Doctoral Degrees (Conservation Ecology and Entomology)

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Browsing Doctoral Degrees (Conservation Ecology and Entomology) by Author "Armstrong, Adrian J"

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    Effects of pine afforestation on native biota and conservation evaluation of afforestable grasslands in motane areas of South Africa
    (Stellenbosch : Stellenbosch University, 1996) Armstrong, Adrian J; van Hensbergen, H. J.; Stellenbosch University. Faculty of AgriSciences. Department of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Pine (Pinus spp.) afforestation generally results in a reduction in the species richness of the native biotic assemblages and in the abundance of species of the original habitat. The biotic assemblage changes in the planted area with the aging of the pines, the bird assemblage from one dominated by species of the original habitat to another dominated by those of a wooded habitat. Wooded-habitat specialists, however, are not generally found in pine plantations. Recovery of the animal and plant assemblages after clearfelling may take many years in the fynbos biome. Vertebrate mediated pollination appears to be disrupted in pine plantations. Plants pollinated by vertebrates and their bird and rodent pollinators are scarce in, or absent from, mature plantations. The proportion of plant species with seeds dispersed by vertebrates increases under plantations, probably due to the pines providing perches for avian frugivores. Native habitat remnants surrounded by pine plantations should be considered as "islands" in an "inhospitable sea", and managed to maintain their biotic complements and ecological processes. Large-scale afforestation with pines is occurring in high rainfall montane grasslands. Evaluations of these grassland for wildlife conservation prior to afforestation have not been done. Grasshoppers, butterflies, birds and small mammals are some key taxa to sample in montane grasslands. Sampling of these four taxa along a gradient of land types was found to be a suitable methodology for a single researcher in conservation evaluations of these grasslands. The land types were defined by altitude, geology and rainfall. Sampling as done at five sites, determined by aspect and topography, on each land type, on four days at each site. Differences in conservation value between land types and between sampling site types in the Maclear district were demonstrated, but rankings differed according to the criterion used. High-altitude land types and low-altitude Protea savanna were most valuable for conserving endemic species. Low-allitude land types with a Molteno sandstone lithology and a high-altitude land type with a Clarens sandstone lithology had the highest conservation values for total numbers of grasshopper genera and species of butterflies and birds. North slopes and crests were important for grasshoppers, valleys and north slopes for butterflies, and valleys and south slopes for small mammals in the district. Taxon richness "hotspots" were not coincident at both the land type and sampling site scales. Nor were the taxon richness and endemicity "hotspots" coincident at the larger scale. Adequately-large areas of all the land types are required to protect the complement of species or all taxa in the afforestable part of the Maclear district. However, incidental observations 111d1ca1ed that a set of five land types may be sufficient. Sub~tituting the highaltitudc, low rainfall, basalt land type for the low-altitude, high rainfall, Molteno sandstone one in this set would protect all the montane endemic species. Most of the afforested farms had high or medium predicted conservation values before afforestation. Nature reserves, necessary for the long-term survival of larger species and some endemics in afforestable regions, should be determined before afforestation begins. Indication of which parts of the Maclear district are most suitable for reservation are given.