Population status and ecology of the globally threatened liverwort Marsupella profunda Lindb. in Britain

Abstract

ABSTRACT Introduction Marsupella profunda Lindb. is known from Britain, Portugal and Macaronesia. Its population status and ecology in Britain were investigated. Methods An inventory of records of Marsupella profunda was prepared, and surveys were conducted at a subset of sites. Population size was measured by counts of ‘individual-equivalents’, defined as occupied 1 m grid cells. Habitat and community composition were recorded by relevés. Key results and conclusions Marsupella profunda is confined to habitat created by china clay quarrying, and mostly occurs on kaolinised granite. It is one of the earliest colonists of this substrate. The longevity of habitat patches is limited mainly by competitive exclusion by other bryophytes and excessive shade from scrub development. It has been recorded from six sites in West Cornwall but presently survives at only one of these, where it will likely become extinct within the next 20 years due to vegetation succession. In East Cornwall, an enormous complex of active and disused quarries within the St Austell China Clay Region supports a large population (10,000–20,000 individual-equivalents), but this is declining because china clay production has decreased greatly over the past 30 years. Attempts to conserve the species by the special protection of areas of land have failed because the quarrying process that originally supplied fresh suitable substrate no longer operates in these areas, habitat management measures have been insufficient, and scrub development has progressed. The future of the species in Britain depends on the uncertain future of commercial quarrying in areas of kaolinised granite in Cornwall.