- Title
- Integration of Eucalyptus coppice regeneration with mechanical harvesting in South Africa
- Creator
- Schwegman, Kylle
- Creator
- Ackerman, S A
- Subject
- Eucalyptus -- Regeneration Harvesting machinery
- Date Issued
- 2017
- Date
- 2017
- Type
- Thesis
- Type
- Masters
- Type
- MSc
- Identifier
- http://hdl.handle.net/10948/21131
- Identifier
- vital:29443
- Description
- In South Africa, ca. 530 000 ha of the plantation area is planted to Eucalyptus spp. which are native to Australia. Commercially grown hardwoods account for 40.5% of the total area planted to trees, yet contribute more than 70% of the timber to the pulpwood market. This is largely attributed to the superior quality of fibre and pulping properties associated with eucalypt plantations, increases in global short-fibre pulp demands. This as well as the ability to reduce the temporary unplanted period and associated re-establishment costs when choosing to regenerate a stand through coppice management. With the unlikelihood of additional eucalypts being introduced into South Africa, and a reduction in genetic gains from 3rd-4th generation tree breading programmes, most of the eucalypts currently planted will be managed for at least one coppice rotation before replanting with improved genetic material if available. This together with the increased use of mechanised silvicultural and harvesting operations, concerns have been raised as to whether the integration of Eucalyptus coppice regeneration and mechanical harvesting in South Africa is both possible and financially viable for the forest industry to practise. The need for integration becomes more important as often mechanised systems have smaller tolerance levels when compared to manual systems. The first trial was situated in Zululand and was implemented to determine the type and severity of stump damage, coppicing potential and coppice growth over the rotation, associated with four types of harvesting and extraction systems on coppice regeneration. Results obtained from these four treatments (harvesting systems that ranged from manual to fully mechanised cut-to-length systems), found that irrespective of the harvesting system used, more damage occurred to the top than bottom half of the stump, with a significant decrease in coppice regrowth with increasing stump damage. Most damage and least coppice regrowth occurred in the extraction rows where the damage recorded could be attributed to vehicle movement, tear-outs and/or log stripping. There was no significant difference between the harvesting systems in terms of stump mortality, final stem stocking and rotation-end volume. Although this trial indicates that the harvesting systems tested had no impact on tree production the severity of damage and/or difference may have been masked by the excellent coppice potential of the species used for this trial (E. grandis x E. urophylla). Based on the results obtained in the first trial, and using five existing data sets, each data set consisted of four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or) where possible to determine the cost benefits associated with each treatment at various levels of stocking over a full rotation period. BOP (best operating practice) and Or (original stocking) refers to treatments with two stems stump-1, and s (single stem) refers to one stem stump-1. Within each of the four treatment sub-sets, treatments with three levels of stump survival were sought (60%; 80%; 100%), in order to assess financial viability of harvesting different coppice regimes (one coppice stem and two coppiced stems stump-1) using a fully mechanised cut-to-length harvesting system was tested. No differences were found between one coppice stem and two coppiced stems stump-1 in terms of financial returns (internal rate of return). Of the four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or), treatments which had two coppice stems stump-1 lead to increased harvesting cost, while coppice stumps with one stem favours mechanised harvesting and reduced harvesting costs. The final trial, which was also implemented in Zululand, tested the timing of reduction of one coppice stem stump-1 at various stump and stem densities in order to develop an appropriate coppice regime that could favour fully mechanised CTL harvesting systems. Although significant differences were detected at 23 months between the additional control (current recommendation) and the various Reduction_ht (3.5 m, 4.5 m, and 6.5 m) treatments for Dbh, Ba, and Stocking. It is likely that these differences may become less with time due to the decrease in absolute and relative differences between the various treatments with time. This thesis indicates that it is possible to successfully integrate eucalypt coppice regeneration and fully mechanised CTL harvesting. As the results obtained showed that despite the harvesting-associated damage found, no significant difference occurred between the harvesting systems tested in terms of stump mortality, stem stocking (after the final reduction) and rotation-end volume. With regards to the financial implications (using internal rates of return - IRR) associated with harvesting coppice stands of one or two stems stump-1, no clear cost-benefits were found between either of these two treatment scenarios. As those factors that contribute to increased volumes per hectare (increased stem numbers and the retention of two stems stump-1), tend to become normalised across a treatment sub-set, this results in increased harvesting costs with a reduction in the IRR. Coppice management regimes need to be investigated that favour fully mechanised CTL harvesting systems (fewer stems to harvest, but with increased volumes per stem). This includes a reduction to one stem stump-1, as opposed to the current recommendations where some stumps have two stems, such as was tested in the final trial. Although initial results were promising, rotation-end data would be needed to determine any longer term impacts from carrying out an early thinning of coppice shoots to one stem stump-1. Future research needs to be carried out to: determine the influence of mechanised harvesting and extraction for difference species of eucalypts, especially for those that do not coppice as well as the species tested in these trials (Eucalyptus grandis x Eucalyptus urophylla), develop harvesting productivity and/or volume models for coppiced stands of one and two stems stump-1 for different Eucalyptus spp., determine financial returns using specifically designed coppice management regimes which optimise the integration of both mechanical harvesting and silvicultural perations.
- Format
- xiii, 83 leaves
- Format
- Publisher
- Nelson Mandela Metropolitan University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela Metropolitan University
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