Molinia caerulea (L.) Moench
2001; Wiley; Volume: 89; Issue: 1 Linguagem: Inglês
10.1046/j.1365-2745.2001.00534.x
ISSN1365-2745
AutoresK. Taylor, A. P. Rowland, Helen E. Jones,
Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoArundineae. An erect, compactly tufted perennial grass, 15–130 (−250) cm high when flowering, forming either tussocks or extensive swards. Rootstock more or less creeping, with both stout and fine roots. Culms erect, slender to somewhat stout, stiff, smooth, with one node towards the base, disarticulating at this node; the basal internode up to 5 cm usually becomes swollen and club-shaped in late summer or autumn and filled with food reserves. Leaf sheaths rounded on the back, smooth, hairy at the top; ligule a dense fringe of short hairs; leaf blades flat, 3–12 mm wide, long-tapering from near the base to a fine point, 10–45 cm long, sparsely pilose, and completely deciduous in the winter. Panicles erect, variable, ranging from very dense and spike-like to open and very loose, dark to light purple, brownish, yellowish, or green, 3–60 cm long, 1–10 cm wide, and have slender, smooth or minutely rough, branches with short, finely ciliate pedicels. Spikelets 4–9 mm long, tapering to a long point, loosely 1–4-flowered, breaking up at maturity beneath each lemma, with a rough axis. Glumes persistent, lanceolate, acute, shorter than the lemmas, membranous; the lower glume 0–1-veined, 1.5–3 mm long, the upper 1–3-veined, 2.5–4 mm long. Lemmas spaced, tapering to an obtuse apex, bluntly 3–5-keeled, firm, smooth, 4–6 mm long. Paleas with minutely rough keels; in fruit, the caryopsis is enclosed by the hardened lemma and palea. Stamens 3, exserted, anthers large (1.5–3 mm long), violet-brown; stigmas purple, styles terminal, very short. Molinia caerulea is a very variable species owing to a combination of phenotypic plasticity and genecological variation. Morphological plasticity is expressed as variation in overall size, in the length and width of leaves, and especially in the length, width and colour of the panicles (Hubbard 1968). Polyploid races of M. caerulea occur in Britain. Within M. caerulea sensu stricto two subspecies may be recognized, but many intermediates occur (Fl. Eur. 5; Sell & Murrell 1996); tetraploid plants forming clumps of a number of single-culmed plants of smaller stature (culms usually < 65 cm) and panicle size (usually < 30 cm) are referable to ssp. caerulea, whereas taller diploid and decaploid tussock-building plants with culms usually 65–125 (160) cm, spreading panicles mostly 30–60 cm long and leaves 8–12 mm wide, belong to ssp. arundinacea (Schrank) K. Richt. (ssp. altissima (Link) Domin, for which known localities in the British Isles are listed by Trist & Sell 1988). Two diverse populations of M. caerulea, one growing on a calcium-rich, alkaline, LeBlanc waste tip (pH 7.54 ± 0.13), the other on an acid moorland (pH 3.9 ± 0.1), were investigated by Salim et al. (1995). A detailed morphometric comparison of the two populations, in terms of the key morphological features which characterize the two subspecies described above, suggested that both are M. caerulea ssp. caerulea. The two populations could be distinguished, however, by differences in height, leaf width, leaf length and gross flower size of plants growing in the field. But an electrophoretic analysis of isoenzymes could not separate the two populations, indicating that they are genetically similar and that differences in size and flowering are presumably plastic responses to environmental factors. When plants from both populations were, however, grown experimentally under identical conditions in both acid and alkaline artificial growing medium, the acid population plants consistently showed significantly greater growth than the alkaline population plants regardless of the nature of the growth medium. This implies that the differences in growth in field conditions may not be merely phenotypic plasticity, but that the two populations may possibly be edaphic ecotypes. Molinia caerulea is a common native species usually abundant and frequently dominating large areas, often to the exclusion of other flowering plants. Ssp. caerulea is widespread in open situations on moors, heaths, bogs, fens, mountain grassland, cliffs and lake shores, always on at least seasonally wet, acid sandy, or peaty ground throughout the British Isles. The much larger ssp. arundinacea (ssp. altissima) occurs in tall vegetation with dense ground cover in fens, fen-scrub, and in fen-like vegetation by rivers and canals, sometimes shaded by Betula and Salix spp., on somewhat base-rich mineral soils with fluctuating water-table; scattered but frequent in suitable places in central and southern Britain, but very scattered in Scotland and southern Ireland (Stace 1997). Molinia caerulea is locally abundant especially in the north and west of the British Isles (Fig. 1) where it occurs in all vice-counties. The area of land in Britain dominated by this species has been estimated at around 600 000 ha or 10% of the uplands (Bunce & Barr 1988). It is widespread in Europe except for some islands, but mainly on mountains in the south (Fig. 2). Outside Europe the species occurs in North Africa, Caucasus and Siberia; introduced in North America. The distribution of Molinia caerulea in the British Isles. (○) Pre-1950; (●) 1950 onwards. Each dot represents at least one record in a 10-km square of the National Grid. Mapped by Mrs J.M. Croft, Biological Records Centre, Centre for Ecology and Hydrology, using Dr A. Morton's DMAP program, mainly from records collected by members of the Botanical Society of the British Isles. The distribution of Molinia caerulea in Europe. The main area of distribution lies between the heavy continuous line; outliers are shown as dots (modified from Vergl. Chor.). The base map is reproduced by permission of the Committee for the Mapping of the Flora of Europe (the bold dashed line shows the limits of Europe). Molinia caerulea is classified as Eurosiberian Boreo-temperate by Preston & Hill (1997). The altitudinal range of M. caerulea in the British Isles extends from sea level to an altitude of 613 m in the English Lake District, in Wales to 701 m on Snowdon, in Ireland to 747 m in Down and to an upper limit of 914 m in the Scottish Highlands (Alt. range Br. Pl.). It ascends to 500 m in northern Norway, to 1230 m at Hardangervidda in southern Norway (Atl. N.W. Eur.), and in the Alps up to 1900 m (Vergl. Chor.). Molinia caerulea is most commonly found on flat ground and on gentle to moderate (< 40°) slopes suitable for the formation of peaty gleys or deep peats, and is generally not favoured by any particular aspect. It tolerates a wide range of irradiance; characteristic habitats include both open, submontane grasslands and mires and the lighter phases of Betula pubescens woodland. Molinia caerulea persists in moderate shade, but tends to produce few flowers under these conditions. Molinia caerulea grows on a diverse range of soil types. These include calcareous surface water gleys over Carboniferous limestone, often drift-covered, as in Upper Teesdale (Pigott 1956), and in calcareous, strongly irrigated mud of silt, sand, gravel and humus over Dalradian limestone in the Scottish Highlands (Pl. Comm. Scot.). In the Norfolk Broads it occurs on ground-water gleys over alluvium in the lower reaches of river valleys, and on basin peats in the upper reaches (Perrin 1961). It is found on blanket peat and basin and flushed peat of low base status in south-west Galloway, and non-calcareous gley soil of low base status in Aberdeenshire (Birse & Robertson 1976). A number of soil types that support the growth of M. caerulea in the British Isles are described by Avery (1990): stagnogley-podzol over lithoskeletal siltstone and sandstone in the Ashdown Forest, East Sussex; humus-ironpan stagnopodzol on loamy drift at Bloxworth, Dorset; ferric stagnopodzol over lithoskeletal mudstone and sandstone or shale at Brendon, Devon; orthic gley soils over loamy drift at Llangadog, Dyfed, and Epping Forest, Essex; and bog peat at Risley Moss, Cheshire, at St Clether, Cornwall and Hartford, Devon. It occurs on brown podzolic soils of the Manod series over base-poor Lower Palaeozoic shales and mudstones close to the Llyn Brianne reservoir, Mid Wales (Soulsby & Reynolds 1994). Molinia caerulea has a bimodal pH distribution with peaks of abundance on both highly acidic soils (pH < 4.0) and calcareous soils of pH > 7.0 (Grime et al. 1988). In British mires it is equally abundant in 'bog', with pH generally < 5.0, low Ca2+, and Cl− and SO42− as the main inorganic anions, and in 'fen' with pH generally > 6.0, high Ca2+ and HCO3− (Cooper & Proctor 1998; Wheeler & Proctor 2000). At both high and low pH, M. caerulea tends to be associated either with moist grassland soils or with soligenous peat having a well-oxygenated soil profile (Armstrong & Boatman 1967). It is most abundant and grows vigorously, however, on sites where there is ground-water movement, good soil aeration and an enriched nutrient supply (Jefferies 1915; Rutter 1955; Webster 1962a; Loach 1966, 1968a; Sheikh 1969a). See also VI (E). James (1962) carried out pot experiments in a cold glasshouse with seedlings of M. caerulea grown in John Innes no. 1 potting compost made using an acidic loam (pH 5.4) unmodified or modified by the addition of CaCO3 or CaSO4, to determine the factors which might bring about the natural exclusion of the species from well-drained calcareous soils. He found that a high concentration of calcium as such is not inimical to the growth of the species under both free-draining and waterlogged soil conditions. When the phosphate level of the well-drained calcareous experimental soil was increased very greatly, the plant grew successfully, suggesting that the inability to obtain phosphorus is a factor that naturally excludes M. caerulea from dry calcareous soils. The nutrient content of soils from three adjacent and closely related wet-heath communities containing M. caerulea as a major component in Bramshill Forest, north-east Hampshire, was determined by Loach (1966). The wet heath site in which the plant was most abundant (Molinietum) had the largest total soil nutrient content and greatest water-table depth and fluctuation, although the topsoil was phosphorus-deficient in comparison with many other soils. The other two wetter sites were also deficient in phosphorus. Loach (1968a) assessed experimentally the relative abilities of the sites to supply nutrients to M. caerulea from the dry matter yields and nutrient uptake of tillers replanted into six small enclosures cleared of standing vegetation in each of the three sites. Tissue concentrations of nutrients in shoots of the plant were greatest in the wet heath and least in the valley bog, and these differences were associated with large and small dry matter yields, respectively. The relative nutrient status of these wet-heath soils can be gauged from the phosphorus concentrations ranging from 30 to 60 mg per 100 g dry tissue, which are extremely low compared with the 100–200 mg per 100 g more commonly found. The availability of the soil nutrients for the growth of M. caerulea was assessed experimentally in a glasshouse, where near-optimal conditions of water supply could be maintained thus eliminating the effects of differences in the degree of waterlogging which occur in the field (Loach 1968a); the growth response of seedlings planted in soil cores from each site to additions of the major nutrients N, P and K, alone and in combination, was monitored. Phosphorus additions, especially in combination with the other elements, caused very large growth increases in all soils. The increase was greatest in the valley bog soil, where there was a fivefold rise from an initially low yield to a level not significantly different from that of the wet-heath soil. The results of a further experiment, in which soil cores were freely drained or waterlogged, showed that drainage without added nutrients did not improve the growth of M. caerulea in valley bog soil, confirming the extreme nutrient deficiency of this soil type. This also suggests that in the three wet-heath sites the differences in the abundance of M. caerulea caused by waterlogging are not to be explained solely in terms of its effect on nutrient uptake. A further experiment was carried out by Sheikh (1969b) in the enclosures cleared of standing vegetation by Loach (1968a); the effects of additional nutrients (N, P, and K) and competition between transplanted material of M. caerulea and Erica tetralix were determined after two seasons' growth. Without additional nutrients there were large differences between sites in the growth of M. caerulea: poor growth on the valley bog (453 mg dry weight per plant) and best on the wet-heath plots (768 mg). The response to nutrients was marked (mean plant dry weight 1315 mg) and the interaction of nutrition with sites was such that site differences disappeared when nutrients were applied. There were no significant effects of competition with E. tetralix on the growth of M. caerulea. Green shoots of dominant M. caerulea collected between mid-July and mid-August from 36 widely ranging, undisturbed, unfertilized habitats throughout Britain were analysed for inorganic element concentrations, together with matching analyses of the soil nutrients (Rowland et al. 1999). Soil pH ranged between 3.1 and 5.8, and the humus content varied widely. There were significant correlations (P < 0.001) between loss-on-ignition and N, P, K, Na, Mg and Ca (P < 0.05) in the soil. Concentrations of Ca, Mg, Zn and Mn in the plant material were significantly correlated (P < 0.001) with extractable levels in the soil. However, the lack of correlation between the measures of soil availability for N, P and K and plant tissue concentrations may indicate that rapid shoot growth in the spring is supported more from stored nutrients, translocated back from the basal internodes, than from concurrent absorption from the soil. The average nutrient demands of M. caerulea for P, K, Ca, Fe and Na were relatively low compared with the mean concentrations in 21 other grass species sampled in the Vegetation Nutrient Survey, whereas they were relatively high for N, Mn and Zn. Widespread acidic grassland dominated by peat-forming M. caerulea (Molinietum caeruleae) is closely related to the main peat vegetation of the northern and western hills, to which it is often marginal (Tansley, Br. Isl.). In the Southern Uplands it is characteristic of considerable areas of grassland on peaty gley podzols (Veg. Scot.). Molinia caerulea freely colonizes the drier parts of the 'blanket bog' of western Ireland and Scotland, and its associates are predominantly wet peat plants (Tansley, Br. Isl.). In the Western Highlands and in Galloway, extensive Molinieto-Callunetum, which occurs on shallow ombrogenous peat, can be regarded either as blanket bog or wet grass-shrub heath. This association often grades into floristically poor Molinia-Myrica mire, where the soligenous influence becomes more definite and in which the co-dominant M. caerulea often shows a dense tussocky habit (Pl. Comm. Scot.). In southern England, M. caerulea is perhaps the most characteristic plant of damp or wet heath and it is nearly as widespread as it is in the above mire communities and on certain types of fen in England and in Northern Ireland (Tansley, Br. Isl.). On the peat of the East Anglian Fens, when Cladium mariscus sedge fens are cut at frequent intervals (every 2 years), apparently stable communities with abundant or dominant Molinia caerulea are produced. Such communities were once widespread but nowadays are quite small in extent (Perring et al. 1964; Wheeler 1980). In these fens, Molinietum is intermediate between luxuriant base-rich fen and acidic bog (Tansley, Br. Isl.). The results of a survey carried out between 1967 and 1969 (Pigott & Wilson 1978) show that an association in which M. caerulea was dominant, and formed a tussocky grassland rooted in a black fibrous peat, occupied a wide zone in the northern and eastern parts of Esthwaite North fen. Although neither mown nor grazed in 1967–9 the species occupied the same area as it did in 1914–16 when part of the area was still cut for hay (Pearsall 1918). In the Scottish Highlands, M. caerulea also occurs locally in wetter places in pinewoods, birchwoods and oakwoods (Steven & Carlisle 1959; Veg. Scot.). In two western oakwoods (Blechno-Quercetum petraeae) in North Wales, M. caerulea occurs in wet areas differentiated by Sphagnum palustre and often S. recurvum (Edwards & Birks 1986); it is present in acidic mires (pH 3.8) at Coed-y-Rhygen; at Coed Ganllwyd it dominates acid boggy areas (pH 4.0) and also occurs in areas of seepage that are base-enriched (pH 4.8). The National Vegetation Classification records M. caerulea in a range of communities (Rodwell 1991a,b, 1992, 1995), and provides community descriptions, distribution, affinities, habitat details, and floristic tables. Molinia caerulea is ubiquitous in the following communities which are synonymous with vegetation referred to above and often termed a Molinietum or 'Molinia grassland': in Molinia caerulea–Potentilla erecta mire (M25), which occurs throughout western Britain, and is especially frequent in south-west England, Wales and southern Scotland, on moist but well-aerated, acid to neutral, peats and peaty mineral soils where there is at least a slight degree of nutrient enrichment; and in the warmer lowlands of southern Britain in Molinia caerulea-Cirsium dissectum fen-meadow (M24), a community of moist to fairly dry peats and peaty mineral soils, circumneutral but somewhat mesotrophic. There are other mire communities in which M. caerulea is constant throughout. In particular, the Scirpus cespitosus(Trichophorum cespitosum)–Erica tetralix wet heath (M15), a compendious vegetation type with few constants and wide variation in the pattern of dominance and in associated flora. Molinia caerulea, Trichophorum cespitosum, Erica tetralix and Calluna vulgaris are all of high frequency, but of the four species, M. caerulea is the most consistent overall and it is often abundant. The community occurs widely at lower altitudes in western and northern Britain, particularly in the western Highlands of Scotland, in south-west Scotland and Wales, and, less extensively, in the Lake District, Dartmoor and Exmoor, characteristically on moist and generally acid and oligotrophic peats and peaty mineral soils. In the eastern and southern lowlands of Britain the Scirpus (Trichophorum)–Erica wet heath is replaced by the Erica tetralix–Sphagnum compactum wet heath (M16), which is characteristically dominated by varying proportions of Erica tetralix, Calluna vulgaris and Molinia caerulea depending on environmental factors, and occurs on acid and oligotrophic mineral soils or shallow peats that are at least seasonally waterlogged. Molinia caerulea is abundant in Scirpus cespitosus (Trichophorum cespitosum)–Eriophorum vaginatum blanket mire (M17), a community on waterlogged ombrogenous peat, dominated by mixtures of monocotyledons, ericoid sub-shrubs and Sphagna, among which Calluna vulgaris, Erica tetralix, Eriophorum angustifolium, Narthecium ossifragum, Potentilla erecta, Sphagnum capillifolium and S. papillosum are the other constant species; it is largely confined to western Britain, being especially widespread in the western Highlands of Scotland and the western Isles and running down through south-west Scotland, the Lake District, west Wales and south-west England. A number of mire communities containing M. caerulea are widespread but local in England and Wales. It is consistently present and often greatly abundant in the field layer of Betula pubescens–Molinia caerulea woodland (W4), in which it shares constancy together with Sphagnum recurvum/palustre, a mire woodland community that is widespread but local throughout the lowlands and upland fringes of Britain, characteristically on thin or drying ombrogenous peats around the margins of blanket mires; also on soligenous peats in valley mires and on peaty gleys flushed with base- and nutrient-poor waters. In Narthecium ossifragum–Sphagnum papillosum valley mire (M21), M. caerulea is abundant in better aerated situations and also constant together with Calluna vulgaris, Drosera rotundifolia, Erica tetralix, and Eriophorum angustifolium, a community of the southern lowlands of Britain on permanently waterlogged, acidic and oligotrophic peats. In Schoenus nigricans–Juncus subnodulosus mire (M13), M. caerulea is locally prominent and also a constant together with Carex panicea, Potentilla erecta,Succisa pratensis, Calliergon cuspidatum and Campylium stellatum, a community that is widespread but decidedly local throughout lowland England and Wales, and confined to peat or mineral soils in and around mires irrigated by base-rich, highly calcareous waters. Molinia caerulea is generally abundant in Schoenus nigricans–Narthecium ossifragum mire (M14), together with the other constants Anagallis tenella, Erica tetralix, Aneura pinguis, Campylium stellatum, Scorpidium scorpioides, Sphagnum auriculatum and S. subnitens, which occurs in the oceanic south-west of Britain, very locally in Cornwall, east Devon, south-east Dorset and the New Forest, characteristically on peats and mineral soils irrigated by moderately base-rich and calcareous ground waters. Molinia caerulea is the most common dominant in Molinia caerulea–Crepis paludosa mire (M26) together with a substantial block of constants and companions, Carex nigra, C. panicea, Equisetum palustre, Filipendula ulmaria, Potentilla erecta, Ranunculus acris, Succisa pratensis, Valeriana dioica and Calliergon cuspidatum, a very local community of moist, moderately base-rich and calcareous peats and peaty mineral soils in the submontane northern and Craven Pennines; and abundant in the Carex echinata and Juncus acutiflorus subcommunities of the Carex echinata–Sphagnum recurvum/auriculatum mire (M6), which are virtually ubiquitous in the upland fringes on soligenous peats and peaty gleys irrigated by base-poor waters in the submontane zone in Britain. In a number of local heathland communities M. caerulea is constant: it is obviously preferential in the Molinia caerulea subcommunity of the Calluna vulgaris–Ulex minor heath (H2), which is particularly extensive in the New Forest; locally extensive in Ulex minor–Agrostis curtisii heath (H3) together with the other constants Calluna vulgaris, Erica cinerea and E. tetralix, on impoverished acid soils with impeded drainage, confined to south Dorset and Hampshire; in Ulex gallii–Agrostis curtisii heath (H4), very similar to the previous example but with the replacement of the one gorse by the other together with Potentilla erecta as an additional constant, on a variety of acid soils in the warm oceanic parts of south-west Britain; on the Lizard peninsula in Cornwall, M. caerulea is frequently of high cover in Erica vagans–Schoenus nigricans heath (H5) together with the other constants Anagallis tenella, Carex pulicaris, Erica tetralix, Festuca ovina, Potentilla erecta, Serratula tinctoria, Succisa pratensis, Ulex gallii and Campylium stellatum, confined to wet base-rich but calcium-poor mineral soils and shallow peats; often abundant in the Agrostis curtisii and Molinia caerulea subcommunities of the Erica vagans–Ulex europaeus heath (H6), with the other constants Agrostis canina ssp. montana, Carex flacca, Erica cinerea, Filipendula vulgaris, Potentilla erecta, Ulex gallii, and Viola riviniana, characteristic on oligotrophic, circumneutral or fairly base-rich, but not lime-saturated, free-draining brown earths, found only on the Lizard peninsula in Cornwall; and also in the Molinia caerulea subcommunity of the widely distributed Calluna vulgaris–Deschampsia flexuosa heath (H9), which primarily occurs on lowland sites in the southern Pennines and North York Moors with more scattered local occurrences through the Midland plain. Molinia caerulea occurs frequently in Carex rostrata–Calliergon cuspidatum/giganteum mire (M9), a community with a widespread but rather local distribution; Carex dioica–Pinguicula vulgaris mire (M10), of widespread but local occurrence throughout northern England and Scotland on soligenous mineral soils and shallow surface peats kept very wet by base-rich, calcareous and oligotrophic waters; Hypericum elodes–Potamogeton polygonifolius soakway (M29), which extends in a well-defined zone from west Surrey, through the New Forest to the south-west Peninsula, up through Wales and into Galloway, on shallow soakways and pools in peats and peaty mineral soils; Juncus subnodulosus–Cirsium palustre fen meadow, Briza media–Trifolium spp. subcommunity (M22b), widely distributed on suitably wet and base-rich soils through the southern British lowlands, particularly in East Anglia, north Buckinghamshire and Anglesey; in the Juncus acutiflorus subcommunity of the Juncus effusus/acutiflorus–Galium palustre rush-pasture (M23), widespread in western Scotland and Wales, exceedingly common at low to moderate altitudes; in Calluna vulgaris–Erica cinerea heath (H10), which occurs widely particularly in south-west Scotland on acid to circumneutral, free-draining soils; and in Agrostis curtisii grassland (U3) on moist base-poor soils, in response to burning and grazing, around the upland fringes of the south-west and in southern parts of the New Forest. In a number of mire communities M. caerulea is occasional: Carex rostrata–Sphagnum recurvum mire (M4) which is widespread but local throughout the north-west of Britain; Carex rostrata–Sphagnum squarrosum mire (M5) with a widespread but fairly local distribution in the north-western parts of Britain; Carex demissa–Saxifraga aizoides mire (M11), a community largely confined to Scotland, where it is common in the southern and central Highlands but also occurs more locally in the Southern Uplands, the Lake District, the northern Pennines and in north Wales; Erica tetralix–Sphagnum papillosum raised and blanket mire (M18), of widespread but local occurrence through the lowlands of Wales and north-west Britain up to the Clyde-Moray line; in the Erica tetralix subcommunity of the Calluna vulgaris–Eriophorum vaginatum blanket mire (M19), found at lower altitudes through Wales and Strathclyde; in the Juncus effusus–Holcus lanatus subcommunity of the Filipendula ulmaria–Angelica sylvestris mire (M27), distributed down the western seaboard of lowland Britain; and also in Calluna vulgaris–Juniperus communis ssp. nana heath (H15) of rather patchy occurrence along the western side of the more northerly mountains, especially Beinn Eighe and Foinaven. In the following communities M. caerulea is also found occasionally: Salix pentandra–Carex rostrata woodland (W3), which occurs locally throughout the submontane zone of northern Britain; in the Rhytidiadelphus triquetrus subcommunity of the Quercus petraea–Betula pubescens–Dicranum majus woodland (W17) found in the more continental parts of eastern Scotland; Sesleria albicans–Galium sterneri grassland, Helianthemum canum–Asperula cynanchica subcommunity (CG9) confined to the Carboniferous Limestone in the lowlands of South Lakeland and north Lancashire; and in Carex paniculata sedge-swamp (S3) widespread around the open-water transitions of the Shropshire meres. Molinia caerulea is scarce in the following woodland communities: Salix cinerea–Galium palustre woodland (W1); Salix cinerea–Betula pubescens–Phragmites australis woodland (W2); Fagus sylvatica–Deschampsia flexuosa woodland (W15); Quercus spp.–Betula spp.–Deschampsia flexuosa woodland (W16); and Quercus petraea–Betula pubescens–Dicranum majus woodland (W17). Molinia caerulea is also scarce in a number of grassland and montane communities: Festuca ovina–Agrostis capillaris–Thymus praecox (polytrichus) grassland (CG10); Festuca ovina–Agrostis capillaris–Alchemilla alpina grass-heath (CG11); Dryas octopetala–Carex flacca heath (CG13); Deschampsia flexuosa grassland (U2); Festuca ovina–Agrostis capillaris–Galium saxatile grassland (U4); Luzula sylvatica–Geum rivale tall-herb community (U17); and Pteridium aquilinum–Galium saxatile community (U20). Molinia caerulea is scarce in a number of mire and swamp communities: Sphagnum auriculatum bog pool community (M1); Sphagnum cuspidatum/recurvum bog pool community (M2); Eriophorum angustifolium bog pool community (M3); in the Empetrum nigrum ssp. nigrum subcommunity of the Calluna vulgaris–Eriophorum vaginatum blanket mire (M19); Anthelia julacea–Sphagnum auriculatum spring (M31); Ranunculus omiophyllus–Montia fontana rill (M35); Phragmites australis swamp and reed-beds (S4); and in Phragmites australis–Peucedanum palustre tall-herb fen (S24). Molinia caerulea is scarce in a number of heathland communities: Calluna vulgaris–Scilla verna heath (H7); Calluna vulgaris–Ulex gallii heath (H8); Calluna vulgaris–Vaccinium myrtillus heath (H12); Calluna vulgaris–Cladonia arbuscula heath (H13); Calluna vulgaris–Racomitrium lanuginosum heath (H14); and in Calluna vulgaris–Vaccinium myrtillus–Sphagnum capillifolium heath (H21). In the submontane belt of Central Europe, purple moor-grass (Molinia caerulea) has become the litter grass par excellence of unmanured litter meadow communities. These communities, including the extreme examples of the floristically rich Cirsio tuberosi-Molinietum on base-rich damp soils and the acid-soil Junco-Molinietum, which are referred to the alliance Molinion, in the order Molinietalia, in the class Molinio-Arrhenatheretea, are now to be found only in the plains north of the Alps and in valleys of the outer Alps themselves (Ellenberg 1988). In the lowlands and to a lesser extent in the montane belt of Central Europe, three groups of pure deciduous woodland types can be distinguished in which M. caerulea occurs in a subassociation on moist-soil, Betulo-Quercetum molinietosum; in subatlantic Birch-Oak woods
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