Browsing by Author "Geldenhuys, Coert J."

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    Age and growth rate determination using growth rings of selected miombo woodland species in charcoal and, slash and burn regrowth stands in Zambia
    (2010) Syampungani, Stephen; Geldenhuys, Coert J.; Chirwa, Paxie W.
    The field of dendrochronology has not been widely applied in tropical species because many scientists generally perceive that such species rarely produce distinct growth rings. This study was undertaken to determine if the key Miombo species produce distinct growth rings and to determine the relationship between the number of growth rings and age of the tree and stem diameter. The results showed a high correlation between number of growth rings and stand age for both charcoal (P < 0.001, r = 0.9246) and slash and burn (P < 0.001, r = 0.9019) regrowth stands. Additionally, the study has revealed high mean annual ring width values ranging from 4.4 to 5.6 mm in both charcoal and slash and burn regrowth stands. The pattern of ring development per year and the mean annual ring width values provide a basis for the use of ring counts in determining the age of Miombo regrowth stands and predicting the merchantable age for key Miombo woodland species. The results can therefore be used in planning the cutting cycles in Miombo woodlands. However, the phenomenon of missing growth rings suggests that the influence of environment in the use of growth rings in age determination need to be considered in areas that experience droughts.
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    Facilitating the recovery of natural evergreen forests in South Africa via invader plant stands
    (SpringerOpen, 2017) Geldenhuys, Coert J.; Atsame-Edda, Angeline; Mugure, Margaret W.
    ENGLISH ABSTRACT: Contrary to general belief, planted and naturalized stands of introduced species facilitate the recovery of natural evergreen forests and their diversity. Forest rehabilitation actions are often performed at great cost: mature forest species are planted, while species with adaptations to recover effectively and quickly after severe disturbance are ignored; or stands are cleared of invasive alien species before native tree species are planted. By contrast, cost-effective commercial plantation forestry systems generally use fast-growing pioneer tree species introduced from other natural forest regions. Such planted tree stands often facilitate the recovery of shade-tolerant native forest species. This paper provides a brief overview of disturbance-recovery processes at landscape level, and how pioneer stands of both native and introduced tree species develop from monocultures to diverse mature forest communities. It uses one example of a study of how natural forest species from small forest patches of 3 ha in total invaded a 90-ha stand of the invasive Black wattle, Acacia mearnsii, over a distance of 3.1 ha at Swellendam near Cape Town, South Africa. The study recorded 329 forest species clusters across the wattle stand: more large clusters closer to and more smaller clusters further away from natural forest patches. The 28 recorded forest species (of potentially 40 species in the surrounding forest patches) included 79% tree and 21% shrub species. Colonizing forest species had mostly larger fleshy fruit and softer small seeds, and were dispersed by mostly birds and primate species. Maturing forest trees within developing clusters in the wattle stand became a source for forest regeneration away from the clusters, showing different expansion patterns. Four sets of fenced-unfenced plots in the wattle stand showed the impact of browsing by livestock, antelope, rodents and insects on the successful establishment of regenerating forest species, and the dramatic effect of excluding browsing. The results support the approach to rather selectively manipulate than clear invader plant stands in the natural forest environment. This approach invests in the natural succession process rather than planting. It protects developing seedlings against browsing by stacking invader plant debris around them, rather than protecting them by means of costly fencing. This forest recovery process through nurse stands of invasive species can be managed, with additional benefits: Indigenous tree species provide for better streambank stability; and the practice provides for local job creation over a 10-year period for harvesting poles and firewood from the manipulative conversion process.
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    A resource survey for medicinal and edible plant species in the four ecological zones of rural Swaziland
    (Academic Journals, 2011) Dlamini, Cliff S.; Geldenhuys, Coert J.
    Increased and uncontrolled harvesting of non-timber forest products (NTFPs) often leads to disappearance of numerous plant species and ultimately forest degradation. The objective of this study was to conduct resource surveys to assess the condition and actual quantities of standing stock of species of edible and medicinal NTFPs, and to do an economic analysis of the value of the standing stock. The methods used incorporated a total of ten sampling plots (50 m × 50 m) under each landscape area in each study area. Various indigenous species of plants that supply NTFPs were captured in the study sites. However, this study indicated a lack of the common NTFP species in most plots sampled over the four natural woodlands. This was assumed to be due to uncontrolled and unsustainable harvesting for commercial purposes that have led to obvious patches in the forest and forest degradation. Economic analysis showed that the standing stock of NTFP species is highly valuable and comparable to results from South Africa and elsewhere. There were highly significant differences in the number of individual stems per species per plot between sites. There were no significant differences in the inventory value per plot between sites.