An assessment of the social ecological system of Mabira forest and environs: implications for vulnerability to climate variability
- Authors: Jjagwe, Aisha
- Date: 2019
- Subjects: Climate hazards
- Language: English
- Type: Thesis , Doctoral , Degree
- Identifier: http://hdl.handle.net/10948/44726 , vital:38163
- Description: Tropical forests are attracting attention in climate change debates considering the fundamental role they play as carbon sinks. Mabira Central Forest Reserve (CFR) found in the Lake Victoria basin region and of significance in achieving the Sustainable Development Goals. It has however undergone drastic degradation since the 1970s and its social economic ecological and environmental functions are at risk. The present study assessed the Social Ecological System (SES) of Mabira CFR and environs as well as the implications for vulnerability to climate variability. It focused on; i) assessment of the spatial temporal changes of Mabira CFR; to which Landsat images of 1975, 1986, 2000 and 2015 were used in combination with ground truthing for a successful classification of land use/cover types. ii) Determine the implications of land use/cover types and forest management options for above ground biomass (AGB) and soil organic carbon (SOC); here Velle, (1995) allometric equation was adopted for the AGB while the Walkley and Black (1934) was used to determine soil organic carbon iii) Determine the implications of land use cover change for livelihood and vulnerability to climate change impacts; to this the Social Ecological systems framework by Ostrom (2009) was adopted to understand the vulnerability implications for land use cover change (LUCC) and Climate variability in a forest based community. The study reveals that heavy deforestation and degradation continue to pose threats to Mabira CFR and environs. Major drivers of LUCC are: population expansion, loss of soil fertility, poor agricultural practices, establishment of roadside markets, industrialization and unclear forestry boundary. Findings indicate that although forest comprised the biggest coverage between 1975 and 2000, it has faced massive reduction between 2000 and 2015. Major forest conversions have been to subsistence farming (5.94%). The implications of LUCC are reflected in; the exposure of soils to degradation as seen from deforestation; soil erosion; carbon sequestration and climate variability constraining livelihoods. AGB and carbon was found highest in the strict nature reserve where on average the parameters noted above were found to be bigger. The recreation buffer had less carbon compared to the strict nature reserve; however the production zone, which had scattered trees with smaller parameters, registered the lowest average total AGB and carbon. Results indicate a perfectly strong relationship between the AGB and carbon variables. Results also indicate that approximately 6,771092.344 tonnes are sunk in the strict nature reserve. SOC analyzed based on the soil carbon percentage content. In terms of soil depth, the 0-10cm and 10-20cm soil layers had relatively similar variations of least square means for carbon than at 20-30cm soil layer. The highest SOC was observed in the soil surface of 0-10 cm depth, with the highest mean of 2.78 % across all the management zones. The amount of soil organic matter also varied with land use /cover types. Study findings reveal that LUCC and land management have a direct influence on soil organic carbon accumulation. Results indicate that LUCC implications for AGB and SOC as well as climate variability lead to livelihood vulnerability. Climate hazards experienced have affected SES, temperature variation range between 1oC -2oC. These variations are likely to increase vulnerability. This study recommends mapping of LUCC to identify priority areas for intervention. Priority should be given to reducing deforestation and restore degraded areas. Future research should focus on building adaptive capacity for forest based communities to mitigate climate change, improving forest tenure as a strategy for climate change impacts, integrating climate change into forest policy reviews.
- Full Text:
- Date Issued: 2019
- Authors: Jjagwe, Aisha
- Date: 2019
- Subjects: Climate hazards
- Language: English
- Type: Thesis , Doctoral , Degree
- Identifier: http://hdl.handle.net/10948/44726 , vital:38163
- Description: Tropical forests are attracting attention in climate change debates considering the fundamental role they play as carbon sinks. Mabira Central Forest Reserve (CFR) found in the Lake Victoria basin region and of significance in achieving the Sustainable Development Goals. It has however undergone drastic degradation since the 1970s and its social economic ecological and environmental functions are at risk. The present study assessed the Social Ecological System (SES) of Mabira CFR and environs as well as the implications for vulnerability to climate variability. It focused on; i) assessment of the spatial temporal changes of Mabira CFR; to which Landsat images of 1975, 1986, 2000 and 2015 were used in combination with ground truthing for a successful classification of land use/cover types. ii) Determine the implications of land use/cover types and forest management options for above ground biomass (AGB) and soil organic carbon (SOC); here Velle, (1995) allometric equation was adopted for the AGB while the Walkley and Black (1934) was used to determine soil organic carbon iii) Determine the implications of land use cover change for livelihood and vulnerability to climate change impacts; to this the Social Ecological systems framework by Ostrom (2009) was adopted to understand the vulnerability implications for land use cover change (LUCC) and Climate variability in a forest based community. The study reveals that heavy deforestation and degradation continue to pose threats to Mabira CFR and environs. Major drivers of LUCC are: population expansion, loss of soil fertility, poor agricultural practices, establishment of roadside markets, industrialization and unclear forestry boundary. Findings indicate that although forest comprised the biggest coverage between 1975 and 2000, it has faced massive reduction between 2000 and 2015. Major forest conversions have been to subsistence farming (5.94%). The implications of LUCC are reflected in; the exposure of soils to degradation as seen from deforestation; soil erosion; carbon sequestration and climate variability constraining livelihoods. AGB and carbon was found highest in the strict nature reserve where on average the parameters noted above were found to be bigger. The recreation buffer had less carbon compared to the strict nature reserve; however the production zone, which had scattered trees with smaller parameters, registered the lowest average total AGB and carbon. Results indicate a perfectly strong relationship between the AGB and carbon variables. Results also indicate that approximately 6,771092.344 tonnes are sunk in the strict nature reserve. SOC analyzed based on the soil carbon percentage content. In terms of soil depth, the 0-10cm and 10-20cm soil layers had relatively similar variations of least square means for carbon than at 20-30cm soil layer. The highest SOC was observed in the soil surface of 0-10 cm depth, with the highest mean of 2.78 % across all the management zones. The amount of soil organic matter also varied with land use /cover types. Study findings reveal that LUCC and land management have a direct influence on soil organic carbon accumulation. Results indicate that LUCC implications for AGB and SOC as well as climate variability lead to livelihood vulnerability. Climate hazards experienced have affected SES, temperature variation range between 1oC -2oC. These variations are likely to increase vulnerability. This study recommends mapping of LUCC to identify priority areas for intervention. Priority should be given to reducing deforestation and restore degraded areas. Future research should focus on building adaptive capacity for forest based communities to mitigate climate change, improving forest tenure as a strategy for climate change impacts, integrating climate change into forest policy reviews.
- Full Text:
- Date Issued: 2019
Optimisation of a legacy product with a history of tablet friability failures utilising quality by design
- Authors: Watkins, Eric
- Date: 2018
- Subjects: Pharmaceutical chemistry , Pharmaceutical industry Pharmacy -- Research
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/36398 , vital:33938
- Description: The concept of Quality by Design (QbD) was introduced as a method of building quality into the product during the initial stages of manufacturing. This study explores the suitability of utilising QbD to optimise a legacy product. With the aid of QbD, a higher level of quality assurance and product knowledge was achieved. Sound scientific and risk-based decisions allowed for a robust manufacturing process with inherent operational quality and flexibility. By the establishment a quality target product profile (QTPP) and determining the influence of the critical processing parameters (CPP's) on the product's critical quality attributes (cQA's) the process understanding of Product X can be more accurately defined. The relationships between several explanatory variables will be explored by using a sequence of Design of Experiments (DoE) to obtain an optimal response. The DoE were performed and analysed using Minitab® statistical software version 17.0 (Minitab Inc., United Kingdom). A Response Surface Methodology (RSM) using a central composite experimental design (CCD) was utilised to capture the data. The data was analysed using the collection of statistical models (ANOVA) to analyse the differences between the means and their associated procedures. Input variables investigated were: compression machine tooling shape, hardness, and loss on drying LOD (post drying). The significant value (α) of 0.05 helped to determine if the null hypothesis would be accepted or rejected. The DoE identified the factors that had the highest risk of affecting the output variables and helped to establish the design space. Post completion of the DoE, a confirmatory batch was made which served as a diagnostic tool for evaluating the effectiveness of the generated model. The establishment of a strategy to control the variables and responses is of critical importance in order to appropriately use the flexibility given to products developed or optimised using QbD principles. This study show that the structured approach used in Quality by Design methodology can be successfully applied to optimise a commercialised legacy product.
- Full Text:
- Date Issued: 2018
- Authors: Watkins, Eric
- Date: 2018
- Subjects: Pharmaceutical chemistry , Pharmaceutical industry Pharmacy -- Research
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/36398 , vital:33938
- Description: The concept of Quality by Design (QbD) was introduced as a method of building quality into the product during the initial stages of manufacturing. This study explores the suitability of utilising QbD to optimise a legacy product. With the aid of QbD, a higher level of quality assurance and product knowledge was achieved. Sound scientific and risk-based decisions allowed for a robust manufacturing process with inherent operational quality and flexibility. By the establishment a quality target product profile (QTPP) and determining the influence of the critical processing parameters (CPP's) on the product's critical quality attributes (cQA's) the process understanding of Product X can be more accurately defined. The relationships between several explanatory variables will be explored by using a sequence of Design of Experiments (DoE) to obtain an optimal response. The DoE were performed and analysed using Minitab® statistical software version 17.0 (Minitab Inc., United Kingdom). A Response Surface Methodology (RSM) using a central composite experimental design (CCD) was utilised to capture the data. The data was analysed using the collection of statistical models (ANOVA) to analyse the differences between the means and their associated procedures. Input variables investigated were: compression machine tooling shape, hardness, and loss on drying LOD (post drying). The significant value (α) of 0.05 helped to determine if the null hypothesis would be accepted or rejected. The DoE identified the factors that had the highest risk of affecting the output variables and helped to establish the design space. Post completion of the DoE, a confirmatory batch was made which served as a diagnostic tool for evaluating the effectiveness of the generated model. The establishment of a strategy to control the variables and responses is of critical importance in order to appropriately use the flexibility given to products developed or optimised using QbD principles. This study show that the structured approach used in Quality by Design methodology can be successfully applied to optimise a commercialised legacy product.
- Full Text:
- Date Issued: 2018
A fibre utilisation comparison of two harvesting systems in eucalyptus grandis in the Kwa-Zulu natal forestry region of South Africa
- Nxumalo, Sikhumbuzo Khethukuthula, McEwan, Andrew
- Authors: Nxumalo, Sikhumbuzo Khethukuthula , McEwan, Andrew
- Date: 2017
- Subjects: Eucalyptus grandis -- South Africa -- KwaZulu-Natal Harvesting -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/20592 , vital:29331
- Description: Global timber demand is increasing as the level of technology continues to improve in many parts of the world. There needs to be more focus on renewable energy resources which will have a reduced negative impact on the environment. There is limited land area for timber plantations and this necessitates effective use of land from both an environmental and a commercial point of view. This research aimed at quantifying and comparing the fibre utilisation of two harvesting systems operating in Eucalyptus grandis pulpwood plantations. This was done using a general linear model, whereby the fibre loss areas were identified and used as the dependent variables, whilst diameter at breast height (DBH), site and harvesting systems were used as the independent variables. The research also aimed at determining the amount of fibre each system could recover, where fibre is lost or gained in each harvesting system and also whether one of the harvesting systems is able to recover more fibre than the other. The research investigated two harvesting systems in Eucalyptus grandis pulpwood plantations. These systems consisted of the full tree chain flail delimber debarker and chipper (FT CFDD&C) system and the cut-to-length (CTL) motor-manual system. These systems operated close to one another to ensure that the research was carried out on comparable paired plots. Two sites were identified to carry out research after a pilot study was done to test the feasibility. Using the FT CFDD&C system, trees were felled by means of a feller buncher. A grapple skidder was used for extraction to the landing, a chain flail delimber debarker (CFDD) for debarking and debranching and a roadside chipper for converting the boles into chips. The second CTL motor-manual system was modified into a tree length system to suit the conditions of the study due to infield chipping requiring longer lengths. Therefore, trees were felled with a chainsaw and debranched and topped infield before tree lengths were extracted to the landing site with the grapple skidder. The CFDD was used for debarking and the chipper converted boles into chips.
- Full Text:
- Date Issued: 2017
- Authors: Nxumalo, Sikhumbuzo Khethukuthula , McEwan, Andrew
- Date: 2017
- Subjects: Eucalyptus grandis -- South Africa -- KwaZulu-Natal Harvesting -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/20592 , vital:29331
- Description: Global timber demand is increasing as the level of technology continues to improve in many parts of the world. There needs to be more focus on renewable energy resources which will have a reduced negative impact on the environment. There is limited land area for timber plantations and this necessitates effective use of land from both an environmental and a commercial point of view. This research aimed at quantifying and comparing the fibre utilisation of two harvesting systems operating in Eucalyptus grandis pulpwood plantations. This was done using a general linear model, whereby the fibre loss areas were identified and used as the dependent variables, whilst diameter at breast height (DBH), site and harvesting systems were used as the independent variables. The research also aimed at determining the amount of fibre each system could recover, where fibre is lost or gained in each harvesting system and also whether one of the harvesting systems is able to recover more fibre than the other. The research investigated two harvesting systems in Eucalyptus grandis pulpwood plantations. These systems consisted of the full tree chain flail delimber debarker and chipper (FT CFDD&C) system and the cut-to-length (CTL) motor-manual system. These systems operated close to one another to ensure that the research was carried out on comparable paired plots. Two sites were identified to carry out research after a pilot study was done to test the feasibility. Using the FT CFDD&C system, trees were felled by means of a feller buncher. A grapple skidder was used for extraction to the landing, a chain flail delimber debarker (CFDD) for debarking and debranching and a roadside chipper for converting the boles into chips. The second CTL motor-manual system was modified into a tree length system to suit the conditions of the study due to infield chipping requiring longer lengths. Therefore, trees were felled with a chainsaw and debranched and topped infield before tree lengths were extracted to the landing site with the grapple skidder. The CFDD was used for debarking and the chipper converted boles into chips.
- Full Text:
- Date Issued: 2017
The use of herbicides for the management of Eucalyptus coppice in South Africa
- Authors: Roberts, Jonathan Cecil
- Date: 2017
- Subjects: Eucalyptus grandis -- South Africa Herbicides -- South Africa
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/20287 , vital:29205
- Description: The effectiveness and relatively low cost of herbicides has led to the near exclusion of non-herbicide methods for controlling weeds in commercial forestry plantations. However, any herbicide used within the forestry context has the potential to be toxic and/or alter ecosystem dynamics. In response to increased public concern, perceptions of risk, and compliance associated with forest certification standards and criterion, there is an increased need to provide alternative methods that can reduce reliance on herbicides. Even though adequate research has been implemented regarding herbicide use, little research has examined the implications of herbicide use or non-use throughout the full rotation. Since herbicide use is integrated within the management of eucalypt regeneration, it is critical that a comprehensive understanding of herbicide use be obtained before informed management decisions can be made. Only once this has been obtained, can reduced and judicious recourse to herbicide use be considered, both within the requirements of certification criteria and of good management practice (economic and site sustainability). The main objective of this thesis was to increase the understanding of herbicide use, as well the cost involved within the context of eucalypt coppice regimes in South Africa. Three field trials (two rotation-end, and one short-term) were implemented to achieve this objective, with herbicide use aimed at either killing eucalypt stumps if replanting, or control of secondary coppice regrowth if coppicing. The first trial was situated in Mpumalanga and evaluated which method of control would be best suited to reducing cost (cost-effective) and reliance on herbicides for killing eucalypt stumps and control of resulting coppice regrowth. Selected cut-stump and basal-frill treatments were included with triclopyr (480 g L-1 a.i.) applied to the cambium of difficult-to-kill Eucalyptus macarthurii H. Deane & Maiden stumps that had previously been coppiced multiple times. The resulting coppice regrowth was either manually removed, or glyphosate (360 g L-1 a.i.) applied to foliage. These treatments were integrated with non-chemical control methods, where E. dunnii Maiden seedlings were planted either between each stump row or within the row, to determine whether such treatments could further reduce the level of coppicing through shading. At rotation end, the different treatments tested had no significant influence on any of the E. dunnii growth variates. As there were no significant differences, the treatment with the lowest overall cost and herbicide used would be preferred. The application of triclopyr to the cut-surface following felling was the most cost-effective treatment. The differences in cost obtained is directly related to required follow-up coppice regrowth control operations and quantity of total herbicide applied (both triclopyr and glyphosate). It was hoped that the non-chemical control method (planting position of seedlings) would reduce the level of coppicing, however, within this trial, this did not occur. The second trial was situated in Zululand on Eucalyptus grandis x E. urophylla coppice that investigated different methods to control secondary coppice regrowth through either manual removal with a bush-knife, or the application of glyphosate (360 g L-1 a.i.) to the foliage. A range of herbicide rates (0.6%, 1.2% and 1.8%) was applied to the foliage of the secondary coppice regrowth when it reached a predetermined mean height (0.5 m, 1.0 m and 1.5 m). The objective was to determine the optimum rate and timing of control and to avoid glyphosate from being over-applied when managing this regrowth. No significant differences were detected between the different treatments for any of the growth variates at rotation end. The use of glyphosate, irrespective of rate and/or timing of application (as assessed by secondary coppice regrowth height) proved to be more cost-effective compared to manual removal of secondary coppice regrowth. Treatment efficacy in terms of treating secondary coppice regrowth increased with an increase in the rate of glyphosate applied (0% < 0.6% < 1.2% < 1 .8%), especially when treated at either 1.0 or 1.5 m in height. Although the volume of the glyphosate used increased with increasing secondary coppice regrowth height (0.5 m < 1.0 m < 1.5 m) due to the larger foliar spraying area, there was little difference in total glyphosate used when comparing the same herbicide rate across the three different heights. The most cost-effective treatment was that where glyphosate was applied at 1.2% when the secondary coppice regrowth was 1-1.5 m. The third trial (also located in Zululand on Eucalyptus grandis x E. urophylla) was implemented to test the knowledge gained in trial two, thereby determinng coppice management regimes that would facilitate mechanised harvesting. In this trial, coppice shoots were reduced to one stem per stump in one thinning operation (coppice reduction heights of 3.5 m, 4.5 m and 6.5 m), with the impact of increased secondary coppice regrowth monitored together with the testing of different control methods. An additional control treatment was included (current best operating practice) with coppice shoots thinned to two stems per stump at shoot height of 3.5 m, and thereafter to original stocking at stem height of 6.5 m. Herbicide rate and timing of application was based on the results obtained in the second trial, with glyphosate applied at 1.2% when the secondary coppice regrowth reached a mean height of approximately 1 m. At the final measurement date, the diameter at breast height for all three coppice reduction height treatments (3.5 m, 4.5 m and 6.5 m) were significantly larger than the additional control treatment. This can be attributed to the allocation of resources to the remaining stem at an earlier age, resulting in a growth benefit. For stocking, the 6.5 m coppice reduction height was significantly higher compared to both the 3.5 m and 4.5 m coppice reduction treatments, while not significantly different from the additional control. In this trial, secondary coppice regrowth had no effect on tree growth. Due to the short duration of this trial, a longer trial period would be necessary to obtain a full understanding of the impacts of the various coppice reduction treatments, and the resulting secondary coppice regrowth influence on selected coppice growth if left untreated. As several previous studies have shown the importance of controlling secondary coppice regrowth, it is recommended not to view the results of this present trial in isolation. On the basis of the results of this research, it can be concluded that the control of coppice regrowth with herbicides is more effective than any of the manual removal treatments in terms of cost, with manual control requiring more follow-up control operations. Even though the manual removal of coppice regrowth had no influence on growth of the remaining stems or planted trees, the potential injury to labourers or growing stock is still of concern. Therefore, the use of herbicides for controlling coppice regrowth would be preferable. However, if reduced herbicide-use is a major criterion, then coppice regrowth can be controlled manually, although at a higher cost.
- Full Text:
- Date Issued: 2017
- Authors: Roberts, Jonathan Cecil
- Date: 2017
- Subjects: Eucalyptus grandis -- South Africa Herbicides -- South Africa
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10948/20287 , vital:29205
- Description: The effectiveness and relatively low cost of herbicides has led to the near exclusion of non-herbicide methods for controlling weeds in commercial forestry plantations. However, any herbicide used within the forestry context has the potential to be toxic and/or alter ecosystem dynamics. In response to increased public concern, perceptions of risk, and compliance associated with forest certification standards and criterion, there is an increased need to provide alternative methods that can reduce reliance on herbicides. Even though adequate research has been implemented regarding herbicide use, little research has examined the implications of herbicide use or non-use throughout the full rotation. Since herbicide use is integrated within the management of eucalypt regeneration, it is critical that a comprehensive understanding of herbicide use be obtained before informed management decisions can be made. Only once this has been obtained, can reduced and judicious recourse to herbicide use be considered, both within the requirements of certification criteria and of good management practice (economic and site sustainability). The main objective of this thesis was to increase the understanding of herbicide use, as well the cost involved within the context of eucalypt coppice regimes in South Africa. Three field trials (two rotation-end, and one short-term) were implemented to achieve this objective, with herbicide use aimed at either killing eucalypt stumps if replanting, or control of secondary coppice regrowth if coppicing. The first trial was situated in Mpumalanga and evaluated which method of control would be best suited to reducing cost (cost-effective) and reliance on herbicides for killing eucalypt stumps and control of resulting coppice regrowth. Selected cut-stump and basal-frill treatments were included with triclopyr (480 g L-1 a.i.) applied to the cambium of difficult-to-kill Eucalyptus macarthurii H. Deane & Maiden stumps that had previously been coppiced multiple times. The resulting coppice regrowth was either manually removed, or glyphosate (360 g L-1 a.i.) applied to foliage. These treatments were integrated with non-chemical control methods, where E. dunnii Maiden seedlings were planted either between each stump row or within the row, to determine whether such treatments could further reduce the level of coppicing through shading. At rotation end, the different treatments tested had no significant influence on any of the E. dunnii growth variates. As there were no significant differences, the treatment with the lowest overall cost and herbicide used would be preferred. The application of triclopyr to the cut-surface following felling was the most cost-effective treatment. The differences in cost obtained is directly related to required follow-up coppice regrowth control operations and quantity of total herbicide applied (both triclopyr and glyphosate). It was hoped that the non-chemical control method (planting position of seedlings) would reduce the level of coppicing, however, within this trial, this did not occur. The second trial was situated in Zululand on Eucalyptus grandis x E. urophylla coppice that investigated different methods to control secondary coppice regrowth through either manual removal with a bush-knife, or the application of glyphosate (360 g L-1 a.i.) to the foliage. A range of herbicide rates (0.6%, 1.2% and 1.8%) was applied to the foliage of the secondary coppice regrowth when it reached a predetermined mean height (0.5 m, 1.0 m and 1.5 m). The objective was to determine the optimum rate and timing of control and to avoid glyphosate from being over-applied when managing this regrowth. No significant differences were detected between the different treatments for any of the growth variates at rotation end. The use of glyphosate, irrespective of rate and/or timing of application (as assessed by secondary coppice regrowth height) proved to be more cost-effective compared to manual removal of secondary coppice regrowth. Treatment efficacy in terms of treating secondary coppice regrowth increased with an increase in the rate of glyphosate applied (0% < 0.6% < 1.2% < 1 .8%), especially when treated at either 1.0 or 1.5 m in height. Although the volume of the glyphosate used increased with increasing secondary coppice regrowth height (0.5 m < 1.0 m < 1.5 m) due to the larger foliar spraying area, there was little difference in total glyphosate used when comparing the same herbicide rate across the three different heights. The most cost-effective treatment was that where glyphosate was applied at 1.2% when the secondary coppice regrowth was 1-1.5 m. The third trial (also located in Zululand on Eucalyptus grandis x E. urophylla) was implemented to test the knowledge gained in trial two, thereby determinng coppice management regimes that would facilitate mechanised harvesting. In this trial, coppice shoots were reduced to one stem per stump in one thinning operation (coppice reduction heights of 3.5 m, 4.5 m and 6.5 m), with the impact of increased secondary coppice regrowth monitored together with the testing of different control methods. An additional control treatment was included (current best operating practice) with coppice shoots thinned to two stems per stump at shoot height of 3.5 m, and thereafter to original stocking at stem height of 6.5 m. Herbicide rate and timing of application was based on the results obtained in the second trial, with glyphosate applied at 1.2% when the secondary coppice regrowth reached a mean height of approximately 1 m. At the final measurement date, the diameter at breast height for all three coppice reduction height treatments (3.5 m, 4.5 m and 6.5 m) were significantly larger than the additional control treatment. This can be attributed to the allocation of resources to the remaining stem at an earlier age, resulting in a growth benefit. For stocking, the 6.5 m coppice reduction height was significantly higher compared to both the 3.5 m and 4.5 m coppice reduction treatments, while not significantly different from the additional control. In this trial, secondary coppice regrowth had no effect on tree growth. Due to the short duration of this trial, a longer trial period would be necessary to obtain a full understanding of the impacts of the various coppice reduction treatments, and the resulting secondary coppice regrowth influence on selected coppice growth if left untreated. As several previous studies have shown the importance of controlling secondary coppice regrowth, it is recommended not to view the results of this present trial in isolation. On the basis of the results of this research, it can be concluded that the control of coppice regrowth with herbicides is more effective than any of the manual removal treatments in terms of cost, with manual control requiring more follow-up control operations. Even though the manual removal of coppice regrowth had no influence on growth of the remaining stems or planted trees, the potential injury to labourers or growing stock is still of concern. Therefore, the use of herbicides for controlling coppice regrowth would be preferable. However, if reduced herbicide-use is a major criterion, then coppice regrowth can be controlled manually, although at a higher cost.
- Full Text:
- Date Issued: 2017
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