Sunday, 15 December 2019

Bryophytes of Watlington Hill

Watlington Hill is a well-known site for chalk grassland bryophytes, although, despite this, relatively few recent records are available for the area (no post-2000 records for the main monad, SU7093, are in the BBS database or on the NBN Atlas for example). However, historically the site has been well searched. Ron Porley, when at English Nature, completed a thorough survey of the Hill in the early 90s, as a part of his work on the chalk grassland of the Chilterns. Porley found the Watlington & Pyrton Hill area to be the richest of the 13 sites he surveyed in terms of chalk grassland specialist bryophytes, recording 46 of his 69 such designated species at the site (although the site was also one of the largest in terms of the area of chalk grassland, estimated at 50.9 ha at that point).

Therefore it was with high expectations that five bryologists assembled at Watlington Hill for the second excursion of the Oxfordshire mossing season (1st Dec. 2019). A number of our group were relatively new to bryophytes, so we started in the woods surrounding the main carpark, demonstrating some of the commoner feather-mosses (pleurocarps) and epiphytes (tree-dwelling bryophytes).

A gentle start to the day!
Our list rapidly swelled, with a number of epiphytes available to demonstrate, including the mosses Orthotrichum stramineum, O. affine, O. diaphanum, Cryphaea heteromalla, and Zygodon conoideus var. conoideus, and the liverworts, Radula complanata, Frullania dilatata, Metzgeria furcata and M. violacea. When I was learning bryophytes around Sheffield in the late 2000s, this would have been considered an impressive haul indeed (at that point, these species were still recolonising after having been previously eradicated from the area due to acidic pollution)! Soon after, David discovered a fallen ash with a superabundance of another epiphyte, Orthotrichum lyellii, a distinctive moss with many brown gemmae covering its leaves. Whilst we often find this on our outings, we normally only find small tufts on standing trees: no doubt our impression is biased by our vision and reach, as this supine ash demonstrated that this species can clearly become locally abundant further up trees!

Orthotrichum lyellii (middle distance) abundant on fallen ash
O. lyellii close-up, showing the brown gemmae

Progressing through the woodland along a track along the edge of the wood, a number of species typical of soil or tree roots were found. The most handsome probably being the liverwort Porella platyphylla, which tends to be found on old limestone walls, graves, hard chalky soils, and the roots of trees on such soils in the Oxfordshire district.

Porella platyphylla on beech root at Watlington.
After lunch, we emerged into chalk grassland, and most of the rest of the excursion was spent crawling around this habitat, as proven by Joshua's tweet below...
A trampled path through the grassland provided us with our first chalk grassland specialists, including Microbryum curvicolle (no photo, but a nice illustration can be found here). Fissidens dubius, Weissia longifolia var. angustifolia, and the tiny stone-covering Seligeria calycina were all also found along this track or in grassland nearby, as well as several other currently infertile small cushion mosses (acrocarps). The idea of returning in the early spring was floated at this point!

Moving into a larger area of grassland on an east-facing slope, David soon located Entodon concinnus, a lovely species normally indicative of rich turf.

Entodon concinnus at Watlington
Sure enough, other species such as Trichostomum crispulum, Hypnum lacunosum and Ctenidium molluscum were all nearby. Mounting the brow of the hill, we encountered the more acid clay-with-flints that often heralds local concentrations of calcifugous species (i.e. those that prefer acid soils). Dicranum scoparium, Polytrichum juniperinum, and P. piliferum were all found in this area.

On circling back to the car park, more rich calcareous turf was found on west and north-west facing slopes, including Ditrichum gracile, Campylium protensum, Plagiomnium affine, Rhytidiadelphus triquetrus, and Brachythecium glareosum. The last was confirmed microscopically back at home, as was Brachythecium salebrosum found in the wood near the carpark at the start of the day. Other species confirmed microscopically included Bryum klinggraeffii, B. ruderale, B. rubens, Fissidens viridulus and Zygodon viridissimus. There were a number of Watlington rarities that we didn't find, but these will hopefully be targeted on the 2020 spring visit previously mentioned! The full list from the day is below.

Ditrichum gracile in chalk grassland at Watlington.
Amblystegium serpens Fissidens dubius Polytrichum piliferum
Barbula convoluta var. convoluta Fissidens incurvus Pseudoscleropodium purum
Barbula unguiculata Fissidens taxifolius Rhynchostegium confertum
Brachytheciastrum velutinum Fissidens viridulus Rhytidiadelphus squarrosus
Brachythecium glareosum Homalothecium lutescens Rhytidiadelphus triquetrus
Brachythecium rutabulum Homalothecium sericeum Seligeria calycina
Brachythecium salebrosum Hypnum cupressiforme var. cupressiforme Syntrichia laevipila
Bryum capillare Hypnum cupressiforme var. lacunosum Syntrichia ruralis var. ruralis
Bryum klinggraeffii Hypnum cupressiforme var. resupinatum Thuidium tamariscinum
Bryum rubens Isothecium myosuroides Trichostomum crispulum
Bryum ruderale Kindbergia praelonga Ulota bruchii
Calliergonella cuspidata Leptobryum pyriforme Weissia brachycarpa var. obliqua
Campylium protensum Microbryum curvicollum Weissia longifolia var. angustifolia
Campylopus introflexus Mnium hornum Zygodon conoideus var. conoideus
Ceratodon purpureus Orthotrichum affine Zygodon viridissimus var. viridissimus
Cryphaea heteromalla Orthotrichum diaphanum
Ctenidium molluscum Orthotrichum lyellii Cephalozia bicuspidata
Dicranella varia Orthotrichum stramineum Frullania dilatata
Dicranum scoparium Oxyrrhynchium hians Lophocolea heterophylla
Didymodon fallax Plagiomnium affine Metzgeria furcata
Ditrichum gracile Plagiomnium undulatum Metzgeria violacea
Entodon coccinus Plagiothecium nemorale Porella platyphylla
Eurhynchium striatum Polytrichum juniperinum Radula complanata

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