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A tour of the bryophyte habitats of Dorset
(v.-c. 9)

... with Bryan Edwards

This tour, written by Bryan Edwards, is essentially the chapter ‘Natural areas and bryophyte habitats’, of Mosses and liverworts of Dorset by Mark Hill and Bryan Edwards. It is reproduced here with permission from the authors and the Dorset Environmental Records Centre.

The book can be purchased for £9.50 + 50p p&p from:

Dorset Environmental Records Centre
Library Headquarters
Colliton Park
Dorchester
Dorset
DH1 1XJ

Tel: 01305 225081
e-mail:derc@dorsetcc.gov.uk



English Natural Areas

England is divided into 181 character areas, of which 23 are exclusively coastal (Countryside Commission & English Nature, 1996). These character areas are now usually called ‘Natural Areas’. Two Natural Areas are completely included in Dorset and three have part of their extent in Dorset and part in adjacent counties. The Dorset Natural Areas correspond basically to geological strata of the underlying rocks.


Blackdowns


The Blackdowns Natural Area is a dissected greensand plateau with clayey valleys derived from the Lias and Trias. It includes those parts of the county to the north and west of the Marshwood Vale and the areas of v.-c. 9 that are now in Devon and Somerset. The area largely comprises farmland used for dairying, with very little arable land. A short stretch of the river Axe flows through it.

There are many small woodlands, particularly along the streamsides, although larger woods such as Wyld Wood have been replanted with beech and conifers. Bickham Wood is a rich site with a characteristic wet woodland assemblage including Hookeria lucens and Trichocolea tomentella on muddy streamsides and Chiloscyphus polyanthos and Fissidens pusillus on inundated boulders. Small remnants of ancient woodland survive at Hewood, Hole Common and Sleech Wood. These have Rhytidiadelphus loreus on the ground and Heterocladium heteropterum var. flaccidum and Lophocolea fragrans on flints.

Small remnants of heathland and mire survive on the hill tops of Coney’s Castle, Lambert’s Castle, Pilsdon Pen and Bewley Down. Champernhayes Marsh was the outstanding mire until the 1960s when planted with conifers. Gulielma Lister recorded Breutelia chrysocoma, Drepanocladus revolvens and Scorpidium scorpioides about 1900; Francis Rose found Sphagnum contortum and S. papillosum in 1954. S. capillifolium and S. magellanicum persisted until 1966. The Wyld Warren also had Sphagnum contortum until 1972 but the site deteriorated rapidly thereafter. The best remaining mire survives at Fishpond Bottom. Sphagnum capillifolium, S. inundatum, S. palustre and S. subnitens are frequent Associated species include Calliergon stramineum, Riccardia multifida and Warnstorfia exannulata. Humphry Bowen found Sphagnum papillosum in 1992.


Wessex Vales


This Natural Area covers all the land to north, west and south of the chalk massif. It is very varied geologically, comprising bands of Cretaceous sands and Jurassic clays, limestones and sandstones. Much of the area is used for dairy farming with only small amounts of arable. This large Natural Area is best described within the following smaller sections, based on the botanical divisions defined by Good (1948).

Blackmoor Vale
This section extends from Shaftesbury in the north to Sherborne in west. It is very much dairying county with little semi-natural habitat surviving except around Lydlinch Common, Deadmoor Common and Rooksmoor. The largest ancient woodland, Duncliffe Wood, was replanted with conifers, but is now being returned to broadleaves by the Woodland Trust. Other ancient woods are Fifehead Wood and Piddles Wood. The latter is a rich site, with Scapania nemorea, Dicranum majus, Hylocomium splendens, Leucobryum juniperoideum and Rhytidiadelphus loreus in the ground flora.

The upper Stour and its tributaries such as the Caundle Brook provide the best habitat in the county for a suite of riparian mosses. Dialytrichia mucronata, Leskea polycarpa and Syntrichia latifolia are frequent on silt covered tree bases. The rare Orthotrichum sprucei is confined to this habitat.

The parish of Holwell was home to H.H. Wood, who intensively recorded the bryophytes. He found Campyliadelphus elodes, Entosthodon obtusus, Orthotrichum rivulare and Weissia rutilans, which have not recently been found in the Blackmoor Vale, but some uncommon mosses, notably Myrinia pulvinata and Pterogonium gracile, have survived.

Halstock Vales and Upper Frome Vales
This section lies to the south of Yeovil and Crewkerne, with streams draining northward to the Bristol Channel. Although there is much intensive dairying, the very varied geology produces areas of interesting semi-natural habitat. Melbury Park is an outstanding site for epiphytic lichens, and the bryophytes are also of great interest. Frullania tamarisci and Zygodon rupestris are abundant on the trunks of many large oaks, with Pterogonium gracile on the bases of a few trees. The basic bark of well-illuminated maple and sycamore supports Leptodon smithii, Leucodon sciuroides, Orthotrichum lyellii and Syntrichia laevipila. Soft limestone beside a stream provides a substrate for Pterogonium gracile and the uncommon liverworts Cololejeunea rossettiana, Lejeunea cavifolia and Plagiochila porelloides.

The area is well wooded although most woodlands are small and many occur along streamsides. Brackett’s Coppice is an interesting wood on wet clay soil. The ground flora includes an abundance of Rhytidiadelphus triquetrus and Thuidium tamariscum, together with in one area the declining Hylocomium brevirostre. Lejeunea cavifolia and Nowellia curvifolia occur on decaying logs. The most interesting feature is the stream, with Mnium stellare on the bank and Dichodontium pellucidum and Hygrohypnum luridum on boulders.

Small wetlands have developed at the junction of the gault and greensand. Aunt Mary’s Bottom near Rampisham is the best example, with Trichocolea tomentella, Aulacomnium palustre, Climacium dendroides, Palustriella commutata var. commutata and Sphagnum palustre. The adjoining alder-sallow wood formerly had Riccardia palmata and Scapania gracilis on rotting logs, but these may have been non-persistent colonists.

Situated on the Dorset-Somerset border above Halstock is Sutton Bingham Reservoir. In dry years the muddy margins support an abundance of Aphanorhegma patens and Riccia cavernosa, with smaller quantities of Leptobryum pyriforme.

Axe Vales
This small section consists of low-lying terrain between Crewkerne and Beaminster, with streams draining northwards to the Axe. The soils are mainly calcareous clays derived from fuller’s earth. The area lacks notable features.

Hooke and Powerstock Vales
The ‘ancient countryside’ between Maiden Newton in the east, Beaminster in the north and Bridport is less intensively farmed than the other sections of the Wessex Vales, with small fields, species-rich hedges, wet flushes, swamp woodland and areas of ancient pasture-woodland.

Powerstock Common and Hooke Park are well known bryologically. Hooke Park is a good site, with Jungermannia atrovirens and Seligeria pusilla on dripping limestone rocks and Dichodontium pellucidum in the stream. Nearby, wet alder-birch woodland at Wytherston Marsh has carpet of Sphagnum fallax and S. palustre under which lurks the strange liverwort Cryptothallus mirabilis. The Wildlife Trust reserve at Lower Kingcombe has extensive areas of unimproved grassland, much of which is bryologically poor, but there are small areas of acid turf with an abundance of Hylocomium splendens and Thuidium tamariscinum. Of most interest are two small acid flushes, with Calliergon stramineum, Philonotis fontana, Sphagnum angustifolium and Warnstorfia exannulata.

Marshwood Vale and Lyme Regis to Bridport coast
The Marshwood Vale is formed of Lias clays and much of the area is used for dairying. Ancient woodlands are small and largely confined to streamsides. There are no hard rock outcrops. The bryophyte flora is typical of rural Dorset, but the lack of special features means that few rare or scarce bryophytes are present.

The coastal strip from Lyme Regis to Bridport is made up of constantly eroding cliffs. Open turf on the cliff edge provides habitat for Acaulon muticum in one of its few Dorset localities. At Eype the flushes on the landslip have an interesting flora including the two hornworts Anthoceros punctatus and Phaeoceros laevis. Greensand boulders in this area support Aloina ambigua and Gyroweisia tenuis. Further inland are the sandy banks and sunken lanes on the Thorncombe Sands; these are noted for Epipterygium tozeri and Schistostega pennata.

Bride and Wey Vales
Like the Marshwood Vale much of this section is intensively farmed, with few notable features. The limestone ridge from Upwey to Portesham retains small areas of unimproved turf and has scattered rock outcrops. The richest site is the old quarry at Portesham which has Aloina aloides, Gyroweisia tenuis, Scorpiurium circinatum and Weissia longifolia var. angustifolia.

Abbotsbury Castle comprises heathland, acid grassland and a small mire. Species present include Aulacomnium palustre, Campylium stellatum var. stellatum, Dicranum bonjeanii and Sphagnum subnitens, all very local outside the Poole basin.

The coast is dominated by Chesil Beach and the Fleet, although the shingle is not stable enough to support much vegetation. The most interesting area lies at the eastern end at Ferrybridge. Here sand is mixed with the shingle producing areas of maritime grassland. The short open turf includes abundant Pleurochaete squarrosa and Syntrichia ruraliformis, with Hennediella heimii and Tortella flavovirens on brackish soil.


South Wessex Downs


This Natural Area includes all the chalk massif except for the Lulworth coast and the Purbeck Ridge. It is split by the rivers Frome, Piddle and Stour and is described in the following sections.

Northeast chalk
This section includes the area north and east of the River Stour. Much of the chalk from Blandford north-east to the Bockerley Dyke on the county boundary is gently undulating arable farmland. Pasture woodland in the former royal forest of Cranborne Chase was underplanted with hazel. There is a rich vascular plant flora but the Chase is not notable for its bryophytes.

The small remnants of chalk grassland are confined to the few steep slopes such as Pentridge Down or ancient monuments including the Ackling Dyke, Badbury Rings, Gussage Hill and Oakley Down barrows. Of these Badbury Rings is particularly interesting. Ditrichum gracile, Entodon concinnus and Weissia sterilis grow in the short turf. On bare soil nearby are Microbryum curvicolle, M. starckeanum and Pottiopsis caespitosa. Between Blandford and Shaftesbury, many steep-sided valleys have escaped the plough and still support downland. Fontmell and Melbury Downs are the largest, with several areas of bryophyte-rich turf. The north-facing slope of Ashmore Down has an abundance of the spectacular Rhodobryum roseum, together with Hylocomium splendens and Tortella tortuosa. The flint scree formerly had Racomitrium lanuginosum. In short turf on the warm south-facing slopes of Fontmell Down there is abundant Entodon concinnus, with Ditrichum gracile, Ephemerum recurvifolium and Pleurochaete squarrosa.

Central chalk
This large section includes the area between the River Stour and the Dorchester-Crewkerne road. Dry valleys and northern scarp retain unimproved downland, but much of the rest of the area has been ploughed. The high ground receives the highest rainfall in the county, resulting in a luxuriant downland sward in which small bryophytes cannot compete, so that only the more robust pleurocarps occur with any frequency. Of most interest are the ancient ash-hazel woodlands that are found on ridge and scarp between Maiden Newton in the west and Shillingstone in the east. These often have extensive areas of flints with a thick bryophyte carpet dominated by Eurhynchium striatum, Rhytidiadelphus triquetrus and Thuidium tamariscinum, together with the more local Dicranum majus, Plagiochila asplenioides and Rhytidiadelphus loreus. The stones themselves have a distinctive flora including Lophocolea fragrans, Plagiochila porelloides, Heterocladium heteropterum var. flaccidum and Taxiphyllum wissgrillii. Plagiochila norvegica is confined to a single such stone in its only British locality. Shaded chalk pebbles in these woods have a very limited flora including Fissidens gracilifolius, Seligeria calycina and Tortella inflexa.

Southern chalk
This section comprises the land between the Dorchester-Crewkerne road and White Horse Hill above Weymouth. Much of the downland is poor in bryophytes, except for White Horse Hill itself with Ephemerum recurvifolium, Pleurochaete squarrosa, Scorpiurium circinatum and Weissia sterilis. The most interesting bryological site is the Valley of Stones near Little Bredy. Here the numerous lichen-rich sarsen stones in the valley bottom support an interesting flora including Frullania fragilifolia, F. tamarisci, Porella obtusata, Grimmia trichophylla, Hedwigia stellata and Pterogonium gracile. Rhodobryum roseum is present in small quantity in the adjoining downland turf.

As well as the large rivers Frome, Piddle and Stour, there are smaller valleys with chalk streams such as the North and South Winterborne, the Bere Stream and River Cerne. The valleys are intensively farmed but retain some interesting habitat. The manor houses had parkland trees, many of which survive today. Avenues, or groups, of ash, lime and sycamore support a rich lichen flora and are particularly important for bryophytes such as Leptodon smithii, Leucodon sciuroides and Syntrichia papillosa.


Isles of Portland and Purbeck


Portland
The Isle of Portland comprises beds of Portland and Purbeck limestone over a bed of Kimmeridge Clay. The centre of the island has been extensively quarried or built up, leaving few areas of the original limestone turf. The coasts have been quarried to some degree, but still retain areas of grassland, landslip, scrub and scree.

West Weares is an extensive area of scree and maritime grassland below West Cliff. It has long been known as a site for Eurhynchium meridionale. The grassland supports much Neckera crispa and Scorpiurium circinatum, with Ephemerum recurvifolium, Microbryum rectum and M. starckeanum on bare soil. Along West Cliff there are extensive areas of open bryophyte-rich turf. Among the patches of Trichostomum spp. and Weissia spp. are the rare liverworts Cephaloziella baumgartneri and Southbya nigrella, together with Eurhynchium meridionale, Gymnostomum viridulum, Microbryum curvicolle and abundant Tortula lanceola.

On the opposite side of the island East Weares is the richest area for calcicolous bryophytes in the county. On sheltered screes below the cliffs there is an abundance of Ctenidium molluscum, Homalothecium lutescens, Hypnum lacunosum and Neckera crispa, together with more demanding calcicoles such as Encalypta streptocarpa and Fissidens dubius. Below the screes are boulders and scrub. Among the carpets of Ctenidium, Homalothecium and Neckera are Porella obtusata, Leucodon sciuroides var. morensis and Tortella tortuosa. Sheltered limestone rocks support Cololejeunea rossettiana, Lejeunea cavifolia, Marchesinia mackaii, Leptodon smithii, Tortella nitida and Zygodon viridissimus var. stirtonii. On boulders with veins of flinty chert there is a different flora including Frullania fragilifolia, F. tamarisci, Grimmia trichophylla and Pterogonium gracile.

The landslip at Penn’s Weare south to Church Ope Cover is similar, but there are more terricolous mosses, including Acaulon triquetrum, Bryum canariense, Ephemerum recurvifolium, Encalypta vulgaris, Microbryum curvicolle and Tortula lanceola.

Recently-worked quarries contain few unusual bryophytes. However, the floors of older abandoned quarries such as Bowers, Broadcroft, King Barrow and Tout have developed open calcareous turf with Cephaloziella baumgartneri, Gymnostomum viridulum, Leiocolea badensis, L. turbinata and Southbya nigrella.

Purbeck
This geologically varied area includes the Purbeck Ridge and all the land to the south, together with the Lulworth chalk west to White Nothe.

The chalk ridge extends for 22 km from Lulworth Cove in the west to Ballard Cliff in the east. It is formed of hardened upper chalk with superficial deposits of flints. Bindon Hill in the west has an area of bryophyte- and lichen-rich scree on the summit. Tortella tortuosa is locally frequent among Anomodon viticulosus, Hypnum lacunosum, Neckera crispa and Scorpiurium circinatum. Of most interest is the presence of Eurhynchium meridionale in its only UK site outside Portland. Further east Great Wood extends for 3 km along the north side of the hill. The bryophyte flora includes Fissidens gracilifolius, Seligeria calycina and Tortella inflexa on the numerous chalk pebbles. Midway along the ridge the Wildlife Trust reserve at Stonehill Down is a rich site. Bryum canariense, Pleurochaete squarrosa and Weissia condensa occur on the south-facing slope; Porella arboris-vitae and Hylocomium splendens are found on sheltered northerly aspects. On terraces in an old chalk pit on West Hill, there are mats of Frullania tamarisci and Porella arboris-vitae among an abundance of Ctenidium molluscum and Hylocomium splendens.

The eastern end of the chalk ridge from Godlingston Hill to Ballard Cliff is the richest site for bryophytes on the Dorset chalk. Pleurochaete squarrosa is frequent in short turf on the warm south-facing slope of Godlingston Hill. On the northern slopes are Frullania tamarisci, Plagiochila porelloides, Porella arboris-vitae and, most notably, Scapania aspera in its only recent Dorset site.

The valley between Tyneham and Swanage is largely agricultural. However, Corfe Common is a rich and well-worked site. Of most interest are the basic flushes, which are unique in Dorset in the abundance of ‘brown mosses’ including Campylium stellatum var. stellatum, Drepanocladus cossonii and Palustriella commutata var. falcata. Philonotis calcarea occurs here in its only Dorset site. There is also a small acid mire with Riccardia multifida, Aulacomnium palustre, Sphagnum capillifolium, S. fallax and Warnstorfia exannulata.

The limestone plateau is largely used for quarrying and agriculture with little semi-natural habitat. The coastal slope from Anvil Point to St Aldhelm’s Head has extensive areas of limestone grassland. Bryologically it is rather poor with the most interesting areas confined to the abandoned coastal quarries. Scorpiurium circinatum is frequent in the turf. Microbryum starckeanum, Tortella flavovirens, Tortula acaulon var. pilifera and T. protobryoides are found on bare soil. The landslips from St Aldhelm’s Head to Chapman’s Pool are similar to those on the east side of Portland. Sheltered rocks among the scrub support Cololejeunea rossettiana, Lejeunea cavifolia, Marchesinia mackaii, Tortella nitida and Zygodon viridissimus var. stirtonii. Below the cliffs is the largest British population of Acaulon triquetrum. Similar limestone undercliffs are found further west at Dungy Head and Gad Cliff. The valley inland from Chapman’s Pool is the only Dorset locality for the very rare Habrodon perpusillus, which grows on the trunk of one ash tree.

The coast from Durdle Door to White Nothe is mainly composed of chalk. The steep slope below Hambury Tout is particularly interesting. The calcicolous ephemerals Acaulon triquetrum, Ephemerum recurvifolium, Microbryum starckeanum, M. rectum, Pterygoneurum ovatum and Tortula lanceola occur on bare soil, and Weissia condensa is present in nearby turf.


Dorset Heaths


This Natural Area, also known as the Poole basin, includes all the land on the Bagshot Beds and the adjoining Reading and London Clays. The rivers Frome, Piddle and Stour flow through area.

Poole basin north
This section includes all the land on Tertiary substrata north-east of the Stour. The band of clay is largely agricultural but there are extensive areas of ancient woodland at Boys Wood, Castle Hill Wood, Holt Forest and Woodlands Park, although the last has been planted with conifers. Bryophytes on the ground under trees are not remarkable but some interesting species are found on the rides.

Holt Heath is the largest remaining area of heathland and mire. Sphagnum cuspidatum and S. tenellum are abundant in the mires; S. magellanicum and S. papillosum are more local. An orange form of Sphagnum fallax replaces S. pulchrum. The heaths between Ferndown and Verwood have largely been built over; the remnants are subject to scrub encroachment and frequent fires. Dicranum spurium was formerly found in a number sites but has not been seen since 1981. Hypnum imponens has its only Dorset site near West Moors, in an area of wet heath that also has Racomitrium lanuginosum. The flora Cranborne Common is similar to that of Holt Heath, although one acid flush supports Calliergon stramineum, Dicranum bonjeanii and Warnstorfia exannulata.

Poole basin central
This area includes the land between the rivers Stour and Frome and the heaths to the west of Wool, together with all of urban Poole. Canford and Upton Heaths are the largest remaining blocks of heathland within Broadstone and Poole. The dry heath is regularly burnt. Campylopus introflexus has largely replaced the native bryophytes. Small mires still support Sphagnum magellanicum and S. pulchrum, but are most notable for S. molle which is locally frequent. The most interesting bryophyte recorded from the area is the rare alien liverwort Telaranea murphyae, which grows on peaty soil and rotting logs under rhododendron in the sheltered conditions of Branksome Chine.

Wareham Forest is a large area of conifer plantation with remnants of heathland and mire vegetation. The rare liverwort Lophozia capitata was recently found in a wet firebreak. The extensive valley mires at Hyde Bog, Morden Bog and Oakers Bog are dominated by Sphagnum papillosum and S. pulchrum, with S. magellanicum and S. molle present locally, along with a full range of bog hepatics. Winfrith Heath in the west has typical acid mire sphagna, and also a basic flush with Campyliadelphus elodes, Drepanocladus revolvens and Scorpidium scorpioides. The heaths between the Piddle and the Frome and around Moreton have been fragmented by sand and gravel extraction. Abandoned workings provide a habitat for a number of interesting liverworts including Diplophyllum obtusifolium, Fossombronia foveolata, Lophozia excisa and, notably, the alien Lophocolea bispinosa.

The London and Reading clays are used mainly for agriculture, but there are areas ancient woodland at Bere Wood, Bloxworth, Lytchett Matravers, Morden and Oakers Wood. Bere Wood has been largely replanted with conifers but is remarkable for the liverwort Fossombronia husnotii, which occurs beside a track. Oakers Wood is a rich site with recent records for Scapania nemorea and Orthotrichum striatum.

Poole basin south
The area between the river Frome and the Purbeck Ridge is very varied, with large blocks of heathland split by forestry plantations. The valley mires of Arne, Creech, Godlingston, Holme, Povington and Stoborough Heaths all support a similar flora with dominant Sphagnum papillosum and S. pulchrum. Sphagnum magellanicum is much more local. Kurzia pauciflora and Odontoschisma sphagni are the commonest bog hepatics. Calypogeia sphagnicola, Mylia anomala and Riccardia latifrons are more local and often confined to flushed sites. On the adjoining wet heath Leucobryum glaucum, Sphagnum compactum and S. tenellum are frequent, and Campylopus brevipilus is widespread but seldom found in quantity. The largest area of heathland survives within the army ranges near Lulworth. Povington Heath is the only recent site for the declining Dicranum spurium, which is found in areas with a long history of grazing. Hartland Moor had a basic flush similar to that at Winfrith, but it was badly burnt in 1976. Drepanocladus revolvens and Scorpidium scorpioides disappeared and have not recolonized the site.

The South Haven peninsula of Studland Heath was the subject of a detailed ecological survey by Cyril Diver during the 1930s. E.W. Jones surveyed and mapped the bryophytes of the peninsula and his specimens and maps are kept by the Centre for Ecology and Hydrology at Winfrith. Jones found Cephaloziella rubella, Lophozia incisa, Scapania irrigua, Campylopus fragilis and Drepanocladus polygamus. C. fragilis survives today among marram-grass on the outer dunes, but has been replaced further inland by C. introflexus. Lophozia incisa has not been refound. Spur Bog is the richest mire, with abundant Sphagnum pulchrum. There is also a small basic flush with Drepanocladus revolvens.



References

Countryside Commission & English Nature. (1996). The character of
England: landscape, wildlife and natural features
. Countryside
Commission, Cheltenham.

Good, R. (1948). A Geographical Handbook of the Dorset Flora. The
Dorset Natural History and Archaeological Society, Dorchester.


 
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