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Stellenbosch University (2020)

RESOURCE USE IN INDIGENOUS FORESTS OF THE EASTERN CAPE, SOUTH AFRICA AND ITS EFFECTS ON BIRD COMMUNITIES

Leaver, Jessica

Titre : RESOURCE USE IN INDIGENOUS FORESTS OF THE EASTERN CAPE, SOUTH AFRICA AND ITS EFFECTS ON BIRD COMMUNITIES

Auteur : Leaver, Jessica

Université de soutenance : Stellenbosch University

Grade : Doctor of Philosophy 2020

Résumé
Indigenous forest represents South Africa’s most limited and fragmented biome, but supports disproportionality high levels of biodiversity. Furthermore, forests provide a range of resources for people, particularly the rural poor, and are thus of high socio-economic value. This is particularly true in the Eastern Cape, which harbours 46% of South Africa’s remaining indigenous forest cover, and some of the country’s most economically impoverished populace. Forest management in this region is thus required to balance the needs of resource users with the conservation of forest biodiversity through sustainable use. However, de facto open-access systems of resource use prevail, and there is concern that unregulated harvesting of forest products is driving forest degradation. Supporting this, a recent study found forest bird ranges to have declined in the region over the past 20 years, despite no loss of forest cover over the same time period. However, little research has investigated the link between resource use, habitat modification and forest avifauna in the Eastern Cape. Consequently, this study aimed to investigate patterns of resource use in state forests across the Eastern Cape ; and the impact of different harvest regimes on forest habitat structure, and avifaunal communities. Specifically, three key resource use types were investigated : understory trees harvested for poles ; canopy trees harvested for crafts and timber ; and bark harvested for medicinal use. Regionally, harvest rates were low to moderate, however, the nature and extent of harvesting was site- and species-specific. Of particular concern was the high rate of ring-barking of focal canopy tree species of medicinal value, resulting in the mortality of 29% of harvested trees. Harvest activities modified habitat structure at the ground, understory and canopy layers, with the severity of impact dependent on the nature and extent of harvesting. Overall, harvest activities increased the frequency of canopy disturbances, with concomitant thickening of ground- and understory-layer foliage. At the regional-scale, avifaunal communities were shaped by variation in forest structure and harvest regimes, mediated by species’ feeding traits. Furthermore, harvest activities negatively affected functional organization of bird communities, dependent on the nature and extent of harvesting, but did not reduce species richness or the diversity of functional traits. At the forest-scale, the bird community in a montane forest was structured by harvest-mediated habitat modification, as well as elevation. Specifically, forest-specialist species richness was negatively affected by habitat modification, while forest-generalist species richness was positively affected. Similarly, avifaunal community composition was affected by habitat modification caused by timber harvesting in a scarp forest. Based on avifaunal reponses to harvesting, findings of this study indicate that resource use may be sustainable, but that better management is required to mitigate negative ecological impacts associated with high levels of extraction. By providing insight into the ecological implications of harvesting, this study contributes to the development of ecologically-informed resource use management strategies. While this represents an important contribution, the sustainable use of forests cannot be achieved without increased capacity of the state to implement management actions which integrate the ecological and social issues of forest management.

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