Susceptibility of Four Species of Cladonia to Disturbance by Trampling in the Cairngorm Mountains, Scotland

(1) Damage to Cladonia uncialis, C. arbuscula, C. rangiferina and C. impexa resulting from human trampling was recorded in kilometre squares with levels of visitor use from 0 to > 18.8 people day-1. (2) Damage declined with distance from paths, and increased with level of use. There was generally little damage 50 m from paths, except on the most heavily used sites. (3) Damage was more extensive at sites which were 'open' in character than at those where use was 'confined'. (4) All four species changed from a pliable to a brittle state at water contents below c. 25%. (5) There is probably widespread slight damage on the 'open' plateau areas of the Cairngorms receiving moderate to heavy visitor use, as well as more serious disturbance of lichens adjacent to paths.