Economically viable ๐๐ถ๐ค๐ข๐ญ๐บ๐ฑ๐ต๐ถ๐ด species and hybrid clones for commercial afforestation of mined sand dunes in the Richards Bay area of KwaZulu-Natal
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Date
2023
Authors
Komakech, Christopher Otim
Journal Title
Journal ISSN
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Publisher
University of the Free State
Abstract
๐๐ฎ๐ฐ๐ธ๐ด๐ฟ๐ผ๐๐ป๐ฑ: Richards Bay Minerals (RBM) is South Africaโs largest mineral sands producer with its principal operations located along the coast just north of Richards Bay in KwaZulu-Natal Province. By dredging the coastal sand dunes, the dune sand becomes nutrient poor and does not support economical land use. Casuarina equisetifolia was initially planted for sand dune stabilisation and fuelwood, but its low economic value was of little benefit to the local community. RBM thus undertook a joint venture with the Council for Scientific and Industrial Research (CSIR) to identify genotypes of tree species that were suitable for deployment on the mined sand dunes as alternatives to C. equisetifolia.
๐ ๐ฒ๐๐ต๐ผ๐ฑ๐: In this longitudinal study, a multi-method approach which also included Principal Component Analysis (PCA) was followed to gather and analyse quantitative data over a 6-year period of tree growth. Four trials were established in an alpha lattice design on the mined sand dunes to test 70 genotypes of Eucalyptus species and hybrids of related species. Single plot trees were planted in 10 replications per trial, making up 700 trees per trial. The traits of survival, diameter at breast height (DBH), and stem quality were measured over the 6-year period. At 6 years of tree growth, 26 trees belonging to 13 genotypes were felled to measure their wood and Kraft properties which included, kappa number, pulpability factor, screen pulp yield, basic density and fibre yield. Coppicing ability and pests and diseases were recorded on 6-month-old felled tree stumps. Through a stepwise approach, several genotypes with the potential for deployment on the mined sand dunes were identified. Identification of genotypes was achieved by ranking the 70 genotypes according to their relative performance of the traits survival, DBH, height and stem straightness, by calculating a Relative Performance Index (RPI). The 13 genotypes of the felled tree population were also ranked according to Relative Performance Index (RPI) values using the traits kappa number, pulpability factor, screen pulp yield, basic density and fibre yield. All 13 genotypes (interspecific Eucalyptus hybrid clones) of the felled trees were ranked in the top 15 of the 70 genotype ranking. It thus made sense that these 13 genotypes were appropriate for deployment on the mined sand dunes. They were analysed for their appropriateness for use in the pulp and paper industry, as well as for the woodchips export market, by calculating Economic Performance Indices (EPI) for both market sectors.
๐ฅ๐ฒ๐๐๐น๐๐: The results clearly showed two categories of genotype suitable for deployment on the mined sand dunes. The EPIs revealed a group of genotypes particularly suited to the pulp and paper industry and they consisted of different interspecific hybrid clones of E. grandis and E. urophylla (GxU). Similarly, the EPIs also revealed a group of genotypes that produced dense wood that would be appropriate for woodchip production for the export market. These genotypes were all different interspecific hybrids of E. grandis and E. camaldulensis (GxC). The relatively high-ranking pure species of E. urophylla (Au7 and Au9) and C. equisetifolia (Cas400 and Cas402) also warrant consideration, because they are deployed as seedlings and are substantially cheaper financially to procure than clonal material.
๐ฆ๐ถ๐ด๐ป๐ถ๐ณ๐ถ๐ฐ๐ฎ๐ป๐ฐ๐ฒ: The knowledge obtained during this study will facilitate the rehabilitation of the mined sand dunes in the Richards Bay area and will also help local communities in gaining access to markets and becoming economically viable.
Description
Thesis (Ph.D. (Conservation Biology))--University of the Free State, 2023
Keywords
Eucalyptus species, clonal hybrids, Richards Bay mined sand dunes, pulp and paper, principal component analysis, performance index, economic index