Thursday, 10 July 2014

Sunday 29 June 2014: Ubley Warren

(Leaders: Nigel Milbourne and Helena Crouch)

Glorious sunshine greeted the sixteen who assembled for this joint meeting of BNHS and Cam Valley Wildlife Group.  After an introduction to the history, management and geology of the reserve, we began to explore this fascinating site, where the legacies of lead mining are evident in the vegetation seen today.  Much of the site comprises uneven gruffy ground where surface layers have been disturbed during mining, resulting in a mosaic of limestone grassland and heathland species, with calcicoles such as Bird’s-foot-trefoil (Lotus corniculatus) and Stemless Thistle (Cirsium acaule) growing alongside calcifuges such as Heather (Calluna vulgaris) and Purple Moor-grass (Molinia caerulea).  Ubley Warren is home to several rare plants.  Much of the turf is Soft-leaved Sedge (Carex montana), so abundant here, yet nationally scarce.  One of the rarest plants in Somerset is Mountain Everlasting (Antennaria dioica), which occurs only on a precarious turf ledge beside a path at Ubley Warren.  For 75 years it was believed to be extinct, but was discovered here in 2005 and persists ... just.  Members were not hugely impressed by this species, or by Slender Bedstraw (Galium pumilum) which was seen on rocks nearby and is not only Nationally Rare but also red-listed as Endangered.  An aberrant Bee Orchid (Ophrys apifera var. badensis) resulted in far more photographic activity.  This variety has two pink sepaloid petals in addition to the three pink sepals.

The larger-scale lead workings (rakes) have produced rocky ravines and limestone crags, which provide a habitat for several rare plants.  We saw the skeletal remains of Hutchinsia (Hornungia petraea), a tiny white-flowered crucifer, in Somerset now found only here and in the Avon Gorge, surviving at both sites on the soil-rock interface thanks to lack of competition in this harsh environment.  A single Wild Service-tree (Sorbus torminalis) clings to the rock face in one rake and was bravely viewed from above by hardy members.  Ubley Warren is home to two rare hawkweeds, both of which were seen in flower on rocks.  Chalice Hawkweed (Hieracium cyathis) grows only here, in Cheddar Gorge and in several sites in south Wales.  Red-tinted Hawkweed (Hieracium angustisquamum), with dark purplish undersides to the leaves, has a very scattered distribution in Britain and Ireland and was seen on a single north-facing rock face.

After exploring the Rakes, we headed out to the western edge of the reserve where Frog Orchid (Coeloglossum viride) was formerly found.  Sadly none were found, but Skylarks (Alauda arvensis) sang overhead as compensation.  Returning across the less frequented southern part of the reserve, a search for Mullein Moth (Cucullia verbasci) caterpillars on Water Figwort (Scrophularia auriculata) was more successful.  There were lots of Dark Green Fritillaries (Argynnis aglaja) flying over the reserve, and we saw several Six-spot Burnets (Zygaena filipendulae) and Forester Moths (Adscita statices) as we walked across the heath. The walk ended with a fantastic view of a Viviparous Lizard (Zootoca vivipara) basking on the boundary wall and a brief sighting of a Small Pearl-bordered Fritillary (Boloria selene) on the other side.
[HJC and NM]

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