoeris radicata and Potentilla reptans all figure occasionally among the perennials, Poa annua, Bromus hordeaceus ssp. hordeaceus and B. sterilis among the annuals.

Sub-communities

Typical sub-community. Apart from the community constants, only frequent records for Trifolium dubium and Hordeum murinum with occasional Vicia sativa and Senecio squalidus are distinctive here.

Crepis vesicaria-Rumex obtusifolius sub-community. Poa annua becomes constant here but better preferential are Crepis vesicaria and Rumex obtusifolius with Poa trivialis, Senecio vulgaris and Cirsium arvense occasional. Seedlings of Buddleja davidii are sometimes found.

Plantago major-Trifolium repens sub-community. Poa annua and Holcus lanatus remain very frequent here but Plantago major and Trifolium repens are more distinctive with Ranunculus repens and Rumex crispus occasional.

Arrhenatherum elatius-Medicago lupulina sub-community. The grass contingent of the vegetation is further augmented here by constant H. lanatus and, more preferential, Arrhenatherum elatius and Agrostis capillaris.

Synonymy

Includes Brassicetum oleraceae Géhu 1962.

Constant species

Festuca rubra, Brassica oleracea, Dactylis glomerata, Daucus carota ssp. gummifer.

Rare species

Brassica oleracea, Ophrys sphegodes, Silene nutans.

Physiognomy

The Brassica oleracea community generally has an irregular grassy cover of Festuca rubra and some Dactylis glomerata with prominent erect or decumbent plants of B. oleracea and a little Daucus carota spp. gummifer Plantago lanceolata is the most frequent associate throughout, but it is never abundant. Cheiranthus cheiri and Sonchus oleraceus, though infrequent, may be conspicuous when flowering.

Sub-communities

Beta vulgaris ssp. maritima sub-community: Brassicetum oleraceae Géhu 1962. B. oleracea is more abundant in this species-poor sub-community and Beta vulgaris ssp. maritima is an additional constant which may be codominant with B. oleracea and Festuca rubra. Maritime species, such as Armeria maritima, Silene vulgaris ssp. maritima and Bromus hordeaceus ssp. ferronii are confined to this sub-community though none is ever abundant.

Ononis repens sub-community. Additional constants here are O. repens, Silene nutans, Centaurea scabiosa and Rumex acetosa. B. oleracea is less abundant here than in the Beta sub-community. Also frequent are Brachypodium pinnatum (which often co-dominates with F. rubra), Hieracium pilosella and Teucrium scorodonia and among the occasional species are some characteristic of calcicolous grasslands including Ophyrs sphegodes (Summerhayes 1968).

The late Tertiary

Here a short account will be given of the development of the flora during the late Tertiary period and the environment within which this development took place. This theme has been elaborated in many textbooks and reviews, for example West (1977), Hantke (1978), Nilsson (1982), Birks (1986), Watts (1988) and Tallis (1991).

During the Miocene epoch about 15 million years ago the flora of the Northern Hemisphere including Europe contained a mixture of tropical, subtropical and temperate elements. The tropical elements are now extinct in Europe. Of the subtropical and temperate taxa many are now extinct in Europe, but still some persist in North America, the Caucasus, and eastern Asia, for example Taxodium, Sequoia, Tsuga, Pseudotsuga, Glyptostrobus, Sciadopitys, Ginkgo, Liriodendron, Liquidambar, Nyssa, Pterocarya, Zelkova and Eucommia.

During the following epoch, the Pliocene, the climate gradually became colder. The reason for this might have been the upheaval of mountain massifs in central Asia and western North America affecting the planetary waves, thereby creating conditions for the accumulation of ice and the development of glaciers in the Northern Hemisphere (Ruddiman & Raymo 1988). During this period the tropical elements died out in Europe while several of the subtropical North American and East Asiatic exotics survived. Tsuga, Magnolia, Carya, Pterocarya, Eucommia, Parrotia and Paeonia even survived the earliest glaciations of the following epoch, the Pleistocene.

During the middle and late Pliocene lowlands existed in the present North Sea, probably extending westwards to Scotland, the Faeroes, Iceland and Greenland and northwards to the Voring Plateau southwest of Lofoten, North Norway (Rokoengen & Ronningsland 1983; Eldholm & Thiede 1986a, b).

According to Jenny (1941) the soil at any given locality is a product of parent materials, climate, biota, aspect and time. One should perhaps add still another factor, input from the air, such as sea spray bringing in magnesium and sodium, or particles from desert areas such as the Sahara bringing in calcium. Today we must also add pollutants from human activity as an important pedogenic factor.

In the soil, mineral particles release plant nutrients by weathering. Different primary minerals contain different ions and some minerals are more resistant to weathering than others. By far the most important ion in northern European soils is calcium. It is the major ion that neutralises organic acids produced by the breakdown of litter, and the availability of calcium controls the pH of the soil layers.

The most easily weatherable minerals are calcite and dolomite. Of the silicates, plagioclases, especially calcium-rich plagioclases, some amphiboles, and epidote release calcium relatively easily on weathering. Less weatherable are the pyroxenes, and still less weatherable are the potassium feldspars and quartz. In general, parent materials from basic rocks (that is with a low silicon content) such as amphibolite and gabbro provide better soils than parent material from acid rocks such as granite, acid gneiss and sandstone. Of the micas, biotite provides potassium relatively easily by weathering, whereas muscovite is more resistant. The rate of weathering also depends upon the surface areas of the mineral particles. A fine-grained parent material, for example a clay, provides more nutrients to plants than a coarse-grained sand under otherwise equal conditions.

Phytogeography, as the name indicates, is the scientific study of the geographical distribution of plants. It is a science combining botany and geography. The subject can be approached in at least two ways.

1. By studying the geographical distribution of assemblages of plants, namely plant communities. This is a phytosociological approach

2. By studying the geographical distribution of individual plant taxa. This is a phytogeographical approach in a restricted sense and it is the approach that this book adopts.

Both approaches are relevant and inter-related. Results obtained from phytosociological studies can throw light on phytogeographical problems and vice versa. The methods used are, however, quite different.

The basic material in phytosociological studies is the relevé, i.e. standardised descriptions of vegetation plots with lists of species and information about their relative quantities or abundances. Sets of relevés are combined into vegetation tables which can be analysed by different methods. One method is to attempt a vegetation classification, the approach used in classical plant sociology. Another approach is to consider the vegetation table as an information matrix which can be represented as points in a multidimensional space. By using different methods, invariably employing computers, relations between relevés and species can be studied. This is the ordination or gradient analysis approach (Gauch 1982).

The basic material in the phytogeographical approach in its restricted sense is data on the occurrences of individual plant taxa. These are summarised verbally in floras, indicating where the plant in question might be found. Little information can be presented in this way, however. An alternative approach is to make distribution maps of plant taxa. These can be made in several different ways.

Several climatic parameters have been calculated for each of the the 50 × 50 km grid squares of Atlas Florae Europaeae (O. Skre, unpublished data). The main source of the primary meteorological information is Anonymous (1973). In some instances where this is insufficient, for instance for Svalbard, information has been taken from other sources. The highest or lowest altitudes for each of the squares have been taken from national atlases. They are considered to be accurate to within about 10 m.

The following parameters have been used as a basis for the comparative maps (Figs. 12–17, 30–38, 42–50 and 54–63).

Winter temperatures (for comparisons with the atlantic and the boreal distribution patterns)

This is the mean temperature of the coldest month for each station. One problem is that in oceanic regions February is the coldest month, whereas in continental stations it is January, and in intermediate areas it is either January or February. To overcome this, we have used the normals of the 5 coldest months at each station. By means of least-square methods a parabola was fitted to the observations. The mean temperature of the coldest month is then the minimum of the parabola. It is always near the temperature of the coldest month.

By comparison with records from neighbouring stations at different altitudes, it is evident that the altitudinal temperature gradient differs as a function of continentality. In Portugal the gradient is about 0.6°C per 100 m altitudinal difference, whereas in northern Russia it is zero.

BI is British Isles, Fe is Fennoscandia. Information on status in the two areas is based on available evidence – i is indigenous, n is aturalised, e is ephemeral, * is endemic to the area.

Wl is the mean temperature (°C) of the coldest month calculated for the lowest altitudes in the Atlas Florae Europaeae squares - to be compared with the distribution of atlantic species.

R is the R-value calculated for the lowest altitudes in the squares – to be compared with the distribution of thermophilic plants.

Wh is the mean temperature (°C) of the coldest month calculated for the highest point in each square – to be compared with the distribution of boreal species.

Tmax is the mean annual maximum temperature (°C) calculated for the highest point in each square – to be compared with the distribution of montane and alpine species.

The sequence of families and genera is according to Flora Europaeabased on D. M. Moore: Check-list and chromosome index. Flora Europaea, 1982. The nomenclature is mainly according to the same source, but modified according to Clapham

et al (1987) and Lid (1985).

Although all species occurring in Northern Europe according to Flora Europaea are listed in this appendix, correlations between their distribution and the four climatic parameteres are only presented for those species where the correlations are realistic and ecologically plausible.

Introduction

Endemics are taxa which occur only in a limited area, for example in the British Isles or in Fennoscandia. Disjuncts are taxa distributed in different areas with considerable gaps in between so that genetic exchange is impossible between the separated populations. Centric distribution relates to limited areas with an extraordinary concentration of endemics and/or disjuncts.

The problems of interpreting endemic or disjunct distribution patterns are, in many ways, very different from the problems of understanding the distribution patterns of the more widespread taxa dealt with previously. In the latter case it is assumed that the distributional area is not limited by the ability of the taxon to spread and that the distribution is therefore limited by environmental factors. This assumption is supported by fossil evidence. Such an assumption cannot be made with respect to endemics and disjuncts. Instead it seems more probable that an explanation of their distributions is to be sought in the history of the populations, namely that they are relicts from earlier, different distribution patterns in the past when the plants could migrate under ecological conditions different from those of today. Such hypotheses should, however, be supported by fossil evidence (Godwin 1975).

In Chapter 4 the history of the flora was outlined based on fossils and geological evidence. The important events to which the flora had to adapt were the Pleistocene glaciations, when ice sheets covered most of Fennoscandia and the British Isles.