Sunday, 8 March 2020

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

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