EFFECTS OF ROCK CLIMBING ON POPULATIONS OF PRESETTLEMENT EASTERN WHITE CEDAR (THUJA-OCCIDENTALIS) ON CLIFFS OF THE NIAGARA ESCARPMENT, CANADA

Cliffs of the Niagara Escarpment support a self-sustaining presettleme nt forest of eastern white cedar (Thuja occidentalis L.) in which some trees are over 1000 years old. Many of the cliffs are also popular lo cations for recreational rock climbing. Our study employed a stratifie d random sampling design to assess the impact of rock climbing on popu lations of cliff-face and cliff-edge trees. Tree density and age struc ture were compared between four climbed and three unclimbed sites in t he vicinity of Milton, Ontario. signs of physical damage were also rec orded for the trees samples at each site. The results showed that livi ng tree density on the cliff face was lower in climbed areas. the age structures of these forest showed that the numbers of older and younge r age classes have been reduced on climbed cliff faces compared with u nclimbed areas. A high percentage of trees on climbed cliff faces show ed evidence of damage by humans. These trends were not as apparent on cliff edges where other disturbances have affected age structure. We r ecommend that cliff faces be explored for the presence of presettlemen t forest and that recreation managers of lands with exposed cliff face s incorporate rock climbing considerations into their management plans . Monitoring programs would help track levels of disturbance. Educatio n of the climbing community would be the most effective long-term solu tion to limiting disturbance in sensitive areas.