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Developing a Taper Model for Pinus elliottii x caribaea in South Africa
Dissertation (MSc (Forest Science))--University of Pretoria, 2016.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613435883159552 |
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| access_status_str | Open Access |
| author2 | Kãtsch, Christoph H. |
| author_browse | Kãtsch, Christoph H. |
| author_facet | Kãtsch, Christoph H. |
| collection | Thesis |
| description | Dissertation (MSc (Forest Science))--University of Pretoria, 2016. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110172 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:06.757Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110172 Developing a Taper Model for Pinus elliottii x caribaea in South Africa Kãtsch, Christoph H. madeleen@klf.co.za Chirwa, Paxie W. Algera, Madeleen Pinus Growth models Environment Taper Hybrids Dissertation (MSc (Forest Science))--University of Pretoria, 2016. Various taper functions have been developed to determine the log class distributions of trees more accurately. The need for several taper models is due to the variability in stem form and taper between tree species and even within species. Therefore, although a lot of studies have been done with regards to taper functions, it remains a field of active study, as more species, hybrids and new areas are explored and introduced into the industry. A promising, but relatively new hybrid, Pinus elliottii x caribaea (Pexc), is being planted commercially in South Africa for which a taper model does not exist. The industry is currently using the pure Pinus elliottii (Pell) model to predict the volumes and log class distributions of Pexc. It has however, been observed that the predicted volumes and log class distributions, differ significantly from the actual volumes and products produced. This study therefore primarily focused on developing a taper model for Pexc in South Africa. Taper data were collected for a total of 178 trees, in the Mpumalanga and Limpopo Provinces, using a random sampling method. Non-destructive sampling was done on 108 trees, using a LacerAce hypsometer, and destructive sampling was done on the remaining 70 trees. Taper data for an additional 185 trees were obtained from Komatiland Forests’ research department, resulting in a total dataset of 363 trees. This dataset contains a subsample that was specifically selected in order to determine if altitude, rainfall, temperature or soil have a significant influence on the taper of Pexc. This additional information was used to establish if region specific taper models might be required for this hybrid. Of the four environmental factors studied, only rainfall had a significant influence on the overall taper of the Pexc trees. The Max and Burkhart segmented taper model as well as the Kozak88, Kozak01 and Kozak02 variable exponent taper models were fitted, compared and tested using the statistical analysis system (SAS). The predictive ability of the models was evaluated based on the results from the mean bias, standard deviation (SD), the standard error of prediction (SEP) and the average percentage deviation (mpctDev). Kozak02 had the best fit overall followed by the Max and Burkhart model (MB76). The MB76 model however, predicted the volumes of the Pexc trees more accurately than the Kozak02 model. This study therefore concluded, that of the four models tested, the MB76 model predicted the volumes and log class distributions of Pexc in the South African industry more accurately and that it might be beneficial to develop a Pexc taper model for each of the rainfall regions to further improve the predictive ability of the model. Plant and Soil Sciences MSc (Forest Science) 2026-05-15T17:26:33Z 2026-05-15T17:26:33Z 16/07/20 2016 Dissertation http://hdl.handle.net/2263/110172 en application/pdf |
| spellingShingle | Pinus Growth models Environment Taper Hybrids Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title | Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title_full | Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title_fullStr | Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title_full_unstemmed | Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title_short | Developing a Taper Model for Pinus elliottii x caribaea in South Africa |
| title_sort | developing a taper model for pinus elliottii x caribaea in south africa |
| topic | Pinus Growth models Environment Taper Hybrids |
| url | http://hdl.handle.net/2263/110172 |