Thesis (PhD (Forest and Wood Science))—University of Stellenbosch, 2006. / Experiments carried out in this study sought to contribute to the understanding of the ecological interactions involved in Uapaca kirkiana seedling establishment and growth in a natural woodland ecosystem. These include soil pH reactions, plant root surface pH change, root exudates that affect the chemical behaviour of the soil in the vicinity of the root, and microbial effects. Although it was difficult to determine which of these factors play a dominant role in the soil-plant relationship, the study contributed to the understanding of the mycorrhizal fungi-host plant association. It revealed the diversity of mycorrhizal fungal species occurring in the different ecological sites, and also analysed the relationship between soil factors. Soil pH and K had significant influences on the fungi population diversity. K was considered important in its role in the translocation of auxins to the root sites where they enhance root susceptibility to mycorrhizal fungal infection. More work needs to be undertaken to establish the role of soil pH.

Thesis (PhD (Forest and Wood Science))—University of Stellenbosch, 2007. / Sustainable livestock production in semi-arid Botswana could be improved through tree planting on-farm to provide much needed protein and shade. Such action can be encouraged if the growth, productivity, nutritional value of trees and their contribution to mass gain of livestock are known.. A study at Malotwana investigated two indigenous species, Acacia galpinii and Faidherbia albida, and two exotic species, Leucaena diversifolia and L. leucocephala, at three spacings in a randomised complete block design replicated five times. The three spacings represented 400, 317 and 241 trees per hectare. The study was conducted over 6.5 years. Indigenous trees were sampled biennially and exotics annually to evaluate crown width, height, stem diameter, stem number and stem volume index. Complete plant harvesting of exotic trees at 2.5, 4.5 and 6.5 years evaluated agroforestry production. Leaves from all four species and pods of exotic species were analysed for chemical composition. Two groups of eight lambs were balanced for mass at selection for an on-farm feeding trial. Browse from exotic trees, comprising a 2:1 ratio of pods to leaves, was fed at 30% as supplement to hay to one group whose mean mass was contrasted with that of the control group fed sorghum bran at 30%. A. galpinii was a promising species, adaptable to planting away from its origin. Its crown width ranged from 5.86 m in high density plots to 6.08 m at low density and was significantly different among stands (p = 0.0406) at 6.5 years. Diameter at breast height (dbh) was significantly different among stands aged 6.5 years (p = 0.0003) and ranged between 10.38 cm at high density to 12.48 cm in low density plots, demonstrating a capacity to provide both shade and poles on-farm. At 4.5 years, F. albida attained a mean height of 4.5 m and 4.5 cm in dbh but suffered 67% mortality during a severe drought. Annual fodder production of 0.647 and 0.996 metric tonnes ha-1 for leaves and pods of L. diversifolia and 1.237 and 1.431 for L. leucocephala was recorded in years of average rainfall. Yields of 0.3 and 0.59 metric tonnes ha-1 were recorded for both species in the driest year. Equally good agroforestry production was obtained from both low and high density stands suggesting that low density plantings, which foster higher plant survival and reduce disease incidence, are best suited to the semi-arid conditions of Botswana. The crude protein of leaves ranged between 16.26 (L. diversifolia) and 25.25% (F. albida). They were highly digestible with more than twice the calcium content livestock require. Crude protein and digestibility measures were significantly different among leaves and varied significantly at different spacings (p<0.0001). Pods of the exotic species contained significantly more protein than the leaves (p<0.0001). Lambs supplemented with browse gained 102.33 g per animal per day while the control group gained 83.95 g. There were significant differences between groups during growth (p<0.05). Growing of A. galpinii, complemented with L. diversifolia and L. leucocephala, can supply short and long term feed, and greatly enhance livestock production while diversifying farm feed sources

Thesis (PhD (Forest and Wood Science))--University of Stellenbosch, 2006. / The discolouration of South African softwood during kiln drying can reduce the value of furniture grade lumber. Thermal discolouration of wood, as found due to heat treatment, produces a homogeneously browner colour in wood than is normally expected. This type of discolouration is attributed to reactions of the macromolecules present in wood and is found in both hard- and softwoods. Yellow stain and kiln brown stain can severely alter the colour of the outer few millimeters of a wooden board and is attributed to the reaction of water-soluble sugars and nitrogenous compounds, present in the wood sap, after deposition at the wood surface due to liquid or capillary water flow during drying. A discussion of the mechanism of discolouration due to yellow stain and kiln brown stain would be incomplete without a good understanding of the liquid flow of water during drying above fibre saturation point. This thesis brings the two concepts of liquid water flow and discolouration in context and is presented in four chapters: • an introduction motivating the aims of the investigation (Chapter 1); • a literature review of factors which may influence discolouration and liquid water flow during drying (Chapter 2); • original manuscripts describing the discolouration of South African softwood and liquid water flow in hard- and softwood (Chapter 3); and • a final conclusion that links up the results from the investigations (Chapter 4). The investigations into the occurrence of yellow stain and kiln brown stain showed that the intensity of these types of discolouration was influenced by geographical origin (and/or climate), tree species, planing depth of dried lumber, and kiln schedule parameters like dry- and wet bulb temperature and time. The characteristic discolouration pattern of yellow stain and kiln brown stain indicated that this stain type was related to the wetline phenomenon that is found during the liquid water flow phase of drying wet wood. Thermal discolouration, on the other hand, occurred homogeneously throughout the volume of lumber and is, therefore, not related to free water flow, but to chemical changes of the macromolecules in wood. The results of the liquid water flow investigations support the invasion percolation theory of drying that states that the largest meniscus will retract into a drying liquid-filled capillary network until it is not the largest meniscus anymore. Fluctuations in the rate of moisture loss from the cores of wood pieces above fibre saturation point were also found. The pattern of fluctuation differed appreciably between Betula verrucosa and Pinus radiata. In both cases, the start of the last phase in rate of moisture loss from the core coincided with a reduction in the cross-sectional area of the drying wood piece. This behaviour is explained by the hypothesis that distinct capillary size classes are emptied of free water, in order, from large to small. As smaller capillaries are emptied, the capillary forces become greater, to the point where the forces are great enough to cause permanent or temporary deformation of the remaining water-filled capillaries. Classification and regression tree analysis was a useful statistical technique to analyse a large multivariate dataset. The importance of kiln schedule temperatures and planing depth to control yellow stain and kiln brown stain was clearly pointed out by the technique, which can help to simplify the control of colour quality during the industrial processing of wood.

Dissertation (PhD (Bosb))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study was conducted to evaluate and compare the water and nutrient relations of three indigenous deciduous tree species, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker and two widely planted eucalypts, viz., Eucalyptus camaldulensis Dehnh and Eucalyptus globulus Labill from Ethiopia. The study was organized as glasshouse and field observations in Ethiopia. Owing to the lack of baseline studies on the water and nutrient relations of the deciduous tree species, the glasshouse experiments involved a wide range of water and nutrient applications. Seedlings were grown with the supply of various levels of water and nutrients during which gas exchange, water potential, relative water content, tissue nutrient content and biomass production were measured. The field observations were limited to the study of surface root distribution and leaf nutrient composition of mature trees and their effects on soil nutrient pool. The observations were made on isolated trees and mixed or pure stands of trees in Badessa area, Eastern Ethiopia. The field site was selected because of the availability of the study species and suitability of the trees for the study. In the glasshouse, increased water deficit significantly reduced predawn leaf water potential, relative water content, stomatal conductance, photosynthetic rate, whole plant water use efficiency, plant height, diameter, leaf area and biomass production. Both of the eucalypts did not grow faster than the deciduous species under well-watered conditions unlike under water stress conditions. C. macrostachyus and C. africana had higher transpiration rates and tissue nutrient accumulations than the other species. They also demonstrated higher biomass allocation to roots than all the other species to support the intensive water and nutrient uptake rate. Due to the ability to re-orient its leaves to avoid direct solar irradiance, M. ferruginea maintained higher tissue water potential and relative water content than all the other species under water stress regimes. The impact of imposed drought was quick and more damaging to the eucalypts compared to the deciduous tree species indicating that the eucalypts may not survive extreme drought conditions unlike the deciduous species that drop their leaves and may remain dormant for weeks. The current study gave new experimental proof that E. globulus was more vulnerable to drought than E. camaldulensis. Soil N stress resulted in an overall reduction of tissue N concentration, N:P ratio, photosynthetic rate, stomatal conductance and photosynthetic water use efficiency in all the species studied. Pants with high foliar nitrogen concentration had higher photosynthetic capacities indicating that N plays a key role in photosynthesis and growth of all the studied species. The current study showed that for all the tree species, more attention has to be given to soil N than to P as soil P had minor effects on the photosynthetic activities of plants of all species compared to N.The investigation on tissue nutrient composition confirmed that N:P ratio could be used to detect Plimitation in plants. However, N:P ratio could not distinguish between N-limitation and combined limitations of N and P. The study of isolated C. africana and C. macrostachyus trees on soils in Badessa, Eastern Ethiopia indicated improved soil N, P and K under tree canopies whereas no effects were observed on the other soil nutrients studied. Similar to glasshouse conditions, C. macrostachyus and C. africana produced extensive surface roots, interfering with crops grown in association. Due to their high nutrient cycling potential the net effect on soil was positive. Comparison of E. camaldulensis woodlot and a mixed stand composed of deciduous species indicated that the fine root biomass in the surface soil under E. camaldulensis was about three times that under the mixed stand. The fine root biomass of E. camaldulensis inside the stand and 10 meters away from the stand were comparable in the surface soils showing the presence of root competition with adjacent crops. Therefore, planting of E. camaldulensis in association or adjacent to croplands should be avoided. Nutrient and carbon pool of soil inside the mixed stand was generally higher than that of E. camaldulensis indicating that trees of the mixed stand recycled more nutrients to the soil. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die verskille tussen water- en voedingstofverhoudings van drie inheemse blaarwisselemde boomsoorte te vergelyk, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker en twee bekende eucalyptus spesies, viz., Eucalyptus camaldulensis Dehnh en Eucalyptus globulus Labil van Etiopië. Die studie het bestaan uit kweekhuis- en veldobservasies in Etiopië. As gevolg van beperkte navorsing ten opsigte van water- en voedingstofverhoudings in bladwisselende boomsoorte, het die kweekhuis-eksperimente bestaan uit 'n wye verkeidenheid water- en voedingstoftoetse. Saailinge is gegroei deur verskillende vlakke van water- en voedingstowwe by te voeg. Gaswisseling, waterpotensiaal, relatiewe hoeveelheid water, hoeveelheid voedingstowwe en produksie van biomassa is gemeet. Die veldobservasies was beperk tot oppervlak-wortelverspreiding en blaarvoedingstof hoeveelhede van volwasse bome, sowel as die effek op grondvoedingstowwe. Observasies was beperk tot geïsoleerde, gemengde en een spesie opstande, in die Badessa area, Oos Etiopië. Die studiearea was gekies op grond van die voorkoms van die gekose boomsoorte, sowel as die toepaslikheid van die bome vir die studie. In die kweekhuis is gevind dat die verhoogte watertekort die pre-sonop blaarwaterpotensiaal, relatiewe hoeveelheid water, stomatiese geleiding, fotosintetiese tempo, heelplant water-gebruikseffektiwiteit, plant hoogte, diameter, blaararea en biomassa produksie beduidend verminder het. Nie een van die eucalyptus spesies het vinniger as die bladwisselende spesies onder voldoende hidrasie gegroei nie. Dit was egter nie die geval onder die waterbeperkte toestande nie. C. macrostachyus en C. africana het ‘n hoër transpirasie tempo sowel as weefselvoedingstof waardes gehad as die ander spesies. Hierdie boomsoorte se wortelbiomassa was ook meer as die ander spesies, om vir die tempo van water- en voedingstofopname te akkomodeer. As gevolg van die vermoë om blare te kan oriënteer om direkte sonlig te vookom, het M. ferruginea ‘n hoër water-weefselpotensiaal en relatiewe waterinname gehad in vergelyking met die ander boomsoorte in beperkte water toestande. Die impak van gëinisieerde droogte het vinnig voorgekom en het meer skade aan die eucalyptus aangerig in vergelyking met die bladwisselende boomsoorte. Dit dui aan dat die eucalyptus-spesie nie ekstreme droogte kan oorleef nie, waar bladwisselende spesies hul blare laat afval en vir weke aan een dormant kan bly. Hierdie studie gee eksperimentele bewyse dat E. globulus minder bestand is teen droogte as E. camaldulensis. Beperkte N in die grond het veroorsaak dat daar ‘n algemene vermindering van weefsel Nkonsentrasie, N:P ratio, fotosintetiese tempo, stomatiese geleiding en fotosintetiese watergebruiks effektiwiteit in al die bestudeerde spesies was. Plante wat oor hoër blaar-stikstofkonsentrasiesbeskik, het hoër fotosintetiese kapasiteite wat aandui dat N ‘n belangrike rol in fotosintese en die groei van al die bestudeerde spesies speel. Die oorhoofse bevindings van die studie was, dat daar meer aandag gegee moet word aan grond-N as P omdat grond-P net ‘n kleiner rol speel in die fotosintetiese aktiwiteite van plante van al die spesies in vergelyking met N. Die ondersoek na weefselvoedingstof hoeveelhede het bewys dat die N:P ratio gebruik kan word om P-tekorte in plante aan te dui. Die N:P ratio kan egter nie die verskil in N-tekorte en gekombineerde tekorte van N en P aandui nie. Die studie van die geïsoleerde C. africana en C. macrostachyus bome op grondtipes in Badessa, Oos Etiopië het verbeterde grond-N, P en K onder kroondak gebiede getoon, daar was egter geen verskille in die ander grondvoedingstowwe wat bestudeer is nie. In toestande gelykstaande aan die van die kweekhuis, het C. macrostachyus en C. africana meer oppervlaksswortels ontwikkel. Die toename aan oppervlakswortels het ingedring op gewasse wat in assosiasie gegroei is, dit het egter ‘n positiewe effek op die grond gehad as gevolg van die hoë voedingstof-siklus-potensiaal. Die E. camaldulensis opstand is gevergelyk met ‘n gemengde opstand van bladwisselende spesies waar daar gevind is dat die fynwortel biomassa in die oppervlak grond onder die E. camaldulensis ongeveer drie keer soveel was as die van onder die gemengde opstand. Kompetisie met aangrensende gewasse is aangeui deurdat die fynwortel biomassa van E. camaldulensis binne die opstand en 10 meter weg van die opstand vergelykbaar was in die oppervlakgronde. Dit dui dus aan dat die plant van E. camaldulensis in assosiasie of aangrensend aan gewasse vermy moet word. Die teenwoordigheid van voedingstowwe en koolstof in die grond van die gemengde opstand was oor die algemeen hoër as die van die E. camaldulensis. Dit is ‘n aanduiding dat die bome van die gemengde opstand meer voedingstowwe aan die grond verskaf.

Thesis (PhD (For))--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This study aims to evaluate the effects of forestry policy on the sustainability of forest resources in Southern Africa. However, the study has confirmed that forestry policy does not operate independently of other policies. Its scope is defined by overarching framework legislation and policy, while it functions within a complex mesh of crosscutting and sectoral policies. Therefore, the implications of these external policies for forest conservation have also been assessed. The method used employs predominantly qualitative assessment of documentary data, which constitute the main contents of the three case studies: South Africa, Tanzania and Zambia. This qualitative information has been transformed into quantitative data, using a scoring scale of one to five for certain indicators of sustainable forest management (SFM). The average score for each country makes up a forest conservation index (FCI), which provides a comprehensive insight into the performance of a country's forestry and other resource conservation policies. South Africa's FCI is estimated at 3, while Tanzania and Zambia's indices have been rounded to 2 each. As South Africa's forestry policy and other biological resource conservation policies came into existence as recent as the mid- and late 1990s, this index suggests that these policies will lead to SFM subject to satisfactory implementation. Indeed, South Africa has a congruous forestry legislation whose regulatory mechanisms are appropriately blended with financial and framework incentives. Its overarching framework legislation and policy define forestry policy, while the crosscutting policies reinforce it. However, the country's performance on intergovernmental and intersectoral policy co-ordination is poor, as well as on the economic valuation of its natural forest resources. Furthermore, the formulation of South Africa's forestry policy was not founded on up-to-date forest resource data. Contrary to the South African case, Tanzania and Zambia's indices indicate the likelihood of unsustainable forest use and management. These countries' existing forestry and other resource conservation policy-making processes are narrow-based and gender-insensitive, rendering them unpopular among policyaffected and policy-connected stakeholders. These inappropriate policies and their blunt instruments distort markets for forest resources, i.e., create situations in which benefits are dissociated from costs, prices from scarcities, rights from responsibilities and actions from consequences. Both forestry policies and their governing tools were not founded on contemporary forest resource data, i.e., they are not issue centred. The countries' framework laws have also failed to institutionalise environmental impact assessment, monitoring and evaluation, intersectoral policy co-ordination, participatory approaches to natural resource management and ownership of environmental assets such as land and forest resources by local communities. The administration of forestry policy requires competent professional and technical staff. South Africa has adequate human resources in the forestry sector, although the personnel appear to lack the necessary skills for participatory forest management for poverty reduction. Tanzania has adequate but ineffective forestry personnel, resutting in lack of law enforcement and corruption while Zambia lacks professional staff to interpret and implement the existing forestry policy. The ineffectiveness and the lack of professional and technical staff, inter alia, is reflected in the high rates of deforestation, which have been estimated at 91,000 halannum for Tanzania and 851,000 halannum for Zambia. Unlike South Africa, both Tanzania and Zambia's sectoral policies fail to cultivate concerns for forest conservation. This situation is aggravated further by the pervasive lack of intra- and intersectoral policy coordination among biological resource conservation divisions and departments. The coherence of South Africa's forestry and other resource conservation policies is attributable to the scarcity of natural forests in the country. Approximately, 7.0% of South Africa's landscape is under forest cover, while Tanzania and Zambia have 37% and 42%, respectively. Decreasing supplies of forest coupled with the increasing demands for forest resources causes the value of forest resources to appreciate. Naturally, there is a stronger need for the forest-scarce South Africa to pursue prudent conservation policies to protect its limited forest than Tanzania and Zambia whose governments treat their respective vast land and forest resources as a safety valve for economic hardship without adequate investment in SFM. In summary, forest resource use and management in Tanzania and Zambia are littered by market and policy failures. It is envisaged that the opportunities and constraints identified in each market and policy failure will inform future forestry and related policy-making process, not only in the concerned countries but also in other African countries experiencing similar forest conservation problems. / AFRIKAANSE OPSOMMING: Hierdie studie het ten doel om die effekte te evalueer wat bosboubeleid het op die volhoubaarheid van woudhulpbronne in Suidelike Afrika. Hierdie studie het egter bevestig dat bosboubeleid nie onafhanklik van ander beleidspunte funksioneer nie. Die omvang daarvan word gedefinieer deur oorkoepelende raamwerkwetgewing en beleid, terwyl dit binne 'n komplekse netwerk van oorkruisende en sektorale beleid funksioneer. Daaom is die implikasies van hierdie eksteme beleidspunte vir woudbewaring ook bepaal. Die metode gebruik, wend hoofsaaklik kwalitatiewe beraming van dokumentere data aan, wat die hoofinhoud van die drie gevallestudies, nl. Suid-Afrika, Tanzania en Zambia uitrnaak. Hierdie kwalitatiewe informasie is omvorm na kwantitatiewe data, deur gebruik te maak van 'n skaal van een tot vyf vir sekere indikators van vohoubae bosbestuur (VBB). Die gemiddelde punt vir elke land vorm 'n woudbewaringsindeks (WBI), wat 'n omvatlende insig verskaf van die land se uitvoering van die bosbou- en bewaringsbeleid van ander hulpbronne. Suid-Afrika se WBI is beraam op 3, terwyl Tanzania en Zambia sa indekse elk tot 2 afgerond is. Siende dat Suid-Afrika se bosbou- en bewainqsoeleld van ander biologiese hulpbronne eers so onlangs as die middel- en laat 1990's in werking getree het, stel hierdie indeks voor dat die beleid sal lei tot VBB, onderhewig aan bevredigende uitvoering daarvan. Suid-Afrika het inderdaad 'n gepaste bosboubeleid, waarvan die regulerende meganismes toepaslik vermeng is met finensiele en raamwerk aansporings. Die oorkoepelende raamwerkwetgewing en beleid definieer bosboubeleid, terwyl oorkruisende beleidspunte dit versterk. Die land se uitvoering van interregerings- en intersektorale beleidkoordinasie, is egter swak, asook in die ekonomiesa waardering van sy natuurlike woudhulpbronne. Verder, is die formulering van Suid-Afrika se bosboubeleid nie gegrond op woudhulpbrondata wat op hoogte was nie. In teenstelling met die Suid-Afrikaanse geval, toon die indeksa van Tanzania en Zcrnbia die waCl'skynlikheid van onvomoubae bosbenutting en -bestuur. Hierdie lande se bestaande beleidvormingsprosasse vir bosbou en bewaring van ander hulpbronne, is eng-gebaseer en geslags-onsensitief, wat dit onpopulsr maak onder beleidgeaffekteerde en beleidverbonde insethouers. Hierdie ontoepaslike beleidspunte en stomp instrumente verdraai markte vir woudhulpbronne, d.i. skep situasies waarin voordele gedissosieer is van kostes, pryse van skaashed, regte van verantwoordelikhede en aksies van nagevolge. Beide bosboubeleidspunte en die leidingsinstrumente is nie gegrond op kontemporere woudhulpbrondata nie, d.w.s. hulle is nie rondom die kwessie gesentreer nie. Die lande se raamwerkwette het ook gefaal daarin om omgewingsimpakberamings, monitering en evaluering, intersektorale beleidkoordinering, deelnemende benaderings tot natuurlike hulpbronbestuur en plaaslike gemeenskappe sa eienaaskai van omgewingsbates, SODS grond en woudhulpbronne in te stel. Die administrasie van bosboubeleid verg bevoegde professionele en tegniese personeel. Sui-Afrika het voldoende menslike hulpbronne in die bosbousektor, hoewel dit voorkom of die personeel nie die nodige vaadiqhede het vir deelnemende bosbestuur vir die veligting van arnoede nie. Tanzanie het voldoende, maa oneffektiewe bosboupersoneel, wat 'n gebrek aan wetstoepassing en korrupsie tot gevolg het, terwyl Zambie 'n tekort het aan professionele personeel om die bestaande bosboubeleid te interpreteer en te implementeer. Die oneffektiwiteit en die gebrek aan professionele en tegniese personeel, onder andere, word gerefiekteer in die hoe tempo van ontbossing, wat beraam is op 91,000 ha/jaCl'vir Tenzenie en 851,000 ha/jaCl'vir Zembie. Anders as Suid-Afrika, faal beide Tanzanie en Zambia se sektorale beleidspunte daain om belange vir woudbewaring te kweek. Hierdie situasie word verder vererger deur die deurdringende gebrek aan intra- en intersektorale beleidkoordinering onder afdelings en departemente van biologiese hulpbronbewaring. Die verband tussen Suid-Afrika se bosbou- en bewaringsbeleid van ander hulpbronne word toegeskryf aan die skaarsheid van natuurlike woude in die land. Ongeveer 7.0% van die Suid-Afrikaanse landskap is bedek met woude, terwyl Tanzanie en Zambia onderskeidelik 37% en 42% bedek is. Verlaagde voorraad van woude, gepaard met die toenemende vraag na woudhulpbronne, het tot gevolg dat die waade van woudhulpbronne styg. Natuurlik is daar 'n groter behoefte vir die woud-arm Suid-Afrika om verstandige bewaingsbeleid na te streef om sy beperkte woude te beskerm as Tanzanie en Zambie, waa hulle regerings hul onderskeie ge\Yeldigegrond en woudhulpbronne behandel as 'n veiligheidsklep vir ekonomiese ontbering, sonder voldoende belegging in VBB. As opsomming, is die benutting en bestuur van woudhulpbronne in Tanzania en Zambia met mark- en beleidsmislukking besaai. Dit word beoog dat die geleenthede en beperkinge wat met elke mark- en beleidsmislukking ge'identifiseer is, toekomstige bosbou en verwante beleidvormingsproses kan inlig, nie net in die betrokke lande nie, maar ook in ander Afrika lande wat soortgelyke woudbewarings probleme ondervind.

Thesis (PhD(For))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Widdringtonia whytei is a tropical endemic, fire-adapted pioneer coniferous tree species within natural fire-fragmented Afromontane forest patches in a confined area on Mulanje Mountain in Malawi. Natural and anthropogenic fires within the surrounding fire-prone landscape, insect attacks, and uncontrolled harvesting of mature trees for timber threaten the survival of W. whytei. This study investigated the effects of population fragmentation on the reproductive biology of W. whytei, through four specific studies: effects of population size, tree size and crown position on viable seed output; seed rain variation among population sizes; effects of temperature and light on viability and germination of W. whytei seeds; and the influence of population size on natural regeneration patterns. The study was conducted during 2008 and 2009 on three sites using three W. whytei population sizes: small (≤10 reproductively mature cone-bearing W. whytei trees), medium (11-20 cone-bearing trees) and large (>20 cone-bearing trees). Data were collected using field and laboratory experiments and a review of secondary information. The effect of fragment size and crown position on viable seed output and seed rain pattern was tested with a nested linear mixed model. The influence of stem diameter (dbh) on viable seed output was tested using a separate data set. The variation in seed rain was explored with a generalised linear model (GLM) with a negative binomial link function. Variations in seed germination was analysed with a Weibull regression model. The influence of fragment size on seedling regeneration was tested with a GLM (binary logistic regression). Viable seed output from W. whytei cones was very low (23%) and was not affected by population size, tree diameter or crown position. W. whytei population size influenced seed rain with large fragments having higher seed rain densities. Number of dispersed seeds was generally very low and poorly dispersed. W. whytei cones are semiserotinous and depends on moderate to severe fires for heavy seedfall and wider dispersal. Such fires did not occur during the study period. Temperature is a critical factor for seed germination. Seeds germinate between 15 and 25°C with the optimum at ~ 20°C either under light or dark conditions. Regeneration density followed the seed rain pattern indicating that seed availability is a critical factor for regeneration. Regular cool fires outside the forest patches and along the edges during the hot dry season, and the thick litter layer and shady conditions inside forest patches, caused most of the seedling mortality. This study highlighted the difficulties W. whytei experiences with low output of viable seed, limited seed dispersal and low seedling regeneration in and around forest patches, i.e. factors important for conservation management of this species. It is recommended that gaps with diameter equal to canopy height and occasional spot fires would promote seed dispersal onto exposed mineral soil for rapid seedling establishment and subsequent population growth. Such natural fire disturbance events may show the true seed rain and seedling establishment patterns in this species. / AFRIKAANSE OPSOMMING: Widdringtonia whytei is ‘n tropiese endemiese, vuuraangepaste pionier naaldhoutagtige boomsoort binne die natuurlike vuurgefragmenteerde Afromontane woudkolle binne ‘n beperkte area op Mulanje berg in Malawi. Natuurlike en menslike vure binne die omringende vuurgeneigde landskap, insekaanvalle, en onbeheerde kap van volwasse bome vir hout bedreig die voortbestaan van W. whytei. Hierdie studie het die effek van populasiefragmentasie op die voortplantingsbiologie van W. whytei ondersoek, deur vier spesifieke studies: die effek van populasiegrootte, boomgrootte en kroonposisie op produksie van lewenskragtige saad; saadreënvariasie tussen populasiegroottes; die effek van temperatuur en lig op lewenskragtigheid en ontkieming van W. whytei saad; en die invloed van populasiegrootte op natuurlike verjongingspatrone. Die studie is gedurende 2008 en 2009 uitgevoer op drie groeiplekke met drie W. whytei populasiegroottes: klein (≤10 keëldraende (volwasse) W. whytei bome), medium (11-20 keëldraende bome) en groot (>20 keëldraende bome). Data is versamel in veld- en laboratorium eksperimente asook 'n oorsig van sekondêre inligting. Die invloed van populasie fragmentgrootte en kroonposisie van bome op saadproduksie en die saadreënpatroon is getoets met ‘n geneste liniêre gemengde model. Die invloed van boomstamdeursnee op die produksie van kiemkragtige saad is met ‘n aparte datastel getoets. Die variasie in saadreënpatroon is met 'n algemene liniêre model (GLM) met 'n negatiewe binomiese skakelfunksie getoets. Variasies in ontkiemingspersentasie van sade is met 'n Weibull regressiemodel ontleed. Die invloed van fragmentgrootte op saailingverjonging is met 'n algemene linêre model (binêre logistiese regressie) getoets. Produksie van lewenskragtige saad in W. whytei keëls was baie lag (23%) en was nie deur populasiegrootte, boomstamdeursnee of kroonposisie beïnvloed nie. W. whytei populasiegrootte het saadreën beïnvloed en groot fragmente het groter saadreëndigthede gehad. Die aantal verspreide sade was in die algemeen baie laag en swak versprei. W. whytei keëls is semi-saadhoudend (serotinous) en is afhanklik van matige tot intense vure vir massiewe saadvrystelling en wyer saadverspreiding. Sulke vure het nie gedurende die studieperiode voorgekom nie. Temperatuur is ‘n kritiese factor vir saadontkieming. Sade ontkiem goed tussen 15 en 25°C met die optimum rondom ~ 20°C onder beide lig en donker toestande. Fragmentgrootte het nie die saailingverjonging in W. whytei beïnvloed nie. Verjongingsdigtheid het die saadreënpatroon gevolg, wat daarop dui dat saadbeskikbaarheid ‘n kritiese factor is vir saailingverjonging. Gereelde koel vure buite die woudkolle en langs die woudrand gedurende die droë warm seisoen, en die dik lae blaarval (litter) en skadutoestande binne ‘n woud, het meeste van die saailingmortaliteit veroorsaak. Hierdie studie het die probleme beklemtoon wat W. whytei ondervind met die lae produksie van kiemkragtige saad, saadverspreiding en saailingverjonging binne en rondom die woudkolle, m.a.w. faktore wat belangrik is vir bewaringsbestuur van hierdie boomsoort. Die aanbeveling word gemaak dat kroonopeninge met ‘n deursnee gelyk aan minstens die kroonhoogte, en sporadiese kolbrande binne die woudkolle kan saadverspreiding op blootgestelde minerale grond vir vinnige saailingvestiging en gevolglike populasiegroei bevorder. Sodanige vuurversteuringsgeleenthede mag die werklike patrone in saadreën en saailingvestiging in hierdie species toon.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Access to secure energy supplies is widely acknowledged as a critical foundation for sustainable development. Rural households are highly dependent on forest resources for their livelihoods including energy needs. Fuelwood is a non-timber forest product (NTFP) that accounts for one of the main uses of forests and woodlands. Despite substantial household electrification programmes in South Africa, the use of fuelwood as a source of energy continues. This study aimed to analyze fuelwood use patterns of two rural villages situated in Keiskammahoek in the Eastern Cape Province of South Africa in order to understand the perceptions of the community members regarding communal tree planting. The study was conducted in two rural villages, namely, Cata and Tshoxa. A total of 120 respondents from both villages were interviewed using semi-structured questionnaires to collect data on the use of fuelwood and evaluate their perception on tree planting. The study revealed that up to 77% of the people living in Keiskammahoek used fuelwood as a major source of energy and that women were the main collectors and users of fuelwood. In the rural Cata, food is cooked in three-legged pots over open fires while in Tshoxa food is mainly cooked over paraffin and electric stoves. The respondents from both villages did not have energy conservation measures in place and improved wood stoves have not been introduced in this region. The local community of Cata was also involved in tree planting on a community level, while both villages were also involved in tree planting at a household level. The study concluded that fuelwood was the most important product from the forests in both rural areas and natural forests were a valuable source of other NTFPs; most notably indigenous fruit products. In addition most of the fuelwood was used for cooking and heating purposes but that there was no deliberate use of energy efficient methods. On tree planting, the study showed that communities from both rural villages have an interest in planting trees around their households; with preference for fruit and shade trees. / AFRIKAANSE OPSOMMING: Toegang tot betroubare energieverskaffing word algemeen erken as 'n uiters belangrike grondslag vir volhoubare ontwikkeling. Plattelandse huishoudings is hoogs afhanklik van bosbronne vir hul bestaan, met inbegrip van energiebehoeftes. Brandhout is 'n nie-hout bosproduk (NHBP) wat beskou word as een van die hoofgebruike van woude en boslande. Nieteenstaande wesenlike elektrifiseringsprogramme vir huishoudings in Suid-Afrika, duur die gebruik van brandhout as 'n bron van energie voort. Hierdie studie het beoog om die gebruikspatrone van brandhout van twee plattelandse dorpe in Keiskammahoek in die Oos-Kaapse Provinsie van Suid-Afrika te ontleed en om die begrip van die gemeenskap aangaande die gemeenskaplike plant van bome te verstaan. Die studie is in twee plattelandse dorpe, naamlik Cata en Tshoxa, uitgevoer. Onderhoude is gevoer met 'n totaal van 120 respondente van beide dorpe deur die gebruik van halfgestruktureerde vraelyste om gegewens oor die gebruik van brandhout in te samel en die respondente se begrip van die plant van bome te evalueer. Die studie het aan die lig gebring dat tot 77% van die mense wat in Keiskammahoek woon, brandhout as 'n hoofbron van energie gebruik en dat vrouens die hoofgaarders en gebruikers van brandhout is. In die landelike Cata word kos in driepootpotte op oop vure gekook terwyl kos in Tshoxa hoofsaaklik op paraffien- en elektriese stowe gekook word. Die respondente van beide dorpe het nie energiebesparingsmaatreëls in plek gehad nie en verbeterde houtstowe is nog nie in hierdie streek ingebring nie. Die plaaslike gemeenskap van Cata was ook betrokke by die plant van bome op 'n gemeenskapsvlak, terwyl beide dorpe ook betrokke was by die plant van bome op 'n huishoudelike vlak. Die studie het tot ’n gevolgtrekking gekom dat brandhout die belangrikste produk van die woude in beide plattelandse gebiede is en dat die natuurlike woude 'n belangrike bron van ander NHBP’s is; veral inheemse vrugteprodukte. Daarbenewens is meeste van die brandhout gebruik vir kook- en verhittingsdoeleindes, maar daar was geen doelbewuste gebruik van energiedoeltreffende metodes nie. Op die gebied van die plant van bome het die studie getoon dat die gemeenskappe van beide plattelandse dorpe belange het in die plant van bome rondom hulle huishoudings; met voorkeur aan vrugte- en skadubome.

Thesis (MscFor)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The purpose of the study was to investigate the effect of mid rotation fertilizer application on leaf area index (LAI), basal area and volume increment in thinned Pinus radiata stands on the most common soils of the Boland region in the Western Cape. The study was conducted on a range of sites in the Boland region of MTO Forestry Company, chosen to reflect the two most common soil types and a water availability gradient in each soil type. A factorial combination of fertilizer treatments with three levels each for nitrogen (N) at 0, 100 and 200 kg ha-1 and phosphorus (P) at 0, 50 and 100 kg ha- 1 was used. This design was replicated four times across a gradient of water availability for each of the two common soil groups, forming a complete trial series. All replications were laid out in P. radiata stands that had received their mid-rotation thinning prior to treatment implementation. LAI, diameter at breast height and height measurements as well as foliar analysis were determined before the implementation of the study in 2008 and then subsequently at predetermined intervals in 2009 and 2010. Leaf area index and stem volume increment were measured in order to evaluate the influence on growth efficiency. LAI was estimated using the gap fraction method with the use of a ceptometer. Volume increment was calculated using diameter and height measurements and basal area was calculated by means of diameter measurements. The abovementioned growth responses were then used to determine the effect of increased nutrient availability on stand growth. There were no significant interactions detected between any of the factors, N, P and water availability class in their effect on LAI, basal area, volume increment and growth efficiency. LAI increment responded significantly to N and P in the first year but only to P in the second year after treatment. Significant basal area responses to N and P were recorded in the second but not the first year. This might have been due to the fact that trees had to re-build their canopies after thinning before a basal area response could be obtained. For the variables where an analysis of total growth response over the two year period was done, basal area increment and volume increment significantly responded to the application of nitrogen but not to phosphorus. Growth efficiency was not significantly influenced by either nitrogen or phosphorus over the full two year monitoring period. Water availability class consistently and significantly influenced basal area increment, volume increment and growth efficiency over the two year period as well as during year one and year two. The best responses generally occurred as a result of the additive effects of N and P. The growth response did not remain the same across the water availability classes. The wetter sites tended to have greater responses than the drier sites. Although these are still early results, the growth responses could be attributed to an increase in LAI. Nutrient analysis through vector analysis indicated that the additional N and P from fertilizer application were taken up by the trees thereby resulting in greater LAI and increased stem wood production. / AFRIKAANSE OPSOMMING: Die studie het ten doel gestel om die effek van mid-rotasie bemesting op blaar oppervlak indeks (BOI), basale oppervlakte- en volume aanwas te ondersoek in gedunde opstande van Pinus radiata op die mees algemene grondtipes van die Bolandstreek, Wes-Kaapland. Eksperimente is uitgelê oor 'n reeks van groeiplekke in die Bolandstreek wat gekies is om 'n water beskibaarheidsgradient te verteenwoordig oor elk van die twee mees algemene grondtipes. 'n Faktoriaal-kombinasie van kunsmisbehandelings met drie vlakke elk van stikstof [(N) teen 0, 100 en 200 kg ha-1] en fosfor [(P) teen 0, 50 en 100 kg ha-1] is toegedien. Hierdie ontwerp is vier maal herhaal oor 'n gradient van grondwater beskikbaarheid, oor elk van die twee mees algemene grondtipes, om sodoende 'n volledige eksperimentele reeks te vorm. Elke herhaling is uitgelê in 'n P. radiata opstand wat reeds 'n mid-rotasie dunning ondergaan het voor implementering van die kunsmis behandelings. Metings van BOI, deursnee op borshoogte, boomhoogte asook blaarmonsters is geneem voor implementering in 2008 en daarna met vooraf bepaalde tussenposes in 2009 en 2010. Die BOI en stam volume aanwas is bepaal om die effek van behandelings op groeieffektiwiteit te evalueer. Die gaping fraksie tegniek is gebruik om BOI te skat met behulp van 'n sonvlek septometer. Volume aanwas is bereken vanaf deursnee en hoogtemetings en basale oppervlak aanwas vanaf deursnee-metings. Metings van al bogenoemde groeireaksies is gebruik om die effek van verhoogde voedingstof beskikbaarheid op opstandsgroei te evalueer. Daar was geen betekenisvolle interaksies tussen enige van die faktore N, P of water beskikbaarheidsklas met betrekking tot reaksies op BOI, basale oppervlak- en volume aanwas of groei-effektiwiteit nie. Die BOI het betekenisvol gereageer op N en P in die eerste jaar, maar slegs op P in die tweede jaar na behandeling. Basale oppervlakte aanwas is betekenisvol verbeter deur N en P in die tweede jaar maar nie in die eerste jaar nie. Dit is waarskynlik as gevolg van die feit dat opstande eers hul kroondak moes herstel (na dunnings) voordat 'n reaksie in basale oppervlak verkry kon word. Vir die veranderlikes waar 'n analise van die groeireaksie oor die volle twee jaar moniteringsperiode gedoen is, het basale oppervlak- en volume aanwas betekenisvol gereageer op stikstof maar nie op fosfor nie. Groei-effektiwiteit is nie betekenisvol geaffekteer deur N of P oor die volle twee jaar moniteringsperiode nie. Water beskikbaarheidsklas het basale oppervlak en volume aanwas asook groei-effektiwiteit betekenisvol en voortdurend beïnvloed in die eerste en tweede jaar, asook gedurende die volle twee jaar moniteringsperiode. Die beste groeireaksie is oor die algemeen verkry waar N en P gesamentlik toegedien is en waar dus aanvullende reaksies verkry is. Groeireaksies het betekenisvol verskil na gelang van water beskikbaarheidsklas, met die grootste reaksie op die natste groeiplekke. Hoewel hierdie vroeë resultate is, kan ons die meganisme van die reaksie primêr toeskryf aan 'n toename in BOI. Vektor analise van blaar voedingstof vlakke het aangedui dat addisionele N en P na kunsmis toediening opgeneem is, wat die weg gebaan het vir 'n toename in BOI en verhoogde volume aanwas.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2005. / The aim of this study was to develop a set of models that will allow the determination of volume for Tectona grandis trees and stands grown in plantation form in Tanzania. As a secondary objective, models describing tree and dominant stand height were developed. Total volume and volume ratio models were fitted that respectively predict total tree volume and merchantable volume. In order to allow the calculation of volume for different product classes and dimensions, taper models were fitted. All the data were collected by non-destructive sampling methods using a Barr and Stroud optical dendrometer. This proved to be an accurate and inexpensive method of collecting data for developing volume and taper models. Sampling stratification was based on age and site quality and as wide a range as possible was covered to ensure adequate representation of all growing sites and ages present in Tanzanian teak plantations. A total of 2617 individual observations were made from 222 trees at three teak plantations. Several models were selected from the literature to describe teak volume and shape. Results indicated that the Schumacher and Hall (1933) volume equation best describes total volume over and underbark to a fixed upper limit of 7.5 cm. Merchantable volume to upper stem diameter and height limits were best described by respectively the Burkhart (1977) volume ratio model and the Cao and Burkhart (1980) modification thereof. Many of the fitted taper models were unable to adequately describe stem shape over the whole stem, mainly due to the large range in tree sizes and ages used in model fitting. The variable form taper model by Perez, Burkhart and Stiff (1990) provided the best results according to various criteria and is recommended for predicting teak underbark diameters to various heights and, if only a single model is required, the merchantable volume. Top height growth of teak stands was adequately described by the generalized Schumacher (1939) model with the value of the exponent k estimated from the sample data. From this a series of anamorphic site index curves were developed. Suitable height-dbh curves were obtained by a simple linear model and predictions improved by including stand age and site index as predictor variables.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2007. / The study was undertaken to determine the potential physiological benefits to plants provided by the double colonisation of host plant roots by endomycorrhizal (AM) and ectomycorrhizal (ECM) fungi, when growing under normal and under salt stress conditions. Plants of the Eucalyptus grandis x E. camaldulensis clone were grown in a sterile soil with 0 and 75 mM NaCl and with or without infection with the fungi Glomus etunicatum (an AM fungus) and Pisolithus tinctorius (an ECM fungus). The Eucalyptus clone formed both ECM and AM in single and double inoculation. The mycorrhizal symbiosis did not provide any nutritional benefits to the hosts. The double colonisation had no effect on plant growth under normal growth conditions while single colonisations of AM and ECM reduced growth. Double colonisation reduced host plant specific leaf mass by 12% and increased total leaf area by 43% compared with the control under these growth conditions. This colonisation also reduced photosynthesis per leaf area by 29% compared with the control. The reduced photosynthesis of the double colonisation did not result in reduced plant growth because these plants may have had a high total plant photosynthesis because of their large total leaf area. The double symbiosis however did not reduce salt stress when host plants were exposed to 75 mM NaCl, while the AM fungus increased plant dry weight by 13% compared to the control. AM and ECM colonisation in the double colonised roots under salt stress was decreased by 18 and 43% compared to that in plants under normal growth. The reduced colonisation may have reduced the fungi’s abilities to be beneficial to the host plant. The double symbiosis is recommended based on the documented positive effects of this symbiosis to plant growth and the considered possible long-term benefits to host plants growing in saline soils.