Department of Forest and Wood Science

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Aboveground biomass and carbon in a South African mistbelt forest and the relationships with tree species diversity and forest structures
(MDPI, 2016) Mensah, Sylvanus; Veldtman, Ruan; Du Toit, Ben; Kakai, Romain Glele; Seifert, Thomas
ENGLISH ABSTRACT: Biomass and carbon stocks are key information criteria to understand the role of forests in regulating global climate. However, for a bio-rich continent like Africa, ground-based measurements for accurate estimation of carbon are scarce, and the variables affecting the forest carbon are not well understood. Here, we present the first biomass study conducted in South Africa Mistbelt forests. Using data from a non-destructive sampling of 59 trees of four species, we (1) evaluated the accuracy of multispecies aboveground biomass (AGB) models, using predictors such as diameter at breast height (DBH), total height (H) and wood density; (2) estimated the amount of biomass and carbon stored in the aboveground compartment of Mistbelt forests and (3) explored the variation of aboveground carbon (AGC) in relation to tree species diversity and structural variables. We found significant effects of species on wood density and AGB. Among the candidate models, the model that incorporated DBH and H as a compound variable (DBH2 × H) was the best fitting. AGB and AGC values were highly variable across all plots, with average values of 358.1 Mg·ha−1 and 179.0 Mg·C·ha−1, respectively. Few species contributed 80% of AGC stock, probably as a result of selection effect. Stand basal area, basal area of the ten most important species and basal area of the largest trees were the most influencing variables. Tree species richness was also positively correlated with AGC, but the basal area of smaller trees was not. These results enable insights into the role of biodiversity in maintaining carbon storage and the possibilities for sustainable strategies for timber harvesting without risk of significant biomass decline.
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.
Age assessment of the bushpig Potamochoerus porcus Linn. 1758 in the southern Cape
(Stellenbosch : Stellenbosch University, 1983-12) Seydack, Armin Hans Wilfried; Bigalke, R. C.; Stellenbosch University. Faculty of AgriSciences. Department of Forest and Wood Science.
ENGLISH ABSTRACT: The bushpig (Potamochoerus 2)orcus) is one of the least studied of the larger African mammals. This contrast to the other two African auids, the is in striking warthog (Phacochoerus aethiopicus) and giant forest hog (Hylochoerus meinertzhgeni), which have been subjected to detailed studies i.a. by Cumming (1970), D'Huart (1978) and Mason (1982). Because the bushpig is a prominent species both in the forest biome and on adjacent agricultural land, autecological research on the species is presently being undertaken to provide information needed for multipurpose forest management. This study on age determination is part of the broader research programme on the species.
Agroforestry : an appropriate and sustainable response to a changing climate in Southern Africa?
(MDPI, 2020-08-21) Sheppard, Jonathan P.; Reckziegel, Rafael Bohn; Borrass, Lars; Chirwa, Paxie W.; Cuaranhua, Claudio J.; Hassler, Sibylle K.; Hoffmeister, Svenja; Kestel, Florian; Maier, Rebekka; Mälicke, Mirko; Morhart, Christopher; Ndlovu, Nicholas P.; Veste, Maik; Funk, Roger; Lang, Friederike; Seifert, Thomas; Du Toit, Ben; Kahle, Hans-Peter
ENGLISH ABSTRACT: Agroforestry is often discussed as a strategy that can be used both for the adaptation to and the mitigation of climate change e ects. The climate of southern Africa is predicted to be severely a ected by such changes. With agriculture noted as the continent’s largest economic sector, issues such as food security and land degradation are in the forefront. In the light of such concerns we review the current literature to investigate if agroforestry systems (AFS) are a suitable response to the challenges besetting traditional agricultural caused by a changing climate. The benefits bestowed by AFS are multiple, o ering ecosystem services, influence over crop production and positive impacts on rural livelihoods through provisioning and income generation. Nevertheless, knowledge gaps remain. We identify outstanding questions requiring further investigation such as the interplay between trees and crops and their combination, with a discussion of potential benefits. Furthermore, we identify deficiencies in the institutional and policy frameworks that underlie the adoption and stimulus of AFS in the southern African region. We uphold the concept that AFS remains an appropriate and sustainable response for an increased resilience against a changing climate in southern Africa for the benefit of livelihoods and multiple environmental values.
Agroforestry development and implementation in South Africa: an assessment of selected case studies
(2016-12) Guiney, Itchell Sandy; Ham, Hannel; Ham, Cori; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Agroforestry (AF) is the integrated approach of producing trees and agricultural crops and/or livestock in a single system on the same piece of land. Elements of AF have been practiced in South Africa (SA) since the late 1800’s, through what’s known as the Taungya system. AF has numerous environmental, economic and social benefits. However, there is limited research in SA to qualify and validate these benefits. The available information and research on AF practices in SA is also highly fragmented, difficult to access or out-dated. There is also no formal national policy or strategy that directly addresses the development and implementation of AF in SA. This national study composed of two phases. The first phase consisted of an assessment of AF development and implementation at the national level where a self-administered questionnaire was distributed to key stakeholders and individuals, involved in the development, promotion and implementation of AF in SA. The second phase entailed the assessment of selected AF projects, using a combination of case studies and survey methods. The results and outcomes of the study provided qualitative and quantitative data on AF development and implementation in SA. This include an analysis of the extent and geographical distribution of AF projects; the major AF systems and practices used; the main barriers factors that hinder the development and implementation of AF. The key organisations developing and implementing AF were defined and an assessment of the main direct and indirect goods and services derived from AF. The strengths, weaknesses, opportunities and threats (SWOT) associated with AF projects; and the design and diagnosis (D&D) of AF systems were also identified. The study concluded that AF systems are currently being developed and implemented in SA at various scales, level and with multiple management objectives, but potential to expand does exist. Several goods and services are also derived from AF systems, which make it a viable sustainable production alternative to conventional production. However, there are a number of barriers (institutional, technical, economic, policy/governance and social) affecting AF adoption, which need to be addressed. One of the recommendations is the development of a national AF policy and strategy. Furthermore, the top ranking national level barriers, which were identified and assessed through the research study, should be addressed. A more comprehensive assessment of the extent and distribution of AF in SA are also required. Finally, a detailed quantitative assessment of the AF goods and services and addressing the outcomes from the D&D of AF case studies in SA is needed.
Analysing taxonomic structures and local ecological processes in temperate forests in North Eastern China
(BioMed Central, 2017) Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Von Gadow, Klaus
Background: One of the core issues of forest community ecology is the exploration of how ecological processes affect community structure. The relative importance of different processes is still under debate. This study addresses four questions: (1) how is the taxonomic structure of a forest community affected by spatial scale? (2) does the taxonomic structure reveal effects of local processes such as environmental filtering, dispersal limitation or interspecific competition at a local scale? (3) does the effect of local processes on the taxonomic structure vary with the spatial scale? (4) does the analysis based on taxonomic structures provide similar insights when compared with the use of phylogenetic information? Based on the data collected in two large forest observational field studies, the taxonomic structures of the plant communities were analyzed at different sampling scales using taxonomic ratios (number of genera/number of species, number of families/number of species), and the relationship between the number of higher taxa and the number of species. Two random null models were used and the “standardized effect size” (SES) of taxonomic ratios was calculated, to assess possible differences between the observed and simulated taxonomic structures, which may be caused by specific ecological processes. We further applied a phylogeny-based method to compare results with those of the taxonomic approach. Results: As expected, the taxonomic ratios decline with increasing grain size. The quantitative relationship between genera/families and species, described by a linearized power function, showed a good fit. With the exception of the family-species relationship in the Jiaohe study area, the exponents of the genus/family-species relationships did not show any scale dependent effects. The taxonomic ratios of the observed communities had significantly lower values than those of the simulated random community under the test of two null models at almost all scales. Null Model 2 which considered the spatial dispersion of species generated a taxonomic structure which proved to be more consistent with that in the observed community. As sampling sizes increased from 20 m × 20 m to 50 m × 50 m, the magnitudes of SESs of taxonomic ratios increased. Based on the phylogenetic analysis, we found that the Jiaohe plot was phylogenetically clustered at almost all scales. We detected significant phylogenetically overdispersion at the 20 m × 20 m and 30 m × 30 m scales in the Liangshui plot. Conclusions: The results suggest that the effect of abiotic filtering is greater than the effects of interspecific competition in shaping the local community at almost all scales. Local processes influence the taxonomic structures, but their combined effects vary with the spatial scale. The taxonomic approach provides similar insights as the phylogenetic approach, especially when we applied a more conservative null model. Analysing taxonomic structure may be a useful tool for communities where well-resolved phylogenetic data are not available.
Analysis of a mechanised cut-to-lenth harvesting operation through use of discrete-event simulation
(Stellenbosch : Stellenbosch University, 2015-03) Rabie, John Frederick; Ackerman, P. A.; Pulkki, Reino Evert; Laengin, Dirk Werner; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Abstract Mechanised timber harvesting operations are rapidly increasing in South Africa, particularly in Eucalyptus pulpwood production. There are however still considerable inefficiencies in implementation and evidence of unnecessary operational variability in current mechanised systems. A typical South African cut-to-length operation for harvesting Eucalyptus pulp logs utilising two excavator-based harvesters and one purpose-built forwarder was studied. The ability of performing discrete-event simulation using R was tested. One of the harvesters and the forwarder were simulated individually and alternative work methods were modelled and compared against the original work method. The changes in productivity based on productive machine hours and cost were recorded. The input data was negatively affected by the large variation in stand and individual tree characteristics. This led to a decrease in model validity. Machine simulation models where however able to capture trends found by other authors. The current method of felling a combination of the four and five tree wide swaths yielded the highest productivity of 11.43 m3 hr -1. Tree size had a notable effect on both the harvester and forwarder productivity. Increasing the tree size from 0.14 m3 to 0.20 m3 and 0.3 m3 led to productivity increases of 5.26 m3 hr -1 and 13.14 m3 hr -1, respectively. When comparing the original mean stack sizes of 2.5 m3, stacks with a mean volume of 5.4 m3 yielded an increase in productivity of 5.91 m3 hr -1. Fitting a larger grapple (1 m2 vs. original 0.8 m2 opening) to the forwarder showed increased productivities across all stack sizes. Forwarder productivity decreased by up to 17.8% with an increase in extraction distance. The largest decrease in forwarder productivity was noted when increasing the on-road travel (both loaded and unloaded) distance from 0 m to 100 m (single road scenario); decreasing by 6.1% when using the standard grapple and 7.6% when using the larger grapple. When using both roads the largest productivity decreases were found when increasing the on-road extraction distance from 0 m to 200 m; decreasing by 15.3% when using the standard grapple and 17.8% when using the larger grapple. Costing of each individual machine was carried out per alternative scenario. Decreases in harvester cost were noted between increasing tree sizes, and forwarder cost increased with extraction distance. Harvester cost decreased by as much as R35.24 m-3 when increasing mean tree volume from 0.14 m3 to 0.3 m3, whereas forwarding cost decreased by a maximum of R1.13 m-3 when extracting larger stacks (5.4 m3), when compared to the observed system (2.5 m3 stacks). Removal of all road travel elements and piling directly at roadside, showed savings of up to R10.21 m-3 when compared to the observed system. R proved to be useful for carrying out discrete-event simulations, however, dedicated simulation probability distributions need to be developed before it can be said that R is highly suitable for discrete-event simulation.
Analysis of the market structures and systems for indigenous fruit trees: the case for Uapaca Kirkiana in Zambia
(Stellenbosch : University of Stellenbosch, 2009-03) Moombe, Kaala Bweembelo; Ham, Cori; Clark, Jeannette; Franzel, Steve; Ackerman, P. A.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Forest and Wood Science.
This study is about marketing of Uapaca kirkiana fruit in Zambia, a fruit that has great economic value especially among the rural and urban poor. It contributes to general food security. In southern Africa, farmers and other stakeholders have identified Uapaca as a priority species for domestication. Current agroforestry initiatives are promoting integration of indigenous trees into farming systems to provide marketable products for income generation. Domestication of trees however, depends on expanding the market demand for tree products. There is considerable evidence that expanding market opportunities is critical for the success of domestication innovations but farmers have been introduced to domestication with little consideration for marketing. The existing market potential can be achieved through sound knowledge on markets and marketing. Information on the marketing of Uapaca fruit is inadequate. This study, therefore, aimed at generating information on the marketing of Uapaca kirkiana fruit, including the basic conditions of demand and supply of the fruit. The main study was conducted in Chipata and Ndola districts in the Eastern and Copperbelt provinces respectively, while fruit pricing was conducted in Lusaka district in Lusaka Province. Questionnaires and participatory research methods were used to collect the data. A total of 37 markets involving 49 collectors, 59 retailers, 189 consumers and 20 government forest workers are included in the study. The study reveals that there is demand for the fresh and secondary products of the fruit and hence substantial fruit trading exists in Zambia. However, the marketing system is characterised by underdevelopment. There is insufficient capacity to satisfy the demand for the fruit and institutional /policy support to Uapaca fruit market expansion. Currently, only basic technology for product development exists. The results suggest a need to address policy and capacity development for expansion of Uapaca kirkiana fruit industry. To improve the Uapaca trade industry, the study proposes developing and scaling up policy strategies, fruit processing sector, research-extension-trader-agribusiness linkages, infrastructure development and knowledge generation for improved understanding of the Uapaca fruit markets.
Analysis of the potential socio-economic impact of establishing plantation forestry on rural communities in Sanga District, Niassa province, Mozambique
(Stellenbosch : University of Stellenbosch, 2009) Landry, Jennifer Ann; Chirwa, Paxie W.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: This thesis assesses the livelihoods of rural households in a proposed green field forestry area, located in Sanga District of Niassa province, Mozambique. The livelihood analysis was used to analyze potential socio-economic impacts of introducing forest plantations to rural households located within the proposed afforestation area. The study made use of household interviews, key informant interviews and secondary data. The sustainable livelihoods framework was used in the research process to develop the household questionnaire and to identify livelihood strategies. Data was analyzed using 331 household questionnaires collected throughout the proposed afforestation area in various communities in the study area. Findings from the study indicated that there is minimal wealth gaps between rural households; but that the introduction of the forestry industry and the subsequent employment created thereof may result in larger wealth gaps between wage earning and non-wage earning households. The study further concludes by linking the potential socio-economic impacts with mitigation recommendations that could be harmonized with FSC Standard requirements for forestry companies interested in developing a forest industry in the study area.
Assessing biological dissimilarities between five forest communities
(SpringerOpen (part of Springer Nature), 2019-06-06) Hao, Minhui; Corral-Rivas, J. J.; Gonzalez-Elizondo, M. S.; Ganeshaiah, K. N.; Nava-Miranda, M. G.; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, Klaus
Background: Dissimilarity in community composition is one of the most fundamental and conspicuous features by which different forest ecosystems may be distinguished. Traditional estimates of community dissimilarity are based on differences in species incidence or abundance (e.g. the Jaccard, Sørensen, and Bray-Curtis dissimilarity indices). However, community dissimilarity is not only affected by differences in species incidence or abundance, but also by biological heterogeneities among species. Methods: The objective of this study is to present a new measure of dissimilarity involving the biological heterogeneity among species. The “discriminating Avalanche” introduced in this study, is based on the taxonomic dissimilarity between tree species. The application is demonstrated using observations from five stem-mapped forest plots in China and Mexico. We compared three traditional community dissimilarity indices (Jaccard, Sørensen, and Bray-Curtis) with the “discriminating Avalanche” index, which incorporates information, not only about species frequencies, but also about their taxonomic hierarchies. Results: Different patterns emerged for different measures of community dissimilarity. Compared with the traditional approaches, the discriminating Avalanche values showed a more realistic estimate of community dissimilarities, indicating a greater similarity among communities when species were closely related. Conclusions: Traditional approaches for assessing community dissimilarity disregard the taxonomic hierarchy. In the traditional analysis, the dissimilarity between Pinus cooperi and Pinus durangensis would be the same as the dissimilarity between P. cooperi and Arbutus arizonica. The dissimilarity Avalanche dissimilarity between P. cooperi and P. durangensis is considerably lower than the dissimilarity between P. cooperi and A. arizonica, because the taxonomic hierarchies are incorporated. Therefore, the discriminating Avalanche is a more realistic measure of community dissimilarity. This main result of our study may contribute to improved characterization of community dissimilarities.
Assessing forest yield and site suitability for Eucalyptus grandis x E. urophylla in coastal Zululand, South Africa, under climate change scenarios
(Stellenbosch : Stellenbosch University, 2022-04) Mfuni, Tiza Ignatius; Drew, David M.; Germishuizen, Ilaria; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: This study aimed to project future mean annual temperature (MAT), mean annual precipitation (MAP), species site suitability, forest yield and the risk of the Leptocybe invasa pest for Eucalyptus grandis x urophylla (E. g x u) in coastal Zululand of South Africa, under two emission scenarios (Representative Concentration Pathway (RCP) 4.5 and 8.5), each for the intermediate term (2041 – 2060) and long term (2081 – 2100). The study utilized projected future climate variables from Global Circulation Models (GCMs) used in phase five of the coupled Model Intercomparison Project (CMIP5) for use in the R version of 3PG (Physiological Processes Predicting Growth) to simulate forest stand volume. The climate data was also combined with recorded presence of the Leptocybe invasa pest to develop an ecological niche model using the Maximum Entropy (Maxent) model and project the possible risk of the pests’ infestation in the study site. Generally, projected future climates revealed increasing MATs amid reducing MAP over most of the study points in both RCP 4.5 and 8.5 as well as shifts in species site suitability for E. g x u. After validating and testing the r3PG model for use in coastal Zululand using field data, the r3PG runs across the future scenarios projected a pattern of reducing volume yield for E. g x u. A second species that was tested, Pinus elliottii, exhibited a relatively more severe trend of reducing yields from the current scenario through the future scenarios. These projected changes were observed amidst a reducing risk of L. invasa over the study grid points in both pathways by the end of the century. Even though the data had some inaccuracies, acquired from third party sources, and based on assumptions from GCMs, this study shows how integrating projected climate information, processed-based growth models and pest risk models can improve the information available to South Africa’s Forest industry. The integration of these data and models could contribute to the preparedness of the forest industry and inform policymaking towards mitigating uncertain climate futures.
Assessing harvesting and postharvest handling practices of Strychnos cocculoides fruit in the Kavango West Region of Namibia
(Stellenbosch : Stellenbosch University, 2016-12) Elago, Selma Ndemutila; Ham, Hannel; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Traditional harvesting methods used by rural people to harvest indigenous fruit remain a challenge in rural communities. Such methods lead to post harvest losses of fruit. This study was conducted in Ncuncuni Constituency of Kavango West Region; Namibia. It focused mainly on two villages namely, Kaguni and Mile 20. The study sought to assess harvesting and postharvest handling practices of Strychnos cocculoides. Specifically the study identified existing harvesting and postharvest handling practices. It assessed the level of postharvest losses of S. cocculoides fruit at different handling practices and maturity stages. It further assessed fruit quality in terms of Total Soluble Solids (TSS), taste, size, and weight. Data was collected between September and October 2015 by means of semi structured and a consumer preferences questionnaire. Focus group discussion and direct observations were also employed during data collection. A total of 160 harvesters and 150 consumers from both study sites were interviewed. The findings indicated the fruit are harvested between June and December mainly by women and children. The fruit were harvested in crop fields and communal forests mainly for consumption and income generation. Fruit were harvested fully mature, half mature and just mature. Climbing the tree and using the stick method to dislodge the fruit to the ground was the two methods used for harvesting. From the field, the fruit were transported to homesteads and markets with a vehicle, donkey/oxen cart, head load or public trucks. The fruit were stored in traditional huts, loose on the ground or in gunny bags in the shade of trees. The fruit were sold next to the main road in both study sites as well as in urban areas within Namibia. The maturity stages at which the fruit were harvested had no significant effect on fruit weight, size and TSS as well as taste in terms of consumer preferences. Poor harvesting and post-harvest handling practices were observed in both study sites. Fruit damage due to cracks bruises, rotting during harvesting, transportation, storage and marketing was the main challenges caused by poor harvesting and handling practices. Fruit were reported to be deteriorating resulting in short shelf life. The poor harvesting handling practices can have a negative impact on the income generated from the sale of the harvested fruit.
The assessment of fire history in plantations of Mpumalanga North
(Stellenbosch : Stellenbosch University, 2003-12) Van der Sijde, J. H. R. (Jan Herman Robert); Theron, Kobus; De Ronde, Neels; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Fire is a threat to all forest plantations. As a result, growers are forced to take active measures to reduce the incidence and extent of fires in their plantations. This thesis is an attempt to collate 846 fire records for eight Komatiland Forests (KLF) plantations in Mpumalanga North for the period 1950 to 1999. Up to now, these reports and the information therein, were not utilised by KLF for planning or for evaluating fire management practices. The only other studies in South Africa, using similar data, were conducted by LeRoux (1988) and Kromhout (1990). A brief background of the forestry industry in South Africa, and in particular Mpumalanga is presented. The main text of the report covers a presentation on fire causes, extent of damage (both in area and in Rand value) and various aspects related to time of ignition and response times. A detailed analysis was done to identify possible relationships between the variables related to compartment, climate and different fire suppression activities. A cause and frequency prediction model was developed that will assist fi re managers in identifying and determining probabilities of fires per cause. Statistical guidelines regarding the planning of fire management around fires caused by honey hunters, lightning, work-related factors, and the activities of people (public, own labour, contractors) are presented. Conclusions were drawn from the results of the analyses of the fire data, which covered a period of 47 years. Recommendations regarding guidelines for strategic fi re management for the Mpumalanga North plantations were made. The main conclusions are: • Statistics on previous fires are very useful in fire management planning as it supplies valuable information on fire causes, time of ignition , past performance related to response times, fire fighting times and damaged caused. • • • • The average area lost due to fires in the study area is 209.9 ha or 0.43% of the plantation area per annum. People-related fires (arson, smokers, picnickers, children and neighbours) caused most of the wild fires (48%), followed by lightning (22%). Some plantations performed poorly, with the occurrence of up to double the number of fires per 1 000 ha of plantation compared to other plantations in the same geographic area. There are definite patterns in the frequency of fires per cause with month of the year. These patterns are valuable for the development of strategies to manage fires caused by honey hunters, lightning fires and work-related fires.
Assessment of trade-offs between timber and carbon values of Pterocarpus angolensis (Kiaat) in the Kavango Region of Namibia : a comparison of current and potential values
(Stellenbosch : Stellenbosch University, 2013-03) Moses, Moses; Ham, Cori; Seifert, Thomas; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Kiaat trees in Namibia are threatened by unsustainable harvesting practice. This study’s aim was to estimate the total value of an average Kiaat tree selected for harvesting with a focus on current timber use value, value of an optimally utilised tree, carbon value, and alternative uses of Kiaat trees. To accomplish this aim, the following specific objectives were set: (1) to estimate the total tree volume and optimum utilisable timber volume of an average Kiaat tree; (2) to estimate the amount and value of carbon stored in the above-ground parts of an average Kiaat tree; (3) to determine timber utilisation levels; and (4) to identify alternative use options to reduce timber losses of Kiaat trees. Previous studies on Kiaat in Namibia and elsewhere focused on growth, development and socio-economical aspects of Kiaat trees. A combination of a socio-economic survey and tree volumes and biomass determination was used to collect data. The survey entailed Kiaat products assessment and face-to-face personal interviews with known key-informants in and around Rundu. Loggers with permits to harvest Kiaat trees were asked to harvest 40 Kiaat trees and data collected from each tree before and after felling included: lower-stem diameter, diameter at breast height (DBH), upper-stem diameter, stem length, stump height, recovered merchantable logs lengths and lower-and-upper diameters and lengths of branches greater than 10 cm in diameter. All canopy parts smaller than 10 cm in diameter were directly weighed, sampled and oven-dried at 105°C until constant weight. Volume of different tree parts was calculated and in combination with basic wood density used to calculate the biomass. It was established that a typically harvested Kiaat tree had an above-ground dry volume of 1.63 m3, of which 1.34 m3 (82%) was utilisable timber volume but that only 0.37 m3 (23%) was used and 0.97 m3 (59%) was left behind in the field. Merchantable logs were mainly cut into planks from which finished products - beds, chairs, doors and tables - were made. An average of 10.7 planks were cut per trunk and the local price of planks was N$45.26 at the time of the study. More income is generated from finished products compared to selling loose planks. Canopy parts were mainly cut into woodcrafts – bowls, music drums, and walking sticks. Current timber use value (N$484.73) surpasses carbon value (N$123.74). A further result of the study was that a significantly higher income could be earned for local livelihoods from Kiaat trees in the Kavango Region if trees were optimally used. Carbon trading is a noble conservation initiative, particularly when trees unsuitable for timber are considered. Use of timber trees exclusively for carbon trading is, however, not a viable option in respect of supporting local people’s livelihoods.
Atomic force microscopy to determine the surface roughness and surface polarity of cell types of hardwoods commonly used for pulping
(Academy of Science for South Africa, 2007) Meincken, M.
ATOMIC FORCE MICROSCOPY CAN BE USED to determine the surface roughness and surface polarity of different cell types originating from hardwood species. This analytical method allows images representing the topography and polarity of a surface to be captured simultaneously at a molecular (nanometre) resolution. The distribution of hydrophilic (polar) groups on these cell surfaces influences the subsequent processing of woodpulp in paper manufacture. These surface properties of fibres, vessel elements and parenchyma cells were investigated for Acacia mearnsii, Eucalyptus grandis, E. dunnii and E. macarthurii. A clear distinction was observed between the cell types and the species in terms of polarity and surface roughness. All four species are currently being used for paper manufacture in South Africa, but not with equal success. This study may help to explain the differences in pulp quality obtained for the various species.
Bioenergy use and food preparation practices of two communities in the Eastern Cape Province of South Africa
(Energy Research Centre, 2010) Chirwa, Paxie W.; Ham, Cori; Maphiri, Stella; Balmer, Marlett
A study was undertaken in two communities that use firewood in the Keiskammahoek area of the Eastern Cape Province of South Africa to understand their behaviour with regard to energy use during food preparation as well as the extent of practising efficient cooking habits. The results showed that despite the high level of electrification, firewood was used in most households (B 60%) for cooking while electricity was mostly used (B 90%) for lighting. Firewood is also preferred for cooking food that takes a long time to prepare, while more convenient sources of energy such as electricity is used for short periods of cooking and re-heating of food. Secondary sources of energy used for cooking included paraffin, dung, leaves and twigs. The study found that there was some deliberate use of energy saving techniques in both communities, although limited and not necessarily practiced with a view to saving energy. Less than half of the respondents soaked hard grains and beans before cooking; while all of them cut food into smaller pieces before cooking commenced. A third of respondents had utensils ready before cooking commenced in one village while two thirds placed utensils and food together before they commenced food preparations in the other village. Pots were covered with lids and water was added in small amounts as required. The heat from fire was not monitored, but fires were extinguished after use. The greatest potential for improvement exists around cooking appliances; where all households were found to be using threelegged pots on open fires when cooking with biomass energy. Open fires are highly inefficient and the use of efficient biomass cook stoves would increase efficiency. It is recommended that in order to reduce the use of biomass-derived energy consumption and expenditure in low-income households, the use of multiple energy sources and portable energy efficient firewood stoves should be promoted. In addition, there should be an aggressive dissemination of information on further processing of fuelwood into forms that can easily be stored and used; and various forms of pre-treatment of hard foods.
Biological control potential of the spotted stem borer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) with the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae
(Stellenbosch : University of Stellenbosch, 2011-08-11) Mekonnen, Tadele Tefera; Tadele Tefera; Pringle, K. L.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: Biological control studies were conducted with isolates of entomopathogenic fungi Beauveria bassiana and Metarrhizium anisopliae from Ethiopia and South Africa against the spotted stem borer Chilo partellus. The study was conducted from April 2002 to April 2003, at the department of Entomology and Nematology, University of Stellenbosch, South Africa. The objectives were to screen these isolates for pathogenicity and to determine the susceptibility of different larval instars; to study the effect of temperature on fungal development and virulence; to investigate food consumption of fungus treated larvae; to determine compatibility of fungal isolates with insecticides; to study the effect of exposure methods and diets on larval mortality; and to evaluate promising isolates under greenhouse conditions using artificially infested maize plants. Four isolates of B. bassiana and six isolates of M. anisopliae were tested against second instar larvae. Of these isolates, B. bassiana (BB-01) and M. anisopliae (PPRC-4, PPRC-19, PPRC-61 and EE-01) were found to be highly pathogenic inducing 90 to 100 % mortality seven days after treatment. In subsequent assays, the fungal isolates were tested against third, fourth, fifth and sixth instar larvae. Second and sixth instar larvae were more susceptible to these isolates than third, fourth and fifth instar larvae. Conidial germination, radial growth and sporulation of the isolates PPRC-4, PPRC-19, PPRC-61, EE-01 and BB-01 were retarded at 15 and 35 0C. A suitable temperature range for the isolates was from 20 - 30 0C. At 25 and 30 0C the isolates induced 100 % mortality to second instar larvae within four to six days. Second and third instar C. partellus larvae were treated with the isolates PPRC-4 and BB-01, and daily consumption of maize leaf was measured. Treatment with the fungi was associated with a reduction in mean daily food consumption. In in-vitro studies, five concentrations (0.1 ppm, 1 ppm, 5 ppm, 10 ppm, and 100 ppm active ingredients) of the insecticides benfuracarb and endosulfan were tested with the isolates PPRC-4, PPRC-19, PPRC-16, EE-01 and BB-01. Increasing the concentration of the insecticides adversely affected germination, radial growth and sporulation of the isolates. In in-vivo studies combining the fungi, PPRC-4 and BB-01,with low concentrations (1 and 5 ppm a.i.), of the insecticides increased the mortality of third instar larvae from 65 to 100 %. Larvae sprayed directly with conidia, exposed to conidia treated leaves and dipped into conidial suspensions suffered high mortality of 98 to 100 %. Larvae exposed to treated leaves and larvae sprayed directly with conidia produced high numbers mycoses in cadavers. Exposure of larvae to treated leaves yielded high sporulation. At a low conidial concentration (1.25x107 conidia/ml), mycosis and sporulation were high. The optimum temperature was 20 0C for mycosis and 15 0C for sporulation. In greenhouse trails, a conidial suspension of 2 x 108 conidia/ml of the pathogenic isolates was sprayed on 3 to 4 week-old maize plants infested with 20 second instar larvae per plant. This resulted in suppression of foliar damage. Treatment with the fungi also reduced stem tunneling and deadheart. In addition, fungal treatment increased mean plant fresh and dry biomass compared to untreated control plants. In general, results from laboratory and greenhouse studies indicated that there was good potential for the use of these fungal isolates for controlling C. partellus larvae.
Biomass modelling of selected drought tolerant Eucalypt species in South Africa
(Stellenbosch : Stellenbosch University, 2013-12) Phiri, Darius; Seifert, Thomas; Ackerman, P. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forestry and Wood Science.
ENGLISH ABSTRACT: The study aims at developing models for predicting aboveground biomass for selected drought tolerant Eucalyptus (E) species (E. cladocalyx, E. gomphocephala and E. grandis x camaldulensis) from the dry west coast. Biomass models were fit for each of the species and a cross-species model was parameterised based on pooled data for all the three species. Data was based on destructive sampling of 28 eucalypt trees which were 20 years of age and additional five five-year old E. gomphocephala trees. Preliminary measurements on diameter at breast height (dbh), height (h) and crown height were recorded in the field. The sampled trees were then felled and samples of discs, branches and foliage were collected. Density of the wood discs and the bark was determined by a water displacement method and computer tomography scanning (CT-scanner). Stem biomass was reconstructed using Smalian’s formula for volume determination and the calculated densities. Upscaling of the crown was carried out by regression equations formulated by employing the sampled branches. Further assessment was carried out on a sub-sample by subjecting the samples to different drying temperatures in a series between 60 and 105ºC. Linear models were parameterised by a simultaneous regression approach based on Seemingly Unrelated Regression (SUR) using the “Systemfit” R statistical package. The predictor variables employed in the study were dbh, d2h and h in which the coefficient of determination (R2), Mean Standard Error (MSE) and Root Mean Standard Error (RMSE) were used to determine the goodness of fit for the models. Akaike Information Criteria (AIC) was also used in the selection of the best fitting model. A system of equations consisting of five models was formulated for each Eucalyptus species. The biomass prediction models had degrees of determination (R2) ranging from 0.65 to 0.98 in which dbh and d2h were the main predictor variable while h improved the model fit. The total biomass models were the best fitting models in most cases while foliage biomass had the least good fit when compared to other models. When the samples were subjected to different drying temperatures, stem wood had the largest percentage change of 6% when drying from 60ºC to 105ºC while foliage had the lowest percentage change of less than 2%.
Biomass prediction models for Colophospermum Mopane (Mopane) in Botswana
(Stellenbosch : University of Stellenbosch, 2009-03) Mutakela, Patrick Silishebo; Bredenkamp, Brian Victor; University of Stellenbosch. Faculty of Agrisciences. Dept. of Forest and Wood Science.
The aim of this study was to develop biomass prediction models for the determination of total aboveground biomass for mopane at three (3) study sites in Botswana. Thereafter, based on the pooled data from the three (3) study sites, recommend one cross-site biomass prediction model that could be used for the indirect estimation of the total aboveground biomass for mopane in Botswana. All the data were collected by destructive sampling from three (3) study sites in Botswana. Stratified random sampling was based on the stem diameter at breast height (1.3 m from the ground). A total of 30 sample trees at each study site were measured, felled and weighed. The 30 sample trees were distributed equally between six DBH classes (Five sample trees per DBH class). Thereafter, using the data from these sample trees, site-specific biomass prediction models for the indirect estimation of total aboveground biomass for mopane were developed as a function of the following independent variables: stem diameter at 0.15 m from the ground; stem diameter at 1.3 m from the ground; stem diameter at 3 m from the ground; crown diameter; and total tree height. The data from the sites were pooled together to develop cross-site biomass prediction models as a function of the given independent variables. The biomass prediction model that provided the best fit at Serule was a linear equation estimated by means of the stem diameter at 1.3 m, while in Sexaxa the biomass prediction model that provided the best fit was estimated by means of the stem diameter at 0.15 m. The biomass prediction model that provided the best fit at the Tamacha site was estimated by means of the stem diameter at 1.3 m. On the basis of the collected data, cross-site biomass prediction models were developed. The cross-site biomass prediction model that provided the best fit was developed from the stem diameter at 1.3 m. This relationship was adopted as the prediction model for the indirect biomass estimation of Colophospermum mopane (mopane) in Botswana.
Bugweed, a short fibre source of high potential
(Stellenbosch : Stellenbosch University, 2003-03) Hoto, N. A. (Nceba Antony); Gerischer, G. F. R.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: The bulk of paper grades destined for the printing industry are produced on modern paper machines which continuously become wider and faster. In order to improve printability, print quality and dimensional stability, such papers contain a large percentage of mineral pigments either in the form of internal loading or external coatings. Although mineral pigments exercise a substantial beneficial effect on paper surface quality, unfortunately these minerals do not contribute towards sheet strength and machine runnability. Today's papermakers are faced with the dilemma of producing highly filled and coated printing papers with low grammages on faster running paper machines, but often lacking the required quality of fibre resources to secure a smooth runnability of such at high speeds. Standard fibre furnishes will have to be upgraded with special types of reinforcing fibres in order to meet the demands of sheet strength and machine runnability. The investigation had succeeded to identify a new suitable fibre resource, which would satisfy the demand of a reinforcing type natural material.

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