Defining critical habitat requirements for a Canadian \u27species at risk\u27 Opuntia humifusa.

Critical habitat is defined in the Species at Risk Act as any habitat in which a species at risk is capable of maintaining self-sustaining populations. Growth and survival of endangered O. humifusa, the Eastern Prickly pear cactus, was compared in field and glasshouse experiments. Conditions (light, soil organic matter, moisture, pH, and macronutrients) differed significantly among habitats at Point Pelee National Park (PPNP). The survival of transplanted seedlings in four habitats at PPNP (back beach, primary successional savanna, secondary successional savanna and deciduous forest) indicated that only two of these habitats (the savannas) would be suitable for O. humifusa over the longer term. Shading and macronutrient treatments in the greenhouse indicated growth was favoured by partial shade; nutrient enrichment enhanced growth, but in the field nutrient supplementation would accelerate secondary succession, to the detriment of O. humifusa.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2006 .M64. Source: Masters Abstracts International, Volume: 45-01, page: 0217. Thesis (M.Sc.)--University of Windsor (Canada), 2006