Masters Degrees (Forest and Wood Science)

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Browsing Masters Degrees (Forest and Wood Science) by browse.metadata.advisor "Crous, Jacob"

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    Silvicultural value chain analysis of short rotation Eucalyptus grandis x urophylla stands in coastal Zululand
    (Stellenbosch : Stellenbosch University, 2018-03) Graham, Daniel John; Ham, Cori; Crous, Jacob; Sale, Giovanni; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: Intensive silvicultural management at establishment is part of commercial practises on short rotation Eucalyptus spp. plantations in South Africa. There is however some uncertainty within the industry whether or not particular activities at plantation level add higher value to the product than the initial investment cost. This study is divided into two sections. Firstly, a case study research method is performed to identify if historical operational data can be used to determine the effect of silvicultural activities on the early height growth and rotational performance of Eucalyptus grandis x urophylla stands in coastal Zululand. The relationship between silvicultural activities and the final tonnes harvested at end of rotation was determined by means of robust regression analysis. Secondly, Microsoft Excel Solver was used to build an optimization simulation model. The model is based on the results from the analysis in the first section. The optimization model provides the lowest cost, highest production and most profitable path through the silvicultural value chain for Zululand North and South respectively. The results from the first section illustrated the important impact that site, climate and other external factors have on the growth and performance of stands, and that stands in Zululand South perform better than stands in Zululand North. Results also indicated that site specific silviculture is very important, with some silvicultural activities showing significantly positive effects on the final tonnes harvested in one region, while the same activities did not have a significant effect in the other region. Results from the operational data analysis were compared to results from published trial research studies. Results related to the effect of pre-plant spray and planting with water on early survival, the effect of fertiliser on final volume growth in Zululand South and the effect of number of weedings on early height growth in Zululand South were contradictory to research studies. The effect of planting with water on early height growth in Zululand North, effect of planting season in both regions and the effect of blanking on final tonnes in Zululand South correlated to results from published research studies. It seems that operational data in the current format is not suitable to demonstrate cause and effect of silvicultural activities. Small changes to operational data collection protocols could enhance the research use of this data substantially. The Excel Solver simulatution model is based on the results of the first section and is only used to illustrate the potential it can have in future management decisons. Results from the Excel Solver simulation illustrated that the highest production and most profitable path is the same path through the silvicultural value chain in Zululand North and in Zululand South. The activities included in these paths did however differ between the two regions. The most profitable path through the silvicultural value chain in Zululand North illustrated a potential cost-benefit of R4716.62 ha-1, while the most profitable path through the silvicultural value chain in Zululand South illustrated a potential cost-benefit of R159.31 ha-1.