Browsing by Author "Marais, Brendan Nicholas"

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    Methods of assessing utilisable sawlog volume of riparian alien invasive forests in the Western Cape Province of South Africa
    (Stellenbosch : Stellenbosch University, 2018-03) Marais, Brendan Nicholas; Drew, David M.; Ham, Cori; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: Alien invasive plant (AIP) species pose a significant threat to biodiversity, water security and agricultural resources. Several river courses in the Western Cape province of South Africa experience a severe problem with AIPs. Working for Water, a government initiative established in 1995 (now part of the Department of Environmental Affairs [DEA] under Natural Resources Management [NRM]), has identified the Berg River as particularly problematic with biomass ear‐marked for clearing. To date, NRM has cleared nearly 3 million hectares of AIPs and creates 20 000 jobs per annum. The Value‐Added Industries (VAI) Programme has been created in an attempt to extract value from cleared biomass instead of leaving it in‐field. This study presents an inventory of riparian alien invasive forests (AIFs) focussing on a method of measuring utilisable sawlog volume for the production of wooden school desks. The results of the sawlog inventory are presented with a type of correction factor, correcting for measured decreases in utilisable volume resulting from deviant stem form. The correction factor is a comparison between conventionally derived standing volume and more in‐depth measurements of tree‐level variables for estimates of higher value sawlogs over five diameter classes at breast height (DBH) classes, for two AIP species (Eucalyptus camaldulensis and Acacia mearnsii) present on the study site. Stem height at first major branching was measured and assessed in the first step of determining the correction factor. Thereafter, stem taper was assessed by measuring diameter at breast height and upper stem diameter at first major branching. This was compared to conventional equations used to derive upper stem diameter at first major branching for a tree of given DBH. Lastly, stem sweep was measured and assessed. The Simsaw 6 software package was used to conduct sawing simulations to acquire insight into the possible range of sawn product volume recovery attainable from AIFs as well as in the creation of the so called sawlog volume creation factor (SVCF) through the input of sawlog dimensions and subsequent volume calculation thereof. The results showed that height at first major branching influenced sawlog volume recoverable from the AIF site with stem taper not featuring as a variable of interest. Furthermore, the presence of stem sweep influenced sawn product volume recovery compared to logs with no sweep. The results of this study are expected to feed into NRM’s Management Unit Clearing Plan (MUCP); software developed for the purposes of visualising the extent of invasion density and the subsequent operations and costs thereof required to clear areas of AIPs completely.