Thursday, 11 January 2018

Hinksey Heights Bryophytes

Botanists enjoying a coffee break in the wood along the valley
Sunday was another winter outing for local botanists, this time on the Hinksey Heights south of Oxford and better attended than the last. Hinksey is in vice county 22 (Berkshire) meaning a day off recording vascular plants for me, but the meeting was focused on bryophytes anyway. The main interest was one of a series of long narrow valleys draining north off the heights, fed by calcareous groundwater emanating from the limestone along the valley sides. There is peat in the upper part of the valley, and it was once an open fen rich in plants such as grass-of-Parnassus but now mostly covered in willow and reed.

The valley is a nature reserve and can be reached from the Hinksey Heights Golf Club via a footpath and board walk leading north-west from the car park (the temptation to botanise which was resisted). The valley opens out at the entrance near its bottom where there are fabulous views of Oxford and its encircling hills to the north and east. The southern slope here supported the only area of Juncus subnodulosus (blunt-flowered rush) fen we came across, but it was rather overgrown.

The stream tumbling over its tufa weirs
This is where we set to bryologising, and as there were a few new-comers to the subject we could share the revelation that is the tiny world of bryophytes, with ample demonstration material provided by the several common species growing on the accumulated fen litter. The only fen moss we found, however, was a scrap of Bryum pseudotriquetrum. The stream within the woodland in the valley bottom had me fantasising of Eucladium and Gymnostomum species, with its spectacular tufa weirs (or barrage tufa) and drifts of petrified leaves and twigs. Tufa is formed where limey waters precipitate calcite (the principle calcium carbonate mineral) onto lower plants and debris, encasing them in stone, and has a specialist bryophyte flora adapted to this highly alkaline environment. The bryophyte flora, however, was rather dull, most surfaces being covered in the pleurocarp Cratnoneuron filicinum, or the thallose liverworts Conocephalum conicum and Pellia endiviifolia. This suite of species followed us up the valley, dominating the weirs, dripping banks of the stream and springs.

The peaty springs higher up were a little richer, but mostly covered in wefts of the common mosses Plagiomnium affine and P. undulatum. Exceptionally, however, and the highlight of the meeting, both species were producing sporophytes, which for P. affine is a very rare occurrence. Most species of Plagiomnium are dioecious (sexes on separate plants) and are shy to produce sporophytes — the only currently known record of P. affine in fruit in Oxfordshire or Berkshire is from nearby Bagley Wood, found by Watson many decades ago.

Fruiting Plagiomnium affine growing with Cratoneuron filicinum in a tufa spring
Like the two Plagiomnium species, most of the mosses and liverworts we recorded were general calcareous woodland plants rather than specialists of wet woodland or fens. We recorded a number of epiphytes such as the increasingly common Orthotrichum pulchellum and O. stramineum, as well as the uncommon and Brachythecium salebrosum growing on an elder. Altogether we recorded 9 liverwort and 38 moss species, but with a few specimens yet to be examined this is not the final tally. Thanks to everyone for an enjoyable meeting!

Brachythecium salbrosum growing on elder (left). The meeting was too early for the pretty capsules of Orthotrichum stramineum (right, April, Blenheim Park) but old dry capsules are distinctively red-brown and flask-shaped.

Wednesday, 3 January 2018

New Year Plant Hunt

Had you been in Peppard on Sunday you might have witnessed Oli Pescott and I striding about the parish, peering into hedges and self confidently looking over garden wall at weeds, for the hunt was on. The New Year Plant Hunt of course, the national scheme run annualy by the BSBI between 30th December and 2nd January, which challenges botanists to find as many wild plants in flower as possible in a continuous three hour period. With Oli for company I managed to do one better than my solo plant hunt which I blogged about last year, and further media coverage was provided with Oli tweeting about our hunt (left). I'd be delighted to hear by any means of other local Hunts, just be sure to submit your records here!

The choice of locality for our Hunt was not the shrewdest as the biggest yields of plants in flower are to be found in areas with a diversity of disturbed habitats, with an abundance of weeds and garden escapes, while Peppard is mostly semi-natural . I thought we'd make it a little bit more fun by seeing how many bryophytes we could find 'flowering' too (i.e. producing sporophytes), and we also kept full lists of both vascular plants and bryophytes! In all we had 20 species in flower, some maybe questionably so — do the cleistogamous flowers of Poa annua (annual meadowgrass) count, and can one ever actually tell whether the tiny-flowered and petal-less Aphanes arvensis (parsley piert) is in flower? In addition to the weeds and garden escapes we had the winter-flowering specialists, with Daphne laureola (spurge laurel) and a male plant of Mercurialis perennis (perennial mercury) on Peppard Common, and some early vernal species such as Ficaria verna (lesser celandine). The total was a few more than my 17 of last year, and better than the bryophytes of which we found only 16 with sporophytes, all commonly producing capsules at this time of year.

Not in flower but the star find of the day was unquestionably the unexpected colony of Saxifraga granulata (meadow saxifrage) in the churchyard of Rotherfield Peppard, seemingly mown with a razor blade. This species had not been seen in the tetrad since the 1960s and previous records (including that of Druce) were unlocalised, so a really good record of this uncommon plant. If you recall, flowering Saxifraga granulata was a highlight of one of the first meetings of the season, lending a nice symmetry to the year. There was further interest among the bryophytes when we found a tiny moss growing on a garden wall — after some head scratching it was suggested that our plants might be the first county record of Leptobarbula berica, but we await confirmation of this.

In total we recorded 173 vascular plant taxa, not a bad haul for December and valuable additional records for Atlas 2020, as well as 51 bryophyte taxa. Oli and I will continue botanising throughout the 'off season', and will next be meeting in Hinksey on the 7th. Please email me if you'd like to join us.

Above: flowering Daphne laureola (spurge laurel) (top) and a male plant of Mercurialis perennis (perennial mercury) (bottom), typical winter flowering plants, found during a New Year Plant Hunt. Right: the delightful sparsely hairy rosette leaves of Saxifraga granulata (meadow saxifrage) growing in All Saint's churchyard in Rotherfield Peppard.