Great bryophytes at Great Tew

Despite Storm Ciara pummelling parts of Britain, no less than five bryologists turned out for our trip to part of the Great Tew estate (the valley at the bottom of SP3730). In the event, despite getting rather wet, the valley sheltered us from the worst of the wind, and the only slightly hairy moment was the explosive crack of a branch coming down further along the valley.

Although bryologists have visited the Great Tew area previously (e.g. Eustace Jones recorded Grimmia orbicularis on the estate, and mentions a record of Orthotrichum tenellum in a "wet wood in valley north of Great Tew"  in his 1953 paper on the mosses of Berkshire and Oxfordshire), very few localised records actually exist in the database of the British Bryological Society (older records tend only to have been entered as hectad summaries). This, then, was a great chance to explore a private woodland (we had permission!) and make some localised records for an area that is not well-represented in records databases.

After picking up various common pleurocarps after dropping into the valley, we also found Isothecium alopecurum on the roots of ash and fertile Cirriphyllum crassinervium nearby on soil. Soon after we found one of the things that we had been hoping for, a tufa-forming stream emerging out of the valley-side, as is often found in cuttings and valleys on the Oolite in the north of Oxfordshire. This particular one was not particularly blessed with bryological interest, although a large stand of Palustriella commutata featured in the centre of the stream, accompanied by Cratoneuron filicinum and Pellia endiviifolia.

Palustriella commutata clump in tufaceous spring

Soon after, an uncommon sight in Oxfordshire was seen, that of Plagiomnium undulatum fruiting. Jones (1953) listed this species as "sterile" in Oxon., and still considered the fact of its fruiting "rare or very rare" after forty more years bryologising in the county (Jones, 1991).

Plagiomnium undulatum in fruit at Great Tew.

By this point of the day we were rather sodden, and thoughts were turning towards home. Perhaps the nicest thing of the afternoon was a good population of the liverwort Plagiochila asplenioides growing along a track through the wood further up the valley side. Whilst this livewort is fairly frequent in ancient woods on heavy basic soils, it is not common in Oxfordshire overall, and is always nice to see.

Plagiochila asplenioides at Great Tew.

And finally, a nice photo of the epiphytic liverwort Metzgeria violacea that seemed extremely happy in the humid environment of this hidden valley.

Metzgeria violacea

Oh, and for the non-bryologists, we also saw Dryopteris dilata growing epiphytically in the crown of a fallen oak, which is not a habitat most Floras list!

Dryopteris dilata growing as an epiphyte on oak (foreground; background fern is Polypodium interjectum)

The full list of bryophytes seen in the valley at Great Tew is given below:

Amblystegium serpens var. serpens	Hypnum cupressiforme var. resupinatum	Zygodon conoideus var. conoideus
Brachythecium rivulare	Isothecium alopecuroides	Conocephalum conicum s.str.
Brachythecium rutabulum	Isothecium myosuroides	Frullania dilatata
Bryum capillare	Kindbergia praelonga	Lophocolea bidentata
Calliergonella cuspidata	Orthotrichum affine	Metzgeria consanguinea
Cirriphyllum crassinervium	Oxyrrhynchium hians	Metzgeria furcata
Cratoneuron filicinum	Oxyrrhynchium schleicheri	Metzgeria violacea
Cryphaea heteromalla	Palustriella commutata s.str.	Pellia endiviifolia
Didymodon sinuosus	Plagiomnium undulatum	Radula complanata
Fissidens gracilifolius	Plagiothecium nemorale	Atrichum undulatum
Fissidens incurvus	Rhynchostegium confertum	Cirriphyllum piliferum
Fissidens taxifolius var. taxifolius	Syntrichia virescens	Didymodon insulanus
Homalothecium sericeum	Thamnobryum alopecurum	Leskea polycarpa
Hygrohypnum luridum	Thuidium tamariscinum	Orthotrichum pulchellum
Hypnum cupressiforme var. cupressiforme	Ulota phyllantha	Orthotrichum stramineum
		Plagiochila asplenioides

Bryophytes of Dorchester (Oxfordshire)

Three bryologists met at Dorchester Abbey (SU5794) on a grey, drizzling morning for the fifth excursion of the season. The Abbey graveyard and buildings proved to have a lot to offer, with a grand total of 41 species, pipping our previous season's best churchyard at Bletchingdon (36 species). Probably the top find was Gyroweisia tenuis on the east facing walls of the Abbey. Gyroweisia can be easily confused with other species, particularly Leptobarbula berica, and the Sussex Bryological Group have an excellent blog on this topic.

Gyroweisia tenuis habitat (with Porella platyphylla in foreground)

The other nice find in the churchyard was Syntrichia papillosa. This is a species that appears to be spreading in lowland Britain, possibly helped by eutrophication of a range of substrates from various sources of nitrogen (e.g. NOx from car exhausts). On the other hand, it may be that the species is just recovering from losses during an earlier period of substrate acidification from SO2 pollution (and the loss of hedgerow elms). For example, Eustace Jones notes that Herbert Napier (recording in Oxon. 1909-1914) reported it as "not uncommon" and suggested that the species had increased since the time of Boswell (recording in Oxon. 1858-1897). Jones himself reported S. papillosa as "certainly rare" (this would have applied to the 1935-1953 period) and describes the species as typically only found in single locations within sites (and gives hedgerow trees, "usually elm", as the habitat). Perhaps at this point the species was still widespread but locally rare, meaning that it was often overlooked during surveys. Certainly it appears to have subsequently declined, as it was only recorded twice in Oxon. in the period 1953-1991 (Jones, 1991).

At Dorchester we found nice stands of the plant on a tombstone, but also on the slats of a park bench, suggesting a novel mode of gemmae movement! See the two pictures of the photogenic S. papillosa below:


The full list from Dorchester Abbey appears below:

Amblystegium serpens	Grimmia pulvinata	Rhynchostegium confertum
Barbula convoluta var. convoluta	Gyroweisia tenuis	Rhynchostegium murale
Barbula unguiculata	Homalothecium sericeum	Rhytidiadelphus squarrosus
Brachythecium rutabulum	Hypnum cupressiforme	Schistidium crassipilum
Bryum argenteum	Hypnum cupressiforme var. lacunosum	Syntrichia latifolia
Bryum capillare	Kindbergia praelonga	Syntrichia montana
Bryum rubens	Orthotrichum anomalum	Syntrichia papillosa
Calliergonella cuspidata	Orthotrichum cupulatum	Zygodon viridissimus var. viridissimus
Didymodon fallax	Orthotrichum diaphanum	Lophocolea bidentata
Didymodon insulanus	Oxyrrhynchium hians	Lunularia cruciata
Didymodon luridus	Phascum cuspidatum	Porella platyphylla
Didymodon nicholsonii	Plagiomnium rostratum
Didymodon sinuosus	Pseudocrossidium hornschuchianum
Didymodon vinealis	Pseudoscleropodium purum
Fissidens taxifolius var. taxifolius	Rhynchostegiella tenella

After lunch we walked a circuit through the Dyke Hills (SU5793) west of Dorchester, and then followed the Thames anti-clockwise back to the town.

The (flooded) Dyke Hills in winter.

The Dyke Hills are an Iron Age earthwork, and covered in a slightly improved form of calcareous grassland, the hills themselves presumably being formed from river gravels excavated locally. The bryophyte flora reflects this. After some time searching, we came up with the following, fairly meagre, list:

Weissia species	Homalothecium lutescens
Barbula unguiculata	Oxyrrhynchium hians
Brachythecium rutabulum	Phascum cuspidatum
Bryum rubens	Plagiomnium affine
Fissidens dubius	Pseudoscleropodium purum

The riverside circuit turned up several expected riverside bryophytes, including Syntrichia latifolia, Cinclidotus fontinaloides, and Dialytrichia mucronata, whilst the close inspection of a multi-stemmed willow in the floodplain of the River Thame at SU580937 yielded an impressive 15 epiphytes on one tree, including more S. latifolia and S. papillosa.