Briza media L.

Authors


  • *

    Abbreviated references are used for standard works, see Journal of Ecology (1975), 63, 335–344. Nomenclature of vascular plants follows Flora Europaea.

  • List Br. Vasc. Pl. (1958) no. 680, 1

A loosely tufted perennial with short rhizomes from which arise vegetative shoots. Culms 15–60 (−100) cm high, slender, erect, 2–3-noded, solitary, smooth. Leaves with dull glaucous to mid-green adaxial and abaxial surfaces, hairless; blades usually 4–20 (−28) cm long, 2–4 (−7) mm wide, with minute acroscopic teeth on the margins, with a slender boat-shaped tip; ribs numerous, closely packed, less obvious on the abaxial surface; sheaths smooth, entire, soon splitting, dark reddish-brown at base; ligules up to 1.5 mm long, membranous, blunt with irregular margins. Culm leaves 3 or 4, uppermost with long sheaths. Panicles 4–10 (−18) cm long, lax, roughly pyramidal, with up to 20 branches, and up to 60 spikelets, sparsely divided, spreading, with scabrous hair-like pedicels 5–20 (−50) mm long and slightly thickened below the spikelets. Spikelets 4–7 mm long and wide, loosely scattered and drooping, broadly elliptic to broadly ovate, laterally compressed, generally purplish-brown, usually breaking up at maturity beneath the lemmas but many spikelets remaining undispersed on the branches and shed from the panicle intact, 4–9 (−12)-flowered. Glumes slightly unequal, deeply concave, hooded at the apex, boat-shaped, 2.5–3.5 mm long, with 3–5 veins, firmly membranous, dull-purple with white and shiny margins. Lemmas 3.7–4.1 mm, strongly cordate at the base, bluntly keeled in the lower half, closely overlapping, rounded on the back, with 7–9 veins, variegated purple and green, with hyaline margin. Paleas flat, thin, almost as long as the lemma, with two keels, narrowly winged. Lodicules 2, linear-lanceolate, acute. Grain enclosed within the papery lemma and palea, c. 2 mm long, rounded on the back, flattened on the front; mean oven-dry weight 0.53 mg. The root system is a dense mat of whitish fibrous roots. The primary roots are up to 1 mm in diameter and are largely unbranched, but there is a dense network of branching secondary roots. The root mass is fairly vertical with an average root length of c. 40 cm. The species produces pale brown rhizomes up to 13 cm long and 1.5 mm in diameter.

Native. Subspecies media occurs throughout the range; subspecies elatior (Sibth. & Sm.) Rohlena occurs in south-east Europe.

Briza media is a widely distributed common species of dry and calcareous, but also moist and acidic grassland, of little herbage value.

I.Geographical and altitudinal distribution

The distribution of B. media in the British Isles is shown in Fig. 1. The species is widely distributed throughout the British Isles on Chalk, Carboniferous, Magnesian and Devonian Limestone, and is also found on circumneutral soils and on some acid soils where these are well-drained. The species is only occasional in the north of Scotland, the Shetland Isles and Orkney Isles and on some of the Western Isles. It has been recorded from the Isle of Man, the Channel Isles and the Isle of Wight but not from the Isles of Scilly. In Wales the species is common on the Lias of South Dyfed and on the calcareous substrata in the south of Powys but occurs less frequently on calcareous substrata of Gwent, Gwynedd and Clwyd (Hyde & Wade 1957). It is widely distributed across central Ireland, but is less common in both the north and the south of Ireland.

Figure 1.

The distribution of Briza media in the British Islea. (○) Pre-1950; (•) 1950 onwards. Each dot represents at least one record in a 10-km square of the National Grid. Mapped by Henry Arnold, Biological Records Centre, Centre for Ecology and Hydrology, using Alan Morton's DMAP programme, mainly from records made by members of the Botanical Society of the British Isles.

Briza media is recorded throughout western Europe but is absent from the Faeroe Islands and Iceland, and is noted only as a casual in the extreme north of Europe in Flora Europaea. It is absent from the Mediterranean islands of the Balearics, Crete, Sicily and Cyprus, and does not occur in the Azores. In northern Europe, B. media is found in the Baltic, Karelia (southern part), Ladoga-Ilmen, Dvina-Pechora (western and southern parts), Upper and Middle Dniepr, the Upper Volga, Volga-Kama, Volga-Done (northern part), Ural (central and southern), Carpathians and the Caucasus (Tsvelev 1984). Dahl (1998) refers B. media to a southern boreal sub-element, and Preston & Hill (1997) assign it to the European temperate floristic element.

Outside Europe, B. media has been recorded from Syria and Turkey, and from Kashmir, Myanmar, Nepal and Tibet. The species is also recorded from South Africa, and from Australia and New Zealand (Vergl. Chor.) as an alien. In North America, the species is introduced and occurs in Connecticut, Massachusetts, Michigan and Vermont in the United States and in British Columbia and Ontario in Canada (Hitchcock 1971).

Briza media is found to 65° N in Europe (Sweden), to c. 30° N in Asia and to c. 50° N in North America.

In England, B. media has an altitudinal range from sea-level to 640 m (Cumbria), from sea-level to 515 m in Wales (Tal-y-Fan), from sea-level to 655 m in Scotland (Atholl) and from sea-level to 427 m in Ireland (Wicklow) (Alt. Range Br. Pl.). It is found to 1870 m in the Alps (Pfl. Exk.), to 3000 m in the Caucasus, to 1000 m in the Carpathians, to 1450 m in the Pyrenees, to 3500 m in Nepal and to 4500 m in the north-west Himalayas.

II. Habitat

(A) CLIMATIC AND TOPOGRAPHICAL LIMITATIONS

Briza media is exposed to annual precipitation of around 1700 mm on the Isle of Mull and to conditions with less than 1 mm precipitation during July and August in southern Spain, where average monthly maximum temperatures are around 43 °C (Meteorological Office 1972). It experiences temperatures as low as −35 °C in January in Estonia; however, the effects of these low temperatures are moderated by an insulating blanket of up to 20 cm of snow, which normally persists from November to the beginning of April (Lippmaa 1931).

No evidence in Britain of wind or insolation damage has been noted, and the species is found on steep dry slopes in the Jura Alps subject to strong insolation, and to Föhn-swept slopes in Germany (Braun-Blanquet 1939).

Briza media is found both on flat ground and on slopes up to about 60°, but is most common on slopes between 20 and 40° (Grime et al. 1988). The species shows no aspect preference in the British Isles nor in western and central Europe.

(B) SUBSTRATUM

Briza media is a component of semi-natural calcareous pastures, scree slopes, quarry spoil and road verges, and has been recorded from old meadows and enclosed pastures (Grime et al. 1988). It is widespread on brown earths, shallow free-draining rendzinas and grey rendzinas overlying chalk and limestone in England, but is less frequent on these in Wales and northern Scotland. Grubb et al. (1969) recorded B. media from tall chalk heath at Lullington Heath, Sussex, and Ivimey-Cook & Proctor (1966) recorded it from limestone heath in the Burren, Co. Clare. The species has also been recorded from wet heathy roadsides and from water meadows on rich soils (Edees 1972), from limestone swamps (Horwood & Noel 1933), grazed fen flushes (Sinker et al. 1985) and from calcareous mires (Grime et al. 1988). It is also recorded from calcareous peats and from clays with impeded drainage (Sinker et al. 1985), from Keuper marls and Carboniferous shales (Newton 1971), from Coal Measures (Graham 1988), from Liassic clays and marls, from Bunter sandstone, from incipient podsols (Balme 1953), from neutral to acidic grassland and heaths (Grose 1957) and from the very acid sands of the Weald, with pH < 4.0 (C. Stace, personal communication). It is recorded from volcanic rocks and stabilized sand dunes in Wales (Benoit & Richards 1961), from coastal sands in Yorkshire (Crackles 1990), and from dry dune pasture at Braunton Burrows, north Devon (Willis et al. 1959). Briza media occurs on brown forest soils, on high base status humic gleys, peaty gleys and flushed peat in Scotland (Gauld & Robertson 1985) and also from raw soils on sandy river shingle (Birse 1980).

Briza media is recorded as occurring in soils of between pH 4.0 and 8.0 but most frequently in soils of around pH 7.0 (Ecol. Atl.).

Soil analyses (methods according to Chem. Anal.) for 15 British sites supporting B. media gave a range of exchangeable calcium and magnesium, extracted with M ammonium acetate (pH 9.0), from 1200 to 7500 mg kg−1 and from 30 to 500 mg kg−1, respectively, while potassium ranged from 30 to 540 mg kg−1. Phosphate phosphorus, extracted with 0.5 m sodium bicarbonate (pH 8.5), ranged from 5 to 39 mg kg−1 and total nitrogen from 0.1 to 1.9%.

In Continental Europe, in addition to soils overlying calcareous rocks, B. media occurs on calcareous moraines (Sterner 1922), on dry shell deposits (Willems 1982), on slate (Andersson 1970) in southern Sweden, on porphyr and gypsum (Meusel 1940), on dry acid soils (Ellenberg 1988) in Germany, and from biotite and granite gneiss in Switzerland (Marschall 1947).

While B. media may be considered as most typically a plant of fairly dry, well-drained calcareous soils, it has a very wide edaphic tolerance, growing successfully in distinctly acidic soils, wet and poorly drained sites and on soils of many different textures.

III. Communities

Briza media is predominantly a species of calcareous grasslands and occurs with a high constancy in the following communities defined by the National Vegetation Classification (Rodwell 1991, 1992).

CG1 Festuca ovina–Carlina vulgaris grassland is found on freely (often excessively) draining rendzina soils with a high base status, on steep and rocky, but stable, slopes on hard limestones, usually with a southerly to westerly aspect and so with a tendency to summer droughting. Often heavily grazed by sheep and rabbits, this community is confined to Devonian Limestone in Devon and to Carboniferous Limestone in Wales and the Mendips. Briza media has an overall constancy of III in CG1 but attains a constancy of IV in the subcommunities of Helianthemum canum and Trinia glauca and a constancy of V in the Koeleria macrantha subcommunity. Constant species, as defined by the NVC, for CG1 and the following communities are given in Table 1.

Table 1.  Constant species of British calcareous grassland communities (see text) containing Briza media
SpeciesCalcareous grasslands
CG1CG2CG3CG4CG5CG6CG8CG9
Avenula pratensisIVIVIV
Avenula pubescensIV
Brachypodium pinnatumVV
Briza mediaVIVIVIIIIVIIIIVIV
Bromus erectusVV
Campanula rotundifoliaIV
Carex flaccaVIVIVVVIV
Carlina vulgarisIV
Centaurea nigraIV
Cirsium acauleIV
Ctenidium molluscumIV
Dactylis glomerataIV
Festuca ovinaVVIVVIVIVIV
Festuca rubraV
Galium sterneriIV
Galium verumIV
Helianthemum nummulariumIVIVIV
Hieracium pilosellaIVIVIV
Hypnum cupressiformeIV
Leontodon hispidusIVIV
Linum catharticumIVVIV
Lotus corniculatusIVIVIVIVIVIV
Pimpinella saxifragaIV
Plantago lanceolataIVIVIVIV
Pseudoscleropodium purumIV
Sanguisorba minorVVVIVV
Scabiosa columbariaIVIVIV
Sesleria albicansVIV
Taraxacum officinale agg.IV
Thymus praecoxVIVIVIVIVV
Thymus praecox/pulegioidesIV
Viola rivinianaIV

CG2 Festuca ovina–Avenula pratensis grassland consists of a rich mixture of grasses and dicotyledons in a closed sward and is traditionally grazed by sheep and rabbits. It occurs most frequently in relatively dry and warm, lowland climates on free-draining calcareous soils derived from calcareous bedrock, often prone to summer droughting. Briza media has a constancy of IV in this community.

CG3 Bromus erectus grassland achieves maximum extent on lightly grazed or ungrazed grasslands over Chalk in the south-eastern areas of Britain, and over the Oolite of the Cotswolds and Northhamptonshire. Briza media has an overall constancy of III in this community, but a constancy of IV in the subcommunities of Centaurea nigra and Knautia arvensis–Bellis perennis.

CG4 Brachypodium pinnatum grassland is also mainly associated with lightly or ungrazed calcareous swards in south-eastern Britain, but is more generally found on the cooler and damper areas of the Chalk and Oolite than is the Bromus erectus grassland, which is more continental in character. Briza media has an overall constancy of III in this community.

CG5 Bromus erectus–Brachypodium pinnatum grassland occurs where B. pinnatum is favoured by amelioration of extreme Continental conditions, but not so greatly as to exclude Bromus erectus. The community is most characteristic on the calcareous, base-rich soils of the Oolite on the north-western fringe of lowland limestones of the Cotswolds and Northhamptonshire/Lincolnshire scarps. Briza media has an overall constancy of IV and of V in the Hieracium spp. subcommunity.

CG6 Avenula pubescens grasslands are found on a variety of gently sloping lowland limestones, mainly in the south of England. The soils are deep and moist, though mostly free-draining alluvial rendzinas, or calcareous brown earths, and in some cases more mesophytic soils occur on flat limestones. This community is lightly grazed by cattle; on sloping limestones it is grazed by rabbits. Briza media has an overall constancy of only II in this community, but achieves a constancy of III in the Dactylis glomerata–Briza media subcommunity.

CG8 Sesleria albicans–Scabiosa columbaria grassland is found only on free-draining calcareous, steep slopes of Magnesian Limestone in Durham, principally on rendzinas rich in calcium and magnesium carbonates. The climate is cool and dry, and the community is a plagioclimax vegetation maintained by grazing of domestic animals and rabbits. Briza media has a constancy of IV in CG8.

CG9 Sesleria albicans–Galium sterneri grassland is found in the northern Pennine submontane or montane climate, over shallow, freely draining but moist, calcareous lithomorphic soils on drift-free Carboniferous Limestone exposures. It forms an important part of upland farm hill-pasture and as such is frequently grazed, mainly by sheep. In CG9, Briza media reaches an overall constancy of IV and a constancy of V in the Carex capillaris–Kobresia simpliciuscula subcommunity.

Briza media occurs with a low constancy (I) in the calcareous grassland community of Festuca ovina–Hieracium pilosella–Thymus praecox/pulegioides (CG7) and in the Festuca ovina–Agrostis capillaris–Thymus praecox grassland (CG10).

Briza media is also a component of the following mesotrophic grasslands.

MG3 Anthoxanthum odoratum–Geranium sylvaticum grassland. This is a northern submontane community almost entirely restricted to a few valleys in northern England where traditional hay-meadow management occurs, and comprises a dense community of grasses and herbs. Briza media attains an overall frequency of I but a frequency of III in the B. media subcommunity. The constant species for this and the following grassland community are given in Table 2.

Table 2.  Constant species of mesotrophic grassland communities (see text for numbering) containing Briza media
SpeciesMesotrophic grasslands
MG3MG5
Agrostis capillarisIVIV
Alchemilla glabraIV
Anthoxanthum odoratumVIV
Centaurea nigraIV
Cerastium fontanumV
Conopodium majusV
Cynosurus cristatusV
Dactylis glomerataIVIV
Festuca rubraIVV
Geranium sylvaticumV
Holcus lanatusIVIV
Lotus corniculatusV
Plantago lanceolataVV
Poa trivialisIV
Ranunculus acrisV
Rumex acetosaV
Sanguisorba officinalisIV
Trifolium pratenseIV
Trifolium repensIVIV

MG5 Cynosurus cristatus–Centaurea nigra grassland occurs throughout the British lowlands. Briza media has a constancy of III in the subcommunity of Galium verum, found mostly over calcareous bedrocks, and a constancy of III in the Danthonia decumbens subcommunity, mainly occurring on the upland margins of northern England and Wales.

The species is also found at a low constancy in the mesotrophic grassland communities of Arrhenatherum elatius (MG1), Arrhenatherum elatius–Filipendula ulmaria (MG2), Alopecurus pratensis–Sanguisorba officinalis (MG4), Cynosurus cristatus–Caltha palustris (MG8), and Holcus lanatus–Deschampsia cespitosa grassland (MG9), and also in the calcifuge sward of Festuca ovina–Agrostis capillarisGalium saxatile grassland (U4). Briza media is also found as a minor component of the Salix repens–Campylium stellatum dune-slack community (SD14).

Briza media is a component of several mire communities; constant species for these are given in Table 3.

Table 3.  Constant species of mire and fen-meadow communities (see text) containing Briza media
SpeciesMire and fen-meadow community
M10M13M22M26
Aneura pinguisIV
Bryum pseudotriquetrumIV
Calliergon cuspidatumVVIV
Campylium stellatumIVIV
Carex dioicaIV
Carex hostianaIV
Carex lepidocarpaIV
Carex nigraV
Carex paniceaIVVV
Carex pulicarisIV
Cirsium palustreIV
Crepis paludosaV
Ctenidium molluscumIV
Drepanocladus revolvensIV
Equisetum palustreIVIV
Eriophorum angustifoliumIV
Filipendula ulmariaIVIV
Holcus lanatusIV
Juncus articulatusIV
Juncus subnodulosusVV
Lotus uliginosusIV
Mentha aquaticaIV
Molinia caeruleaVV
Pinguicula vulgarisV
Potentilla erectaIVIV
Ranunculus acrisIV
Schoenus nigricansV
Succisa pratensisIVIV
Valeriana dioicaV

M10 Carex dioica–Pinguicula vulgaris mire is typically a soligenous mire kept very wet by base-rich, calcareous and oligotrophic waters. This is predominantly a community of north-western Britain, where the cool, wet climate influences the structure and floristics of the vegetation. Most stands are grazed by large herbivores and trampling by these plays a large part in maintaining an open community. Briza media has a constancy of IV in the Briza media–Primula farinosa subcommunity and an overall constancy of II.

M13 Schoenus nigricans–Juncus subnodulosus mire is confined to peat or mineral soils irrigated by base-rich, highly calcareous and oligotrophic waters. This community is often found below springs and seepage lines, or on flushed margins of valley mires, and is restricted to the warmer southern parts of Britain. Some stands have been affected by mowing, burning and peat-digging; grazing sometimes affects the floristics and structure of the vegetation. Briza media has a constancy of V in the Briza media–Pinguicula vulgaris subcommunity and an overall constancy of II.

M22 Juncus subnodulosus–Cirsium palustre fen-meadow is predominantly a community of moderately mesotrophic and moist, base-rich peats and mineral soils found in lowland southern Britain. It occurs either around well-developed flushes, springs and mires or delineates the influence of more ill-defined areas of surface waters. The identity of the community is maintained by mowing and/or grazing. Briza media has a constancy of IV in the Briza media–Trifolium spp. subcommunity and an overall constancy of II.

M26 Molinia caerulea–Crepis paludosa mire is a very local community of moderately base-rich, moist, calcareous peats and peaty mineral soils in the submontane grasslands of the northern Pennines. It can be found either as a stable component around open waters and mires, but also on flushed slopes in soligenous situations, often subject to grazing. Briza media has a constancy of V in the Festuca rubra subcommunity and an overall constancy of III.

Briza media is also a minor component in the Molinia caerulea–Cirsium dissectum fen-meadow (M24) and the Cratoneuron commutatum–Carex nigra spring community (M38).

Briza media is recorded from Scotland (Birse 1980) from the Polygono–Helictotrichetum pratensis association which is a woodland replacement community created by grazing on rendzinas and shallow brown, calcareous soils. The characteristic species are Avenula pratensis, Carex caryophyllea, Helianthemum nummularium, Koeleria macrantha, and Polygonum viviparum. Birse (1980) also describes B. media as a minor component of the Anthyllido–Rhacomitrietum canescentis association, a pioneer community of river flood plains.

In Ireland, B. media is recorded from the mesotrophic grassland Cynosurus cristatus–Centaurea nigra (MG5), which is the typical grassland of well-drained pastures over limestone, usually grazed by cattle. O’Sullivan (1982) records B. media from the Junco–acutiflori–Molinietum association of wet meadows, together with Cynosurus cristatus, Lotus corniculatus, Phleum pratense, Trifolium pratense and Trifolium repens.

Briza media is also recorded by Ní Lamhna (1982) from the Festuco–Galietum maritimi sand dune vegetation of Malahide Island, north of Dublin, which is found on middle dunes of grass-dominated, ungrazed or very lightly grazed, vegetation. Differential species are Anthoxanthum odoratum, Briza media, Dicranum scoparium, Euphrasia occidentalis, Koeleria macrantha, Potentilla sterilis, Pteridium aquilinum, Rosa pimpinellifolia, Thymus praecox and Trifolium repens.

Ivimey-Cook & Proctor (1966) recorded B. media from the Galium verum–Asperula cynanchica nodum, a calcareous dune community of the Burren, Co. Clare, together with Agrostis stolonifera, Asperula cynanchica, Carex flacca, Ctenidium molluscum, Euphrasia salisburgensis, Festuca ovina, F. rubra, Galium verum, Lotus corniculatus, Plantago lanceolata, Prunella vulgaris, Thymus praecox and Viola riviniana, and also from the Hyperico–Dryadetum association. This is a shrub-dominated community found on leached organic soil over bare limestone. Characteristic species are Calluna vulgaris, Danthonia decumbens, Dryas octopetala, Empetrum nigrum, Hylocomium splendens, Hypericum pulchrum, Hypnum cupressiforme var. ericetorum, Neckera crispa, Polygala vulgaris and Rosa pimpinellifolia. Ivimey-Cook & Proctor (1966) also recorded B. media from a Burren calcareous spring community, together with Anagallis tenella, Cardamine pratensis, Carex lepidocarpa, C. panicea, Juncus articulatus, Molinia caerulea, Pinguicula vulgaris and Succisa pratensis.

Briza media has been observed by the author in a lightly shaded railway cutting, and on roadsides in the shade of pines in Sutherland. It has been recorded from a stream-side in a pine plantation in Spain, in oak woods in the Pindos Mountains of Greece, in sparse oak-wood in southern Sweden, in forest-steppe in central Europe, in Juniper drifts in Estonia and in a deciduous coniferous forest in Nepal.

In continental Europe, B. media occurs in a number of associations of the Brometalia erecti throughout western Europe; these occur on dry steep slopes throughout the Alpine range, in dry rocky places in France and Belgium, the deeper moister soils of the Danube and Rhine valleys and also on more humid slopes of the Alps. Briza media also occurs in some associations of the class Arrhenatheretalia. A range of communities containing B. media, with a frequency of III and above, is given in Tables 4 and 5 to illustrate its geographical and ecological range. The latter is, like the edaphic range, very wide, embracing dry and damp habitats, including lowland, montane and alpine sites, so involving a high number of vascular plant species associated with B. media.

Table 4.  A selection of the communities in which Briza media occurs in Continental Europe
Habitat and communityRegionReference
Group 1. Moderately dry to damp pastures and river valleys
Carex flacca communitySwedenAndersson (1970)
Cirsium oleraceum–Polygonum bistortaGermanyHundt (1958)
Origano–Brachypodietum agrimonietosumPolandKotańska (1970)
Molinietum medioeuropaeumGermanyEllenberg (1988)
Sesleria–Filipendula hexapetalaEstoniaLippmaa (1931)
Group 2. Montane, subalpine and alpine
Andropogonetum grylli insubricumSwitzerland & ItalyBraun-Blanquet (1939)
Antherico–BrometumSwitzerlandWillems (1982)
Carex humilis–Trinia glaucaItalyBraun-Blanquet (1939)
Centaurea nigrae–ArrhenatheretumGermanyOberdorfer (1978)
Mesobrometum collinumFranceWillems (1973)
Trisetum flavescentisAustriaKnapp & Knapp (1953)
Group 3. North-facing slopes over gypsum
Parnassio–Seslerietum variaeGermanySchubert (1963)
Group 4. Dry shelly and glacial deposits, rock outcrops
Helicto–CaricetumSwedenWillems (1982)
Koelerio–FestucetumPolandKornaś (1949)
Solidagini–HelictotrichetumDenmarkWillems et al. (1981)
Group 5. Chalk slopes
MesobrometumGermanyBraun-Blanquet (1939)
Seslerio–PolygaletosumFranceStott (1971)
Phleetum phleoidis–Sedetosum montaniFranceBraun-Blanquet (1939)
Group 6. Forest-steppe
Seslerietum rigidaeGermanyMeusel (1940)
Table 5.  Species associated with the groups given in Table 4
SpeciesGroup
123456
Abies alba+
Achillea millefolium+
Achillea ptarmica+
Agrimonia eupatoria++
Agrostis capillaris+
Agrostis gigantea+
Agrostis stolonifera+
Alchemilla vulgaris agg.++
Alopecurus pratensis+
Anemone nemorosa+
Angelica sylvestris+
Antennaria dioica+
Anthericum ramosum+
Anthoxanthum odoratum+++
Anthriscus sylvestris+
Anthyllis vulneraria+++
Arabis hirsuta+
Armeria maritima+
Arrhenatherum elatius+
Asperula cynanchica++
Aster linosyris+
Avenula pratensis+++
Avenula pubescens+
Bellis perennis++
Brachypodium pinnatum+++++
Bromus erectus++
Calamagrostis arundinacea+
Calluna vulgaris+
Caltha palustris+
Campanula persicifolia+
Campanula rotundifolia++
Campanula scheuchzeri+
Cardamine pratensis+
Carex caryophyllea++
Carex diversicolor+
Carex flacca++
Carex hartmanii+
Carex humilis++
Carex panicea++
Carlina acaulis+
Centaurea jacea+++
Centaurea nigra+
Centaurea scabiosa+++
Cerastium fontanum ssp. scandicum++
Chrysopogon gryllus+
Cirsium acaule++
Cirsium helenioides+
Cirsium palustre+
Cirsium tuberosum+
Coeloglossum viride+
Coronilla varia+++
Crepis biennis+
Crepis paludosa+
Crocus vernus ssp. albiflorus+
Cynosurus cristatus+
Cytisus supinus+
Dactylis glomerata++
Danthonia decumbens+
Daucus carota+
Deschampsia cespitosa+
Equisetum arvense+
Eriophorum angustifolium+
Euphorbia cyparissias+++
Fagus sylvatica+
Festuca ovina+
Festuca pratensis++
Festuca rubra++++
Festuca rupicola+
Filipendula ulmaria+
Filipendula vulgaris+
Fragaria vesca+
Fragaria viridis+
Fraxinus excelsior+
Galium boreale+
Galium mollugo++
Galium uliginosum+
Galium verum++
Genista tinctoria+
Geranium sanguineum++
Globularia vulgaris+
Gymnadenia conopsea+
Helianthemum nummularium+++
Helianthemum ovatum+
Hieracium pilosella+++
Hieracium vulgatum group+
Hippocrepis comosa+
Holcus lanatus++
Hypericum perforatum++
Inula hirta+
Juncus articulatus+
Juncus conglomeratus+
Knautia arvensis++
Koeleria macrantha+
Koeleria pyramidata+
Lathyrus pratensis++
Leontodon hispidus++
Leucanthemum vulgare++
Linum catharticum+
Linum tenuifolium+
Listera ovata+
Lotus corniculatus+
Luzula campestris+
Luzula multiflora+
Lychnis flos−cuculi++
Medicago lupulina+
Mentha arvensis+
Molinia caerulea+
Myosotis scorpioides+
Nardus stricta+
Onobrychis arenaria+
Ophrys apiflora+
Ophrys insectifera+
Ophrys sphegodes+
Origanum vulgare+
Parnassia palustris+
Peucedanum cervaria+
Peucedanum oreoselinum+
Phleum phleoides++
Pimpinella major+
Pimpinella saxifraga++++
Pinus nigra+
Plantago lanceolata++++
Plantago media+
Platanthera chlorantha+
Poa pratensis++
Polygala amarella++
Polygala comosa+
Potentilla erecta++
Potentilla reptans++
Potentilla tabernaemontani+
Primula auricula+
Primula veris+
Primula vulgaris+
Prunella grandiflora+
Pulsatilla vulgaris+
Ranunculus acris++
Ranunculus bulbosus+
Ranunculus repens+
Rhinanthus minor+
Rumex acetosa++
Rumex arifolius+
Salvia pratensis+
Sanguisorba minor+
Sanguisorba officinalis+
Saxifraga aizoides+
Scabiosa columbaria++++
Scabiosa ochroleuca++
Sedum ochroleucum ssp. montanum+
Serratula tinctoria+
Sesleria albicans++
Sesleria caerulea+
Sesleria rigida+
Silaum silaus+
Silene nutans+
Silene vulgaris+
Solidago virgaurea+
Sorbus aria+
Stachys officinalis++
Stachys recta+
Succisa pratensis+
Syringa sp.+
Taraxacum officinale agg.+
Tetragonolobus maritimus+
Thalictrum minus+
Thymus serpyllum++++
Tragopogon pratensis ssp. orientalis+
Trifolium alpestre+
Trifolium dubium+
Trifolium montanum+++
Trifolium pratense+
Trifolium repens++
Trifolium rubens+
Trinia glauca+
Trisetum flavescens+
Trollius europaeus+
Valeriana dioica+
Veronica spicata+
Vincetoxicum hirundinaria++

IV. Response to biotic factors

It is reported that B. media is a poor competitor which fails to persist in derelict grassland (Šikula 1978; Grime et al. 1988), while Watt (1974) described it as showing a reduced frequency in ungrazed chalk grassland enclosed for 34 years. That B. media is not a good competitor is supported by the work of McLellan et al. (1997), who noted in a removal experiment that B. media was more productive with increasing gap size between plants. They concluded that the species appears to be negatively affected by a high density of neighbours and that it is suppressed by diffuse competition at normally observed densities.

Sinker et al. (1985) reported that B. media persisted in grassland mown annually, and Baker (1937) observed it was present in hay meadows which were grazed during the period of autumn to early spring and then mown in mid-July However, Mitchley & Willems (1995) noted that in Dutch grasslands, subjected to an autumn mowing regime, this was insufficient to prevent taller grasses, such as Brachypodium pinnatum, from suppressing most other growth, including that of B. media.

Briza media appears able to withstand a reasonably heavy grazing regime: it is a component of high constancy in for example the calcareous grassland communities of Festuca ovina–Carlina vulgaris (CG1) and Festuca ovina–Avenula pratensis (CG2) which are reported as being often heavily grazed by sheep and rabbits, and B. media is also described from a woodland plagioclimax community in Central Perthshire, Scotland, which is maintained principally by the grazing of cattle, red deer, rabbits and hares (Gauld & Robertson 1985). Šikula (1978) noted that the species is readily grazed by cattle and Sinker et al. (1985) reported that it is tolerant of heavy grazing; it is also recorded as frequent on sites heavily grazed by rabbits in Hertfordshire (Dony 1967). However, although the species might be tolerant of heavy grazing, a simulated grazing experiment by the author, with clipping at three height regimes every two weeks for 10 weeks, resulted in the greatest production of material in the unclipped control plants.

Sinker et al. (1985) reported that B. media is very tolerant of trampling. Plants on the edges of paths produce more horizontal rosette-type growth, but no inflorescences have been observed by the author on these prostrate, trampled plants.

Lloyd (1968) noted that fire significantly stimulated the production of inflorescences in B. media in the summer following a spring burn, but by the following year no significant stimulus to flower production remained.

V. Response to environment

(A) GREGARIOUSNESS

Briza media is usually found as scattered plants in ungrazed grassland, with a few groups of tillers joined by short rhizomes. In grazed grassland and on screes it grows as small tussocks. Briza media never produces large tussocks; even after 2 years in cultivation the average tussock diameter was only about 12 cm.

(B) PERFORMANCE IN VARIOUS HABITATS

Table 6 illustrates that Briza media is more productive in damp to wet habitats in comparison to dry ones, with longer leaves, culms and panicles. Leaf width, however, is not significantly different. The number of spikelets is also significantly greater in damp, ungrazed grassland compared with dry, ungrazed grassland. Although reported as absent from woodland (Grime et al. 1988), the species has been found in lightly shaded sites by the author, where it has flowered and set seed. Leaf and culm measurements and spikelet number in a shaded railway cutting were not significantly different from those of ungrazed grassland plants (Table 6). However, B. media does not flower where the irradiance is less than c. 50% of full sun (see VI (E)).

Table 6.  Mean (± SE) morphological measurements for Briza media from different habitats
VariableHabitat*
Dry ungrazed grasslandLightly grazed grasslandShaded railway cuttingDamp ungrazed grasslandCalcareous mire
  • *

    Dry ungrazed grassland: Skirethorn; Lightly grazed grassland: Littondale; Shaded railway cutting: Halton Gill; Damp ungrazed grassland, Wharfedale; Calcareous mire: Ribblesdale. All in North Yorkshire.

Leaf length (cm)14.4 (1.0)6.3 (0.5)15.2 (1.4)18.1 (1.1)19.6 (0.6)
Leaf width (mm)4.2 (0.3)2.5 (0.1)3.5 (0.2)3.2 (0.2)5.3 (0.3)
Culm length (cm)35.9 (0.9)30.9 (2.3)38.7 (1.9)46.1 (2.0)40.0 (2.2)
Panicle length (cm)7.9 (0.3)6.3 (0.3)7.6 (0.5)10.1 (0.5)10.0 (0.3)
No. of spikelets26.1 (1.7)19.6 (1.8)25.5 (3.2)30.7 (2.4)N/A

The species sets seed throughout its range.

(C) EFFECT OF FROST, DROUGHT AND WATERLOGGING

As B. media grows almost as far north as the Arctic Circle and to 4550 m in the Himalayan Range, it is presumably frost tolerant, and no evidence of frost damage has been observed in Britain. Davison (1964), carrying out field experiments, noted that seedlings of B. media suffered no mortality during the winter, and tolerated snow cover from December to March.

When B. media is subjected to water deficits the inner leaves of a tiller become inrolled and the outer leaves quickly dry and become ‘ridged’ in appearance and droop. Many of the leaves also become twisted giving a spiralling effect. As the tips of the leaves necrose they often develop a purplish coloration before becoming straw-coloured and dying.

The species appears to be principally a drought avoider, as most of its leaves are produced by the end of April before the onset of periods of drought. Briza media does not seem to develop any rooting strategies to combat drought as seen for example in Koeleria macrantha (Dixon 2000). Reader et al. (1992) observed that the rooting depth of B. media in unwatered soil was no different from that in watered soil, and they concluded that its roots are unable to ‘seek out’ water in unwatered soil.

As Briza media occurs in damp to wet meadows and is a component of calcareous mire communities (Wheeler 1980), it appears moderately tolerant of waterlogging. In a pot experiment in which plants were subjected to normal watering, one-third, two-thirds and total waterlogging conditions for 1 year, the one-third waterlogged plants had the longest leaves and the greatest shoot and root dry weights: there was no significant difference in shoot weight between those watered normally and those subjected to two-thirds and total waterlogging. Leaf lengths for the normally watered and the two-thirds waterlogged plants were not significantly different, and that for the totally waterlogged plants was only just significantly less than for the one-third waterlogged. However, plants with two-thirds and total waterlogging had significantly lower root dry weights than those of the normally watered plants.

VI. Structure and physiology

(A) MORPHOLOGY

Briza media has a dense fibrous rootstock with short thick rhizomes which terminate in leafy shoots. It appears to have little plasticity in its rooting depth and Reader et al. (1992) observed that species which regenerate both from seed and vegetatively, as does B. media, show less plasticity in seedling rooting depth than do species which regenerate from seed only. Mean rooting depth of B. media in well-watered loam in West Yorkshire was c. 40 cm, while Kotańska (1970) reported a mean rooting depth of 30 cm in a xerothermic grassland on a shallow brown rendzina.

The leaf sheaths of B. media are brown, fibrous and moderately persistent, as are the leaves, decomposing slowly, and so adding to the litter layer.

Solitary growth in Briza media results in small tussocks, which increase mainly by the production of short leafy tillers produced at the tips of the short rhizomes. In longer vegetation B. media grows as straggly groups of just a few tillers.

Briza media invests heavily in roots, rather less in inflorescences and much less so in leaves. Twenty young plants (each of 3 tillers) cultivated in good loam in West Yorkshire for a year gave a mean dry weight (± SE) per plant of 12.7 (± 1.4) g inflorescences (culms and panicles), 28.0 (± 3.2) g roots and 8.3 (± 1.3) g shoots (living and dead). Thus the culms comprised 26%, the roots 57% and the tillers 17% of the total dry weight. This is the same pattern as that shown by Avenula pubescens, which invested 57% in roots, 30% in inflorescences and 12% in tillers (Dixon 1991).

At the time of harvesting (mid July) the living shoots provided about three-quarters of the total shoot material.

Stomatal counts from plants in grazed limestone grassland in North Yorkshire gave a mean of 61.4 (± 4.4) mm−2 for the adaxial leaf surface and 46.5 (± 3.2) mm−2 for the abaxial surface: the counts were made at three positions along the length of 20 leaves. The stomata occur in rows between the veins, with rather more stomata around the middle of the leaf and fewer towards the tip.

(B) MYCORRHIZA

Briza media is listed as being vesicular-arbuscular mycorrhizal by Harley & Harley (1987) and they reported a high colonization rate from July to September. Read & Haselwandter (1981) noted that B. media from the northern calcareous Alps had a typically 60% colonization (Glomus sp.), while Mejstrik (1972), describing a Molinietum caeruleae association from Bohemia, also reported that B. media was strongly colonized.

Grime et al. (1987) observed that B. media produced its highest yield when ungrazed and with mycorrhizal infection, and its lowest yield also when ungrazed but with no mycorrhizal infection, compared with grazed, with and without mycorrhizal infection. They noted, however, that the effects of grazing were not significant; that is the effect of grazing was to nullify the influence of the mycorrhiza.

(C) PERENNATION: REPRODUCTION

Briza media is a hemicryptophyte. Its leaves die back gradually once flowering has commenced, but plants retain a number of green leaves throughout winter until early spring when new growth starts. Vegetative growth is slow and the species never produces large tussocks, but a clone can extend beyond the extent of the original tussock by rhizome growth of at least 6 cm year−1. It flowers in the first summer after germination and can produce a moderate number of inflorescences; in cultivation in a good loam these ranged from 7 to 70 (mean 29.4 ± 4.4) after one year's growth.

McLellan et al. (1997) reported that B. media largely recruits vegetatively and they comment that this is a general strategy where pre- and post-dispersal seed predation is high and the low soil fertility leads to an opportunistic flowering. Briza media failed to flower during the course of their experiment, which covered the flowering period, further demonstrating the low frequency of flowering in nutrient-poor habitats. It produces a transient seed bank during the summer, when the caryopses are shed; these germinate nearly synchronously in the autumn. There is a complete absence of germinable seeds during spring and early summer (Thompson & Grime 1979).

(D) CHROMOSOMES

The basic number is seven. Diploids with 2n = 14 are recorded from Britain (Fl. Br. Isl.), from Portugal (Férnandes & Queiros 1969), from the Canary Isles (Bramwell et al. 1971) and from Italy (Tornadore et al. 1974). Tetraploids with 2n = 28 have been recorded from Poland (Frey et al. 1977) and from Bulgaria (Kožuharov et al. 1974). Accessory chromosomes are found in B. media (Bosemark 1957). Nuclear DNA (2C value) = 16.9 pg nucleus−1 (Grime et al. 1988).

(E) PHYSIOLOGICAL DATA

Seedling relative growth rate is given by Grime et al. (1988) as 1.0–1.4 week−1.

Ellenberg (1988) described B. media as light-loving, and not found where the relative light flux is less than 40%, and although observed by the author in lightly shaded places, it has not been recorded from woodlands. Briza media can tolerate quite deep shading in a non-competitive situation, but cannot flower and set seed. Plants grown under neutral artificial shading with reduction in light flux of 43, 33 and 26% produced much longer leaves (means of 46.4 ± 2.6, 48.1 ± 2.4 and 36.3 ± 3.8 cm, respectively, compared with a mean unshaded leaf length of 18.3 ± 0.9 cm). Leaf width narrowed progressively with decrease in light flux from 6.6 ± 0.3 mm for unshaded plants to 6.4 ± 0.3, 4.9 ± 0.1 and 3.9 ± 0.2 mm, respectively. The same pattern of elongated, narrow leaves is also shown by the tussock grasses Deschampsia cespitosa (Davy 1980), Sesleria albicans (Dixon 1982) and Avenula pratensis (Dixon 1991). However, the non-tussock producing grasses Avenula pubescens and Trisetum flavescens, while producing longer leaves, do not differ significantly in leaf width from plants from unshaded habitats (Dixon 1991, 1995).

Both tiller and root dry weights declined significantly with increase in shading: unshaded plants gave a mean total tiller weight of 6.5 ± 0.4 g and the shaded plants 4.0 ± 0.6, 2.8 ± 0.3 and 1.8 ± 0.3 g, while mean root dry weights for the unshaded plants was 7.8 ± 1.2 g and for the shaded plants 3.2 ± 0.5, 1.0 ± 0.3 and 0.6 ± 0.1 g, respectively. The SLA increased from 2.1 in unshaded plants to 2.4, 2.7 and 3.4 for the percentage light flux reductions stated above. Briza media did not flower under any of the shading regimes.

When compared with Koeleria macrantha, a species also generally found in well-lit places, under the same shading regime, B. media showed a much lower production of both shoots and roots (Dixon 2000).

Although B. media is listed as having a wide amplitude in relation to soil moisture (Ellenberg 1988) it does not appear to be very drought resistant. Milnes et al. (1998) compared the response of B. media and Koeleria macrantha to drought and noted that, while both species showed a similar sensitivity to drought with respect to soil drying and water content, B. media died after 20 days of drought while K. macrantha responded with renewed growth to re-watering at that point.

However, a similar experiment by the author with B. media found that after 28 days of droughting, in plants re-watered and then harvested 7 days later, 6% of the total shoot material was still living and none of the plants had died completely. In an experiment with a variable watering regime, in which plants were grown in John Innes compost with a 14-h day and 18 °C day and 14 °C night temperatures, and were watered for 2, 4, 6, 8, and 10 days out of every 14 days, two-thirds of the plants subjected to the most severe regime (2 days watering) had died by the time the experiment was terminated after 10 weeks. No plants died in any of the other regimes, but the 4-day regime had between 40% and 80% dead shoot material at the end. Total shoot and root dry weights, however, declined significantly with increasing severity of water stress.

Two hours after excision, detached leaves of B. media grown under ‘dry’ conditions (watered very sparingly twice a week) exhibited a water deficit of only 35% of that shown by excised leaves of plants which had been watered freely and kept in a humid environment.

The results of these experiments suggest that, while B. media cannot withstand severe droughts, it nevertheless shows adaptability to some degree of droughting.

Calcium, nitrogen and phosphorus requirements were investigated in sand-culture experiments in a growth cabinet with a light flux density of 1500 µmol m−2 s−1 over a 14-h day at 22 °C and a night temperature of 18 °C. Calcium was supplied from 5 to 200 mg L−1 as Ca(NO3)2 with NaNO3 added to maintain a constant level of nitrogen (see Bradshaw et al. 1958). Briza media responded with increased yield to the increasing levels of calcium, although the yields of both shoots and roots were not significantly different between 50 and 200 mg L−1. This is in contrast to calcicolous species such as Avenula pratensis and A. pubescens (Dixon 1991), Trisetum flavescens (Dixon 1995) and Koeleria macrantha (Dixon 2000) (which showed significant increases in yields with 200 mg L−1) reflecting perhaps its distribution on neutral to acidic soils as well as calcareous soils, and a reduced ability to exploit high levels of calcium.

With nitrogen levels of 3, 9, 27, 81 and 243 mg L−1, supplied as Ca(NO3)2 and NaNO3 for the highest level (see Bradshaw et al. 1964), an optimum yield was obtained at 81 mg L−1, which was significantly different from those of the other treatments: this pattern reflects those of Avenula pratensis, A. pubescens and Koeleria macrantha (Dixon 1991, 2000). Root growth in B. media was affected more detrimentally than shoot growth at the highest concentration of 243 mg L−1. Briza media is considered to be a species more common on nitrogen-poor soils than nitrogen-rich soils and it might be thought that such species would show adaptations for efficiency in utilization of nitrogen. However, van der Werf et al. (1993) compared B. media, characteristic of nitrogen-poor soils, with Dactylis glomerata, characteristic of nitrogen-rich soils, at a range of nitrogen availabilities. They found that with a low nitrogen supply there was no difference in either the rate of photosynthesis or the photosynthetic nitrogen use efficiency, but with a high nitrogen supply the efficiency with respect to leaf nitrogen was significantly higher for D. glomerata than for B. media. The authors suggested that efficiency in utilization of available nitrogen is no more a characteristic of non-nutrient demanding species, such as B. media, than for nutrient-demanding species, such as D. glomerata.

The response of B. media to phosphorus, supplied as NaH2PO4 at 4, 8, 16 and 32 mg L−1 gave the highest yield at the lowest level of 4 mg L−1. There was a (just) significant decrease at 8 and a very big decrease at 16 and 32 mg L−1, these last two concentrations not giving significant differences from one another. This response is different from those of Avenula pratensis and A. pubescens (Dixon 1991) and of K. macrantha (Dixon 2000), which all showed optimum yields at 8 mg L−1.

Willems (1980) and Ryser et al. (1997) found that B. media was completely suppressed (by competition presumably) in grasslands where nutrient additions of nitrogen or phosphorus, or a combination of the two, were added to chalk grassland. However, Grime & Curtis (1976) found that adding phosphate fertilizer to weeded limestone grassland plots, containing seedlings of four species including B. media, produced a significant increase in the yield of B. media after growth for 5 weeks, and Jeffrey & Pigott (1973) also found that adding phosphate fertilizer to sugar limestone grassland in Teesdale led to a positive response by B. media, with a 5-fold increase in cover. The findings of Grime & Curtis and of Jeffrey & Pigott may seem a little surprising when the low requirement in sand culture for 4 mg L−1 is considered. However, phosphorus is usually limiting in limestone grasslands and the sugar limestone in Teesdale was reported by Jeffrey & Pigott as being severely deficient (added phosphate is also likely to be partly immobilized at high pH in limestone sites as hydroxyapatites). Sesleria albicans did not respond markedly either to these phosphate additions (Jeffrey & Pigott 1973) and in sand culture this species had a very low optimum requirement of 2 mg L−1 (Dixon 1982).

Ryser et al. (1997) examined phosphorus allocation in three grassland species (Brachypodium pinnatum, Dactylis glomerata and B. media). They observed that phosphorus was allocated to roots and shoots differently depending on how much was added, and that with decreasing phosphorus supply the concentration of the element in the roots of B. media decreased less than in the leaves. Tissue concentration of organic nitrogen decreased with decreasing phosphorus supply and the N : P ratio was lower for B. media than for the other two species, which had similar ratios. Phosphorus concentration increased in all plant parts with increasing supply and at the highest rate both D. glomerata and B. media had very high values. This might indicate luxury uptake, at least in B. media with a low requirement for this element.

Cooper (1976) reported that an ecotype of B. media collected from dolomitic limestone was more tolerant to high concentrations of magnesium than ecotypes collected from Carboniferous Limestone. The dolomitic population showed a more efficient calcium uptake, and more efficient exclusion and greater tolerance of high tissue magnesium concentration than did the Carboniferous Limestone population.

Grime & Hodgson (1969) examined the susceptibility of various species to aluminium toxicity and found B. media to be very susceptible to aluminium; only 0.05 mm aluminium was required to inhibit root growth in one-week-old seedlings. They commented that there is a very close correlation between the relative frequency of calcicolous plants on soils of pH < 4.5 and susceptibility to aluminium toxicity: Grime et al. (1988) list the occurrence of B. media in only c. 1% of quadrats sampled with soil pH between 4.0 and 5.0.

(F) BIOCHEMICAL DATA

Phytoecdysteroid compounds, generally accepted as being a deterrent to insect predators, are reported as being found associated predominantly with the European species of the genus Briza. The following compounds were reported to be present in the leaves of B. media (greatest amounts) and also in the roots and seeds: ecdysone, 20-hydroxyecdysone, polypodine B, abutasterone, pterosterone and sidisterone (Savchenko et al. 1998).

VII. Phenology

Grime et al. (1985) commented that initial growth of B. media in spring appeared to rely on expansion of overwintering leaves. However, new tillers appear in northern England around the end of March and by the end of May all overwintering leaves are dead and most of the seasons new tillers have been produced. Al-Mufti et al. (1977) noted that the weight of shoot material in B. media remained fairly constant throughout the year but showed a temporary increase at the time of flower production in spring, and Mitchley (1988) found very little variation in leaf number per tiller, but that the period of maximum leaf mortality was June to August, which coincides with flowering.

In northern England, culms start to elongate by the end of April and by the end of May panicles are emerging. Anthesis takes place during mid- to late June and seed is shed during July, August and sometimes September The panicles are a purplish-brown during anthesis, becoming straw-coloured as the caryopses ripen. Germination in the field occurs mainly in September and October.

VIII. Floral and seed characters

(A) FLORAL BIOLOGY

Reproduction is amphimictic: cleistogamous flowers are not produced. Beddows (1931) reported that B. media set fewer seeds on selfing than any other species examined, while Murray (1974) classed B. media as completely self-incompatible and noted that the species has large anthers (2.2–2.5 mm long), produces copious pollen and has the large feathery stigma typical of outbreeders. Knuth (Poll. 3) observed that the anthers of B. media dehisce for the first time early in the morning and for a second time between 6 and 7 pm.

(B) HYBRIDS

None recorded.

(C) SEED PRODUCTION AND DISPERSAL

The unit of dispersal is the caryopsis firmly enclosed within the lemma and palea; these form a propagule which is about 2 mm long and is subrotund, convex on the outside and concave within. Propagules either disarticulate individually at maturity (the majority) or in groups of several florets (usually those at the top of the spikelet) but sometimes an entire panicle branch is shed, with 2–5 spikelets. Many of the spikelets remain intact on the panicle and will probably be freed only when the panicle disintegrates.

A potted tussock of B. media with 53 inflorescences was placed on a 1.5-m2 greased polythene sheet at the end of July and left until the end of October 2000. The number of propagules which fell onto this were recorded and removed. At the end of October, an estimated 75% of the propagules were still attached to the parent plant. Of the estimated 25% shed, 15% of these were collected between 50 cm and 1 m from the parent plant and only 3% were collected beyond 1 m. This very low dispersal may reflect the weather conditions during most of the period, when it was exceptionally wet and all the inflorescences were waterlogged.

The number of florets for B. media ranges from 4 to 9 and occasionally to 12, but most commonly there are seven florets per spikelet. The mean number of inflorescences on cultivated plants was 29 and the mean spikelet number 36. Thus taking an average number of seven florets per spikelet one tussock could theoretically produce in one year 7308 seeds. However, the number of inflorescences observed in field specimens is much lower.

Ridley (Pl. Disp.) records B. media as being dispersed in whirlwinds (these normally occur during July–August) either as cut material from hay fields or as whole plants torn up by the wind.

As the propagule does not possess an awn, and thus lacks a mechanism for drilling it into the soil, germination occurs on the surface.

(D) VIABILITY OF SEEDS: GERMINATION

Germination tests on samples of 200 seeds, from a bulk gathering in North Yorkshire, after 4 months’ dry storage at room temperature, were carried out in a growth cabinet with a light flux of 1500 µmol m−2 s−1 over a 12-h day at 20 °C when temperature was not being investigated. Seed freshly harvested in July and placed immediately on moist filter paper gave 23% germination. After dry storage at room temperature in the laboratory for 1 month, germination was 30% and after 3 months’ storage 86% germination was obtained, showing that a period of after-ripening is beneficial.

Briza media will germinate between 5 °C and 30 °C, with an optimum around 20 °C (86% germination). Germination at 20 °C commenced after 7 days and was completed in 12. This was not significantly different from germination at 15 °C (79%) where germination commenced after 8 days and was completed in 16. Germination at 25 and 30 °C was significantly lower with only 38 and 35% germination, which commenced after 6 days at both temperatures and was completed in 14 and 20 days, respectively. Germination at 5 °C was very slow, with germination not starting until 2 months after moistening and then occurring very sporadically over the next 5 months, to give a total of 55%.

Pre-chilling and freezing for 8 weeks gave 88 and 87% germination, respectively, which was not significantly different from the untreated control with 86%. Germination with seeds submerged in distilled water gave 81%, while preheating seeds to 40, 60 and 80 °C gave 90, 81 and 81% germination, respectively. Germination in total darkness was 82% and there was no effect on the rate of germination.

(E) SEEDLING MORPHOLOGY

Hydration of the propagule results in a separation of the lemma and palea. The radicle emerges from the proximal end of the grain. Simultaneously the coleoptile emerges from between the lemma and the palea; it extends to about 8 mm and then splits to reveal the first true leaf. Seedling development is shown in Fig. 2.

Figure 2.

Dispersal units and seedlings of Briza media: (a) dry caryopsis – upper left adaxial surface, upper right and lower left abaxial surface; (b) after imbibition – as for (a); (c) 8 days after germination; (d) after 15 days; (e) after 20 days; (f) after 30 days. Germination was on moist filter paper, with 14-h days, a day temperature of 20 °C and a night temperature of 16 °C. (a)–(d) to same scale, and (e) and (f) to same scale.

IX. Herbivory and disease

(A) ANIMAL FEEDERS OR PARASITES

Briza media is readily grazed by mammals, particularly cattle, but there are very few records of invertebrate grazing. Grime et al. (1968) found that it was unpalatable to snails and the author has not seen any slug damage on plants in cultivation. Briza media is, however, grazed by the following insects: Leptopterna ferrugata (Fallén) (Hemiptera: Miridae) – larval stages; Apamea scolopacina (Esper) (Lepidoptera: Noctuidae) – larvae mine stems; Phytomyza nigra Meigen (Diptera: Agromyzidae) – larvae mine stems. Larvae and adults of the mite Eriophyes tenuis Nalepa (Acari: Eriophyidae) also feed on leaves and flowers of B. media, causing leaf rolling and sterility.

(B) PLANT PARASITES AND DISEASES

The leaves of B. media may be infected by the rusts Puccinia coronata CDA, Puccinia glumarum (Schm.) Erikss. and Henn., and Puccinia graminis Pers., by the rust Uromyces brizae GM., E. Mull. and Terr. and by the smut Ustilago striiformis (West.) Niessel (Vad. para. Pilze). The Ascomycete Pyrenophora trichostoma (Fr.) Fuckel is also recorded from dead stems and sheaths of Briza media (Ellis & Ellis 1985).

X.History

There is no record of the early postglacial history of Briza media (Godw. Hist.). The species was first recorded by Pena & Lobel (1570) as ‘Phalaris pratensis minor … herbidis pratensis busque. Angliae oritur’ (First Rec.).

Acknowledgements

My thanks are due to Dr D. J. Hambler for helpful advice and criticism, to Dr L. K. Ward for information from the Phytophagous Insect Data Bank, to S. Davidson for drawing Fig. 2 and to Henry Arnold, Biological Records Centre, for preparing Fig. 1. I also thank the Editors and Prof. C. Stace for their valuable comments on the manuscript.

Ancillary

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