Doctoral Degrees (Forest and Wood Science)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/545

Browse

Browsing Doctoral Degrees (Forest and Wood Science) by Subject "Biomass"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Selected key ecosystem services, functions, and the relationship with biodiversity in natural forest ecosystems
    (Stellenbosch : Stellenbosch University, 2016-12) Mensah, Sylvanus; Seifert, Thomas; Veldtman, Ruan; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: Ecosystem services (ES) are the benefits people obtain from ecosystems. Biodiversity is a relevant component in this context, as it supports most ecosystem functions. The worldwide decline in natural ecosystem biodiversity and degradation of ecosystems will likely limit the opportunities to improve the services provided if an explicit focus is not put on their maintenance and improvement in future management decisions. This thesis aims at contributing to the knowledge base of ES provision and its relation with biodiversity in South African Mistbelt forests. First, a socio-empirical study was conducted with households from different localities in Limpopo province to assess the relative importance and use of ES by local population. Questionnaires, descriptive rank analysis, logistic regressions and Poisson mixed effect models were used. Results revealed that provisioning and supporting ES (timber and firewood, edible plants and honey) were the most important, and that age, gender, income as well as prior recreational experiences played important roles in respondents’ perceptions. “Timber and firewood” and “honey” were selected for further investigation in Mistbelt natural forests in Limpopo. Second, the potential of Mistbelt forests as foraging habitat for managed honey bees, and as tree biomass and carbon sinks was investigated. Forest inventory was conducted to collect data on woody plant species (plant density, diameter, total height, pollen and nectar values of honey bee plant species; branch and wood core samples, leaf area, plant maximum height). The diversity of honey bee plant species, temporal availability of honey bee forage and relationship of plant diversity with forage production, were explored, using descriptive analysis and general linear models. As results, 48% of the woody plant species recorded in the inventory were honey bee plant species. The highest potential of forage supply was observed during the last quarter of the year. Bee plant species richness, not overall plant richness, showed the greater effect on forage provision. New multispecies biomass models were established and used to estimate aboveground biomass and carbon stocks, and examine the relationship of aboveground carbon with tree species diversity and structural variables. Allometric models with “DBH2xH” were the best fitting. Biomass and carbon stand values of 358.1 Mg ha-1 and 179.0 Mg ha-1, respectively, were obtained. Basal area of most important species, and of largest trees, as well as plant richness were positively correlated with carbon stock. The relationship of biomass and carbon stock with biodiversity components was the final focus. An analysis scrutinised the effects of taxonomic diversity on carbon storage. Correlations were explored through functional traits-based diversity and dominance, using structural equation and linear mixed-effects models. Results showed that taxonomic diversity effects on carbon stock were positive, and mediated by functional diversity and functional dominance. The effects, however, were greater for functional diversity than for functional dominance. In sum, a novel contribution was made to the ES provision of South African Mistbelt forests, which provides a base for the assessment of these forests and their contribution and underpins the need to protect these ecosystems as a natural heritage.