Sunday April 16th 2017 – Alfred’s Tower and western section of Stourhead Estate

A small group – Claire, Alan and Marion, Sharon and myself – gathered at the car park near Alfred’s Tower in the west part of the National Trust’s Stourhead Estate. It was surprisingly quiet for Easter Sunday. Perhaps visitors were off on the Easter Egg Hunt near the main entrance. We had come to explore the forest rides and flushes that are an important feature of this area, which sits on a Greensand ridge, known historically as the Forest of Selwood. This fascinating region forms the boundary of three counties, Wiltshire, Somerset and Dorset, and in a way is at the heart of the Wessex Bryology Group’s work. Unlike the arable chalklands to the east and the dairy farming of the clay vales to the south and west, the soils here are acid, with occasional ragstone rocks. Springs run off the ridge, which, where they meet the lower mudstone, form flushes rich in wetland bryophytes.

We headed south along the boundary of North Somerset (VC6) and South Wiltshire (VC8), and after recording a few common epiphytes headed down a slope to the east. Here among the decaying stems and branches of a dense conifer plantation we quickly found populations of Sematophyllum substrumulosum. Once we had our eye in for this small pleurocarp, we were able to pick it out on the horizontal decorticated branches and trunks (but not stumps) of felled trees in deep shade. Its shiny, slightly tawny-green colour contrasted with the pale matt green of the abundant Hypnum jutlandicum. The clincher when one looked more closely were the frequent capsules, held horizontally on a long seta and almost egg-shaped. So far, this is one of only two sites for this plant in VC8. This appears to be a plant on the move and has now been recorded widely across southern Britain, after only being discovered in the UK recently.

Sematophyllum substrumulosum

The edge of the ride, produced more typical acid plants, reminiscent of a western acid oakwood: abundant Plagiothecium undulatum, Rhytidiadelphus loreus, Diplophyllum albicans, Lepidozia reptans, Calypogeia fissa, Dicranella heteromalla, Tetraphis pellucida, and Polytrichastum formosum. Further down the slope some excellent patches of Pohlia wahlenbergii were found. Sharon found some Fossombronia, but sadly we couldn’t find any mature capsules. As we headed down the valley the ground became wetter and following a small stream, we son encountered plenty of Hookeria lucens, Plagiochila asplenioides, Chiloscyphus polyanthus, Aneura pinguis and the first Sphagnum for the day: S. palustre.

Our target for the lunchbreak was a valley in an area known as Convent Bottom. Here in a swampy Alder carr with frequent Ash, we found some lovely hummocks of Trichocolea tomentella, a rare plant in south Wiltshire. The epiphytes were now becoming more lush, and the trees had a good range of species including Frullania tamarisci, various Orthotrichum including frequent O. striatum, and all three of the commoner Metzgeria. Alan and Marion headed off for home (it was Easter Sunday after all!) after lunch, while the remainder of the party worked their way further along the valley. After some false starts we found our way to a part of the woods which Sharon and I had visited some years ago and felt had potential for some exciting finds. And so it proved. In one small area near a pond we found copious amounts of fruiting Physcomitrium pyriforme and more Sphagnum, including S. fimbriatum and S. subnitens. Sharon had been looking out for a suitable place for the tiny Colura calyptrifolia, and sure enough having found a Grey Willow growing in a suitably humid spot over a stream she found a nice population of this plant, which was new to VC8. This site is probably one of the most south-easterly for this species. This strange-looking liverwort with its flask-shaped structures has been spreading southwards in recent decades, much like it appears the Sematophyllum found earlier has been heading north.

Trichocolea tomentella

We checked out some more glades on the way back to the cars, picking up a few more species, including Leucobryum glaucum that seems quite scarce in the woods. A good day was had by all. Although we missed the NT Egg Hunt, we found some jewels tucked away in the Stourhead Estate.

Andrew Branson

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