http://scholar.sun.ac.za:80/handle/10019.1/546 2017-07-16T02:44:54Z 2017-07-16T02:44:54Z Muyambo, Phillip http://scholar.sun.ac.za:80/handle/10019.1/101267 2017-05-15T07:28:19Z 2017-03-01T00:00:00Z

Modelling aboveground biomass and nutrient export in South African Pinus elliottii Muyambo, Phillip ENGLISH ABSTRACT: The objective of this study was to develop an allometric model for Pinus elliottii grown in the Tsitsikamma region of the Eastern Cape province in South Africa. 20 trees were destructively sampled were within a chronosequence of three ages in plantations with uniform attributes. In-field data were collected of DBH (diameter at breast height) and height (H). Samples of discs, branches and foliage were collected from the felled trees. Variables collected from the biomass samples were used for biomass and nutrient export modeling. Density of the wood discs and bark was determined by a water displacement technique. Stem biomass was reconstructed using Smalian’s volume formula. To develop a set of linear models for biomass prediction, dry mass of the sampled biomass components was regressed against logarithmically transformed predictors that included DBH, H, and DBH2H. Models were chosen based on goodness-of-fit assessment statistics and parsimony. A two-step process was used to upscale samples to tree level and from tree to stand level using the allometric models. For additivity purposes, logarithmic transformed (ln) DBH was used as a single predictor to determine the aboveground biomass (AGB) at stand level. The estimated AGB for the 16 (522 SPH), 28 (347 SPH) and 33 (380 SPH) years old P. elliottii trees were 99, 254 and 205 Mg haˉ¹ respectively. The BEF values of this study which were 0.81, 0.96 and 1.37 for Site 1, 2 and 3. Macro-nutrients export increased with stand age. The estimated N export due to harvesting stemwood and bark alone was 388.7 kg ha-1 in younger trees (16 years) and 720.7 kg ha-1 in older trees (28 and 33 years). A larger export of micro-nutrients such as Mn, Fe and Zn is potentially through harvesting of needles.; AFRIKAANSE OPSOMMING: Die doel van die studie was om ‘n allometriese model vir Pinus elliottii wat groei in die Tsitsikamma area van die Oos-Kaap provinsie in Suid Afrika, te ontwikkel. 20 bome wat destruktief getoets is, is gebruik binne ‘n krono-orde van drie ouderdoms groepe in plantasies met uniforme kenmerke. Veld data was versamel van DBH (diameter by bors hoogte) en hoogte (H). Monsters van stomp skuiwe, takke en blare was versamel van die gesaagde bome. Veranderlikes wat ingesamel is van die biomassa monsters was gebruik vir die biomassa en voedingstowwe uitvoer modelering. Die digtheid van die hout skuiwe en bas was bepaal deur water ‘n verplasing tegniek. Stam biomassa was geherkonstruktireer met behulp van Smalian’s se volume formule. Die droë massa van die biomassa monsters is met behulp van regressive gebruik om ‘n stel lineêre modelle te ontwikkel wat biomassa voorspel teen logaritmies getransformeer voorspellers wat DBH, H, en DBH2H ingesluit. Modelle is gekies deur middel van orde-van-pas analise statistieke en parsimonie. ‘n Twee-stap skaal proses was gebruik om monsters op te skaal tot boom grootte en van boom grootte tot vak grootte, met behulp van alometriese modelle. Logaritmiese (ln) veranderde DBH was gebruik as enkel voorspeller vir die op skalings proses om bo-grond biomassa van ha orde te voorspel. Die berame AGB vir die 16 (522 SPH), 28 (347 SPH) en 33 (380 SPH) jaar oue Pinus elliottii bome was 99, 254 en 205 Mg haˉ¹ onderskeidelik. Die BEF waardes vir die studie was 0.81, 0.96 en 1.37 vir ligging 1, 2 en 3. Makro-voedingstowwe uitvoer toegeneem met die stand ouderdom. Die geskatte N uitvoer as gevolg van die oes stemwood en bas alleen was 388,7 kg ha-1 in jonger bome (16 jaar) en 720,7 kg ha-1 in ouer bome (28 en 33 jaar). 'N Groter uitvoer van mikro-voedingstowwe soos Mn, Fe en Zn is potensieel deur die oes van. Thesis (MScFor)--Stellenbosch University, 2017.

2017-03-01T00:00:00Z Nyawali, Bechani http://scholar.sun.ac.za:80/handle/10019.1/100889 2017-05-15T06:56:54Z 2017-03-01T00:00:00Z

Structure, conduct and performance of honey markets in Zambia’s dryland forests Nyawali, Bechani ENGLISH ABSTRACT: This research study assessed the commodity value chain structure, conduct and performance in relation to honey markets in Zambia’s dryland forest. The objectives were to (a) identify stakeholder’s strategic activities influencing honey markets, (b) assess the demand and supply of honey and bee products, (c) assess effects of the structure of the value chain on markets, and (d) to evaluate the distribution of revenue, costs and profit margin along the value chain. Field surveys were conducted to gather information from 164 stakeholders identified as beekeepers, honey hunters, processors, transporters, wholesalers, retailers, consumers, donors, input suppliers, training institutions and regulatory authorities. Results indicated that there was a disparity between the years of experience and production volume amongst beekeepers. Older beekeepers with more years of experience used traditional “local style” bark beehives that produced low output volumes while younger beekeepers with less years of experience made use of “modern style”, manufactured, Kenya Top Bar hives that produced substantially (p < 0.05) more honey. In the Kitwe district, significantly more honey (p < 0.05) was supplied to markets in a longer value chain dominated by modern style beekeepers than in the Kapiri Mposhi district where a shorter value chain was dominated by local style beekeepers. The difference was attributed to lower honey volumes for Kapiri Mposhi producers than Kitwe. In addition, Kitwe’s profit margin per litre of honey was distributed across all the stakeholders, with the greater share of profit received by wholesalers while in Kapiri Mposhi retailers received the largest profit margin. Honey output could potentially increase in Zambia if the disparity between experience and output was addressed and financial support given to more experienced honey producers that would enable them to modernise their style of beekeeping. Alternatively, young honey entrepreneurs should be cultivated who are receptive to modern techniques and dynamic in marketing. The Kitwe value chain also illustrated that better organisation along the value chain will increase production and shift beekeeping from a subsistence focus (as observed at Kapiri Mposhi) to a more commercial focus.; AFRIKAANSE OPSOMMING: Hierdie navorsingstudie het die kommoditeitswaardeketting se struktuur, gedrag en prestasie in verhouding tot heuningmarkte in Zambië se droëlandwoude ondersoek. Die doelwitte was om (a) belanghebbendes se strategiese aktiwiteite wat heuningmarkte beïnvloed te identifiseer, (b) die aanvraag en voorsiening van heuning en heuningbyprodukte te bepaal, (c) die effekte van die struktuur van die waardeketting op market te ondersoek, en (d) die verspreiding van inkomste, kostes en winsmarges in die waardeketting te evalueer. Veldopnames is uitgevoer om inligting van 164 belanghebbendes in te samel. Belanghebbendes sluit in byeboere, heuningjagters, verwerkers, vervoerders, groothandelaars, kleinhandelaars, verbruikers, skenkers, insetverskaffers, opleidingsinstansies en regulatoriese instansies. Resultate het aangedui dat daar ‘n dispariteit is tussen die jare ondervinding en produksievolume onder byeboere. Ouer byeboere met meer jare ondervinding gebruik tradisionele “plaaslike styl” baskorwe met lae uitsetvlakke terwyl jonger byeboere met minder jare ondervinding, “moderne styl” vervaardigde “Kenya Top Bar” korwe gebruik wat beduidend (P < 0.05) meer heuning produseer. In die Kitwe distrik is beduidend meer heuning (P < 0.05) aan markete voorsien deur ‘n langer waardeketting wat deur modern style byeboere oorheers is as in die Kapiri Mposhi distrik met ‘n korter waardeketting en oorheersend plaaslike styl byeboere. In Kitwe was die winsmarge versprei tussen al die belanghebbendes met ‘n groter deel van die wins wat deur groothandelaars ontvang is terwyl kleinhandelaars die meeste wins ontvang het in Kapiri Mposhi. Heuning uitsette kan potensieel verhoog in Zambië as die dispariteit tussen ondervinding en uitsette aangespreek kan word en finansiële ondersteuning aan byeboere met meer ondervinding gegee kan word. Dit sal hulle instaat stel om hulle styl van byeboerdery te moderniseer. Andersins behoort jong heuning entrepreneurs gekweek te word vir wie modern tegnieke en dinamiese bemarking aanvaarbaar is. Die Kitwe waardeketting het geïllustreer dat beter organisasie langs die waardeketting produksie kan verbeter en byeboerdery van ‘n bestaansfokus (soos waargeneem in Kapiri Mposhi) tot ‘n meer kommersiële fokus kan verskuif. Thesis (MScFor)--Stellenbosch University, 2017.

2017-03-01T00:00:00Z Mander, Nicola http://scholar.sun.ac.za:80/handle/10019.1/100832 2017-05-12T13:39:22Z 2017-03-01T00:00:00Z

Evaluating the sustainability, development impact and natural capital impact of invasive alien plant based value-adding enterprises Mander, Nicola ENGLISH ABSTRACT: Invasive alien plants (IAPs) are a significant threat to South Africa’s biological diversity, water security and agricultural resources, and are associated with increasing human and ecological vulnerability to climate change. In response to this threat, the South African government established the Working for Water Programme (now part of the Department of Environmental Affairs [DEA] Natural Resources Management [NRM] Programme), which has cleared nearly three million hectares of IAPs since its inception in 1995. The Programme has also provided jobs and training to more than 20,000 people each year from amongst the most marginalised sectors of society. However, despite significant government investment in the DEA NRM Programme, IAPs continue to spread. In addition, most of the felled IAP biomass is left in situ, which can result in a significant fire hazard. In response, government began promoting the use of IAP biomass as an input material for value-adding activities. This was also expected to increase the economic sustainability and social benefits from IAP eradication, as well as encourage private sector investment into IAP clearing. The DEA NRM Programmes’ support of IAP biomass value-adding enterprises has yielded variable outcomes, with many of the enterprises initially assisted proving unsustainable. This raised the question: “what makes IAP biomass value-adding enterprises survive or fail?” This research study has evaluated a selection of existing, failed and emerging IAP biomass based value-adding enterprises with the aim of determining the key internal structural factors that make these enterprises sustainable. In addition, criteria that affect the performance of these enterprises in creating jobs, developing human capital and restoring natural capital, in line with the key aims of the DEA NRM Programme, were identified. A Multi-Criteria Decision Analysis tool was developed and used to evaluate and compare the enterprises studied. A further aim of the study was to identify the kinds of support that the DEA NRM Programme should provide to IAP biomass value-adding industries to leverage the best possible outcomes. The study findings suggest that government and private enterprise need to work together in establishing IAP biomass value-adding industries. However, appropriate structuring of such relationships is important to ensure there is sufficient value and fair sharing of risk between the partners. Government will not only need to carefully select the enterprises that it partners with to ensure its investment has maximum impact, it will also need to invest in the development of the IAP biomass industry sector through developing markets for IAP products and filling key research and development gaps that are unaffordable for the private sector.; AFRIKAANSE OPSOMMING: Indringerplante is 'n groot bedreiging vir Suid-Afrika se biologiese diversiteit, water sekuriteit en landbou hulpbronne, en word geassosieer met 'n toenemende menslike en ekologiese kwesbaarheid tot klimaatsverandering. In reaksie op hierdie bedreiging het die Suid-Afrikaanse regering die Werk vir Water Program (nou deel van die Departement van Omgewingsake [DEA] se Natuurlike Hulpbronbestuur [NRM] Program) tot stand gebring wat sedert sy ontstaan op 1995 byna drie miljoen hektaar indringerplante skoongemaak het. Die program het ook voorsiening gemaak vir werksgeleenthede en opleiding aan meer as 20,000 mense elke jaar uit die geledere van die mees gemarginaliseerde sektore van die samelewing. Ten spyte van aansienlike regeringsbelegging in die DEA NRM Program, het die indringerplante probleem steeds uitgebrei. Daarbenewens, word die meeste van die afgekap indringerplante biomassa in die veld gelaat wat kan lei tot 'n aansienlike brandgevaar. In reaksie hierop het die regering begin om die gebruik van indringerplante biomassa, as 'n inset materiaal vir waardetoevoegende aktiwiteite, te bevorder. Dit was verwag dat dit die ekonomiese volhoubaarheid en maatskaplike voordele van indringerplante uitwissing sal verhoog, en ook privaatsektor belegging in indringerplante uitwissing aanmoedig. Die DEA NRM Programme se ondersteuning van indringerplante biomassa-waardetoevoeging ondernemings het veranderlike uitkomste opgelewer. Baie van die aanvankik ondersteunde ondernemings was onvolhoubaar. Dit lei tot die vraag: "Wat laat indringerplante biomassa-waardetoevoeging ondernemings oorleef of misluk?”. Hierdie navorsingstudie het 'n seleksie van die bestaande, mislukte en opkomende indringerplant biomassa gebaseer waardetoevoeging ondernemings geëvalueer met die oog op die bepaling van die belangrikste interne strukturele faktore wat hierdie ondernemings volhoubaar maak. Daarbenewens is kriteria wat die prestasie van hierdie ondernemings beinvloed in die skep van werkgeleenthede, die ontwikkeling van menslike kapitaal en die herstel van natuurlike kapitaal, in ooreenstemming met die sleutel doelwitte van die DEA NRM Program, geïdentifiseer. 'n Multi-kriteria besluit analise-instrument is ontwikkel en gebruik om die ondernemings wat bestudeer is, te evalueer en te vergelyk. 'n Verdere doel van die studie was om die aard van die ondersteuning wat die DEA NRM Program moet verskaf aan indringerplante biomassa-waardetoevoeging bedrywe, om die beste moontlike uitkomste te verkry, te identifiseer. Die studie bevindinge dui daarop dat die regering en private ondernemings moet saamwerk in die vestiging van indringerplante biomassa-waardetoevoeging nywerhede. Toepaslike strukturering van verhoudings is egter belangrik om te verseker dat daar voldoende waarde en billike risiko deling tussen die vennote is. Die regering moet nie net ondernemings versigtig kies met wie dit vennootkappe vorm om maksimum beleggings impak te verseker nie, dit moet ook belê in die ontwikkeling van die biomassa bedryfsektor deur die ontwikkeling van markte vir indringerplant produkte en vulling van sleutel gapings in navorsing en ontwikkeling wat onbekostigbaar vir die private sektor is. Thesis (MScFor)--Stellenbosch University, 2017.

2017-03-01T00:00:00Z Proller, Marco http://scholar.sun.ac.za:80/handle/10019.1/100814 2017-05-12T12:34:55Z 2017-03-01T00:00:00Z

An investigation into the edge gluing of green Eucalyptus grandis lumber using a one-component polyurethane adhesive Proller, Marco ENGLISH ABSTRACT: South Africa is a timber-scarce country with a relatively small portion of only about 1% of its total land area being used for commercial forestry. Due to an increasing demand for timber but restrictions regarding the expansion of plantation area, the country is expected to experience a shortage of softwood supply for saw logs in the near future. The predominant hardwood species Eucalyptus grandis is, despite good strength and stiffness properties, at present for the most part used for wood chip or pulp and paper production. This is mainly owing to growth stresses, splitting, and the low dimensional stability of the wood, which therefore could not comply with the requirements of the South African national standard for sawn eucalyptus timber (SANS 1707-1 2010). As wood defects often develop or aggravate during the drying stage, the edge-bonding of Eucalyptus grandis lumber in its wet state was considered to possibly inhibit this behaviour. This study consisted of two experiments. In the first experiment shear tests were used to determine the influence of various material and processing variables on the bonding quality of green Eucalyptus grandis wood with a moisture-curing one-component polyurethane adhesive. The experimental design for this investigation comprised 16 groups with different combinations of parameters for wood density, moisture content, adhesive spread rate and pressure. Ten samples per group were tested for shear strength. The penetration behaviour of the one-component polyurethane adhesive into the wood structure was additionally investigated on samples with extreme results, employing a micro CT scanner. All tested samples clearly exceeded the minimum shear strength for cross-laminated timber products according to EN 16351 (2015). Better results were generally obtained for samples with an increased moisture content of roughly 60% compared to specimens with a lower moisture content around fibre saturation point, which could be linked to an enhanced adhesive penetration. In the second experiment the potential of edge gluing green Eucalyptus grandis boards before kiln drying in order to inhibit the development of certain wood defects was investigated. Edge-glued panels were produced from wet material above fibre saturation point and kiln-dried together with non-edgebonded control boards from the same material source. After drying, the panels were sawn apart into single boards, graded regarding the development of check, split, bow, cup and twist and compared to the results obtained for the control boards. The ability of stress-relief grooves in boards to reduce the development of defects was also investigated. The results showed that the edge gluing of green Eucalyptus grandis lumber before kiln drying could not decrease the number of board rejections according to the SANS 1707-1 (2010) requirements for sawn eucalyptus timber. Cup could be significantly decreased, while twist was only reduced for boards without pith. Stress-relief grooves did not have a significant influence on the development of any of the investigated defects but caused severe deformation and damage in some of the boards. Further investigations should be carried out on mass timber products such as cross-laminated timber, where green edge-glued and kiln-dried Eucalyptus grandis panels could be used as a component.; AFRIKAANSE OPSOMMING: Suid Afrika het min boshulpbronne met slegs ‘n klein gedeelte, van ongeveer 1%, van sy landoppervlak wat gebruik word vir bosbou. Daar word verwag dat ‘n groeiende vraag na soliede saaghout en krimpende plantasie-area sal lei tot ‘n tekort in naaldhoutprodukte in die nabye toekoms. Die mees aangeplante loofhoutspesie, Eucalyptus grandis, word ten spyte van goeie sterkte -en styfheidseienskappe hoofsaaklik vir pulp en spaanderproduksie gebruik. Dit is hoofsaaklik as gevolg van groeispannings, spleting, en swak dimensionele stabiliteit van die hout – wat veroorsaak dat dit nie voldoen aan die vereistes van soliede Eucalyptus saaghout nie (SANS 1707-1 2010). Houtdefekte ontwikkel of vererger dikswels gedurende die drogingsfase en hierdie studie ondersoek die inhiberende potensiaal op defekformasie van die aanmekaarlym van planke terwyl dit steeds nat is. Die studie bestaan uit twee eksperimente. In die eerste eksperiment is skuiftoetse gebruik om die invloed van verskeie material –en prosesseringsveranderlikes op die lymlaskwaliteit van groen (nat) Eucalyptus grandis planke wat met ‘n enkelkomponent poli-uretaanlym gelym is. Die eksperimentele ontwerp vir hierdie studie bestaan uit 16 groepe wat met verskillende kombinasies van houtdigtheid, voggehalte, lymhoeveelheid, en druk geheg is. Tien monsters per groep is getoets vir skuifsterkte. Die penetrasiegedrag van die lym in die houtstruktuur is ondersoek met mikro-CT skandering. Al die getoetsde monsters het die minimum skuifsterktevereiste volgens die EN16351 (2015) standaard behaal. Beter resultate is oor die algemeen verkry met hoër voggehalte van bykans 60% in vergelyking met monsters wat by veselsversadigingspunt was – waarskynlik as gevolg van beter lympenetrasie. In die tweede eksperiment is die potensiaal ondersoek van nat aanmekaarlym van planke in panele voor oonddroging om drogingsdefekte te minimeer . Kant-gelymde panele is vervaardig van groen (nat) Eucalyptus grandis en gedroog saam met individuele kontroleplanke . Na droging is die panele weer losgesny in planke en gegradeer ten opsigte van oppervlakkrake, spleting, boogtrek, koppievorming, en draaitrek en vergelyk met die individuele kontroleplanke. Die vermoë van spanningsgleuwe in die planke om defektvorming te inhibeer is ook ondersoek. Die resultate wys dat die kantlym van groen Eucaluptus grandis planke voor oonddroging nie die plank afgradering volgens SANS 1707-1 (2010) kon verminder nie. Koppievorming kon beduidend verminder word, terwyl draaitrek slegs verminder kon word in nie-pitplanke. Spanningsgleuwe het nie ‘n beduidende invloed gehad op die vorming van enige van die defekte nie, maar het erge deformasie en skade in sommige planke veroorsaak. Verdere ondersoeke moet gedoen word op groot-houtprodukte (“mass timber products”) soos kruisgelamineerde hout, waar heel panele gebruik kan word as ‘n komponent. Thesis (MScFor)--Stellenbosch University, 2017.

2017-03-01T00:00:00Z Melane, Mandlakazi http://scholar.sun.ac.za:80/handle/10019.1/100116 2017-02-21T05:41:29Z 2016-12-01T00:00:00Z

Evaluation of the potential of non-woody invasive plant biomass for electricity generation Melane, Mandlakazi ENGLISH ABSTRACT: Invasive alien plants (IAPs) threaten the existence of plant and animal biodiversity as they cause destruction to the natural habitats they invade. In South Africa the Natural Resource Management (NRM) programme clears these plants. In efforts to add value to the clearing operation, the NRM Programme’s objective is to utilise the cleared IAP biomass for economic purposes, thereby contributing to the sustainable management and control of invasive species. The objectives of this study were to assess the potential and the economic viability to supply non-woody IAP biomass for electricity generation. The study was conducted on biomass samples from 13 common non-woody IAPs in South Africa namely: Arundo donax (Giant reed), Lantana camara (Lantana), Pontederia cordata (Pickerel weed), Ricinus communis (Castor-oil plant), Opuntia ficus-indica (Sweet prickly pear), Solanum mauritianum (Bugweed), Atriplex nummunlaria (Saltbush), Cestrum laevigatum (Inkberry), Senna didymobotrya (PB Cassia), Chromoleana odorata (Chromoleana), Eichhornia crassipes (Water hyacinth), Cerus jamacaru (Queen of the night) and the Agave sisilana (Sisal plant). Properties, such as density, moisture content, calorific value, ash content and volatile content, elemental composition as well as processability and estimated drying time were determined in order to assess the suitability of the biomass for different thermo-chemical conversion techniques (combustion, gasification and pyrolysis). This study only assessed the potential of non-woody IAPs for electricity generation, with the main focus on thermochemical conversion. Although some of the species might be suitable for bio-chemical conversion, a detailed overview of biochemical pathways is beyond the scope of this study. The second part of the study examined the economic and financial perspective of the biomass supply to generate electricity, in which the harvesting, chipping and transport costs of the biomass were considered. The results of this study showed that non-woody invasive biomass has the potential to be used as feedstock for electricity generation through combustion. None of the species were found to be suitable for gasification or pyrolysis due to their high silica, chlorine and ash content. Sweet prickly pear, Water hyacinth, Queen of the night, Sisal, Pickerel weed and the Castor-oil plant had a too high moisture content and would be best suited for energy production through biochemical conversion pathways. The total average cost to harvest and transport non-woody IAP chips to an energy plant was R33/GJ, which is approx. 50% more expensive than other biomass feedstocks (Forestry residues and woody IAPs). Overall when taking physical, chemical and financial aspects into consideration Giant reed, Saltbush, and Chromoleana were the best species to be utilised as feedstock. However, without a “fuel cost subsidy” from the NRM programme, the harvesting of non-woody alien invasive species for energy production is unlikely to be financially viable.; AFRIKAANSE OPSOMMING: Indringerplante bedreig die voortbestaan van plant en dier biodiversiteit omdat hulle natuurlike habitate indring en vernietig. In Suid Afrika word hierdie plante verwyder deur die Natuurlike Hulpbron Bestuur (NHB) program. In pogings om waarde toe te voeg tot skoonmaakoperasies het die NHB program ‘n doelwit om die verwyderde indringer biomassa te gebruik vir ekonomiese doeleindes. Hierdie doelwit dra by tot die volhoubare bestuur en kontrole oor indringerplante. Die doelwitte van hierdie studie was om die potensiaal en ekonomiese volhoubaarheid van die voorsiening van nie-houdagtig indringerplante vir elektrisiteitsopwekking te ondersoek. Die studie is uitgevoer op biomassa mosters van 13 van die mees algemene nie-houdagtige indringerplante in Suid Afrika, genaamd: Arundo donax (Spaansriet), Lantana camara (Lantana), Pontederia cordata (Jongsnoekkruid), Ricinus communis (Kasterolieplant), Opuntia ficus-indica (Soet turksvy), Solanum mauritianum (Luisboom), Atriplex nummunlaria (Soutbos), Cestrum laevigatum (Inkbessie), Senna didymobotrya (Grondboontjiebotterkassia), Chromoleana odorata (Parafienbos), Eichhornia crassipes (Waterhiasint), Cerus jamacaru (Nagblom) and the Agave sisilana (Sisalplant). Eienskappe soos digtheid, voginhoud, kalorifiesewaarde, as-inhoud, vlugtigheidsinhoud, elementsamestelling sowel as verwerkbaarheid en droogtyd is bepaal om sodoende die geskiktheid van die biomassa vir verskillende termo-chemiese omsettings metodes te bepaal (verbranding, gassifikasie en pirolise). Die studie het slegs die potensiaal van nie-houtagtige indringerplante vir elektrisiteitsopwekking ondersoek met die hoof fokus op termo-chemiese omsetting. Alhoewel sommige van die spesies geskik mag wees vir bio-chemiese omsetting is ‘n gedetaileerde oorsig van die bio-chemiese prosesse buite die bestek van die studie. Die tweede deel van die studie ondersoek die ekonomiese en finansiele perspektief van biomasa voorsiening om elektrisitiet op te wek. Dit sluit in die ontginning, versnippering en vervoerkostes van die biomassa. Die resultate van die studie wys dat nie-houdagtige indringer biomassa die potensiaal het om as roumateriaal gebruik te word vir elektrisiteits generasie deur verbranding. Geen van die spesies was geskik vir gassifasie of pirolisie weens hoë silica, chloor en as inhoud. Soet turksvy, Waterhiasint, Nagblom, Sisal, Jongsnoekkruid en die Kasterolieplant het ‘n te hoë voginhoud en sal mees geskik wees vir bio-chemise opsettings metodes. Die totale gemiddelde koste van ontginning en vervoer van nie-houdagtige indringerplante tot by die energie aanleg was R 33/GJ, wat nagenoeg 50% duurder is as ander biomass roumateriaal (Bosbou residu en houtagtige indringerplante). Ontginning en vervoerkostes vergelyk ongunstig met die van biomassa roumateriaal tipes soos bosbou afval en houdagtige indringerplante. Wanneer die fisiese, chemiese en finansiele aspekte oorweeg word is Spaansriet, Soutbos en Parafienbos die beste spesies vir bio-energie roumateriaal. Sonder ‘n brandstof subsidie vanaf die NHB program is die ontginning van nie-houdagtige indringerspesies vir energie produksie nie finansieel haalbaar nie. Thesis (MScFor)--Stellenbosch University, 2016.

2016-12-01T00:00:00Z Guiney, Itchell Sandy http://scholar.sun.ac.za:80/handle/10019.1/100075 2017-02-20T12:56:40Z 2016-12-01T00:00:00Z

Agroforestry development and implementation in South Africa: an assessment of selected case studies Guiney, Itchell Sandy ENGLISH ABSTRACT: Agroforestry (AF) is the integrated approach of producing trees and agricultural crops and/or livestock in a single system on the same piece of land. Elements of AF have been practiced in South Africa (SA) since the late 1800’s, through what’s known as the Taungya system. AF has numerous environmental, economic and social benefits. However, there is limited research in SA to qualify and validate these benefits. The available information and research on AF practices in SA is also highly fragmented, difficult to access or out-dated. There is also no formal national policy or strategy that directly addresses the development and implementation of AF in SA. This national study composed of two phases. The first phase consisted of an assessment of AF development and implementation at the national level where a self-administered questionnaire was distributed to key stakeholders and individuals, involved in the development, promotion and implementation of AF in SA. The second phase entailed the assessment of selected AF projects, using a combination of case studies and survey methods. The results and outcomes of the study provided qualitative and quantitative data on AF development and implementation in SA. This include an analysis of the extent and geographical distribution of AF projects; the major AF systems and practices used; the main barriers factors that hinder the development and implementation of AF. The key organisations developing and implementing AF were defined and an assessment of the main direct and indirect goods and services derived from AF. The strengths, weaknesses, opportunities and threats (SWOT) associated with AF projects; and the design and diagnosis (D&D) of AF systems were also identified. The study concluded that AF systems are currently being developed and implemented in SA at various scales, level and with multiple management objectives, but potential to expand does exist. Several goods and services are also derived from AF systems, which make it a viable sustainable production alternative to conventional production. However, there are a number of barriers (institutional, technical, economic, policy/governance and social) affecting AF adoption, which need to be addressed. One of the recommendations is the development of a national AF policy and strategy. Furthermore, the top ranking national level barriers, which were identified and assessed through the research study, should be addressed. A more comprehensive assessment of the extent and distribution of AF in SA are also required. Finally, a detailed quantitative assessment of the AF goods and services and addressing the outcomes from the D&D of AF case studies in SA is needed.; AFRIKAANSE OPSOMMING: Agrobosbou (AF) is die gekombineerde verbouiing van bome en landbou gewasse en/of diere op dieselfde grondeenheid. AF het dus verskeie omgewings, ekonomiese en sosiale voordele. Dit word al sedert die 1800’s beoefen in Suid Africa (SA) in die vorm van die Taungya sisteem. Daar is egter beperkte navorsing oor AF in SA om dié voordele te kwantifiseer en te bevestig. Verder is beskikbare inligting van AF sisteme in SA baie gefragmenteerd, moeilik om te bekom of verouderd. Daar bestaan ook geen formele strategie of beleid wat die ontwikkeling en implimentering van AF in SA direk aanspreek nie. Hierdie nasionale studie het uit twee eenhede bestaan. Die eerste fase het die AF ontwikkeling en implementering op nasionale vlak ondersoek deur middel van ‘n self geadministreerde vraelys wat aan belanghebbendens, betrokke by die bemarking en implementering van AF in SA, uitgestuur is. Die tweede fase was die assessering van geselekteerde AF projekte deur middle van ‘n kombinasie van gevallestudies en direkte waarnemings. Gevolglik het die uitslag kwalitatiewe en kwantitatiewe data van AF ontwikkeling en implementering in SA aangedui. Dit het ook ingesluit die geografiese verspreiding en grootte van die AF projekte; die AF sisteme wat toegepas word; moontlike hindernisse ten opsigte van ontwikkeling en implementering. Die sleutel organisasies in die ontwikkeling en implementering van AF was ook geïdentifiseer en geassesseer om die direkte en indirekte goedere en dienste van AF te lys. Verder is die sterkpunte, swakpunte, geleenthede en bedreigings (SWOT) geassosieer met AF projekte; die ontwerp en diagnose van die AF sisteme ook geïdentifiseer. Gevolgtrekkings wys dat AF sisteme in SA tans op verskeie vlakke ontwikkel en geimplementeerd word met verskillende bestuursdoelwitte. Die moontlikheid van uitbreiding is dus moontlik. Verskeie goedere en dienste afkomstig vanaf die AF sisteme kan ook help om AF as ‘n volhoubare en suksesvolle alternatiewe konventionele manier van produksie te vestig. Daar is egter verskeie hindernisse (institusionele, tegniese, ekonomiese, beleid / bestuur en sosiale) wat eers oorkom sal moet word. Een van die aanbevelings is die ontwikkeling van ‘n nasionala AF beleid en strategie om die hindernisse aan te spreek. ‘n Meer omvattende assessering van die verspreiding en effek van AF in SA moet onderneem word. Laastens, ‘n gedetailleerde kwantatiewe assessering van die goedere en dienste verkry uit AF sisteme asook die uitkomste van die ontwerp en diagnose van die AF gevallestudies in SA moet eers onderneem word. Thesis (MFor)--Stellenbosch University, 2016.

2016-12-01T00:00:00Z Gresse, Lodewyk Christoffel http://scholar.sun.ac.za:80/handle/10019.1/98778 2016-05-25T07:38:16Z 2016-03-01T00:00:00Z

The impact of repeated prescribed burning in semi-mature pine plantation forests of Mpumalanga on fuel loads, nutrient pools and stand productivity Gresse, Lodewyk Christoffel ENGLISH ABSTRACT: Wild fires in South Africa destroy vast areas of plantations annually and a growing need exists to reduce the fire risk effectively, economically and sustainably. Periodic prescribed burning is viewed by many researchers and managers as the only cost effective method to reduce fire damage and risk, and as such is being implemented on a large scale in SA. This thesis documents the effects of repeated prescribed burning operations on fuel load reduction, tree damage and stand growth rate, as well as nutrient dynamics in the system. Five field trials in semi-mature P. elliottii and P. patula plantations were laid out in Northern Mpumalanga during January 2014 to determine the effect of under-canopy burning on fuel loads, nutrient pools and stand productivity. Each trial consisted initially out of three control, three first burn and three second burnt plots. Fuel reduction. Under-canopy burning treatments were of low to moderate intensity with an average predicted FLI ranging between 44 and 602 kW m-1. With burning, the forest floor (FF) was significantly reduced in all trials (6.3 t ha-1 and 12.9 t ha-1 in P. elliottii and P. patula trials per burning event, respectively). Small quantities of additional litterfall (that would counter the initial goal of FF reduction) were noted for a single month in 3 out of 5 trials, but the short duration of this effect meant that the cumulative effect was insignificant. Average litterfall rates per species were 5.52 and 8.82 t ha-1 yr-1 for P. elliottii and P. patula, respectively. In general, the highest litterfall rate occurred during the winter months and the lowest during the summer months. The goal of FF reduction to values around 10-15 t ha-1 can be achieved with two prescribed burns in many P. elliottii stands (with smaller FF’s), but it may require at least 4 burning events in some P. patula stands with FF loads of more than 50 t ha-1. A significant reduction in understorey vegetation was still evident 8 months after treatment implementation except for one trial but species abundance returned to pre-burn levels 14 months after treatment implementation with no changes in species composition. Effects on stand condition and growth. Crown damage was restricted to one trial whilst root combined with cambium damage occurred in two trials, a result attributed to the smouldering effect of the FF. Among burning treatments, only Non-significant dbh and BA increment differences were evident, 4 and 12 months after treatment implementation but a highly significant seasonal effect could be seen in all trials: dbh increment was 61% higher in summer than in winter. Nutrient dynamics. FF nutrient loss was directly related to FF consumption by fires, with N loss varying from 33 – 119 kg ha-1; P, K, Ca and Mg losses averaging 3.8, 12.6, 72.4 and 17.2 kg ha-1. An increase in foliar macro nutrient concentration of freshly fallen needles was observed, but only during the first month after treatment implementation. Most soil nutrients showed modest changes that were not significantly different from other burning treatments. Modest increases in soil pH was observed with one in 5 trials recording a significant increase in pH (KCl) after the second burn. Total N mostly decreased with increasing number of burning treatments, but this effect was only of a significant magnitude in one out of 5 trials. Exchangeable Mg showed a small increase in all trials after burning, but the magnitude of this effect was only significant in one out of 5 trials. In conclusion: The evidence collected across 5 replicated experiments showed that significant fuel reduction (in FF and understorey) is attainable with 2 to 4 low intensity, repeated prescribed burning events under pine tree canopies. There appears to be minimal damage to trees and no significant short term response in diameter increment after repeated prescribed burns. The effect on nutrient dynamics in the system is modest and non-significant in most cases.; AFRIKAANSE OPSOMMING: Bosbrande vernietig jaarliks groot plantasie areas in Suid-Afrika en daarom bestaan daar ʼn groeiende behoefte om die brandrisiko op ʼn effektiewe, ekonomiese en volhoubare wyse te verminder. Periodieke beheerde brande word deur baie navorsers en bestuurders geag as die enigste koste-effektiewe metode in die vermindering van vuur skade en brandstof ladings en daarom word dit grootskaals geïmplementeer in SA. Die tesis dokumenteer die effek van herhaalde voorgeskrewe brand operasies op brandstof vermindering, boom skade en opstandsgroei, as ook nutriënte dinamika in die sisteem. Vyf veldproewe is uitgelê in semi-volwasse P. elliottii en P. patula plantasies in die Noordelike gebied van Mpumalanga gedurende Januarie 2014 om die effek van onderboom-brande op brandstofladings te bepaal so ver dit nutriënte poele en opstandsproduktiwiteit betref. Die navorsingspersele het elk aanvanklik bestaan uit drie kontrole, drie eenmalig gebrande en drie tweemalig gebrande persele. Brandstoflading vermindering. Onder-boom brande het ʼn lae tot matige intensiteit gehad met ʼn voorspelde vuurfront intensiteit wat gewissel het tussen 44 en 602 kW m-1. Deur middel van beheerde brand is die bosvloer-ladings beduidend verminder in al die navorsingspersele (6.3 t ha-1 en 12.9 t ha-1 per enkele brand in P. elliottii en P. patula persele onderskeidelik). Klein addisionele verskille in naaldeval (wat die oorspronklike doelwit van bosvloer lading-vermindering sou teenwerk) is aangeteken gedurende die eerste maand na behandeling in 3 van die 5 persele, maar die kort tydsduur van hierdie tendens het beteken die kumulatiewe effek nie beduidend was nie. Die gemiddelde naaldeval tempo per spesie was 5.52 en 8.82 t ha-1 yr-1 vir P. elliottii en P. patula onderskeidelik. Daar is bykomend gevind dat die hoogste natuurlike naalde-val tempo gedurende die wintermaande voorkom en die laagste naalde-val in die somermaande. Die doelwit van brandstoflading vermindering na waardes tussen 10-15 t ha-1 kan behaal word in twee beheerde brande in meeste P. elliottii opstande (met kleinerige bosvloer ladings), maar minstens 4 brande mag benodig word in sekere P. patula opstande met aanvanklike bosvloer ladings groter as 50 t ha-1. ʼn Beduidende afname in kreupelbosgroei was merkbaar 8 maande na implementering van behandelings (met uitsondering van een perseel), maar die aantal spesies per behandeling het vinning teruggekeer na voor-brand hoeveelhede: teen 14 maande na behandeling was daar geen verskil meer bemerkbaar in spesie samestelling nie. Effek op boom kondisie en groei. Kroondakskade was beperk tot een navorsingsperseel en ʼn kombinasie van wortel en kambium skade het in twee persele voorgekom – ʼn resultaat toegeskryf aan die smeulende effek van die bosvloerbrand. Die verskille in dbh en basale oppervlak groei-tempo tussen behandelings was nie beduidend op tydstip 4 en 12 maande na implementering van behandelings nie, maar ʼn hoogs beduidende seisoenale effek is waargeneem in al die persele: die aanwas in dbh was 61% hoër in somer as winter. Nutriënte dinamika. Bosvloer-nutriënte inhoud was sterk gekorreleer met die afname in bosvloer lading, en die verlies aan N was tussen 33 en 119 kg ha-1; P, K, Ca en Mg verliese was gemiddeld 3.8, 12.6, 72.4 en 17.2 kg ha-1 oor al die persele. ʼn Toename in makro nutriënt-konsentrasies van vars – gevalde dennenaalde is gevind gedurende die eerste maand na behandeling. Die vlakke van nutriënte in die bogrond het meestal matige veranderings getoon wat nie beduidend verskil het van ander brand persele nie. Matige toenames is gevind in grond-pH, met ʼn beduidende toename in pH (KCl) merkbaar in slegs een van die 5 tweevoudig-gebrande persele. Totale N in die bogrond het meestal afgeneem met toenemende brand behandelings, maar die effek was sleg beduidend in een van die vyf persele. Uitruilbare Mg in die bogrond het ʼn klein toename getoon oor al die persele na brande, maar die omvang van die effek was slegs beduidend in een van die vyf persele. Ten slotte: Die bewyse versamel oor al 5 gerepliseerde eksperimente wys dat ʼn beduidende afname in brandstoflading (bosvloer en kreupelbos) haalbaar is met 2 tot 4 lae intensiteit, voorgeskrewe brande onder denneboom kroondakke. Daar blyk minimale skade op bome te wees en geen beduidende kort termyn reaksie in deursnee groei na herhaalde beheerde brande is gevind nie. Die effek op nutriënte dinamika in die sisteem is beskeie en nie-beduidend in meeste gevalle nie. Thesis (MScFor)--Stellenbosch University, 2016.

2016-03-01T00:00:00Z Erasmus, Justin http://scholar.sun.ac.za:80/handle/10019.1/98473 2016-05-18T05:57:53Z 2016-03-01T00:00:00Z

The effect of planting density on Pinus patula stem form, wood properties and lumber strength and stiffness Erasmus, Justin ENGLISH ABSTRACT: Faster growth and reduced harvesting age are causing a reduction in the stiffness of structural lumber from South African-grown pine plantations. A number of studies have shown the positive effects of high planting densities as a tool to improve the mean modulus of elasticity (MOE) of structural lumber. The objective of this study was to investigate the effect of planting density on stem form, wood properties and the strength and stiffness of structural lumber of young Pinus Patula – the most important and extensively planted commercial softwood in South Africa. In the first part of this study, four different planting density treatments (403, 1097, 1808 and 2981 stems/ha) from an 18-year old P. patula spacing trial located in Mpumalanga, South Africa were sampled non-destructively. Stem slenderness, stem curvature, and the dynamic modulus of elasticity (MOEfak) were measured on 171 standing trees. Increment cores were removed from 40 trees for measurement of density, microfibril angle (MFA) and ring width using the Silviscan 3 technology. Planting density had a significant effect on stem curve with the lowest planting density having the highest mean stem curve. Planting density also had a highly significant effect on stem slenderness. The MOEfak increased greatly with increases in planting density. MFA was significantly influenced by both planting density and year ring number and the interaction between them. The mean MFA at similar ring numbers decreased significantly from the 403 stems/ha treatment toward the higher planting densities (1808 and 2981 stems/ha). Planting density had a limited effect on wood density. MFA seems to be the mechanism through which the tree compensates for the instability caused by a high slenderness ratio. Density, on the other hand, did not correlate with slenderness at all and was probably mostly influenced by environmental and growth factors. In the second part of this study, a total of 37 trees from two commercial compartments, planted at different densities, were processed into 71 logs, cant-sawed into lumber, and tested for static MOE, modulus of rupture (MOR), density, and warp. The first compartment was 18 years old, planted at 1334 stems/ha and thinned to 827 stems/ha at age 11. The second compartment was 17 years old, planted at 1667 stems/ha and was unthinned. Lumber from the 1667 stems/ha compartment had a mean MOE of 8967 MPa compared to a mean MOE of 7134 MPa for the 1334/827 stems/ha compartment. Based on this evidence and results from previous studies, it seems as if planting density has a large effect on the stiffness of young P. patula lumber and that planting density may be used as a practical management intervention to increase the stiffness of lumber.; AFRIKAANSE OPSOMMING: Vinnige groei en ‘n afname in rotasie-ouderdomme van SA dennehoutplantasies het ‘n afname in die styfheid van strukturele planke veroorsaak. Bestaande navorsing dui op ‘n positiewe verwantskap tussen hoë plantdigtheid en die modulus van elastisiteit (MOE) van hout. Die doelwitte van hierdie studie was om die effek van plantdigtheid te ondersoek op stam vorm, houteienskappe en die sterkte en styfheid van jong Pinus patula – die mees aangeplante naaldhoutspesie in SA. In die eerste deel van hierdie studie is vier verskillende plantdigtheidbehandelinge (403, 1097, 1808 en 2981 stamme/ha), vanaf ‘n 18 jaar oue P. patula spasiëringsproef, geleë in Mplumalanga, SA, nie-destruktief gemeet. Stamslankheid, stamkurwe en die dinamiese modulus van elastisiteit (MOEfak) is op 71 staande bome gemeet. Met behulp van die Silviscan 3 apparaat was inkrementboorsels verwyder vanaf 40 bome vir die meting van digtheid, mikrofibrilhoek (MFA) en jaarringwydte. Plantdigtheid het ‘n beduidende effek op stamkurwe getoon, met die hoogste gemiddelde stamkurwe gevind in die laagste plantdigtheidbehandeling. Plantdigtheid het ook ‘n hoogs beduidende effek op stamslankheid getoon met MOEfak wat baie toegeneem het met ʼn verhoogde plantdigtheid. Beide plantdigtheid en jaarring-nommer en die interaksie tussen die twee, het ‘n beduidende invloed gehad op MFA. Die gemiddelde MFA van soortgelyke jaaring-nommers het ‘n beduidende afname getoon van die 403 stamme/ha behandeling teenoor die hoër plantdigtheidbehandelings (1808 en 2981 stamme/ha). Plantdigtheid het ‘n klein invloed op houtdigtheid getoon. Dit wil blyk asof die MFA die meganisme is waardeur die boom kompenseer vir die onstabiliteit wat veroorsaak word deur ʼn hoër slankheid. In teenstelling, het digtheid nie ʼn korrelasie getoon met slankheid nie, maar was waarskynlik beïnvloed deur omgewings -en groeifaktore. In die tweede deel van hierdie studie was ‘n totaal van 37 bome vanaf twee kommersiële kompartemente, geplant teen verskillende digthede, verwerk in 71 saagblokke, gekantsaag tot planke en getoets vir statiese MOE, breekmodulus (MOR), digtheid en deformasie. Die eerste kompartemente was 18 jaar oud, geplant teen 1334 stamme/ha en uitgedun na 827 stamme/ha op 11-jarige ouderdom. Die tweede kompartement was 17 jaar oud, geplant teen 1667 stamme/ha en was nie gedun nie. Planke vanaf die 1667 stamme/ha kompartement het ʼn gemiddelde MOE van 8967 MPa gehad in teenstelling met ‘n gemiddelde MOE van 7134 MPa vir die 1334/827 stamme/ha kompartement. Dus, gebaseer op hierdie bewyse en uitslae van vorige studies, blyk dit dat plantdigtheid ‘n groot effek het op die styfheid van jong P. patula hout en dat plantdigtheid as ‘n praktiese bestuursingryping gebruik kan word om die styfheid van hout te verbeter Thesis (MScFor)--Stellenbosch University, 2016.

2016-03-01T00:00:00Z Pienaar, Louis Otto http://scholar.sun.ac.za:80/handle/10019.1/98459 2016-05-09T11:47:23Z 2016-03-01T00:00:00Z

Modeling above-ground biomass of selected tree species within a Mistbelt forest in KwaZulu Natal Pienaar, Louis Otto ENGLISH ABSTRACT: The objective of this study was to develop species-specific allometric models for selected natural forest species within a forest forming part of the Southern Mistbelt Forest Group, close to the town of Richmond in KwaZulu Natal. The objective was met by determining the tree dimensions (diameter at breast height (DBH) and tree height) of the forest. The collected variables were used and the most dominant species in terms of their basal area coverage: Xymalos monospora and Celtis africana were selected for biomass modeling. The allometric models were developed from a two-step stratified sampling approach. Population dimensions were determined from sample plots, where-after trees were sampled for biomass representing the collected dimensions. The dry mass of the sampled components were used in a regression modeling approach to develop a set of species-specific and combined species linear models. The best models were selected based on goodness-of-fit model evaluation criteria (GOF) and parsimony principles and a two-step upscaling process was used to upscale samples to tree level and from tree to stand level. DBH and basic density were significant predictors of total above-ground biomass (AGB) and diameter as single predictor produced consistently good results. Diameter was used throughout the upscaling process to determine the biomass per ha. The estimated AGB for X. monospora, C. africana and all the species were 62.98, 93.56 and 230.86 Mg haˉ¹ respectively. Estimated AGB for all species compared well with results from other biomass studies. Future research can investigate remote sensing applications in combination with the field sampling to estimate forest biomass more cost effectively over larger areas.; AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om spesie-spesifieke allometric modelle vir geselekteerde natuurlike woudspesies te ontwikkel in 'n woud wat deel vorm van die Suidelike Misbelt woudgroep, naby die dorp Richmond in KwaZulu-Natal. Die doel was bereik deur die bepaling van die boom dimensies (deursnee op die bors hoogte en boomhoogte) van die woud en deur gebruik te maak van die versamelde veranderlikes, is die mees dominante spesies in terme van hul basale area dekking: Xymalos monospora en Celtis africana gekies vir modellering. Die allometriese modelle is ontwikkel uit 'n twee-stap gestratifiseerde steekproefneming benadering. Bevolkings dimensies is bepaal van die monster erwe, waar-na ‘n steekproef van die bome verteenwoordigend van die versamelde dimensies bemonster is vir biomassa bepaling. Die droë massa van die monster komponente is in 'n regressie modelerings benadering tot 'n stel van spesie-spesifieke en gekombineerde spesies lineêre modelle ontwikkel. Die beste modelle is gekies op grond van beste model evalueringskriteria en model spaarsamigheidsbeginsels en 'n twee-stap opskaling is gebruik om monsters op te skaal tot boom vlak en van boom tot vlak staan. Deursnee op borshoogte en basiese digtheid was beduidende voorspellers van die totale bogrondse biomassa en deursnee as enkele voorspeller het konsekwent goeie resultate gelewer. Deursnee is dwarsdeur die opskalings proses gebruik om die biomassa per ha te bepaal. Die beraamde totale bogrondse biomassa vir X. monospora, C. africana en al die spesies tesame was 62.98, 93.56 en 230.86 Mg haˉ¹ onderskeidelik. Beraamde totale bogrondse biomassa vir alle spesies het goed vergelyk met die resultate van ander biomassa studies. Toekomstige navorsing kan afstandswaarnemings tegnieke in kombinasie met die veld steekproefneming ondersoek om biomassa meer koste-effektief oor groter gebiede te bepaal. Thesis (MScFor)--Stellenbosch University, 2016.

2016-03-01T00:00:00Z Kadas, Marios http://scholar.sun.ac.za:80/handle/10019.1/98426 2016-05-30T08:03:57Z 2016-03-01T00:00:00Z

Greyscale-density calibration of an industrial CT scanner for wood microdensitometry Kadas, Marios ENGLISH ABSTRACT: The microdensitometry of wood, that is the quantification of density in the micrometre scale, is important for different scientific disciplines such as wood science, dendrochronology, dendroecology, dendroclimatology, and biomass determination and in the industrial applications of engineered wood. With the advent of industrial computed tomography scanners, powerful equipment for density measurement is available. However, the methodological framework for wood density determination with those machines is not fully established, because possible error sources have not so far been analysed and described sufficiently. Thus, the objective of this study was the development of a methodology, in order to quantify wood density with an industrial computed tomography scanner. In this study, industrial cone-beam computed tomography was used for the microdensitometry of wood. Fifty stacks of stem discs from an equal number of Pinus radiata trees were used as the sample dataset. Firstly, the fifty stacks were scanned along with selected reference materials, which were measured for density in a conventional way. Then, fifty linear regressions were performed between the conventionally-determined density and the grey value of the reference materials. A strong correlation (mean R2=0.998) between conventionally-determined density and grey value was observed. The regressions also provided calibration equations, which could translate a given grey value to a certain density. For validation purposes, the fifty calibration equations were tested on extra reference materials. The density from the computed tomography scanner had a mean absolute error of 0.008 g/cm3 (σ=0.004) and a mean percent error of 1.4% (σ=0.7). Additionally, one of the calibration equations was applied to the creation of tree ring density profiles. An important result of the study was that it was not possible to deduce a sole calibration equation, as typically done with densitometers and medical computed tomography scanners. Thus, the calibration of each scan was inevitable, due to the various degrees of freedom of the industrial computed tomography scanner.; AFRIKAANSE OPSOMMING: Die mikrodensitometrie van hout, dws die kwantifisering van die digtheid op die mikrometer skaal is belangrik vir verskillende wetenskaplike dissiplines soos houtwetenskap, dendrochronologie, dendro-ekologie, dendro-klimatologie, biomassa bepaling en vir die industriële gebruik van verwerkte hout. Met die koms van die industriële tomografie skandeerders is kragtige toerusting vir die meting van houtdigtheid beskikbaar. Die metodologiese raamwerk vir die bepaling van hout digtheid met die masjiene is egter nog nie ten volle ontwikkel nie. Dit kan aanleiding gee tot metingsfoute wat nie voldoende geanaliseer en beskryf word nie. Die doel van hierdie studie is dus om ‘n metode te ontwikkel om houtdigtheid te kwantifiseer deur die gebruik van ‘n industriële tomografie-skandeerder. In hierdie studie is industriële laser ligstraal tomografie gebruik om die mikrodensitometrie van hout te bepaal. Vir die monster datastel is vyftig stapels van die stam skywe van 'n gelyke aantal Pinus radiata bome gebruik. Eerstens is die vyftig stapels geskandeer saam met geselekteerde verwysingsmateriaal wat vir digtheid gemeet is op 'n konvensionele manier. Daarna is vyftig lineêre regressies ontwikkel tussen die digtheid wat bepaal is deur die konvensionele digtheidsmetode en die grys waarde van die verwysing materiaal. Met die studie is waargeneem dat daar ‘n sterk korrelasie (R² = 0.998) is tussen die digtheid gemeet deur die gebruik van die konvensionele metode en die gryswaarde. Die regressies voorsien ook kalibrasie vergelykings, wat 'n gegewe grys waarde kan assosieer met 'n sekere digtheid. Vir validerings doeleindes, is die vyftig kalibrasie vergelykings getoets op ekstra verwysingsmateriaal. Die digtheid gemeet deur die tomografie-skandeerder het 'n gemiddelde absolute afwyking van 0.008 g/cm³ (σ=0.004) en 'n gemiddelde 1.4% (σ=0.7) fout getoon. Verder is een van die ontwikkelde kalibrasie vergelykings toegepas om boomring digtheidsprofiele te skep. Die studie het bevind dat ‘n enkele kallibrasie vergelyking nie gebruik kan word soos tipies met die gebruik van densitometers en mediese tomografie skandeerders nie. Die industriële tomografie-skandeerder moes dus gekalibreer word met elke skandering as gevolg van die verskillende grade van vryheid wat bevind is in die studie. Thesis (MScFor)--Stellenbosch University, 2016.

2016-03-01T00:00:00Z Rust, Stephanus Marthinus http://scholar.sun.ac.za:80/handle/10019.1/98097 2016-01-18T07:38:16Z 2015-12-01T00:00:00Z

Classification of timber from Pinus radiata trees exposed to forest fires Rust, Stephanus Marthinus ENGLISH ABSTRACT: This study aimed to classify wood from trees that were exposed to forest fires with regards to their end use. Exposure to high temperatures over time is known to degrade wood in various ways. This degradation could limit the end use by altering mechanical, chemical and physical properties, leading to difficulty in processing or failing to meet required specifications for various grades. In this study wood from Pinus radiata trees that were exposed to forest fires of different levels of heat intensity was analysed with regards to its anatomical and physical changes. Trees were visually classified into three classes of burn severity. Moisture content measurements were taken from 135 standing trees, divided among the three classes. 30 trees, 10 from each of the three classes, were sampled and used for CT analysis. Samples were taken to include growth from before and after the fire. Two samples were taken from each tree, one from the charred and one from the uncharred side. The CT data was analysed and used to measure properties like growth ring width, cell wall thickness, lumen diameter and cell wall density. The data was used to compare properties from the charred and uncharred sides within a given year, as well as compare properties between years. The study showed that there were significant differences in the MC between the burnt and unburnt sides of trees from classes 2 and 3. The difference between the MC measurements on the burnt sides of three classes differed significantly from each other. Lightness measurements were taken on samples from classes 2 and 3. These samples showed no significant difference between the burnt and unburnt sides for either of the two classes. The samples from the less exposed class were lighter, but not significantly so. The macroscopic wood density was determined using core samples. A decrease in wood density was observed with an increase in fire exposure. The mean densities for all three classes however still fulfilled the requirements for structural timber set by the SABS. Growth ring width, cell wall thickness and lumen diameter analysis gave varied results, with some cases showing a decline in properties while others were seemingly unaffected. For many of the outcomes of this study, results found by previous studies could not be reproduced.; AFRIKAANSE OPSOMMING: Hierdie studie het gepoog om bome wat aan plantasiebrande blootgestel is volgens hul eindgebruik te klassifiseer. Dit is bekend dat blootstelling aan hoë tempreature hout in vele maniere afbreuk. Hierdie afbreuking kan die eindgebruik van die hout beperk deur die meganiese, fisiese en chemiese eienskappe sodanig te verander dat dit kan lei tot probleme met verwerking of ongeskiktheid vir sterktegrade. In hierdie studie is Pinus radiata bome wat aan plantasiebrande van verskillende grade blootgestel is ondersoek in terme van hul fisiese en anatomiese veranderinge. Bome is visueel in drie klasse van verskillende brandskade gegroepeer. Voglesings is op 135 staande bome, verdeel tussen die drie klasse, geneem. Monsters is van 30 bome, 10 uit elke klas, geneem vir CT analiese. Monsters is so geneem dat dit groei van voor en na die brand ingesluit het. Daar is twee monsters van elke boom geneem, een van die gebrande en een van die ongebrande kant. Die CT data is geanalieseer en gebruik om eienskappe soos jaarringwydte, selwanddikte, lumendiameter en selwand digtheid te meet. Die data is gebruik om eienskappe tussen die gebrande en ongebrande kante, sowel as tussen jare te vergelyk. Die studie het gewys dat daar noemenswaardige verskille is tussen die voginhoud van die gebrande en ongebrande kante van bome uit klasse 2 en 3. Die voginhoud van die gebrande kante van al drie klasse verkil ook noemenswaardig van mekaar. Ligtheidmetings is gedoen op monsters van klasse 2 en 3. Die monsters het nie ‘n noemenswaardige verskil tussen die gebrande en ongebrande kante getoon nie. Alhoewel die klas 2 monsters ligter vertoon het as die klas 3 monsters, was die verskil nie betekenisvol nie. Houtdigtheid is bepaal deur fisiese metings op die monsters wat vir die CT skandering gebruik is te doen. ‘n Daling in digtheid met ‘n toename in blootstelling aan die brand het duidelik na vore gekom. Die digtheid is egter nog hoog genoeg om aan die vereistes vir strukturele hout te voldoen, soos die die SABS bepaal. Jaarringwydte, selwanddikte en lumen diameter het wisselende resultate opgelewer, met sommige gevalle wat ‘n afname in eienskappe wys en ander wat ooglopend onveranderd was. Vir vele van hierdie uitkoms kon die resultate van vorige studies nie bevestig word nie. Thesis (MSc)--Stellenbosch University, 2015.

2015-12-01T00:00:00Z Kayofa, Fillemon http://scholar.sun.ac.za:80/handle/10019.1/97146 2015-07-01T14:11:17Z 2015-04-01T00:00:00Z

Natural regeneration potential of Pterocarpus angolensis (Kiaat Tree) in the dry forests of northern Namibia Kayofa, Fillemon ENGLISH ABSTRACT: Pterocarpus angolensis is one of the timber tree species that regenerates naturally in the dry forest of Namibia, mainly assisted by the influence of forest fires. Tree development goes through a prolonged suffrutex stage to reach the sapling stage and then, finally, the bole tree stage. This study focused on assessing the main factors facilitating the development of Pterocarpus angolensis seedlings through the suffrutex stage to the sapling stage in Namibia dry forests. To achieve the study objectives three study locations (Okongo and Ncumcara Community Forests and Caprivi State Forest) were selected, representing a rainfall gradient. Within each study location, two different fire history treatments (recently burnt (RB) and recently unburnt (RU)) were selected, and four plots were randomly selected from each fire history treatment. Face to face individual interviews was conducted with community members surrounding the three forests to obtain indigenous knowledge information about Pterocarpus angolensis tree development. Seedlings and saplings found in all plots were counted and measured (tree height and diameter at breast height (DBH)) while trees more than 3 m high were only counted and measured for DBH. Laboratory analysis was performed to determine basic soil texture and nutrient status. In addition, destructive sampling was done on individual trees in the seedling and sapling stages at each study location. The destructive samples allowed for estimation of biomass in above and below ground components, determination of carbohydrate storage in the taproots and estimation of tree age by counting growth rings on the neck disc of the taproot sample. These measures could shed light on the tree development through the suffrutex stage. The main agents causing Pterocarpus angolensis tree damage and stand disturbances observed are drought, fires, insects, diseases, temperature, lightning, wind, animals and humans. Forest fires were found to be one of the major disturbances in all the study locations, particularly damaging to seedlings when fire intensity is high. Likewise, the most important factors influencing the tree development from seedlings to sapling and sapling to bole tree stages are soil water, soil fertility, plant competition, sunlight and fires. Through counting growth rings of taproot neck discs, it is estimated that the ages of seedlings most commonly range from 5 to 12 years in the dry forests of Okongo, Ncumcara and Caprivi. The soil texture in the three forests is dominated by sand, with the soil reaction usually being moderately acidic while the soils have low levels of organic carbon, phosphorus and exchangeable base cations. This study revealed that Caprivi State Forest (location with the highest rainfall) has the highest stand density followed by Okongo Community Forest and Ncumcara Community Forest with the lowest. Trees were grouped into different DBH and height classes. The highest numbers of trees are found in DBH class 0 – 10 cm and in height class 0.6 – 1.0 m at Okongo Community Forest but at Ncumcara and Caprivi many of the trees are in height class 1.1 – 1.5 m. The mean DBH difference is significant between locations but not significant between fire history treatments. A higher abundance of mature trees are found at Okongo Community Forest while a greater abundance of saplings occur at Ncumcara Community Forest which shows a significant difference between study locations. Seedling abundance is the same across study locations and fire history treatments. The difference in stand structure between study locations appears to be strongly influenced by different management regimes on the three locations. A majority of respondents from all the study locations alleged soil water followed by soil fertility as the main influential factors to Pterocarpus angolensis development. Again, most of the respondents revealed that seedling takes 4 – 7 years to reach sapling stage and their main environmental disturbance is fire. Tree cutting by members of the community was also perceived by the respondents as an important non-environmental disturbance. The most abundant tree development stage perceived by respondents was mature trees while seedlings rated the sparsest stage. Based on the respondents no silvicultural practices are performed to promote Pterocarpus angolensis growth. It follows that the Kiaat trees are currently growing without human intervention that might enhance their development. A combination of social survey (interview) and ecological survey provided reliable information on ecological processes. A weak positive significant correlation relationship existed between shoot mass (aboveground biomass) and taproot mass (belowground biomass), meaning when the taproot mass increases the shoot mass also increases. Analysis of non-structural carbohydrates (NSC) storage in taproots showed that both sugar and starch contents in the taproots could facilitate the survival of the tree during suffrutex stages and its rapid growth thereafter. Based on this study Pterocarpus angolensis regeneration in these three dry forests is poor because seedling abundance is the lowest compared to saplings and mature trees. These study findings can be used as the basis for further studies to predict Pterocarpus angolensis natural regeneration in the dry forests, as well as input when management regimes are being developed for the dry forests of North Namibia.; AFRIKAANSE OPSOMMING: Pterocarpus angolensis (Kiaat) is een van die boomspesies wat natuurlik verjong in die droë bosveld van Namibië, met die hulp van bosbrande. Die boom ontwikkel deur ʼn lang semi-struik stadium waartydens die boompies as saailinge bekendstaan. Daarna ontwikkel dit deur die jongboom stadium tot dit uiteindelik die kroon stadium bereik. Hierdie studie fokus op die faktore bydra tot die ontwikkeling van Pterocarpus angolensis van die semi-struik stadium na die jongboom stadium in die droë bosveld van Namibië. Om die doelstellings van die tesis te bereik is drie studiegebiede gekies langs ʼn reënvalgradiënt (naamlik Okongo en Ncumcara gemeenskapsbosse asook Caprivi Staatsbos). Binne elke studiegebied is twee behandelings met verskillende brandgeskiedenis gekies (gebrand of nie-gebrand in die onlangse verlede). Vier persele is ewekansig uit elk van hierdie behandelings gekies vir eksperimentering. Persoonlike onderhoude is gevoer met gemeenskapslede wat in die omgewing woon ten einde inheemse kennis en inligting te versamel oor die ontwikkeling van die jong Pterocarpus angolensis bome. Alle saailinge en jongbome wat voorkom in die persele is getel en gemeet (boomhoogte en deursnee op borshoogte (DBH)) terwyl bome wat hoër as 3 m is, slegs getel en vir DBH gemeet is. Laboratoriumtoetse is gedoen op grondmonsters ten einde ‘n basiese beskrywing van die grondtekstuur en voedingstofstatus te verkry. Verder is destruktiewe bemonstering toegepas op bome in beide die saailing en jongboom stadium op elke studiegebied. Hierdie bemonstering het dit moontlik gemaak om bogrondse en ondergrondse biomassa te skat, om die opberging van koolhidrate in die penwortels te bepaal, en ook om die boom ouderdom te skat vanaf jaarringe in die nek van die penwortel monster. Hierdie metings kon lig werp op die boomontwikkeling deur die semi-struik stadium. Die faktore wat skade aan Pterocarpus angolensis bome veroorsaak asook versteuring van die opstande waarin die bome voorkom is droogte, brande, insekte, siektes, temperatuur uiterstes, weerlig, wind, diere en mense. Die bevindinge dui op bosbrande as een van die belangrikste versteuringsfaktor in al drie studiegebiede; dit is veral skadelik vir saailinge in die semi-struik stadium wanneer die vuurintensiteit hoog is. Die faktore wat die boomontwikkeling van saailing, na jongboom en kroonstadium beïnvloed is hoofsaaklik grondwater, grondvrugbaarheid, plantkompetisie, sonlig en brande. Die ouderdom van saailinge (bepaal vanaf jaarring tellings in die nek van penwortel monsters) van die meeste saailinge én jongbome is na raming tussen 5 en 12 jaar vir die droë bosse in die studiegebiede van Okongo, Ncumcara en Caprivi. Die grondtekstuur van hierdie studie se drie bosgebiede is hoofsaaklik sanderig, met ’n effens suur grondreaksie terwyl die gronde lae vlakke van organiese koolstof, fosfor, en uitruilbare basiese katione bevat. Die studie het aangedui dat Caprivi staatsbos (met die hoogste reënval) die digste opstande huisves, gevolg deur Okongo en dan Ncumcara gemeenskapsbos, met die laagste digtheid. Bome is gegroepeer in verskillende DBH en hoogte klasse. Die meeste bome kom voor in die DBH klas van 0-10 cm en in die hoogteklas van 0.6 – 1.0 m by Okongo, maar by Ncumcara en Caprivi is daar meer bome in die hoogteklas van 1.1 - 1.5 m. Die gemiddelde DBH verskil is betekenisvol tussen studiegebiede, maar is nie betekenisvol verskillend tussen brandgeskiedenis behandelings nie. ’n Hoër voorkoms van volwasse bome is by Okongo aangetref, terwyl ’n hoër voorkoms van jongbome by Ncumcara waargeneem is, en hierdie verskil was statisties betekenisvol. Die voorkoms van saailinge is soortgelyk oor alle studiegebiede en brandgeskiedenis behandelings heen. Die verskil in die struktuur van die opstande op die drie studiegebiede word skynbaar sterk beïnvloed deur verskillende bestuurspraktyke wat in elke gebied toegepas word. Die meerderheid van respondente van al drie studiegebiede beweer dat grondwater, gevolg deur grondvrugbaarheid die belangrikste faktore is wat P. angolensis ontwikkeling beïnvloed. Meeste van die respondente onthul dat saailinge 4 tot 7 jaar neem om die jongboom stadium te bereik en dat die belangrikste versteuringsagent bosbrande is. ʼn Belangrike nie-omgewingsfaktor wat verantwoordelik is vir versteuring in die bosse is mense wat bome, lote en/of takke afsaag. Respondente is van mening dat volwasse bome die grootteklas met die mees algemene voorkoms is, terwyl saailinge die skaarsste grootteklas uitmaak. Die respondente het aangedui dat geen boskultuurpraktyke toegepas word om die groei van P. angolensis aan te help nie. Die gevolgtrekking is dus dat die Kiaatbome tans groei sonder menslike ingryping om hul ontwikkeling te verbeter. Die kombinasie van persoonlike onderhoude en ʼn ekologiese opnames het betroubare inligting rakende ekologiese prosesse opgelewer. ’n Swak positiewe, maar betekenisvolle korrelasie bestaan tussen die massa van die bogrondse lote en die penwortelmassa, wat beteken dat die lote se massa toeneem met toenemende wortelmassa. Analise van opgebergde nie-strukturele koolhidraatreserwes in die penwortel toon dat beide suiker- én styselinhoud in die penwortels die oorlewing van die boom in die struikstadium aanhelp, asook sy vinnige groei na die struikstadium. Die feit dat die saailinge minder volop is as jongbome en volwasse bome in hierdie studie dui aan dat verjonging van Pterocarpus angolensis in hierdie droë bosse maar swak is. Die bevindinge van die studie bevat inligting wat gebruik kans word (a) as die grondslag van verdere studies op die natuurlike verjonging van Pterocarpus angolensis in droë bosse, en (b) as inset wanneer bestuursaanbevelings vir die droë bosse van Noord Namibië ontwikkel word. Thesis (MSc)--Stellenbosch University, 2015.

2015-04-01T00:00:00Z Jooste, Guillaume Hendrik Christiaan http://scholar.sun.ac.za:80/handle/10019.1/96834 2015-07-01T14:10:28Z 2015-04-01T00:00:00Z

Periodic drought effects on afrotemperate forests in the Southern Cape of South Africa Jooste, Guillaume Hendrik Christiaan ENGLISH ABSTRACT: Understanding the effects of climate change is one of the cardinal issues within the natural resource management circles. Increased droughts are part of these changes. Afrotemperate forests, as well as their drier Afromontane counterparts suffer from periodic and seasonal droughts respectively. To better understand the effect of droughts on these forests, three key species namely Olea capensis (Iron wood), Podocarpus latifolius (Common Yellow wood) and Pterocelastrus tricuspidatus (Candle wood), were analysed using dendroecologic techniques. Two sites in the Southern Cape were selected according to a West-to-East moisture gradient, with the drier site being close to George and the medium moist site at the Diepwalle estate in the vicinity of Knysna. Growth ring measurements from each of the species were used to calculate basal area and basal area increment during the lifetime of the trees. Drought years for the sites were then selected based on the Standardised Precipitation and Evapotranspiration Index (SPEI), also indicated by the growth during the drought periods. Differences in growth patterns for all three species were observed. An event analysis was then used to quantify the difference in the resistance (Rt), recovery (Rc), resilience (Rs) and relative resilience (RRs). With values standardised around one (Rt, Rc and Rs) and zero (RRs), it was seen that the Candle wood had the highest (~0.92) resistance and the Yellow wood had the highest (~1.3) recovery after the drought. Iron wood stood apart from the other two species in the sense that it only reacted negatively towards the drought one year after the event in most cases. It was concluded that each of the species were significantly different in their reactions towards drought. This specific difference in drought reaction can give way to the possibility that the species together adapted to relieve the stress of a short drought by splitting the available resources over a longer period.; AFRIKAANSE OPSOMMING: Dit is van uiterse belang vir bestuur doeleindes om die veranderende klimaat oor die wêreld te verstaan, insluitend die droogtes wat daarmee gepaard gaan. Die Afrotemperate woud-tipe, asook sy droeër teenstaander, die Afromontane, lei gereeld aan sporadiese en seisonale droogtes. Om hierdie woud-tipe se reaksie tot droogtes beter te verstaan, was drie boom spesies naamlik Ysterhout (Olea capensis), Kershout (Pterocelastrus tricuspidatus) en gewone Geelhout (Podocarpus latifolius), gekies vir die gebruik in ‘n dendro-ekologiese studie. Twee areas was gekies van ‘n wes-tot-oos droogte gradient, met die droeër blok in die George omgewing en die meer vogtige een naby aan Knysna. Die jaarring metings van elke boom was gebruik om beide die basale oppervlakte en die basale oppervlak groei per jaar aan te teken. ‘n Gestandardiseerde reenval en evapotranspirasie indeks (SPEI) was gebruik om vas te stel jare waarin matige tot sterk droogtes gebeur het. Hierdie gekose jare het aanduiding gegee dat daar wel ‘n verskil waargeneem was in die groei patrone van elke spesie gedurende die droogtes. ‘n Gebeurtenis analise is gebruik om ‘n kwantitatiewe verskil te kon sien in die weerstand (Rt), herstel (Rc), weerstandbiedendheid (Rs) en relatiewe weerstandbiedendheid (RRs). Die was waargeneem dat Kerhout die hoogste weerstand (0.92) toon, terwyl die Geelhout ‘n hoër herstel waarde (1.3) gehad het. Ysterhout het apart van die ander twee spesies gestaan in dìe dat dit eers een jaar na die droogte ‘n reaksie getoon het teenoor die droogte. Dit was dus gevind dat daar spesifieke verskil is tussen al drie van die spesies teen opsigte van stres reaksies was. Hierdie verskil kan dan wel ook moontlik aandui dat hierdie spesies en woud-tipe op so ‘n anier aangepas is dat dit die stress gedurende ‘n kort droogte versprei oor ‘n langer tydperk. Thesis (MSc)--Stellenbosch University, 2015.

2015-04-01T00:00:00Z Scheepers, Gerhardus Petrus http://scholar.sun.ac.za:80/handle/10019.1/96019 2015-07-01T14:11:27Z 2014-12-01T00:00:00Z

The effect of wood ash on the soil properties and nutrition and growth of Eucalyptus grandis x urophylla grown on a sandy coastal soil in Zululand Scheepers, Gerhardus Petrus ENGLISH ABSTRACT: A field trial of six replications was established to test the effect of various wood ash and fertilisers application rates on soil chemistry, tree nutrition and early growth rate of a clonal Eucalyptus grandis x urophylla stand. Wood ash from pulpmills is currently disposed of in landfills. Increasing costs and potential environmental risks have driven companies to investigate alternative disposal methods. Ash consists of a combination of carbonates, hydroxides and other calcium containing minerals that induce the liming effect if ash is applied to a soil. The trial was established near Richards Bay in October 2013 on a sandy soil with a low buffer capacity and a pH of approximately 5.5. The trial consists of four wood ash application rates in combination with three levels of fertiliser, viz. no fertiliser, 150 g conventional NPK fertiliser mixture, or 320g NPK controlled release mixture. Fertiliser mixtures and application levels were based on previous fertiliser trials in the region. Ash application rates for the field trial were based on a lab incubation study done with soil samples from Richards Bay, to which increasing amounts of lime were added. The study tested wood ash application rates of 0, 300, 600 and 1200 kg/ha. Field measurements were taken at 4 and 8 months after trial establishment. The primary objective was to investigate which application levels in combination with the type of fertiliser could be applied to soils without negatively affecting the stand nutrition or increase the levels of potentially harmful elements in the soil; thus investigating the feasibility of safely disposing wood ash on plantation soils as an alternative disposal method. Soil nutrient concentrations were not affected by individual wood ash treatments, but more a product of the time interval after the ash additions were made. Soil C, P, K+ and Mg2+ showed decreased concentrations from 4-8 months after establishment. Ca2+ concentrations increased in the same time interval. In addition, Na+ and B concentrations decreased from 4-8 months. Soil heavy metal concentrations for Cd, Hg, Cr and Pb, analysed for 0-1200 kg/ha ash rates, were well below toxic levels at both time intervals. Wood ash induced a temporary liming effect. Mean soil pH increased with 0.6 units for the period 0 - 4 months and decreased with 0.4 units at 4 - 8 months after trial establishment. Foliar nutrient analyses and assessment techniques revealed sub-optimal nutrient concentrations for P, K and Zn at 4 and 8 months of age. Concentrations were defined as sub-optimal, as none of the nutrients were below critical levels. Foliar heavy metal concentrations for Cd, Hg, Cr and Pb, measured at both time intervals, were less than 1mg/kg. The small concentrations found in this project were attributed to the low bioavailability of all four elements and were likely a product of the edaphic factors at Richards Bay, which was representative of a large greater portion of the Zululand coastal plain sites. The response in biomass index ranged between 13 % and 683 % relative to the control treatment (A0F0). Results showed that application of purely wood ash, or in combination with a supplementary N and P source increased growth up to 8 months after trial establishment for wood ash applications up to 1200 kg/ha. This project demonstrated that 1200 kg/ha wood ash can safely be disposed of on a typical Zululand coastal sand with little environmental risk and no supressed growth, provided that it is balanced with an appropriate NP fertiliser.; AFRIKAANSE OPSOMMING: ‘n Veldproef met ses herhalings is in Oktober 2013 uitgelê met die doel om die uitwerking van verskillende vlakke hout as en kunsmis toedienings op die grond-voedingstof status, boom-voedingstof status en die groei-tempo van ‘n Eucalyptus grandis x urophylla hibried plantasie te bestudeer. Hout as by pulpmeulens word tans weggegooi op stortingsterreine. Toenemende onkostes vir storting en die omgewingsrisiko’s gebonde aan stortingsterreine, dryf maatskappye om verbeterde en meer omgewingsvriendelike metodes te ondersoek om van die as ontslae te raak. Hout as bestaan uit ‘n reeks karbonate, hidroksiede en kalsium bevattende minerale en is verantwoordelik vir die bekalkingseffek op die grond na toediening. Die veldproef is geleë naby Richardsbaai op ‘n sanderige grond met n lae bufferkapasiteit en pH van ongeveer 5.5. Die proef het vier hout as vlakke getoets, gekombineer met drie vlakke van bemesting: geen, 150g konvensionele landbou kunsmis (CV) óf 320g beheerd-vrystellende kunmis (CRF). Die kunsmismengsels en vlakke van bemesting is gebaseer op bestaande of voltooide bemestingseksperimente in die streek. Hout as vlakke was bereken in gekontroleerde laboratorium toestande en gebaseer op ‘n inkubasie studie met grond monsters verkry vanaf Richardsbaai, waarby toenemende vlakke suiwer landboukalk gevoeg is. Die veldproef het hout as vlakke van 0, 300, 600 en 1200 kg/ha getoets. Veld metings is op 4 en 8 maande na behandeling geneem. Die primêre doelwit van die studie was om te bepaal watter vlak hout as en kunmis kombinasie toegedien kan word, sonder om die grond-voedingstof status negatief te beïnvloed of ‘n potensiële skadelike uitwerking op die plantasie groei te veroorsaak. Die uiteinde van die studie was om die haalbaarheid van hout as toedienings op plantasie gronde te bestudeer relatief tot die huidige praktyk van storting, insluitend die risiko van moontlike skadelike newe-effekte. Grondvoedingstatus was nie beduidend beïnvloed deur individuele hout as toevoegings nie, maar was eerder ‘n funksie van die tydsduur sedert behandeling. Grond koolstof, P anione, K+ en Mg2+ konsentrasies het beduidend afgeneem in die periode van 4 - 8 maande na behandling. Die Ca2+ konsentrasies het toegeneem tussen 4 en 8 maande en terselfdertyd het Na+ en B konsentrasies afgeneem. Die swaarmetaal status, spesifiek vir Cd, Hg, Cr en Pb, vir toevoegings van 0-1200 kg/ha hout as was beduidend laer as toelaatbare vlakke in gronde op albei tydsintervalle. Die hout as het ‘n tydelike toename in grond pH veroorsaak. Die gemiddelde pH het tussen 0 - 4 maande toegeneem met 0.6 eenhede en gedurende 4 - 8 maande afgeem met 0.4 eenhede. Blaarontledings en voedingstof assesseringsmetodes het sub-optimale konsentrasies vir P, K en Zn getoon op die ouderdom van 4 en 8 maande. Voedingstof konsentrasies is as sub-optimaal geklassifiseer, omdat konsentrasies nooit laer as kritieke waardes vir gebreksimptome was nie. Die inhoud van Cd, Hg, Cr en Pb in blare was aansienlik kleiner as 1 mg/kg op albei tydsintervalle. Die merkwaardige lae konsentrasies wat in die projek aangeteken is, word toegekryf aan die lae bio-beskikbaarheid van al vier elemente as gevolg van die edafiese faktore eie aan die Richardsbaai omgewing (en ook aan groot dele van die Zoeloelandse kusvlakte). Die groeireaksie (bepaal as biomassa indeks op ouderdom 8 maande) het gewissel van 13 % - 683 % groter as die kontrole behandeling (A0F0). Resultate het bewys dat toedienings van suiwer hout as, of hout as gekombineer met ‘n addisionele N en P kunsmisbron die groei postief beïnvloed tot op die ouderdom van 8 maande. Die studie het bewys dat 1200 kg/ha hout as veilig toegedien kan word op die sandgronde van die kusgebiede in Zululand, met minimale omgewingsrisiko en geen tekens onderdrukte groei nie, mits dit gebalanseer word met ‘n geskikte NP kunsmisbron. Thesis (MScFor)--Stellenbosch University, 2014.

2014-12-01T00:00:00Z Atsame-Edd, Angeline http://scholar.sun.ac.za:80/handle/10019.1/86642 2015-06-30T11:54:00Z 2014-04-01T00:00:00Z

Regeneration dynamics of natural forest species within a stand of the invasive alien Acacia mearnsii along the Buffeljagsrivier, Swellendam, South Africa Atsame-Edd, Angeline ENGLISH ABSTRACT: Several studies have shown that stands of invasive alien plants in the natural forest environment can facilitate the rehabilitation and recovery of such forests and challenged the general and global perception that such invasive species threaten the biodiversity and functioning of natural vegetation systems. The aim of this study was to develop an understanding of the dynamics of the spread and establishment of natural forest species in a large stand of the invasive alien plant species Acacia mearnsii (Black wattle) along the Buffeljagsrivier, Western Cape, South Africa. Several patches of Moist forest, Dry forest and Riparian forest occur along the Buffeljagsrivier, above the Buffeljagsrivier dam. The stand of Black wattle consists of 90 ha for a distance of 3.12 km. The main objective was pursued through four specific objectives: (i) to map and assess the patterns in the distribution, size and species composition of the natural forest clusters within the Black wattle stand; (ii) to determine the relationship between natural forest clusters establishing within the Black wattle stand and the neighboring natural forest patches as potential seed sources for the developing forest clusters; (iii) to determine the subsequent spread of natural forest species from the developing forest clusters into the rest of the Black wattle stand; and (iv) to synthesize the information on the dynamics of the spread and establishment of natural forest species into the Black wattle stand as a basis for developing general guidelines for the conversion of invasive alien plant stands in the forest environment towards regrowing natural forest. In total, 329 clusters of natural forest species were GPS recorded and mapped (Arc-GIS) in three zones (Proximal, Intermediate and Distant in relation to the forest patches) within the Black wattle stand: 266 small clusters (one to three reproductively mature trees), 36 medium sized clusters (four to nine trees) and 27 large clusters (more than 10 trees). Large clusters were abundant in the zone close to the natural forest patches and the number of small clusters increased with increasing distance from the forest patches. A total of 28 species of 20 families were recorded. Natural forest species are therefore able to establish within a Black wattle stand. The relationship between natural forest clusters establishing within the Black wattle stand and the natural forest patches as potential seed sources was studied by sampling the stand composition along transects through the stands. A total of 55 rectangular plots (20 m x 10 m, 200 m2) were sampled across forest patches and forest clusters. Hierarchical clustering analysis, using number of stems of a species per plot, identified three main groups and 10 sub-groups. All the sampled forest clusters were included in four of the five Riparian forest sub-groups. Most Moist and Dry forest species were absent from the forest clusters. The three main forest types differed in their general characteristics and site conditions, and this was supported by the ordination analyses: aspect, slope and canopy closure. The developing forest clusters within the Black wattle stand related more to the Riparian forest in terms of similar very gentle south-westerly slope and mean stem diameter. This suggested Riparian forest to be the primary seed source of the establishing forest clusters within the Black wattle stand. However, the large-sized stems of common species were not significantly different between Riparian forest patches and forest clusters, suggesting that large-sized stems in the forest clusters could be part of remnant forest patches, which could act as local seed sources. Detailed evaluation of species importance values and stem diameter distributions showed that some important Moist and Dry forest species are present in the forest clusters. The conclusion was that every type of forest patch contributes to a greater or lesser degree to the development of forest clusters within the Black wattle stand. Seven large clusters were selected to sample the regeneration of natural forest species within 18 m from the forest cluster boundary. Two species lists were generated; one of species from adjacent natural forest patches, and another from 59 forest clusters of all sizes sampled throughout the wattle stand. The results indicated that (1) Mature trees of well-established forest clusters were the main seed sources for the cluster expansion in all directions; (2) Three different patterns were observed in terms of the distance of expansion of regeneration from the clusters: a decrease in regeneration with increasing distance from the cluster margin; increasing regeneration with increasing distance from the cluster; and no distinct pattern with a lack of regeneration of the dominant species of a forest cluster. The 40 species recorded within the Buffeljagsrivier site include a wide range of fruit and seed characteristics. Four main groups of woody species were identified, based on their presence/absence in forest patches and forest clusters. The presence/absence of most species can be explained in terms of their fruit/seed characteristics and dispersal mechanisms. The majority of recorded woody species were most likely dispersed by birds and mammal, particularly Rameron pigeons and baboons. In conclusion, a conceptual framework was developed to guide the rehabilitation of stands of light demanding invasive stands in the forest environment. Several topics for further research were identified.; AFRIKAANSE OPSOMMING: Verskeie studies het gewys dat opstande van uitheemse indringerplante in die woudomgewing kan die rehabilitasie en herstel van sulke woude fasiliteer, en daag die algemene en globale persepsie uit dat sulke indringerplantspecies die biodiversiteit en funksionering van natuurlike plantegroeisisteme bedreig. Die doel van hierdie studie was om ‘n beter begrip te ontwikkel van die dinamika vir die verspreiding en vestiging van inheemse woudspesies binne ‘n omvangryke opstand van die uitheemse indringerplant, Acacia mearnsii (swartwattel), langs die Buffeljagsrivier, Wes-Kaap, Suid Afrika. Verskeie kolle (‘patches’) van Vogtige, Droë- en Oewerwoud kom langs die Buffeljagsrivier voor. Die swartwattel opstand van ongeveer 90 ha groei langs die Buffeljagsrivier oor ‘n afstand van 3.12 km, tussen die dam en die woudkolle aan die stroom-op kant van die swartwattelopstand. Die hoofdoel is nagevolg deur vier spesifieke doelwitte: (i) om die groepies (‘clusters’) vestigende inheemse houtagtige plantsoorte binne die swartwattelbos te karteer en die patrone in hul verspreiding, grootte en spesies samestelling binne die swartwattelopstand te evalueer; (ii) om die verwantskap tussen natuurlike woudgroepies wat binne die swartwattelopstand vestig en die aangrensende woudkolle as potensiële saadbronne vir die ontwikkelende woudgroepies te bepaal; (iii) om die daaropvolgende verspreiding van inheemse woudspesies vanaf die ontwikkelende woudgroepies binne die res van die swartwattelopstand te bepaal; en (iv) om die inligting oor die dinamika van die verspreiding en vestiging van die woudspesies binne-in die swartwattelopstand saam te vat as ‘n basis vir die ontwikkeling van algemene riglyne vir die omskepping van uitheemse indringerplantopstande in die woudomgewing na hergroeiende inheemse woud. In totaal is 329 groepies van inheemse woudspesies aangeteken (via GPS) en gekarteer (Arc-GIS) in drie sones (nabygeleë, intermediêre en afgeleë) binne die swartwattel opstand: 266 klein groepies (een tot drie voortplantingsvolwasse bome), 36 medium-grootte groepies (vier tot nege bome) en 27 groot groepies (10 of meer bome). Groot groepies was volop in die sone naby aan die woudkolle en die aantal klein groepies het toegeneem met toenemende afstand vanaf die woudkolle. ‘n Totaal van 28 species van 20 families is aangeteken, en spesies soos Canthium inerme, Celtis africana, Gymnosporia buxifolia, Rapanea melanophloeos en Vepris lanceolata was algemeen binne die swartwattelopstand. Dit is daarom moontlik vir inheemse woudspesies om binne die swartwattelopstand te vestig. Die verhouding tussen inheemse woudgroepies wat binne die swartwattelopstand vestig en die woudkolle as potensiële saadbronne is bestudeer deur die opstandsamestelling langs transekte deur die opstande te bemonster. ‘n Totaal van 55 reghoekige persele (20 x 10 m, 200 m2) is opgemeet: nege in Droeëwoudkolle, 17 in Vogtige woudkolle, 20 in Oewerwoudkolle, en nege in die woudgroepies binne the swartwattelopstand. Hiërargiese Groeperingsanalise, gebaseer op aantal stamme van ‘n spesies per plot, het drie hoofgroepe en 10 sub-groepe ge-identifiseer: Vogtige woud met drie sub-groepe, Oewerwoud met vyf sub-groepe, en Droeëwoud met twee sub-groepe. Al die gemete woudgroepies is in vier van die Oewerwoud sub-groepe ingesluit. Die meeste Vogtige en Droeëwoud spesies was afwesig van die woudgroepies. Die hoof woudtipes (Droog, Vogtig, Oewer) verskil in hul algemene eienskappe en groeiplektoestande, en dis ondersteun deur die ordinasie-analises: aspek, helling en kroonsluiting. Die ontwikkelende woudgroepies binne die swartwattelopstand was nouer verbonde met Oewerwoud in terme van soortglyke baie geleidelike suid-westelike helling en gemiddelde stamdeursneë. Dit veronderstel dat Oewerwoud is die primêre saadbron van die vestigende woudgroepies binne die swartwattelopstand. Baie inheemse woudspesies kom egter oor die verskillende groepe en sub-groepe voor, met goeie verjonging oor die gemeenskappe. Die stamdeursneë van goter stamme van algemene spesies was niebeduidend verskillend tussen die Oewerwoudkolle en die woudgroepies, en dit veronderstel dat die groter stamme in die woudgroepies kan deel wees van oorblywende woudkolle, wat as plaaslike saadbronne kan dien. Gedetaileerde ontleding van spesies belangrikheidswaardes en stamdeursneëklasverdelings het getoon dat sommige belangrike Vogtige en Droeëwoud spesies is wel teenwoordig in die woudgroepies. Die gevolgtrekking was dat elke tipe woudkol in a mindere of meerdere mate bydra tot die ontwikkeling van die woudgroepies binne die swartwattelopstand. Sewe groot woudgroepies is geselekteer om die woudverjonging binne 18 m vanaf die woudgroepierand te bemonster. Twee spesieslyste is saamgestel; een van spesies van die aangrensende woudkolle, en een van spesies van 59 woudgroepies van alle groottes wat deur die hele swartwattelopstand aangeteken is. Die resultate het aangetoon dat (1) volwasse bome van goed-gevestigde woudgroepies was die hoof saadbronne vir die uitbreiding van die woudgroepies in all rigtings; (2) drie verskillende patrone is waargeneem in terme van die afstand van uitbreiding van verjonging weg vanaf die woudgroepies: ‘n afname in verjonging met toenemende afstand vanaf die groepierand; toenemende verjonging met toenemende afstand vanaf die woudgroepie; en geen beduidende patroon met ‘n gebrek aan verjonging van die dominante spesies van die woudgroepie. Die 40 spesies wat binne die Buffeljagsrivierstudiegebied aangeteken is het ‘n wye reeks vrug- en saadeienskappe ingesluit. Vier hoofgroepe van houtagtige spesies is geïdentifiseer, gebaseer op hul aan- of afwesigheid in die woudgroepies and woudkolle: spesies algemeen in die woudkolle en teenwoordig in die woudgroepies; spesies spesifiek to bepaalde woudkolle en teenwoordig in die woudgroepies; spesies teenwoordig in die woudkolle maar afwesig van die woudgroepies; en spesies afwesig van die woudkolle maar teenwoordig in die woudgroepies. Die aan- of afwesigheid van die meeste spesies kan verduidelik word in terme van hul vrug/saadeienskappe en verspreidingsmeganismes. Die meerderheid van aangetekende houtagtige spesies was meeswaarskynlik deur voëls en soogdiere versprei, veral Geelbekbosduiwe en Bobbejane. Ten slotte, ‘n konsepsuele raamwerk is ontwikkel om die rehabilitasie van opstande van ligafhanklike indringerspesies in die woudomgewing te rig. Verskeie onderwerpe vir verdere navorsing is geïdentifiseer.; RESUME: Plusieurs études ont montré que les peuplements de plantes exotiques envahissantes dans le milieu de forêt naturelle peuvent favoriser la réhabilitation de ces forêts contestant par-là, la perception générale et globale que ces espèces envahissantes menacent la biodiversité et le fonctionnement des systèmes de végétation naturelle. L’objective de cet étude était de mieux comprendre le dynamisme d’établissement et de propagation dans une forêt naturelle des espèces forestières au sein d’un large peuplement de l'espèce de plantes exotiques envahissantes Acacia mearnsii (acacia noir) le long de Buffeljagsrivier, Western Cape, en Afrique du Sud afin d’élaborer des axes directives de réhabilitation relative aux recouvrements d’espèces invasive. La forêt de Buffeljagsrivier s’étale sur un gradient de petites parcelles de forêt allant de forêt sèche, humide et marécageux. Au milieu de ces parcelles de Buffeljagsrivier, on circonscrit un peuplement d’acacia noir estimé à 90 ha sur une distance de 3,12 km. L’objective principal s’est poursuit à travers quatre sous objectives à savoir: (i) cartographier et évaluer les formes d’ invasions dans la distribution, la taille et la composition des recouvrements des espèces de forêt naturelle à l’intérieur du recouvrement d’acacia noir servant comme preuve possible de l’existence et établissement des espèces de forêt naturelle sous un recouvrement d'une espèces invasive; (ii) de déterminer la relation entre les recouvrements de forêt naturelle s’établissant á l’intérieur du peuplement d’acacia noir et ceux de la forêt naturelle avoisinante humide, sèche et marécageuse pouvant être considéré comme sources potentiel de semences conduisant au développement des premiers recouvrement cités; (iii) de déterminer l’étalement subséquent des espèces de la forêt naturelle à partir des recouvrements d’ acacia noir se développant à l’intérieur du reste du peuplement de l’Acacia noir; (iv) Synthétiser les informations sur la dynamique de la propagation et l'établissement d'espèces forestières naturelles dans l’acacia noir comme une base pour l'élaboration des lignes directrices générales pour la conversion de peuplements de plantes exotiques envahissantes se trouvant dans l'environnement de la forêt vers des repousses des forêts naturelles. Au total, 329 recouvrements d'espèces forestières naturelles ont été GPS enregistrées et cartographiées (Arc -GIS) dans trois zones (Proximale, Intermédiaire et Eloignée par rapport aux parcelles de forêt avoisinantes) dans le peuplement de l'acacia noir: 266 petits recouvrements avaient un à trois arbres matures, 36 recouvrements de taille moyenne avaient quatre à neuf arbres matures et 27 larges recouvrements avaient plus de 10 arbres matures. La visualisation de la carte a révélé que les larges recouvrements de forêt mature étaient abondant dans la zone proche des parcelles de forêt naturelle avoisinantes et que de petits recouvrements de jeunes arbres de forêt naturelles croissaient en nombre à mesure que la distance depuis les parcelles de forêts naturelles adjacentes s’élargissait. Un total de 28 espèces appartenant à 20 familles a été répertorié. Deux familles, Rubiaceae suivit de Anacardiaceae ont dominé l’echantillon. Les espèces forestières naturelles sont donc en mesure de s’établir dans un peuplement d'acacia noir. L’échantillon qui a servi à l’évaluation des sources de semences pour le développement des recouvrements de forêt naturelle à travers l’investigation de la relation entre les recouvrements de forêt naturels qui s’établissent à l’intérieur du peuplement d’acacia noir et les parcelles de forêt avoisinantes humide, sèche et marécageuse était constitué de 55 placettes rectangulaires de 200m2 le long de layons à travers le site d’étude. Une analyse hiérarchique des recouvrements réalisée sur la composition des espèces de l’échantillon a révèle que la forêt marécageuse concentre les espèces les plus fréquentes des recouvrements de forêts, et que la majorité des espèces présentes sur les parcelles des forêts sèches et humides étaient absente dans l’ensemble des recouvrements des forêts de l’acaci noir. Les trois principaux types de forêts différaient dans leurs caractéristiques générales et les conditions du site, et cela a été appuyé par l’analyse d’ordinants à partir de trois facteurs environnementaux, la pente, l’angle d’inclinaison par rapport au soleil, et la fermeture de la canopée. Les recouvrements de foret en développement au sein de l'acacia noir se sont trouvés davantage liés à la forêt marécageuse en termes de pente plate orientée sud-ouest et en diamètre moyen des arbres. Ces résultats ont désigné la forêt marécageuse comme la première source potentielle de semences permettant l’établissement des recouvrements de forêt à l’intérieur des peuplements d’acacia noir. Cependant, les souches d’arbres de grande taille des espèces communes entre les parcelles de forêts marécageuses et les recouvrements de forêt dans l’acaci noir n'étaient pas significativement différents, suggérant ainsi que ces arbres de grande taille trouves dans les recouvrements de foret pourraient faire parties des parcelles de forêt subsistantes de la dernière turbulence. Elles pourraient constituer des sources locales de semences. Par ailleurs, une évaluation détaillée des valeurs d'importance des espèces et des distributions des diamètres des souches d’arbres a montré que certaines espèces importantes de forêts humides et sèches sont présentes dans les recouvrements de foret. Finalement l’on conclue que chaque type de parcelles de forêt contribue plus ou moins à l’établissement des recouvrements de forêt dans le peuplement de l'acacia noir. Sept grands recouvrements de foret ont été sélectionnés pour étudier la régénération des espèces forestières naturelles sur un rayon de 18 m depuis la limite du recouvrement de foret. Deux listes d'espèces ont été générées, l'une des espèces de parcelles de forêt naturelle adjacentes, et une autre venant des 59 recouvrements de foret, toutes tailles confondues le long de l'acacia noir. Les résultats ont indiqué que (1) Les recouvrements de forêts, lorsque bien matures et bien établies devenaient les principales sources de semences pour leur expansion sur toutes les directions; (2) Trois allures différentes ont été observées en fonction de la distance de l'expansion de la régénération autour des recouvrements: une diminution de la régénération avec l'augmentation de la distance; une croissance de la régénération avec une distance croissante depuis les revcouvrements de foret, et pas d’allure particulaire voire une absence de régénération de certaines especes pourtant dominant dans les recouvrements de foret. Les 40 espèces recensées sur le site deBuffeljagsrivier comprennent un large éventail de caractéristiques de fruits et de graines. Quatre principaux groupes d'espèces ligneuses ont été identifiées, en fonction de leur présence / absence dans des parcelles de forêt et les recouvrements de forêt. De façon générale, la présence / absence de la plupart des espèces a pu être expliquée en termes de caractéristiques de leur fruits/graines et les mécanismes de dispersion. La majorité des espèces ligneuses enregistrées sont susceptibles d’être dispersées par les oiseaux et les mammifères, en particulier les pigeons rameron et les babouins vues sur le terrain. En conclusion, un cadre conceptuel a été élaboré pour guider la réhabilitation de peuplements envahissants de lumière en milieu forestier. Plusieurs sujets pour des recherches plus poussées ont été identifiés. Thesis (MScFor)--Stellenbosch University, 2014.

2014-04-01T00:00:00Z Lindner, Gerard Eckard http://scholar.sun.ac.za:80/handle/10019.1/86621 2015-07-01T14:10:19Z 2014-04-01T00:00:00Z

Development of potential height growth and diameter increment models for the parameterisation of an individual tree growth model for Pinus elliottii plantations in South Africa Lindner, Gerard Eckard ENGLISH ABSTRACT: Individual tree models, as opposed to stand models, have the potential to greatly improve sensitivity of forest growth models to changing conditions such as silvicultural amendments, irregular stand structures, etc. It was the purpose of this study to extend two sub-components of a European individual tree growth model to introduce individual tree growth modelling concepts in South Africa using Pinus elliottii as a study species. Two main objectives were established: Modelling the potential height of stands across different site qualities and modelling diameter increment using a potential modifier approach with a combination of competition indices that change in importance according to the edaphic conditions of the site. Potential height modelling used three steps in order to achieve this objective. The first was to compare site index models based on different model fitting techniques, namely nonlinear least squares, generalised nonlinear least squares and nonlinear mixed effects models. The nonlinear mixed effects model proved to be superior in terms of achieving the principles of regression assumptions and model fit for the data range observed. The second step was to fit potential height using nonlinear quantile regression on observed spacing trial height measurements. This proved to be a robust technique able to capture potentials according to the defined Chapman-Richards model structure. The final step was to use the predicted site index as a site classification variable in order to predict potential height. While some small deviation occurred, potential height seems to be well correlated to site index and validation on selected sites suggested that site index can be used to model potential height until a more sophisticated site classification model is used for future improvement of the model. Diameter increment modelling followed six major steps in order to apply the full parameterisation methodology of an age-independent diameter increment model dependent on tree diameter and competition. Diameter increment potentials were fit using site index as a predictor of the potential height curves. Multiple competition indices were tested on two sites to obtain a combination of two indices, which can capture overtopping and local crowding effects. Principle components analysis and variance inflation factors calculation were applied to test for collinearity between indices. Suitable combinations were tested resulting in a combination of the KKL and Local Basal Area competition indices. Changing importance of the two indices were observed on the two sites tested indicating a shift in the mode of competition according to a water gradient. These were combined in a deterministic potential modifier model, which mimicked competitive stages over age; however the validation showed a skewed distribution, which was not sensitive to stand density gradients. A stochastic model was constructed to model variance from observed residual plots using linear quantile regression to determine bounds for a truncated normal distribution which generates random deviates for a predicted increment. The stochastic element significantly improved the performance and sensitivity of the model, however the model was still not sensitive enough at very high and very low spacing densities. All in all two key models for an adaptation of an individual tree growth simulator to South African conditions were successfully demonstrated. The two main objectives were achieved; however some indicated improvements could be made, especially for the competition indices where the sensitivity of competition to changing resource limitation according to site and temporal scales needs to be further investigated. Furthermore, the full set of models for simulating individual tree growth still needs to be applied. Overall, as a methodological approach, the study outlined problems and future improvements, introduced new concepts and can serve as a guideline for future parameterisation of an individual tree growth model.; AFRIKAANSE OPSOMMING: In vergelyking met vakgroeimodelle, het individuele-boomgroeimodelle die potensiaal om die sensitiwiteit van plantasiegroeimodelle vir veranderende omstandighede soos aanpassings in boskultuur, onreëlmatige vakstrukture, ensovoorts, drasties te verbeter. Die doel van hierdie studie was om twee subkomponente van ‘n Europese individuele-boomgroeimodel uit te brei om sodoende individuele-boomgroei modelleringskonsepte in Suid-Afrika bekend te stel. Pinus elliottii is gebruik as studiespesie. Twee hoofdoelstellings is bepaal. Eerstens, die modellering van hoogtegroei potensiaal van opstande oor verskeie vlakke van groeiplek kwaliteit. Tweedens, die modellering van deursnee-aanwas deur gebruik te maak van ‘n potensiaal matigingsbenadering “potential modifier approach“ met ‘n kombinasie van kompetisie-indekse waarvan die belangrikheid verander volgens die edafiese toestande van die groeiplek. Die hoogtepotensiaalmodellering bestaan uit drie stappe. Tydens die eerste stap word groeiplek bonniteitsmodelle vergelyk op grond van verskillende modelpassingstegnieke, naamlik nie-lineêre minimum kwadrate, algemene nie-lineêre minimum kwadrate en nie-lineêre gemengde effek modelle. Laasgenoemde het die beste gevaar in terme van die beginsels van regressiemodelle asook die mate waarin die model die waargeneemde data pas. Tweedens is hoogtegroei potensiaal gemodelleer deur nie-lineêre kwantielregressie op waargeneemde hoogtes van spasiëringseksperimente toe te pas. Die metode is robuust en in staat om potensiale volgens die gedefinieerde Chapman Richards modelstruktuur vas te vang. Laastens is die voorspelde bonniteits indeks as ‘n groeiplek klassifasie veranderlike gebruik om sodoende die hoogtegroei potensiaal te voorspel. Alhoewel klein afwykings voorgekom het, blyk hoogtegroei potensiaal goed gekorreleer te wees met bonniteits indeks. Uit validasie op geselekteerde groieplekke blyk dit dat bonniteits indeks gebruik kan word om hoogtegroei potensiaal te modelleer totdat ‘n meer gesofistikeerde groeiplek klassifikasiemodel beskikbaar is wat die model verder sal kan vebeter. Die volledige parametriseringsmetodiek van ‘n ouderdoms-onafhanklike deursnee-aanwas model wat afhanklik is van boomdeursnee en kompetisie bestaan uit ses hoof prosesse. Nie-lineêre kwantielregressie is gebruik om deursnee-aanwaspotensiale te pas vir verskeie groeiplekke. Dié is gekombineer met ‘n bonniteits indeks om ‘n nuwe model te vorm waarmee hoogtegroeipotensiaal kurwes voorpel kon word. Daar is met veelvuldige kompetisie-indekse op twee groeiplekke geëksperimenteer om ‘n kombinasie van slegs twee indekse te vind wat die effekte van oorskaduwing en plaaslike verdringing kan vasvang, te vind. Hoof komponent analise “Principle components analysis” en variansie inflasie faktore berekening “variance inflation factors calculation” is gebruik om vir kollineariteit tussen die indekse te toets. Gepaste indekskombinasies is getoets. ‘n Kombinasie van die KKL en plaaslike basale oppervlakte “Local Basal Area” kompetisie-indekse het die beste resultate gelewer. Die twee indekse is as volg geselekteer. Veranderings in die belangrikheid van elk van die indekse is waargeneem op die twee toetspersele. Dit dui op ‘n verskuiwing in die modus van kompetisie afhangend van ‘n watergradiënt. Die twee indekse is gekombineer in ‘n deterministiese potensiaal matigings model wat die kompeterende stadiums oor ouderdom naboots. Validasie het egter ‘n skewe verdeling wat nie sensitief vir opstandsdigtheidsgradiënte is nie, gewys. ‘n Stogastiese model is ontwikkel om variansie in die residuele grafieke te modelleer. Lineêre kwantielregressie is gebruik om grense vir ‘n afgestompte normaalverdeling wat ewekansige afwykings vir ‘n voorspelde aanwas te bepaal. Die stogastiese element het die prestasie van die deterministiese model merkbaar verbeter. Selfs met die stogastiese element, is die model egter steeds nie sensitief genoeg vir baie hoë en baie lae opstandsdigthede nie. Ter opsomming is twee modelle vir ‘n aanpassing van ‘n individuele-boomgroeisimuleerder vir Suid- Afrikaanse toestande suksesvol gedemonstreer. Die twee hoofdoelstellings is bereik. Daar is egter steeds ‘n paar aangeduide verbeterings wat aangebring kan word. Die sensitiwiteit van die kompetisie-indekse op hulpbronbeperkings wat verander op grond van die ruimtelike en temporale skale moet veral verder bestudeer word. Verder moet die volle stel modelle wat benodig word om individuele-boomgroei te modelleer nog toegepas word. As ‘n metodologiese benadering, het die studie probleme uitgewys en toekomstige verbeterings aangedui, nuwe konsepte bekendgestel en kan dus dien as ‘n riglyn vir toekomstige parametrisering van individuele-boomgroeimodelle. Thesis (MScFor)--Stellenbosch University, 2014.

2014-04-01T00:00:00Z Ndalowa, Dan http://scholar.sun.ac.za:80/handle/10019.1/86247 2015-06-30T11:40:46Z 2014-04-01T00:00:00Z

Evaluation of carbon accounting models for plantation forestry in South Africa Ndalowa, Dan ENGLISH ABSTRACT: The role that forestry plays in climate change mitigation is well recognized by countries that ratified the Kyoto protocol agreement. Though climate change mitigation strategies provide a strong incentive to quantify current patterns of forest carbon sources and sinks, this exercise (carbon accounting) is not as simple as it sounds. This is proven by the vast number of techniques and methodologies available, from models to softwares programmes created in response to the need to estimate carbon sequestration. The study aimed at gaining an understanding of the current carbon sequestration estimation methodology and models in use by the South African Forestry Industry. A survey was undertaken amongst forestry industry stakeholders in which 77% of respondents agreed to the need for a carbon sequestration model for South Africa. This model should have qualities that the forestry industry and all stakeholders agreed with. . A search of freely available models and software was conducted. The aim was to find freely available model(s) that would be readily applicable and adoptable to South African conditions. A Multi Criteria Analysis was carried out using “ideal qualities” for a carbon model as weighting. This resulted in the selection of two models, CASMOFOR and CBM CFS 3, which obtained the highest sum product total from the analysis. These together with FICAT, which came as a recommendation from the questionnaire survey, were compared in the analysis. Carbon values were calculated from yield table volumes by Kotze et al. (2012). A conversion of these volumes to biomass and carbon was done using Dovey (2009) biomass expansion factors and a biomass to carbon conversion value of 0.5 g C/g dry matter, following procedures by Matthews (1993). The first comparison was made on how the model results related to the yield table estimates from Kotze et al. (2012). When carbon values were compared per hectare, it was found that the FICAT model differed significantly from the rest. A second comparison looked at the models’ prediction of the carbon accumulated in NCT’s Enon plantation outside Pietermaritzburg. The Hungarian model, CASMOFOR, was the better predictor as it produced the lowest Mean Squared Error (MSE). Based on the results from the survey and model analysis a number of recommendations can be made regarding the current carbon accounting situation in South Africa. One of the main recommendations is that information sharing among the industry’s stakeholders should improve if the industry is to reach consensus on which methodology to adopt in their business practices.; AFRIKAANSE OPSOMMING: Die rol wat bosbou speel in klimaatsverandering-bekamping is welbekend onder lande wat die Kyoto protokol ooreenkoms onderteken het. Alhoewel klimaatsverandering-bekamping strategieë ‘n sterk aansporing bied om huidige patrone van woudkoolstof bronne en sinkte te kwantifiseer, is hierdie oefening nie so maklik soos dit klink nie. Die bewys hiervan is die groot aantal tegnieke en metodes, wat wissel van modelle tot sagteware programme wat ontwikkel is om koolstofsekwistrasie te meet. Die doelwit van die studie was om die huidige koolstofsekwistrasie metodes en modelle wat deur die Suid Afrikaanse Bosbou Bedryf gebruik word, beter te verstaan. ‘n Vraelysopname is onderneem onder bosbou-industrie deelnemers, waarin 77% van respondente saamgestem het dat dit nodig is dat Suid Afrika ‘n koolstofsekwistrasie model moet hê. Die model moet eienskappe hê waarmee die bosbou-industrie en alle deelnemers saamstem. ‘n Soektog na vrylik beskikbare koolstofmodelle en sagteware programme is onderneem. Die doelwit was om modelle te vind wat geredelik aangepas kan word vir Suid Afrikaanse toestande. ‘n Multi-kriteria analise is uitgevoer met die “ideale eienskappe”vir ‘n koolstofmodel as gewigte. Die resultaat was die seleksie van twee modelle, CASMOFOR en CBM CFS 3, wat die hoogste telling in die ontleding behaal het. Hierdie modelle, tesame met FICAT, wat aanbeveel is deur respondente van die vraelys opname, is vergelyk in ‘n ontleding. Koolstofwaardes is bereken vanaf opbrengstabelle wat deur Kotze et al. (2012) ontwikkel is. Die omsetting van hierdie volumes na biomassa en koolstof is gedoen deur Dovey (2009) se biomassa uitbreidingsfaktore en ‘n biomassa na koolstof omsettings faktor van 0.5 g C/g droëmassa te gebruik (Matthews, 1993). In die eerste vergelyking van die modelle is gekyk hoe die modelle vergelyk met koolstof berekeninge vanaf die Kotze et al. (2012) opbrengstabelle. Wanneer koolstofwaardes per hektaar vergelyk word is gevind dat FICAT beduidend verskil van die ander modelle. In ‘n tweede vergelyking is gekyk na hoe die modelle die koolstof wat in NCT se Enon plantasie buite Pietermaritzburg versamel is, voorspel. Die Hongaarse CASMOFOR model was die beste voorspeller. Anders as die FICAT en CBM CFS 3 modelle het dit die laagste Gemiddelde Vierkante Fout gehad. Na gelang van die resultate van die vraelysopname en die modelontleding kan ‘n aantal aanbevelings gemaak word oor die huidige koolstofberekening situasie in Suid Afrika. Een van die hoof aanbevelings is dat die uitruil van inligting tussen industrie deelnemers moet verbeter as die bedryf eenstemmigheid oor die metode van koolstofberekening wil bereik. Thesis (MScFor)--Stellenbosch University, 2014.

2014-04-01T00:00:00Z Phiri, Darius http://scholar.sun.ac.za:80/handle/10019.1/85739 2015-07-01T14:11:07Z 2013-12-01T00:00:00Z

Biomass modelling of selected drought tolerant Eucalypt species in South Africa Phiri, Darius ENGLISH ABSTRACT: The study aims at developing models for predicting aboveground biomass for selected drought tolerant Eucalyptus (E) species (E. cladocalyx, E. gomphocephala and E. grandis x camaldulensis) from the dry west coast. Biomass models were fit for each of the species and a cross-species model was parameterised based on pooled data for all the three species. Data was based on destructive sampling of 28 eucalypt trees which were 20 years of age and additional five five-year old E. gomphocephala trees. Preliminary measurements on diameter at breast height (dbh), height (h) and crown height were recorded in the field. The sampled trees were then felled and samples of discs, branches and foliage were collected. Density of the wood discs and the bark was determined by a water displacement method and computer tomography scanning (CT-scanner). Stem biomass was reconstructed using Smalian’s formula for volume determination and the calculated densities. Upscaling of the crown was carried out by regression equations formulated by employing the sampled branches. Further assessment was carried out on a sub-sample by subjecting the samples to different drying temperatures in a series between 60 and 105ºC. Linear models were parameterised by a simultaneous regression approach based on Seemingly Unrelated Regression (SUR) using the “Systemfit” R statistical package. The predictor variables employed in the study were dbh, d2h and h in which the coefficient of determination (R2), Mean Standard Error (MSE) and Root Mean Standard Error (RMSE) were used to determine the goodness of fit for the models. Akaike Information Criteria (AIC) was also used in the selection of the best fitting model. A system of equations consisting of five models was formulated for each Eucalyptus species. The biomass prediction models had degrees of determination (R2) ranging from 0.65 to 0.98 in which dbh and d2h were the main predictor variable while h improved the model fit. The total biomass models were the best fitting models in most cases while foliage biomass had the least good fit when compared to other models. When the samples were subjected to different drying temperatures, stem wood had the largest percentage change of 6% when drying from 60ºC to 105ºC while foliage had the lowest percentage change of less than 2%.; AFRIKAANSE OPSOMMING: Die doel met hierdie studie is om modelle vir die voorspelling van die bogrondse biomassa van drie droogte-bestande Eucalyptus (E) spesies (E. cladocalyx, E. gomphocephala en E. grandis x camaldulensis), gekweek op die droë kusvlakte in Wes-Kaapland, te ontwikkel. Biomassa modelle vir elk van die spesies is gepas en ’n model gegrond op die gekombineerde data van al drie die spesies, is geparameteriseer. Verder is die biomassa variasie onder verskeie droogingstemperature vasgestel. Die data versameling is uitgevoer gegrond op die destruktiewe mostering van 28 Eucalyptus bome wat 20 jaar oud was en ’n bykomende vyf vyfjarige E. gomphocephala bome. Die aanvanklike mates, naamlik deursnee op borshoogte (dbh), boomhoogte (h) en kroonhoogte is in die veld opgemeet. Die gemonsterde bome is afgesaag en monsters van stamhout skywe, takke en die bas is versamel. Die digtheid van die skywe en die bas is deur die waterverplasing metode, en Rekenaar Tomografie skandering (“CT-scanning”) vasgestel. Stam biomassa is rekonstrukteer deur gebruik te maak van Smalian se formule vir die vasstelling van volume en berekende digtheid. Die opskaal van die kroon biomassa is gedoen met behulp van regressie vergelykings van gekose takmonsters. Submonsters is onderwerp aan ’n reeks van verskillende drogingstemperature tussen 60 en 105ºC. Lineêre modelle is deur ’n gelyktydige regressie benadering gegrond op die Seemingly Unrelated Regression (SUR) wat ’n“Systemfit” R statistiese pakket gebruik, parameteriseer. Die voorspeller veranderlikes wat in hierdie studie gebruik is, is dbh, d2h en h waarin die koëffisient van bepaling (R2), gemiddelde standaardfout (MSE) en vierkantswortel van die gemiddelde standaardfout (RMSE) gebruik is om vas te stel hoe goed die model pas. Akaike Inligting Kriteria is gebruik vir die seleksie van die gepaste model. ’n Reeks vergelykings wat bestaan uit vyf modelle is vir elke Eucalyptus spesie geformuleer. Die biomassa voorspelling model het waardes vir die koëffisiente van bepaling (R2) opgelewer wat strek van 0.65 to 0.98% en waarin dbh en d2h die hoof voorspelling veranderlikes is, terwyl h die pas van die model verbeter. Die totale biomassa model het in die meeste gevalle die beste gepas en die blaarbiomassa die swakste as dit met die ander modelle vergelyk word. Tydens droging vind die grootste persentasie verandering van 6% by stamhout plaas tussen temperature van 60ºC tot 105ºC, en die kleinste persentasie verandering van minder as 2% by blare. Thesis (MScFor)--Stellenbosch University, 2013.

2013-12-01T00:00:00Z Ackerman, Simon Alexander http://scholar.sun.ac.za:80/handle/10019.1/85874 2015-07-01T14:11:08Z 2013-12-01T00:00:00Z

The effect of irregular stand structures on growth, wood quality and its mitigation in operational harvest planning of Pinus patula stands Ackerman, Simon Alexander ENGLISH ABSTRACT: The practice of combining row and selective thinning in commercial pine plantation silviculture carries the risk of unwanted irregularities in tree distribution within the stand. This situation is aggravated with poor tree selection during marking. The potential consequences of poor tree selection are gaps created along row removals, which are necessary for access to harvesting operations. These gaps lead to spatially asymmetric growing space among adjacent trees. The effect of irregular stand structures on tree morphology and growth are investigated in this study, and are based on two stands of Pinus patula, (Schiede ex Schlechtendal et Cham.) in Langeni plantation, South Africa. This study focuses on two aspects. Firstly, a comparison between trees grown in all-sided and one-sided spatial competition situations in order to assess if there are differences in growth and selected quality parameters. Secondly, the mitigation of irregular structures using a simulation based study on changing the planting geometry in order to investigate the effect on harvesting in terms of stand impact, simulated harvesting productivity and harvesting system costs. Results showed that trees grown in an irregular competitive status have significantly larger crown diameters, crown lengths, longer and thicker branches, disproportionately one sided crown growth and a reduction in space-use efficiency. Simulations indicated that changing planting geometry from the current 2.7m x 2.7m to 2.3m x 3.1m and 2.4m x 3m would result in up to a 20% reduction of machine trail length and fewer rows being removed for machine access. The simulation of harvesting thinnings showed that various planting geometry alternatives increased harvesting productivity by 10% to 20% and reduced overall thinning harvesting cost by up to 11%. This study successfully investigated the factors that potentially negatively affect saw timber quality and volume production of the stand at final felling. It also illustrated the applicability of simulation methods for testing harvesting scenarios and developing economically viable alternatives.; AFRIKAANSE OPSOMMING: Die praktiese kombinasie van ryuitdunning en seleksiedunning in kommersiële denneplantasies dra die risiko van ongewensde onreelmatighede in die verspreiding van bome in die opstand. Hierdie situasie word vererger deur swak boomseleksie tydens die merk van dunnings. Die potensiële gevolge van swak boomseleksie is die ontstaan van onreelmatige gapings tussen boomkrone, veral langs die rydunnings, wat nodig is vir toegang tydens die ontginning van die hout. Dit lei daartoe dat die bome langs die dunningsrye asimmetriese ruimtes het om in te groei. Die effek van onreelmatige opstandstrukture op boom-morfologie en -groei word in hierdie studie ondersoek in twee Pinus patula, (Schiede ex Schlechtendal et Cham.) vakke te Langeni plantasie, Suid-afrika. In die studie word daar gefokus op twee aspekte. Eerstens word bome wat onder toestande van eweredige ruimetlike kompetisie groei vergelyk met die wat onder toestande van eensydige ruimtelike kompetisie groei om sodoende vas te stel of daar verskille is in die groeipatroon aan die hand van geselekteerde gehalteparameters. Tweedens word daar gefokus op die verbetering van onreelmatige opstandstrukture deur gebruik te maak van ’n simulasie-gebasseerde studie om veranderinge in die aanplantingsgeometrie te ondersoek met die doel om die effek van plantspasieering op ontginningsimpakte, gesimuleerde ontginningsproduktiwiteit en -sisteem koste te bepaal. Die resultate het getoon dat bome wat onder toestande van onreelmatige spasieering en kompetisie groei krone met groter deursnee asook langer lengtes ontwikkel, langer en dikker takke het, disproporsionele, eensydige kroongroei en ’n reduksie in ruimte-gebruik toon, wat die groeidoeltreffendheid nadelig beinvloed. Simulasies met betrekking tot die verandering in boomaanplantgeometrie vanaf die huidige 2.7m x 2.7m na 2.3m x 3.1m en 2.4m x 3m het gedui op ’n reduksie van 20% in die masjienpadafstand en na minder rye wat uitgehaal moes word om die toegang van masjiene moontlik te maak. Die simulasie van die ontginning van dunnings het getoon dat verskillende aanplantgeometriealternatiewe die ontginningsproduktiwiteit met 10% tot 20% verbeter het, en die algehele dunningsoeskoste met tot 11% verminder het. In hierdie studie is die faktore, wat die gehalte van saaghoutkwaliteit en volume tydens die finale oes van die plantasie potensieel negatief mag beinvloed, suksesvol ondersoek. Dit illustreer ook die geskiktheid van simulasietoepassings vir die toets van ontginningsalternatiewe en die ontwikkelling van meer ekonomies voordelige praktyke . Thesis (MScFor)--Stellenbosch University, 2013.

2013-12-01T00:00:00Z Wise, Andre http://scholar.sun.ac.za:80/handle/10019.1/85876 2015-07-01T14:15:23Z 2013-12-01T00:00:00Z

A spatial approach to edge effect modelling for plantation forestry Wise, Andre ENGLISH ABSTRACT: One of the major objectives in plantation forestry is to achieve a high level of homogeneity of distribution and dimension of trees within the stand. Precise planting geometries, intensive silviculture and genetic selection are used to achieve this homogeneity. However, a natural variability is still introduced by micro-­‐site conditions and disturbances. A substantial source of variation is caused by edge effects of neighbouring stands or other land use forms. The edge effect causes trees at the stand edge to develop differently from trees in the interior of the stand. The overarching objective of this study is to simulate the edge effect based on average stand interior variables as typically received from an enumeration and spatial information on the current and historic stand neighbourhood. With re-­‐introducing this natural variance as well as its spatial pattern, we expect to derive improved planning information. A major aim is thus separating the effect of the edge interaction from the other factors contributing to stand variance and quantifying the result in terms of stand output. A methodology is introduced for quantifying interaction at stand edges between a given stand and its neighbouring stands over its lifetime. Transferring the edge interaction value from the edges to all the trees within the stand is then done by applying inverse distance weighting interpolation from the edges to the tree position within the stand. Once an edge interaction value has been calculated for each point, the extent of the edge effect is quantified. The spatial extent of the edge effect is derived empirically from an existing fully spatially mapped stand by means of breakpoint regression. The expected variance as a result of edge influence is then quantified by producing a set of models, which can reproduce the effect of the edge interaction on tree height, diameter and volume. The edge effect is treated as a dynamic interaction for which the temporal aspect needs to be considered, because the current spatial structure of a stand is influenced by its current neighbourhood, but also by the historic development of the neighbourhood in relation to the stand in question. Each stand therefore undergoes an edge effect which is completely unique to that stand, within a given time period. For this reason the presented methodology is a spatial-­‐temporal one, aimed at providing a way in which growth and yield forest modelling can be augmented by the inclusion of the edge effect in a practical way. To explicitly quantify edge effects, the natural variance had to be separated into a component explained by edge effect and a second component introduced by other factors such as micro site conditions and disturbance. The second component is treated as an unexplained residual variance. In order to provide a realistic simulation of a stand output at a finer, tree level, this second stand variance needs nonetheless to be quantified. The variance attributable to factors other than the edge effect is mimicked by generating a random number by means of a parameterised stochastic process based on the variance of the inner stand region, which is beyond the reach of the edge effect. In this way, a realistic spatial pattern of a plantation forest stand, taking into account the edge effect and combining it with the natural stand variance is achieved. This study, within the field of plantation forest management, aspires to land use optimization both in terms of productive capacity estimation and for the provision of information for effective land use management planning. It makes use of open source software resources namely the R framework and QGIS and explores aerial stereophotogrammetry as an option for data collection.; AFRIKAANSE OPSOMMING: Een van die hoofdoelwitte in plantasie bosbou praktyk is hoё vlakke van homogeniteit met betrekking tot die verspreiding en die dimensies van die bome in die plantasie opstand. Simetriese aanplantings, intensiewe bosboupraktyk en genetiese seleksie word gebruik om hierdie homogeniteit te verkry. Natuurlike verskille word egter nog steeds gevind as gevolg van groeiplek mikro toestande en ander versteurings in die opstand. Een van die hoofbronne van hierdie variasie is die randeffekte van buurplantasies en ander gebruike van grond. Hierdie randeffekte veroorsaak dat bome aan die rand van die opstand anders ontwikkel as die bome binne in die opstand. Die oorhoofse doelwit met hierdie navorsing is om die randeffekte te simuleer. Hierdie randeffekte is gegrond op die gemiddelde binneopstand boom veranderlikes soos afgelei uit die opmeting en uit ruimtelike inligting oor die huidige en geskiedkundige toestande in die omgewing. As hierdie natuurlike variasies asook die ruimtelike patrone weer in berekening gebring word, verwag ons om beter beplanningsinligting te bekom. ’n Belangrike doelwit tydens hierdie navorsing is dus om die effek van die rand-­‐interaksie te skei van die effek van ander faktore wat bydra tot variasies binne-­‐in die opstand en om die resultaat in terme van plantasie produksie te kwantifiseer. ’n Metodiek word voorgestel vir die kwantifisering van die interaksie op die rande tussen die opstand en die buuropstande tydens die leeftyd van die opstand. Die oorplasing van die rand interaksie waarde van die rand af na al die bome in die plantasie word dan gedoen deur om geweegde inverse afstand interpolasie vanaf die rand tot by die ligging van die boom, toe te pas. As die rand interaksie waarde vir elke punt bereken is, kan die omvang van die randeffek gekwantifiseer word. Die ruimtelike omvang van die rand effek is, met die gebruik van breekpunt regressie, empiries afgelei van ’n bestaande ten volle karteerde plantasie. Die verwagte variasie as gevolg van die randeffek word dan met die gebruik van ’n stel modelle gekwantifiseer, wat dan die effek van die rand interaksie op boomhoogte, deursnit en volume kan weergee. Die randeffek word as ’n dinamiese interaksie beskou waarvan die tydsaspek in ag geneem moet word, want die huidige ruimtelike struktuur van die plantasie word beïnvloed deur die huidige omgewing asook deur die historiese ontwikkeling van die omgewing met betrekking tot die opstand onder bespreking. Elke opstand ondergaan ’n randeffek wat uniek is aan daardie plantasie op die gegewe tydstip. Die doelwit is om ’n wyse te vind waarvolgens groei-­‐en-­‐opbrengs plantasie modellering deur die insluiting van randeffek op ’n praktiese wyse, aangevul kan word. Om hierdie rede is die aanbevole metodiek ruimtelik-­‐tydelik en gerig daarop om ’n wyse te vind waarvolgens groei-­‐en-­‐opbrengs modellering deur die insluiting van die randeffek, op ’n praktiese wyse aangevul kan word. Om randeffek eksplisiet te kwantifiseer, moes die natuurlike afwyking gedeel word in die komponent wat die gevolg is van die randeffek, en ’n tweede komponent wat die gevolg is van ander faktore soos mikroligging toestande en versteurings. Die tweede komponent word behandel as ’n onverklaarde oorblywende afwyking. Hierdie tweede plantasie afwyking moet nogtans kwantifiseer word om sodoende ’n realistiese simulasie van plantasie opbrengs op ’n fyner boom vlak te verkry. Die afwyking wat toegeskryf kan word aan faktore buiten die randeffek, word nageboots deur om ’n lukrake nommer (wat gebaseer word op die afwyking van die binne-­‐plantasie gebied wat buite die strekwydte van die randeffek is) deur middel van ‘n geparameteriseerde stogastiese proses te genereer. Sodoende word ’n realistiese ruimtelike patroon van ’n plantasie opstand verkry, wat die randeffek in ag neem en dit kombineer met die natuurlike plantasie afwyking. Thesis (MScFor)--Stellenbosch University, 2013.

2013-12-01T00:00:00Z