Llanelli Naturalists Newsletter - February 1999 - No 4
JMS Bevan

Introduction

Tracts. of permanent grassland have been a characteristic feature of the British landscape since the Neolithic pastoralists first arrived here some 6000 years ago (Rackham 1986). Prior to their arrival, the country was clothed with a dense, more-or-less continuous cover of woodland - Rackharn's so-called 'wildwood' - which developed in the wake of the retreating ice sheets, following the close of the last glacial period approximately 10,000 years ago. Armed with his flint axes and grazing animals, Neolithic man began to clear the wildwood and turn the countryside into a patchwork of woodland, arable and grassland. In time these areas of grassland developed a rich flora, derived mainly from species inhabiting woodland glades and other open areas, and also from more cosmopolitan plants capable of tolerating both shaded and open conditions.

In Britain's temperate climate, grassland is therefore not a wholly natural or 'climax' habitat type. It is maintained by anthropogenic factors like grazing or mowing, and would revert rapidly back to woodland if such management ceased. For this reason, ecologists often describe long-established, non-intensively farmed grassland as 'semi-natural'. The term 'unimproved' is also used widely, reflecting the unexploited agricultural potential of the land.

British grasslands have traditionally been managed as pasture or meadow. Pastures provide permanent grazing for livestock, while meadows are shut up during the main summer growth period, with the resulting hay crop conserved for winter fodder. Early farming communities quickly learnt that productive grasslands were a valuable asset, and manured and managed their fields accordingly to maintain soil fertility. Both grazing and mowing involve the steady removal of soil nutrients, and the dunging of livestock coupled with the spreading of manure formed the main means of maintaining the fertility of the land. For many, many centuries semi-natural grasslands were in harmony with their maker, providing reasonably productive agricultural land whilst, albeit inadvertently, retaining high botanical diversity. Britain developed a diverse range of grassland cornmunities, each controlled and maintained by natural ecological factors like climate, geology and soils, interwoven with the underlying effects of traditional management.

The last century has seen a dramatic decline in the extent of semi-natural lowland grassland. Modern farming practices, particularly the use of artificial inorganic fertilisers, have greatly increased the productivity of agricultural grasslands. Many former flower-rich hay-meadows and pastures have now been replaced by lush green fields dominated by Perennial Rye-grass Lolium perenne and other agricultural species, with just a lirnited range of nutrient-demanding forbs like White Clover Trifolium repens and Common Mouse-ear Cerastium fontanum; the majority of grassland plants are unable to compete against the vigorous growth of grasses and are quickly lost from the sward. Numerous dry grassland communities which were formerly widespread in Britain have now become scarce as a result of agricultural intensification, and similarly many damp grasslands have been lost through drainage and subsequent improvement. Such losses were borne out in a review of grassland surveys by Fuller (1987), who estimated that only 3% of unimproved lowland grassland present in England and Wales in 1930 still remained intact in 1984. Similarly, many grassland plant species which were once a common feature of the countryside are now becoming increasingly rare and localised (Rich & Woodruff 1996).

Distribution of semi-natural grassland in Carmarthenshire

Carmarthenshire has retained a reasonably rich semi-natural grassland resource compared to most parts of England and Wales. Notable concentrations of both dry and wet grasslands still remain on the Coal Measures in the south, where a significant amount of land has escaped agricultural intensification. Coal mining and its associated metal industries dominated this area until recently, and many local inhabitants practised only small-scale, non-intensive farming as a means of supplementing their other incomes. Several good grasslands have recently been lost through opencast, but overall the coalfield remains an important area for unimproved grassland, with numerous colonies of the internationally threatened Marsh Fritillary butterfly Eurodryas aurinia and a host of other invertebrates strongly associated with old damp pastures.

Further concentrations of semi-natural lowland grassland also occur on the Old Red Sandstone between Trap and Llanddeusant in the Brecon Beacons National Park. This rather sparsely populated area has also been less intensively farmed, probably because of extensive summer grazing rights on nearby Mynydd Du (T R Morgan, pers. comm.).

The remainder of lowland Carmarthenshire comprises relatively productive agricultural land with comparatively little unimproved grassland. Areas of wet pasture sometimes remain in valley bottoms, but good examples of dry semi-natural grassland are very few and far between, occurring as isolated islands within a sea of rye-grass and clover: they are often confined to steeper slopes proving inaccessible to farm machinery, or comprise just small fragments in neglected field corners.

Grassland phytosoclology

The main British grassland types have recently been characterised and described within the framework of the National Vegetation Classification (NVC). Development of the classification was co­ordinated by Lancaster University - with funding initially from the Nature Conservancy Council (NCC) and subsequently from the Joint Nature Conservation Committee (JNCC) - and aims to systematically cover all the major plant communities in Britain. The community descriptions are in the process of being published in a series of volumes entitled British Plant Communities (Rodwell 1991 et seq.), with damp grassland types covered in Volume 2 and dry grassland communities in Volume 3.

Grassland communities In CarmarthenshIre

A range of grassland NVC communities occur in lowland Carrnarthenshire and these are briefly outlined below. Much of this information is derived from a detailed 'Phase II' survey of semi-natural lowland grasslands in the county, which was initiated in 1987 by the former NCC and subsequently completed between 1991 and 1997 by the Countryside Council for Wales (CCW). The project forms part of a Wales-wide grassland survey programme, the main airns of which are to characterise and evaluate the principality's semi-natural grassland vegetation and to assess the distribution and extent of its component communities.

The principal dry semi-natural grassland community in Carmarthenshire is the NVC type MG5 (Cynosurus cristatus-Centaurea nigra grassland). This vegetation was formerly very comrnon throughout lowland Britain, being the characteristic community of freely-draining, circumneutral brown soils which have not been heavily fertilised. It is, however, very easily improved and recent decades have seen a considerable decline in its extent. MG5 grassland is typically composed of a species-rich mixture of grasses and forbs, the latter providing fine displays of colour through the summer months. Among the grasses, characteristic species include Common Bent Agrostis capillaris, Crested Dog's-tail Cynosurus cristatus, Sweet Vernal-grass Anthoxanthum odoratum and Red Fescue Festuca rubra. There is usually a high cover and rich diversity of forts, with Common Knapweed Centaurea nigra, Red Clover Trifolium pratense, Cat's-ear Hypochoeris radicata, Yellow-rattle Rhinanthus minor and Common Bird's-foot-trefoil Lotus corniculatus among the commonest species. The trefoil in particular is very sensitive to fertiliser application and its presence is generally indicative of good quality, unimproved habitat. Tormentil Potentilla erecta and Devil's-bit Scabious Succisa pratensis  can be frequent in slightly acidic stands, and the community occasionally provides a refuge for uncommon species like Greater Butterfly-orchid Platanthera chlorantha, Lesser Butterfly-orchid P. bifolia, Adder's-tongue Ophioglossum vulgatum and Moonwort Botrychium lunaria.

There are numerous stands of Cynosurus-Centaurea grassland scattered through lowland Carmarthenshire, although it remains a scarce and declining habitat. Most is concentrated in the coalfield and on the Old Red Sandstone in the Brecon Beacons National Park. The majority of sites are fairly srnall - usually less than one hectare - and many have suffered some partial agricultural modification which reduces the botanical interest of the sward. Nevertheless, several notable examples still remain in the county and these constitute an increasingly important conservation resource.

Well characterised MG5 typically lacks rye-grass or other agricultural species and White Clover occurs at only low cover. Applications of artificial fertiliser result in rapid conversion to more productive Lolium perenne-Cynosurus cristatus grassland (MG6), which constitutes the major permanent agricultural grassland type in lowland Britain. There is in effect a continuum between the two communities and intermediate vegetation is not uncommon. MG6 is generally dominated by various grasses which characteristically include rye-grass and often other agricultural species like Timothy Phleum pratense and Meadow Foxtail Alopecurus pratensis. There is only a limited number of forbs, the main species being White Clover, Common Mouse ear, Ribwort Plantain Plantago lanceolata and Meadow Buttercup Ranunculus acris. MG6 grassland is ubiquitous throughout lowland Carmarthenshire; together with reseeded Lolium perenne leys (MG7), it comprises the vast majority of dry grassland in the county.

Calcicolous grassland - grassland occurring over thin calcareous soils - is extremely rare in Carmarthenshire, being confined to a few tiny stands along the thin band of Carboniferous Limestone, which forms the northern rim of the Carmarthenshire coalfield. There has been a long history of quarrying along the outcrop, reducing the extent of this habitat further. The remaining fragments are often very species-rich and are characterised by the presence of numerous lime-loving species including Salad Burnet Sanguisorba minor, Common Rock-rose Helianthemum nummularium and Wild Thyme Thymus praecox. In Carmarthenshire plants like these often find their only locus in stands of calcicolous grassland.

Much of the county's calcicolous grassland is not easily placed in an NVC community. Most stands are secondary in origin, having developed over old lime spoil or on abandoned quarry faces. Some vegetation shows affinities with Festuca ovinaHieracium pilosella, Thymus praecox/pulegiodes grassland (CG7), although this community is more typically associated with summer-parched chalky substrates in Breckland.

Dry acidic grassland is also very scarce in lowland Carmarthenshire, although there are extensive tracts of Festuca ovina-Agrostis capillaris, Galium saxatile grassland (U4) and Nardus stricta, G. saxatile grassland (U5) on the upland plateaux and fringes of Mynydd Du and Mynydd Mallaen. Stands of U4 grassland occur very locally at lower altitudes, but this community is typically confined to free-draining, oligotrophic (nutrient-poor) substrates, and soils in the deep Carmarthenshire lowlands are generally too fertile to support it.

The wet oceanic climate of the area strongly favours the development of damp grassland vegetation, and south-west Wales is renowned for its sizeable tracts of 'rhos pasture', which is broadly analogous to the 'Culm grassland' of Devon and Cornwall and the wet grasslands of south-west Scotland. These wet pastures are typically composed of a mosaic of several damp grassland communities and in Britain are largely restricted to the western oceanic fringe. In a European conservation context, this pronounced Atlantic distribution takes on even greater significance.

The two principal rhos pasture communities in Carmarthenshire are Molinia caerulea, Potentilla erecta mire (M25) and Juncus effusus/acutiflorus-Galium palustre rush-pasture (M23). M25 is a rather variable community and takes in most types of acidic Molinia pasture on poorly-draining soils. It is typically dominated by Purple Moor-grass Molinia caerulea, often growing in its dense tussocky form, with associates such as Tormentil, Devil's-bit Scabious, Sharp-flowered Rush Juncus acutiflorus and Carnation Sedge Carex panicea. A particular feature of Carmarthenshire M25 is the constant presence of the white umbellifer, Whorled Caraway Carum verticillatum; this species has a very restricted global distribution, being largely confined to the western seaboard of Britain, with distinct concentrations in south-west Wales. In less grazed situations there can be a prominent tall-herb component, where Wild Angelica Angelica sylvestris, Marsh Willowherb Epilobium palustre and Meadowsweet Filipendula ulmaria become frequent. Other stands are more heathy, indicated by the presence of dwarf shrubs like Cross-leaved Heath Erica tetralix and Heather Calluna vulgaris. Indeed, where the cover of ericoids increases, M25 can often grade into Scirpus cespitosus-Erica tetralix wet heath (M15).

M23 rush-pasture, the other main rhos pasture community, is characterised by a high cover of tall rushes, principally Soft Rush Juncus effusus and Sharp-flowered Rush, together with a reduced cover of Purple Moor-grass. These are typically accompanied by a suite of poor-fen herbs, including Common Marsh-bedstraw Galium palustre, Greater Bird's-foot-trefoil Lotus uliginosus, Marsh Thistle Cirsium palustre, Lesser Spearwort Ranunculus flammula and Ragged Robin Lychnis flos-cuculi.

There is often some localised acid flushing, marked out by small stands of Carex echinata-Sphagnum recurvum/auriculatum mire (M6). This vegetation is generally dominated by a mixture of Purple Moor-grass and short sedges - including Star Sedge Carex echinata, Carnation Sedge and Common Yellow-sedge C. demissa - while other stands are characterised by a high cover of tall rushes. Constant throughout the community, however, is the luxuriant carpet of various bog mosses Sphagnum spp., which imparts a distinctive 'stamp' to the sward.

Rhos pasture was formerly very common throughout lowland Carmarthenshire, but drainage and agricultural improvement have considerably reduced its extent. Some sites have also become overgrown through lack of grazing and subsequent scrub invasion. Nevertheless numerous good examples remain scattered throughout the county, their distribution mirroring that of MG5 grassland, with most sites concentrated in the coalfield and on the Old Red Sandstone in the Brecon Beacons National Park.

A notable feature of many of the coalfield and Old Red Sandstone sites is the additional presence of Molinia caerulea-Cirsium dissectum fen-meadow (M24). This community is confined to more base-enriched soils, and is largely absent from most of Carmarthenshire and indeed many other parts of Wales where generally acidic soils prevail. M24 is floristically similar to M25, often having a high cover of Purple Moor-grass, but is characterised by the additional presence of the mildly base-demanding Meadow Thistle Cirsium dissectum, which provides great splashes of purple through June and July. In well characterised examples there is also a suite of basiphilous sedges including Tawny Carex hostiana, Flea C. pulicaris and Glaucous Sedge C. flacca, alongside the distinctive nodding heads of Quaking Grass Briza media. Uncommon species include Petty Whin Genista anglica, Dyer's Greenweed G. tinctoria and Whorled Caraway.

Grassland conservation in CarmarthenshIre and the rest of Wales

The rapid decline of unimproved lowland grassland over recent decades makes it a key habitat for conservation attention. CCW's grassland survey programme makes a significant contribution towards the UK's BIOdiversIty Action Plan commitments (Anon. 1994), providing much needed basic information on the distribution and extent of semi-natural lowland grassland in Wares. Other key objectives of this survey work are to systematically identify the best remaining grassland sites in Wales and ensure that a representative series are protected as Sites of Special Sceintific Interest (5551)

In 1992 CCW also launched its Tir Cymen scheme in the DInefwr part of Carmarthenshire and in the two other plot areas of Meirionnydd and Swansea The scheme offers farmers financial incentives to manage their farm in an environmentally sensitive manner, and has proved particularly successful in Dinefwr, with almost hat of the districts eligible lard already entered into the scheme Many sites visited during CCW's Phase II survey of Dinefwr are now covered by Ti Cymen management agreements. complementing me top tier of sites selected as SSSI's The scheme also offers considerate opportunities for habitat restoration as required under the UK Biodiversity Action Plan.

Similar financial packages are available to farmers elsewhere in Wales: the ESA Scheme, administered by the Welsh Office Agriculture Department (WOAD), operates in the various Environmentally Sensitive Areas, while those areas outside the ESA and Tir Cymen regions are covered by the Habitat Scheme (again administered by WOAD). Welsh Office recently carried out a review of agri-environment schemes in Wales. and as a result are soon to launch a single Wales-wide scheme - Tir Gofal - to replace the present three. The new scheme will draw upon the best features of the three pre-. cos ones but will be based on the whole-farm approach of Tir Cymen. Such schemes are raising awareness of grassland conservation in Wales. and hopefully with continued support will prove a major tool in conserving and enhancing what remains of this important wildlife habitat.

Tnese various grant-aid schemes are now being streaming by their replacement with the all-Wales agri-environment scheme. Tir Gofal, administered by CCW

References

Anon (1994). Biodiversity: The UK Acton Plan. HMSO. London.

Fuller. R.M. (1987) The changing extent and conservation interest of lowland grasslands in England and Wales: a review of grassland surveys 1930-84 Biological; Conservator 40. 281-300. Racknam. O. (1986) The History of the Countryside Dent, London.

Rich. T.C.G & Woodruff, E . (19%). Changes in the vascular plant Navas of England and Scotland between 1930-t960 and 1987-1988. the 8581 Monitoring Scheme. Biological Conservation 75, 217-229

Rodwell, J. S. (ed.) (1991 el Seq.)_ British Plant Communities Cambridge University Press. Cambridge.

Acknowledgements

I would like to thank my colleagues Ian Megan. Richard Morgan, Graham Motley Dr David Stevens and Dr Nigel Stinger for helpful comments on an earlier draft of this article.

J M S Bevan. Countryside Council for Wales. 56 RHosmaen Street, Llandeilo SA19 5HA