Clint Crisp-Moss

Clint Crisp-moss, Tortella densa, is a small acrocarpous moss in the family Pottiaceae found on exposed limestone pavement, cliff ledges, and calcareous rock outcrops in temperate Europe, with strongholds in the Yorkshire Dales, the Burren of Ireland, and similar karst landscapes. The common name 'clint' refers to the raised limestone blocks of limestone pavement habitats, and 'crisp-moss' describes the crinkled, crisped appearance of the dry leaf margins. When moistened, the leaves uncurl and spread, revealing the characteristic nerve extending to the leaf tip. Tortella densa forms dense, cushion-like or turf-forming colonies on exposed limestone surfaces and in sheltered grykes (the fissures between clints), tolerating periodic desiccation and temperature extremes. Limestone pavement is a rare and highly specialized habitat that supports a distinctive community of plants, mosses, liverworts, and invertebrates, and is legally protected in the United Kingdom and Ireland as a priority habitat under European conservation law. The loss of limestone pavement to quarrying, the covering of surfaces by soil and vegetation succession, and the removal of clint-surface plants by collectors have threatened specialist bryophytes of this habitat. Clint Crisp-moss is considered of conservation concern in Britain and Ireland.