Students

Current students

---

Mr Gerard Lindner (Ph.D. candidate)

Gerard, who is currently based in the Sabie area, and spends part of his time managing a timber farm, is researching the question of error in models.  He is particularly interested in understanding and quantifying error propagation.  He is exploring the components of error in dominant height models and Site Index prediction, as well as errors in field measurements and how these propagate through to errors in final volume estimation.

 

 

Mr Erich Seifert (Ph.D. candidate)

Accurate data on forest structure, stocking volume, biomass, and potential product yield forms the base for efficient forest management. Traditional methods are constrained to only a few tree variables such as tree height and diameter. Information on utilisable stem length, stem taper and sweep, which govern the product yield in a saw mill to a large degree are only estimated by models or not available at all. In consequence stand specific variability is not fully accounted for. The last decades brought about new methods for measuring more tree variables. In particular, high-resolution airborne sensors and new terrestrial sensors such as laser scanning are promising technologies that have undergone successful tests for their application in Forest Mensuration.

Airborne photography is based on the combination of overlapping photographs and provides areal data of a wider spatial range. Modern photogrammetric algorithms such as Structure from Motion (“SfM”) are used to calculate three-dimensional point clouds by combining a large amount of photos. Corresponding points, which identify the same features on different photos are used for this registration process. It has been successfully demonstrated that these methods can be used to determine the crown surface and derive tree heights. Additionally, the usage of multi-spectral imaging allows for identifying tree species. However, airborne photography is not able to provide accurate information on below-canopy structures such as stems and branches.  Certainly, a key challenge is that a successful combination of these methods requires an exact spatial alignment (registration) of terrestrial and airborne derived point clouds.

The objective of Erich’s thesis is to develop novel algorithms for extracting tree and tree parts from remotely sensed data, which can be used for improved combination of dense point clouds from terrestrial laser scanning and high-resolution airborne imagery for forestry applications.  Erich is co-supervised by Prof Jan van Aardt (Rochester Institute of Technology (RIT), USA).

Mr Kevin Kiptoo (Ph.D. candidate)

Ms Gugu Gama (Ph.D. candidate)

Gugu Gama was born in Newcastle which is a city located in the province KwaZulu Natal. She later moved to Johannesburg and received her bachelor’s degree in Botany and Biochemistry from the University of Johannesburg. With great interest in wood and bark anatomy, she furthered her studies and obtained her M.Sc. degree from the University of Johannesburg majoring in Plant Anatomy and Molecular Systematics and Plant Evolution. She has a background in lianescent species portraying an uncommon formation of cambial variant in the genus Grewia. Gugu is therefore excited to join the EucXylo team and expand her knowledge on wood formation in Eucalyptus species. The first aspect of her Ph.D. research will investigate the dynamics of xylem growth in Eucalyptus cladocalyx focusing on the relationship among growth and climate under varying climate conditions in South Africa. Learn more about Gugu’s work here.

 

 

Mr Rafael Keret (Ph.D. candidate)

Rafael was brought up and currently resides in Cape Town, South Africa. Throughout school he has always had a passion for the sciences and showed a great deal of interest for how the biological world functions. To further fuel his thirst for knowledge he obtained his B.Sc. in Molecular Biology and Biotechnology at Stellenbosch University. During varsity Rafael found the field of Plant Biotechnology to be quite fascinating and therefore he pursued his B.Sc. (Hons) and M.Sc. at the Institute for Plant Biotechnology (IPB). Currently, he has joined the EucXylo team, at the Department of Forest and Wood Science, as a Ph.D. candidate, with experience in molecular work, tissue culture and hormonal regulation in plant tissues. His research at the DFWS, is in collaboration with the IPB, under guidance from Dr D. Drew and Dr PN. Hills. Outside of the academic world, Rafael enjoys playing sport, being active, the great outdoors and working on mechanical items. Learn more about Raf’s work here.

 

 

Mr Mpilo Khumalo (Ph.D. candidate)

Mpilo Khumalo grew up in Bergville, a small town in the beautiful valleys of the Drakensberg mountains in KwaZulu Natal. He obtained his B.Sc. in Biological Sciences, B.Sc. (Hons) in Ecology and Environmental Sciences, and M.Sc. in Ecosystems Ecology from the University of the Witwatersrand. His M.Sc. research focused on Wood respiration in southern African savanna ecosystems supervised by the distinguished Professor Bob Scholes and under the mentorship of Professor Sally Archibald. His research expertise ranges from plant physiology to modelling various ecophysiological processes from tissues to ecosystem level. He has joined Stellenbosch University as a Ph.D. candidate under the EucXylo research group at the Department of Forest and Wood Science. His Ph.D. research will relate xylogenesis (wood formation) in several Eucalyptus varieties to various ecophysiological and biogeochemical processes, for example, evapotranspiration, sap flow, carbon fluxes (namely photosynthesis, sequestration and respiration), and plant resource allocation, all which are mainly driven by changes in climate and environmental conditions. Learn more about Mpilo’s work here.

Mr Brian Mandigora (Ph.D. candidate)

Empirical growth models are important forest management and planning tools. However, in light of the more frequent extreme climate events like floods and droughts experienced over the past few decades, it has become more difficult to accurately forecast forest growth and yield. Past rotations no longer accurately explain future rotations in commercial plantations. Furthermore, current models do not explain how wood properties; which are highly commercially significant; respond to daily climatic events like rainfall. Brian, who is co-supervised by Prof Ben Du Toit, is seeking in his Ph.D. to develop cutting-edge models for growth, yield and wood properties at appropriate spatial and temporal scales in the KwaZulu-Natal region of South Africa. He will make use of data from two collaborating forest companies, Mondi and SAPPI from research plots to build and validate the models. Brian is originally from Zimbabwe, where he obtained his bachelor’s degree. He subsequently undertook an M.Sc. degree from Stellenbosch, before beginning his Ph.D. in 2018. His interests lie in the development and application of models to manage challenges, as well as to exploit opportunities, that climate change and climate variation present in agriculture, particularly forestry.

Ms Yenziwe Mbuyisa (M.Sc. candidate)

Yenziwe N Mbuyisa grew up in the small town of Ladysmith KZN. She has a Rhodes University undergraduate degree in environmental science and geology, and an Honours degree in environmental science from the same university. Her interest in trees and climate change was stimulated during an internship program with the Rhodes Restoration Research Group (RRRG) in 2019, where she worked under the guidance of Dr Kathleen Smart and Mr Mike Powell. During this time Yenziwe refined her knowledge on basic plant physiology and picked up skills at the Waainek experimental green house facility, where she ran germination trials on seventeen thicket species and also worked with different electron microscopes to assess the anatomy of these species. Yenziwe’s M.Sc. will be looking at the water use efficiency of different Eucalyptus clones using stable isotopes. This project will be a collaborative effort between EucXylo and the Global Change Biology Group (GCBG) under the supervision of Prof Guy Midgley and Dr David Drew.

 

Ms Lucy Nevhungwili (M.Sc. candidate)

Lucy was born and raised in Lwamondo Village outside of Thohoyandou in the Limpopo province. She obtained her undergraduate degree in B.Sc. Agriculture (Forestry specialization) from University of Venda and a Postgraduate diploma in Forestry and Wood Science from the University of Stellenbosch. She has always been interested in the processes behind plant development and improving plant species. Lucy is excited to join the EucXylo team because it is a diverse group with different interests and she believes there is a lot to learn.

 

 

Mr Chris Tonkin (M.Sc. candidate)

Learn more about Chris’ work here.

Chris grew up in Cape Town and did his undergrad in Conservation Ecology at Stellenbosch University. He developed an interest in Climate Change and did his fourth-year thesis studying the impacts of Climate Change on the productivity and photosynthetic rate of C4 grasses in South Africa. He is currently starting his M.Sc. at Stellenbosch University, focusing on calibrating a sap flow model, first developed by Prof Kathy Steppe et al (2006), for two Eucalyptus spp. and then applying a drought treatment to the trees to simulate how the species may respond to Climate Change. His project is a cross departmental study between the Botany and Forestry departments at Stellenbosch University and he is being co-supervised by Prof Guy Midgley, Dr David Drew and Prof Stephanie Midgley. Eucalyptus trees have been observed to be very effective at sequestering carbon from the atmosphere. This may make them a viable species for combating Climate Change by taking carbon dioxide out of the atmosphere. It is therefore important to understand how the trees themselves will be affected by Climate Change, and whether they can still effectively sequester carbon under predicted Climate Change conditions.

 

---

Mr Matthew van Eyssen (M.Sc. candidate)

Matthew van Eyssen was born in Cape Town and moved to Paarl when he was 6. He obtained his B.Sc. in Forest and Wood Science at Stellenbosch University, where his focus was on Wood Product Science. Matthew is excited to join the EucXylo team to expand his knowledge in Forestry, specifically focussing on Eucalyptus. Prof. Dave Drew will act as his main supervisor, but the project will also involve a collaboration with Wood Product Science and there Prof. Brand Wessels will be his co-supervisor. The project will involve an in-depth analysis on wood structure, as well as silvicultural regimes to see if there are any strong indictors that could assist with cell wall collapse. In his free time, Matthew enjoys fixing things or inventing objects to ease or improve life. Wood has always fascinated him and throughout his study, his love for it has grown. For Matthew it is a great honour to be able to do his M.Sc. in Forestry and Wood Sciences for the next two years with the Hans Merensky Chair in Advanced Modelling of Eucalypt Wood Formation.

 

---

Graduates

Dr Justin Erasmus (Ph.D.)

Structural lumber is the single most important product category for local sawmills making up 75% of all sawn softwood products in South Africa. The competitiveness of this product category in local and international lumber markets, and against alternative building materials such as steel, depends to a large extent on the mechanical product performance. Several studies in recent years have displayed an alarming trend of poor stiffness properties of SA pine – lumber from some tree resources have mean modulus of elasticity (MOE) values up to 25% lower than required for the most common structural grade in the country.  The effect of different variables on wood formation will improve the current understanding of wood cell development. The variation and causal relationships between environment and specific cell properties of wood such as MFA is currently not well understood.

Justin’s study uses a semi-process-based modelling approach to explore the effect of a dynamic environment (climate, soil nutrition, competition) on the wood formation of P. patula – the most important commercial softwood in South Africa. This will be a first for this species.  Expanding on existing modelling frameworks for P. patula will contribute to using it commercially in South Africa as a practical decision-support tool and help identify further areas in the wood formation processes which are not well understood. Together with a lumber MOE model, the framework will aid in understanding influencing factors on MOE and assist in forest management decision-making.  Overall, the outcome of this study could be used in integrated growth, wood property, processing, and economic software models which should ultimately provide forest growers and processors with a superior cultivated resource to successfully grade products to higher strength classes and increase the value yields from structural lumber manufacturing.  Dr. Drew co-supervised Justin’s study with Dr. Brand Wessels (Stellenbosch University).

Dr. Alta Saunders (Ph.D.)

Learn more about Alta’s work here.

Alta grew up Cape Town and obtained a B.Sc. in Conservation Ecology and M.Sc. in Botany from the University of Stellenbosch. During her M.Sc. she was part of the 73rd research team stationed on Marion Island, and focused on using remote sensing techniques to capture plant responses to environmental change. After her studies she worked in the agriculture sector for two years before coming back to university to start her Ph.D studies. Her interest in using models to explain plant response to environmental changes and how these models can be implemented, has led her to the shift her focus to the forestry sector.

 

Mr Oluwaseun Gakenou (M.Sc.)

Learn more about Oluwaseun’s work here, and see his LinkedIn profile here.

Oluwaseun was born and raised in Lagos, Nigeria. He received his bachelor’s degree in Forestry and Wildlife Management from the Federal University of Agriculture Abeokuta (FUNAAB). His project was aimed at using a simple process-based, stand level model called 3-PG (Physiological Principles Predicting Growth) and satellite driven data to calculate biomass production, and also provide information on the growth dynamics of Eucalyptus grandis x urophylla hybrids under varying climate conditions in South Africa. Due to the limitations of the conventional empirical growth models and complexity of process-based models, the 3-PG model was developed to bridge the gap between conventional empirical growth and yield models and process-based carbon-balance models, coupled with the objective of providing a forest management tool with practical value to Forest managers. This model has been adopted in several countries due to its simplicity, availability (free access to the code and software) and practicality. Although, it had been tested for Eucalyptus grandis in South Africa, it had not been tested for Eucalyptus clones, such as Eucalyptus grandis x urophylla. The objectives of this project were to adapt the model (i.e. developing a parameter set) for EGU species under South African conditions, as well as to test the model and to compare the predictions with an empirical model.

 

Ms Gabigabi Sibiya (M.Sc.)

Gabi was born and raised in a small town called Amsterdam which is located in the Mpumalanga Province of South Africa.  Her M.Sc. project is using the process based model called CABALA (an acronym for CArbon BAlance), originally developed by Dr. Michael Battaglia (CSIRO, Australia) to provide silvicultural decision support for Eucaluptus globulus plantations. The main objectives for her project are to (1) parameterize CABALA for Eucalyptus grandis x urophylla hybrids in South Africa and (2) test how CABALA will perform in the Southern African environment through comparing the results produced by CABALA with those empirical field data.

 

Ms Gloria Burengengwa (M.Sc.)

Gloria is from Burundi where she pursued her undergraduate studies in Mathematics. She already has a Master’s degree in Mathematical Sciences at Stellenbosch University, which she did through the African Institute for Mathematical Sciences (AIMS). In her present M.Sc., she is interested in applying mathematics in a climate change context, which brought her to the Forestry Department.  Her research, co-supervised by Dr Drew and Prof Cang Hui,  is focused on a rural area of Zululand at the north of Durban. She is exploring optimal approaches using different mathematical modelling techniques to develop a spatial, daily grid of important daily and or monthly weather variables which will contribute of the improvement of models of agricultural and forest plantation growth.

Mr Ben van Heerden (M.Sc.)

Ben looked at variation in root biomass in plantation eucalypts.  His thesis is available here.

Mr Johan Stefan (M.Sc.)

South Africa has agreed to voluntary alignment and compliance with the United Nations Framework Convention on Climate Change, countries Reducing Emissions from Deforestation and Forest Degradation and Intergovernmental Panel on Climate Change initiatives through the South African Department of Environmental Affairs. These initiatives necessitate reduction of greenhouse gas emission, mitigation of the causes and effects of past emissions and adaption to climate changes caused through past emissions. Commercial forest plantations can play a role in mitigating the effects of anthropogenic climate change through capture of atmospheric carbon dioxide (CO₂) and storage of carbon (C) in tree biomass, dead organic matter and soil carbon pools.

Understanding the role of South African forest plantations in mitigating climate change starts by accurately quantifying the carbon stored in it’s different carbon pools. Unfortunately, some forest carbon pools have been studied to a lesser extent compared to others such as the carbon captured in decomposing woody roots. Johan aims in his M.Sc study, supervised by Prof Ben Du Toit and Dr David Drew,  to determine the potential of decomposing Eucalyptus grandis x urophylla hybrid woody roots for storing carbon in one of the main pulp wood production areas of South Africa.

Mr Philip van Niekerk (M.Sc.)

Philip developed a set of biomass models for Eucalyptus grandis x nitens. His thesis is available here:

Mr Philip Muyambo (M.Sc.)

Philip developed a set of biomass models for Pinus elliottii. His thesis is available here.