Masters Degrees (Forest and Wood Science)

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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 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.
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 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.
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.
Calibrating rotation age for eucalyptus pellita and eucalyptus grandis x urophylla to optimize market returns for transmission poles and plywood in Ghana
(Stellenbosch : Stellenbosch University, 2023-03) Taziwa, Gerald; Ham, Cori ; Dash, Jonathan; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: There has been over-reliance on Tectona grandis and Ceiba pentandra for the manufacture of utility poles and plywood in Ghana. Miro Forestry has for the past eight years been growing various tree species including Eucalyptus pellita (Pellita) and E. grandis x urophylla (GU) on large- scale plantations for the first time in Ghana. However, optimum silvicultural regimes and growth and yield models are yet to be defined since the company is in its first full rotation. In this study, the determination of optimal rotation age for Pellita and GU for poles and plywood production was investigated. A combination of the market conditions, processing technology, silviculture regimes and Miro’s existing growth and yield functions were used to determine a suitable rotation age along with appropriate silvicultural treatments. Market analysis for pole size distribution and a plymill experimental study for peeler log processing were the benchmarks used to establish the optimum pole and peeler log specification to satisfy market demand and mill configuration. A taper function was used to calculate the tree size from which these logs can be produced. Once the optimal tree was ascertained, an investigation into the best regime to follow for poles and plywood ensued. This gave guidance on optimum silviculture regimes to grow the ideal tree for poles and plywood. Miro’s existing growth and yield functions within the Microforest software package were used to simulate different thinning scenarios to investigate growth response to thinning. Stocking, thinning intensity and frequency of thinning were altered to test their effect on the growth dynamics of the trees. Rotation age was defined by diameter growth and the time it took to reach the sizes of the optimum pole or peeler log. The results from this study showed that the optimum pole tree had a DBH of 23 cm and a height of 23.3 m. The optimum plywood tree had a DBH of 31 cm and a height of 30.8 m. The simulation results in Microforest showed that a two-thinning regime of 600 stems per hectare gave more favourable results and that GU would achieve diameters of 23 cm for poles at 8.5 years. Pellita would not be able to achieve those diameters even over a much longer rotation. Both species would not achieve the dimensions for an optimum plywood tree within the range of conditions tested. However, the plymill recovery for the smaller diameter class of 15-20 cm was not significantly different from the 20-30 cm class. A tree whose DBH is 21 cm and a height of 21.5 was also ideal for plywood and it produced logs whose average diameter fell within the 15-20 cm diameter class. A two-thinning regime would achieve these dimensions at six years for GU and 11 years for Pellita. GU had a biological and economic rotation of six and seven years respectively. The slower- growing Pellita had a biological rotation of 7.3 years, and the economic rotation was seven years. This study illustrates that when markets demand very specific product dimensions, the use of biological and economic rotation ages would be subservient to technical rotation age.
Cambial responsiveness in four eucalypt varieties to onset of drought as well as spring conditions
(Stellenbosch : Stellenbosch University, 2024-02) Nevhungwili, Mashudu Lucy; Drew, David Michael; Eckert, Michelle; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT:Xylogenesis is a highly dynamic and seasonal process resulting from variations in cell production by the meristem (vascular cambium). This process results in the formation of secondary xylem and phloem cells within the period of active wood formation, leading to increased stem radius. This study explored secondary wood formation amongst four Eucalyptus varieties (Eucalyptus grandis, Eucalyptus grandis x nitens, Eucalyptus grandis x urophylla and Eucalyptus urophylla)in response to change in environmental conditions. It focussed on two study periods (an induced drought and spring period)in order to see how sensitive the varieties are to drought along with the responsiveness of the varieties to change in growth conditions during spring. To answer these questions, two-year old trees growing in an uncontrolled environment with Mediterranean climate were monitored during drought induced (March) and spring growth (August-September) seasons of 2022. Repeated wood core sampling, together with diameter change measurements, were carried out twice a week during drought induced period and once a week during spring period. Environmental data was obtained from a weather station placed adjacent to the trees. From the selected trees wood samples were extracted using a Trephor corer in a descending spiral pattern. Microcores were cut, stained, and fixed in the laboratory to produce anatomical sections, which were then observed under both Brightfield and Fluorescence microscopic imagery. The developing zone width (cambial and expanding cells zone) along with the cells in two stages of xylogenesis (cell division and differentiation) were analysed using QuPath. The results of the drought induced period showed that irrigation suspension had the greatest effect on wood formation in all studied varieties. Trees experiencing stress showed a decreased cell production as drought progressed, indicating ceased cambial activity, resulting to narrower developing zone contributing to a decreased tree size. After temporal irrigation during this period, varieties showed recovery which was observed in both stem radius and cell production. The response in the developing zone was however delayed in Eucalyptus grandis x urophylla and Eucalyptus urophylla. The response to irrigation application showed that the cambium of trees was in an eco-dormancy stage before irrigation application. The results on irrigated trees during spring period showed an active cambium during late-winter to early spring with no spring start up evident. Rainfall during this season did not show noticeable effects on wood formation across all varieties. The response of the varieties showed different maximum temperatures for wood formation during spring period. Eucalyptus urophylla showed to be sensitive to daily temperatures of above 16°C, while other varieties were sensitive to temperatures above 17°C. Results from this study lead to the conclusion that secondary wood formation in Eucalyptus varieties growing in the Mediterranean climate is controlled by how favorable the environment is.
Camelthorn (Acacia erioloba) firewood industry in Western Cape, South Africa
(Stellenbosch : Stellenbosch University, 2003-04) Raliselo, 'Muso Andreas; Milton, S. J.; Kleynhans, T. E.; Pepler, D.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: The reliance of firewood demand on indigenous trees such as Acacia erioloba is a continuing phenomena despite the concern that over-exploitation of these resources will degrade the environment. This study tested the hypothesis that the cutting of A. erioloba in the Northern Cape is driven by (a) market demand in the Western Cape, (b) ignorance of the long-term ecological consequences and/or (c) ignorance of legislation along the chain of custody of this product. The assumption is that whoever is involved in the A. erioloba firewood industry (resource owner, trader or user) is neither aware of the protected status of the resource nor the negative consequences associated with the over-exploitation of the resource or they are driven by short term monetary gains. Therefore, there is a need to understand the needs of every participant in the chain and to further find out if there may be substitutes for A. erioloba firewood. The results of this study show that there is a market for firewood in the study area and that this demand is driven mainly by the availability rather than the quality of firewood. It will also be shown that Acacia mearnsii which is available in the study area is a better product than A. erioloba and therefore it can be a suitable replacement but consumers were found to bum almost everything that would give them embers. The most preferred firewood in the study area is A. cyclops. The concept of indigenous trees is not clearly understood by retailers and consumers. The major role players in the supply chain were found to be the retailers and the transport owners who may be targeted when firewood trade is to be stopped in the short-term. The results further highlighted the fact that the majority of consumers were aware that indigenous trees were protected in South Africa but the majority of retailers were not aware. The study recommends that firewood trade should be stopped completely by strict enforcement of the law or by the involvement of every role-player and/or that the trade should be regulated.
Cellulose nanocrystals isolated from South African invasive wood species
(Stellenbosch : Stellenbosch University, 2018-03) Raatz, Kyle Franco; Meincken, Martina; Lutz, Marietjie; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: The increased use of cellulose nanocrystals (CNC) due to their high strength, environmentally friendly and renewable source presents a possibility to add value to the potential waste product of South African invasive trees. This material, with its superior characteristics, has been used in a variety of applications including heart valves, microelectronics pumps and liquid crystal displays (LCD). In this study CNCs obtained from two invasive hardwood species, namely acacia, eucalyptus were compared to CNCs isolated from commercial cellulose, with an unknown wood source and from pine, a softwood. CNCs were synthesised via acid hydrolysis and then characterised with Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Dynamic light scattering (DLS), Atomic Force Microscopy (AFM) and Differential Scanning Calorimetry (DSC). No clear difference was determined between hardwoods and softwoods and CNCs synthesised from invasive tree species were found to be similar, if not superior, to CNCs from commercial cellulose
Chemical properties of thermally degraded E. dunnii and E. macarthurii
(Stellenbosch : Stellenbosch University, 2019-04) Van Groeningen, Trevor James; Meincken, Martina; Stellenbosch University. Faculty of Agrisciences. Dept of Forest and Wood Science.
ENGLISH ABSTRACT: Wild fires in South Africa lead to the destruction of an average of 14 000ha of forest plantation annually. In order to reduce the loss of resources the possible recovery of wood after a wildfires was investigated. For this study two eucalyptus species - Eucalyptus dunnii and Eucalyptus macarthurii were selected, as plantations of these species are located in high risk fire regions. The main objective of this study was to determine, at which temperature wood degrades to such an extent that it is no longer suitable for the production of pulp and to find out if differences between different species exist. The aim was to determine whether wood that has been exposed to wildfires can still be used. The change in chemical composition of E. dunnii and E. macarthurii wood was determined before and after exposure to temperatures ranging from 150°C to 220°C. The cellulose, lignin and extractive content, as well as the molecular weight of cellulose were determined as a function of temperature to determine the change in chemical composition that can be expected after exposure to elevated temperatures. The acid insoluble lignin content decreased with increasing temperature, while the acid soluble lignin content increased. As a result, the total lignin content was only reduced by 2%, but the composition of the lignin has clearly changed. The ethanol extractive and water extractive content decreased with increasing temperature for both species. The cellulose content of E. dunnii showed a de facto increase due to the decrease of extractive and lignin content. The cellulose content of E. macarthurii remained relatively unchanged. The molecular weight of both species decreased after exposure to 150°C and reached a low of 160 000 after exposure to 160°C. However, after exposure to a temperature of 170°C the molecular weight began to increase, which was caused by the disintegration of low molecular weight amorphous cellulose. In order to utilise wood from fire damaged trees the wood exposed to a temperature of 160°C and higher must be removed to ensure the wood is suitable for pulp production.
Chemical vegetation management in Pinus radiata plantations in South Africa
(Stellenbosch : Stellenbosch University, 1995-12) Gous, S. F.; Theron, J. M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest & Wood Science.
ENGLISH SUMMARY: Pinus radiata is the most important timber tree planted in the western, southern and eastern Cape of South Africa, covering approximately 60000 hectares. The natural vegetation in these areas is mainly macchia, but exotic invaders like the Acacia and Hakea spp. cause severe problems. Macchia vegetation cannot be controlled successfully by means of slashing, hoeing or burning, because it resprouts rapidly in response to these treatments. Weed control in P. radiata plantations is mainly performed manually. In this study the objective was to search for an alternative, more effective, cheaper, vegetation management option to manual weeding. Trials were conducted where a number of herbicides (acetochlor, glyphosate, hexazinone, imasapir, metsulfuronmethyl, tetrapion and thiazopyr) were tested under different vegetation management treatments. These included the effect of seasons on herbicide efficacy. Preemergent herbicides were added to knockdown herbicides to test if longer relief from weeds could be obtained. Different application methods were also tested. Intra-row weeding was compared to total chemical weeding. Glyphosate at 1500g active ingredient per hectare (a.i./ha) and hexazinone at 2000g a.i./ha produced the best results for total weed control. In the southern Cape, weed control in summer was significantly better than weed control in any other season. No significant difference existed between intra-row weeding and total weeding. Chemical vegetation management was less expensive and more efficient than manual weed control.
Classification of timber from Pinus radiata trees exposed to forest fires
(Stellenbosch : Stellenbosch University, 2015-12) Rust, Stephanus Marthinus; Meincken, Martina; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: This study aimed to classify wood from trees that were exposed to forest fires with regards to their end use. Exposure to high temperatures over time is known to degrade wood in various ways. This degradation could limit the end use by altering mechanical, chemical and physical properties, leading to difficulty in processing or failing to meet required specifications for various grades. In this study wood from Pinus radiata trees that were exposed to forest fires of different levels of heat intensity was analysed with regards to its anatomical and physical changes. Trees were visually classified into three classes of burn severity. Moisture content measurements were taken from 135 standing trees, divided among the three classes. 30 trees, 10 from each of the three classes, were sampled and used for CT analysis. Samples were taken to include growth from before and after the fire. Two samples were taken from each tree, one from the charred and one from the uncharred side. The CT data was analysed and used to measure properties like growth ring width, cell wall thickness, lumen diameter and cell wall density. The data was used to compare properties from the charred and uncharred sides within a given year, as well as compare properties between years. The study showed that there were significant differences in the MC between the burnt and unburnt sides of trees from classes 2 and 3. The difference between the MC measurements on the burnt sides of three classes differed significantly from each other. Lightness measurements were taken on samples from classes 2 and 3. These samples showed no significant difference between the burnt and unburnt sides for either of the two classes. The samples from the less exposed class were lighter, but not significantly so. The macroscopic wood density was determined using core samples. A decrease in wood density was observed with an increase in fire exposure. The mean densities for all three classes however still fulfilled the requirements for structural timber set by the SABS. Growth ring width, cell wall thickness and lumen diameter analysis gave varied results, with some cases showing a decline in properties while others were seemingly unaffected. For many of the outcomes of this study, results found by previous studies could not be reproduced.
Co-production of furfural and wood composite products from bio-based processing residues
(Stellenbosch : Stellenbosch University, 2020-03) Soludongwe, Siviwe Mlamli; Tyhoda, Luvuyo; Chimphango, Annie F. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
ENGLISH ABSTRACT: There is an increased environmental concern to move from a petroleum-based economy to a more bio-based economy. Lignocellulosic materials have been shown to be a good source of building blocks for value-added products such as furfural. The integration of lignocellulosic material in a biorefinery concept proves to be necessary and beneficial in the industry and global context. The lignocellulosic material was sourced locally and included sugarcane (Saccharum officinarum) bagasse, Blue gum (Eucalyptus globulus) and Long-leaved wattle (Acacia longifolia). The lignocellulosic materials were pre-treated with NaOH aimed at enhancing the flexural and physical properties of the manufactured panels as well as extracting hemicelluloses. The effect of the treatment on fibres and resultant by-products were evaluated using wet chemical and instrumental methods, such as high-performance liquid chromatography (HPLC), molecular weight, size-exclusion chromatography (SEM) and Fourier-transform infrared spectroscopy (FTIR). In the present study, the co-production of composite panels and furfural was investigated. The aim was to integrate the biorefinery concept in using biomass waste and alkali pre-treatment to produce furfural. The composite panels were manufactured using untreated and alkaline treated lignocellulosic material, while furfural was produced from the pre-treated by-products. Moreover, this study set out to simultaneously add value to the by-products from pretreated lignocellulosic material by producing furfural, which had not been done previously. In order to produce the furfural, a central composite statistical design (CCD) was used with independent variable temperatures (150-170 °C), time (30-90 min) and the response variable furfural yield, while acidic concentration (2wt%) and solid loading (14wt%) were kept constant. The experimental conditions were sourced with reference to literature to mimic the industrial standards. The interaction of the independent variables and their effect on the produced furfural were evaluated using the Pareto analysis of variance. Response surface models were used to develop and predict the parameters yielding optimum furfural yield. The yields of furfural from the acid hydrolysis of the extracted hemicelluloses was 39, 45 and 44 mol% for sugarcane bagasse, E.globulus and A.longifolia, respectively. These values were slightly lower than the predicted values from the CCD. The low furfural yields led to a Pareto chart showing no confidence of independent variables on the furfural yield. Furthermore, the performance of the treated materials compared to untreated materials were evaluated on the properties of the manufactured composite panels, such as modulus of elasticity (MOE), modulus of rupture (MOR), water absorption and thickness. Based on the results, the treated lignocellulosic materials enhanced the properties of the composite panels as compared to the untreated lignocellulosic materials. In the treated panels the modulus of rupture was 10.42 MPa, 11.13 MPa and 6.4 MPa for sugarcane bagasse, E. globulus and A. longifolia, respectively. The manufactured panels met the minimum requirements and are classified as low density to medium density boards according to ANSI A208.1. These panels prove useful in the wood panel industry as core material for solid doors.

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