1390 Western rustwort Marsupella profunda
Description and ecological characteristics
Western rustwort Marsupella profunda is a small reddish liverwort which colonises moist, crumbling mica-rich weathered granite and china clay waste. It nearly always occurs in small populations and is rare and threatened throughout its range. It was detected in Cornwall after examination of herbarium specimens and was rediscovered at a single small hill with old china-clay workings during a survey in 1993. More recent survey led to a better understanding of its distribution, and in 1996 it was found to be present on banks of china clay spoil at another location in quantity, with the more widespread Marsupella sprucei and the common liverwort Nardia scalaris. M. profunda was most abundant on acidic clay surfaces that had been exposed for little more than five years, where other vegetation was only just beginning to colonise. Since then it has been found at several additional localities.
Marsupella profunda is a pioneer species which is probably fairly mobile within its very restricted habitat, new plants growing rapidly from spores as older plants are eventually out-competed by surrounding vascular plant vegetation. It will not tolerate heavy shade, and some populations are threatened by scrub invasion. Active vegetation management of sites is required to prolong their suitability for this species.
European status and distribution
Marsupella profunda is a very rare liverwort, endemic to Europe and known only from a small number of sites in Portugal, Madeira, the Canary Islands and south-west England. Its status in Europe is Vulnerable.
UK status and distribution
Marsupella profunda is known in the UK from ten sites in Cornwall. Its status in Britain is Vulnerable. Cornwall supports a large proportion of the known global population. M. profunda is very similar to the more widespread M. sprucei, and can easily be overlooked.
Site selection rationale
Western rustwort Marsupella profunda is the only Annex II priority species which presently occurs in the UK. Site selection has taken into account the priority status of this species, and the importance of UK populations in a European context. The two sites where it is a primary reason for selection support the largest known populations in the UK, and the SAC series holds a very high proportion of the total UK resource. The protected sites should act as a source for colonisation of new localities which are constantly being created through china clay extraction in the surrounding areas.
Lower Bostraze and Leswidden
Cornwall and Isles of Scilly
This site comprises two closely adjacent locations selected for western rustwort Marsupella profunda. The colony at Lower Bostraze is in the southern half of a disused china-clay quarry where extraction ended around 1991. There are many exposed clay surfaces with little or no colonisation by bryophytes and vascular plants. Filamentous green algae are however widespread on the clay. Most vascular plants present are only immature individuals, with heather Calluna vulgaris and bell heather Erica cinerea the most common species. Lower Bostraze supports the largest population of western rustwort, with an estimated 4,000 cm2 cover, while Leswidden supports an estimated 200 cm2. Leswidden is also a former china-clay quarry, where working ceased before 1965. Banks of clay spoil have been exposed more recently during work to clear and flatten the area to the south now used as a coal merchant’s yard. As at Lower Bostraze, the clay surfaces are colonised by filamentous green algae and, very sparsely, by calcifuge vascular plants such as heather Calluna vulgaris and bell heather Erica cinerea.
St Austell Clay Pits
Cornwall and Isles of Scilly
This is one of three sites selected for western rustwort Marsupella profunda. St Austell Clay Pits is located in mid-Cornwall within china clay workings, and comprises three sub-sites.
SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection
- Tregonning Hill Cornwall and Isles of Scilly
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