Thesis (MScFor)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Information on the external shape and internal properties of a tree such as the branch structure, tree ring widths and formation, and defects such as resin pockets is important for many forest –and wood science researchers as well as for the forest and wood processing industries. Resin pockets are internal defects associated with some softwood species, and are undesirable in some wood applications such as furniture and veneer. A tool that is often used in research to obtain this information is the Computed Tomography scanner. The high cost of the scanner, as well as the cost of transporting logs to the scanner, limits the application range of this equipment. An alternative, lower cost method would be beneficial for many researchers interested in tree shape and macroscopic internal tree characteristics. The objectives of this study were to: - Design, construct and test a mobile system that can be used in field to obtain a three‐dimensional model of a log or tree stem indicating selected macroscopic internal characteristics and, - Interpret results to explain the occurrence and causes of resin pockets in Pinus patula from the Mpumalanga escarpment, South Africa. A system for dissecting and measuring trees in field was designed, constructed and tested. The metal frame was used to cut a stationary, fixed log into discs and obtain digital images of crosssections along the stem axis. The frame was capable of processing logs with maximum dimensions of 3 m in length and 45 cm in diameter. Software was developed to convert the digital images into three‐dimensional models of logs and trees to demonstrate properties such as the external shape of the trees, branch structure and pith location. Properties such as ring width were measured from the images obtained. The study was conducted in the Mpumalanga escarpment to obtain three‐dimensional models of Pinus patula trees and to establish the reason for formation of resin pockets in these trees. Four 3 m logs from twenty‐four trees from three compartments were dissected and digitally reconstructed into three‐dimensional models. A total of 61 cross sections with resin pockets were identified from the 2750 cross cut images taken 20 cm apart along the longitudinal axis of the log. It was not possible to accept or reject conclusively any of the existing hypotheses for the cause of resin pocket formation. The formation of Type 2 resin pockets was most probably due to felling damage during thinning operations. It seems likely that wind damage and possibly insects might be responsible for the formation of Type 1 resin pockets. / AFRIKAANSE OPSOMMING: Kennis in verband met die interne eienskappe van ‘n boom soos takeienskappe, jaarringwydte en vorm, en harsholtes is belangrik vir sommige bos ‐en houtkundige navorsers. Die toerusting wat huidiglik algemeen gebruik word om inligting van hierdie aard te bekom is ‘n CT skandeerder. Die metode is egter duur as gevolg van hoë kapitale koste van die toerusting sowel as die vervoerkoste van stompe na die CT‐fasiliteit. ‘n Meer ekonomiese alternatief sal vir baie navorsers van waarde wees. Harsholtes in hout lei tot afgradering van hout en fineer. Die doel van die studie was twee‐sydig: - Om ‘n stelsel te ontwerp en bou wat ‘n drie‐dimensionele model van ‘n boom kan skep wat sommige makroskopiese, interne eienskappe weergee, en - Om die voorkoms en oorsaak van harsholtes in Pinus Patula van die Mpumalanga platorand te ondersoek. ‘n Raam is ontwerp en vervaardig wat in die plantasie gebruik word. Die raam kan stompe van tot drie meter lengte met ‘n maksimale diameter van 45 cm hanteer. Die raam is gebruik om snitte deur die stompe te maak, ‘n afstandmeting tot by die gesaagde oppervlak word deur ‘n lasermeter geneem en ‘n kamera neem ‘n foto. Sagteware word dan gebruik vir die uitkenning van sekere dele in elke beeld sowel as die samestelling van ‘n drie‐dimensionele model. Data‐insameling met die raam is in Mpumalanga gedoen. Die raam is in die tydperk getoets en het goed gefunksioneer. Vier stompe elk vanaf vier‐en‐twintig bome vanuit drie afsonderlike kompartemente is verwerk op die raam en volledige drie‐dimensionele modelle geskep vir hierdie bome insluitend hul eksterne vorm, takeienskappe en pitvorm (“pith location”). Ongeveer 2750 foto’s van dwarssnitte is tydens data‐insameling geneem. Net 61 van die foto’s het harsholtes bevat. Geen definitiewe oorsaak van harsholtes kon bepaal word nie. Tipe 2 harsholtes word waarskynlik as gevolg van skade tydens uitdunning van bome gevorm. Wind en insekte lyk na die mees waarskynlike oorsake van Tipe 1 harsholtes.

Thesis (MScFor)--Stellenbosch University, 2013. / 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 (PhD(For))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Pinus patula is the most intensively planted conifer in the tropics and sub‐tropics. In South Africa Pinus patula plantations are the main saw‐log resource for structural lumber production. Improved intensive silvicultural practices and tree breeding have resulted in marked increases in the rate of growth. To reap the financial benefits of the faster growth, plantation managers are more and more inclined to reduce rotation ages, which inevitably results in the production of higher proportions of juvenile wood at final harvest, and lumber which often does not meet the minimum requirements for stiffness for structural lumber. Knowledge of the variation and the accurate prediction of the mechanical properties of the timber of standing trees can have various benefits for growers and processors of trees. It can be used for tree allocation to different processing facilities, for processing production planning, and to assist tree breeders to screen and select for superior breeding material. The objectives of this study were (1), to examine the within‐ and between‐tree variation in wood properties of young South African grown Pinus patula trees known to have important impacts on the suitability of sawn lumber for structural purposes and (2), to develop empirical prediction models for the flexural lumber properties from standing Pinus patula, based on variables that could be assessed non‐destructively from standing trees. Sample material was obtained from 170 trees (16‐20 years old) established in 17 compartments along the Mpumalanga escarpment of South Africa. A large number of variables which could be obtained non‐destructively from the trees while they were still standing, were measured. The trees were subsequently felled and two logs, 2.1 m in length, were extracted from each tree at two height positions. The 340 logs were processed into 1402 pieces of lumber for further measurements and destructive testing. Results showed that the mean modulus of elasticity measured on edge (MOEedge) was far below the limits set for structural grade softwood timber in South Africa. All the desirable properties for structural lumber improved with distance from the pith with the exception of the 5th percentile value for modulus of rupture (MOR), which was higher at the pith than for the boards processed adjacent to the pith. Boards processed from the lower part of the stem were superior in most of the important properties compared to those higher up in the stem. Separate multiple regression models for predicting the average dynamic MOE (MOEdyn) of individual boards, trees and compartments were developed. The models managed to explain 68%, 60% and 95% of the variation in MOEdyn respectively. The models developed for MOR explained 40% and 42% of variability at board and tree level respectively. At compartment level, 80% of the variation in the 5th percentile MOR value could be explained by the model. Sensitivity analyses showed that site index at base age of 10 years, acoustic time‐of‐flight, wood density and ring width were the most influential variables in the MOE models. The models indicated that tree slenderness during early growth seems to play a major role in determining the dynamic MOE and MOR of lumber. This is in agreement with Euler’s buckling theory and the bending stress theory. Microfibril angle (MFA) and density were measured on radial strips taken from a sub‐sample of trees with the Silviscan 3 technology. The mean microfibril angle per year ring in Pinus patula varied between 7o and 29o. In general MFA decreased with distance from the pith and height above ground level. A multiple regression model including microfibril angle, density and ring width explained 71% of the variation in the dynamic MOE of boards. Sensitivity analysis on the model showed that microfibril angle and density had roughly equal influences on predicting the MOEdyn of Pinus patula boards. / AFRIKAANSE OPSOMMING: Pinus patula is die mees aangeplante naaldhoutspesie in die tropiese en sub‐tropiese areas van die wêreld. Dit is die grootste bron van saagblokke vir die produksie van strukturele hout in SA. Intensiewe boskultuurpraktyke en boomteling het gelei tot ‘n merkbare verhoging in die groeitempo van die spesie. Plantasiebestuurders is gevolglik geneig om rotasie‐ouderdomme te verlaag, wat lei tot ‘n groter persentasie jeughout wat nie aan die minimum styfheidvereistes van strukturele hout voldoen nie. Kennis van die variasie en die akkurate voorspelling van die meganiese eienskappe van staande bome kan voordele inhou vir beide die verbouers en verwerkers van bome. Dit kan byvoorbeeld van hulp wees met die toewysing van bome aan verwerkingsfasiliteite, vir produksiebeplanning, en vir ondersteuning met die keuse van teelmateriaal vir boomtelers. Die doelwitte van hierdie studie was (1), om die binne– en tussenboomvariasie in die houteienskappe, wat ‘n bepalende invloed het op die geskiktheid van jong Suid Afrikaanse Pinus patula bome vir strukturele hout produksie, te ondersoek en (2), om empiriese modelle vir die voorspelling van die buigeienskappe van planke te ontwikkel, gebaseer op veranderlikes wat niedestruktief op staande Pinus patula bome ge‐evalueer is. Monsters vir die studie is verkry vanaf 170 bome (16‐20 jaar oud), geplant in 17 vakke op die Mpumalanga platorand van Suid Afrika. ‘n Groot aantal veranderlikes is nie‐destruktief gemeet op die staande bome waarna die bome gevel is en twee saagblokke, 2.1m in lengte, is op twee hoogte posisies uit elke boom verwyder. Die 340 blokke is verwerk tot 1402 planke vir verdere metings en destruktiewe toetse. Resultate het getoon dat die gemiddelde modulus van elastisiteit gemeet op die dwarskant (MOEedge) aansienlik laer was as wat vereis word vir strukturelegraad hout in Suid Afrika. Al die gewenste eienskappe het toegeneem met afstand vanaf die murg behalwe die 5de persentiel breekmodulus (MOR), wat hoër was vir murgplanke as vir aangrensende planke. Planke afkomstig van die laer dele van die stam het oor die algemeen beter eienskappe gehad as planke afkomstig van die hoër dele. Veelvuldige regressiemodelle kon 68%, 60% en 95% van die variasie in die gemiddelde dinamiese MOE (MOEdyn) op die vlak van onderskeidelik individuele planke, bome en vakke verklaar. Die modelle vir MOR kon 40% en 42% van die variasie op onderskeidelik plank‐ en boomvlak verklaar. Die model vir 5de persentiel MOR van vakke kon 80% van die variasie verklaar. ‘n Sensitiwiteitsanalise het aangetoon dat groeiplekindeks op ouderdom 10, akoestiese vlugtyd, digtheid en jaarringwydte die belangrikste veranderlikes was wat MOEdyn beïnvloed het. Die modelle het aangetoon dat die slankheid van bome tydens vroeë groei vermoedelik ‘n belangrike invloed op die MOEdyn en MOR van planke het. Dit is in ooreenstemming met Euler se knikteorie en die buigsterkteteorie. Die mikrofibrilhoek en digtheid van ‘n steekproef van die bome is gemeet met die Silviscan 3 apparaat. Die gemiddelde mikrofibrilhoek per jaarring het tussen 7 o en 29o varieer. Hierdie variasie was hoofsaaklik afhanklik van boomhoogte en aantal jaarringe vanaf die murg. ‘n Veelvuldige regressiemodel wat mikrofibrilhoek, digtheid en jaarringwydte insluit, kon 71% van die variasie in MOEdyn verklaar. ‘n Sensitiwiteitsanalise op die model het aangetoon dat mikrofibrilhoek en digtheid ongeveer ewe belangrik was wat betref hulle invloed op die voorspelde MOEdyn van Pinus patula planke.

Due to the opportunity for afforestation in South Africa being severely limited, extensive research is being carried out on obtaining more wood per given area, improving the quality and value of the wood and on gaining a better understanding of how wood properties influence the characteristics of the pulp it produces. The last mentioned is the main focus of this study. If the variations in pulp, due to variations in wood properties, are better understood, then the existing fibre resource could be more efficiently managed and utilised to maximise its value. The main objective of this study was to determine how variation in physical and chemical properties, from the existing P.patula resource drives variation in pulp strength properties. It is well known that differences in tree age and site index lead to major sources of variation of various wood properties. These two easily measured variables were used in this study to capture a significant amount of variation in the wood of the aforementioned genus that enters a mill. Samples were obtained from two extremes in site quality, as measured by site index, (viz. good and poor sites) and three age ranges (viz. 9-10 years, 13-14 years and 20-21 years) from the KwaZulu-Natal Midlands. Wood chips from each of the six sites were pulped for various lengths of time, using the Kraft pulping method and under the same pulping conditions. A wide range of anatomical and chemical properties of wood and pulp were measured to characterise these samples as extensively as possible. All pulp samples were beaten in a PFI mill, at four different levels. The freeness values of the beaten samples were measured. The physical properties measured on handsheets made from the pulp included sheet density, burst index, tear index, tensile index, tensile energy absorbed, stretch and zero-span tensile strength. Regression models were developed to quantify the impact of the measured variables on each of the strength properties. Principal component analysis was performed on the wood characteristics measured and indicated that tree age is a more critical source of variation in wood properties than site index. The predictions of whole tree wood properties from the properties measured at breast height were excellent. Pulping studies showed that pulp yield, at kappa 20-30, increased with tree age. Wood cellulose proved to be a very good predictor of pulp yield. Xylose and mannose appeared to be most resistant to degradation during pulping. The low yield pulps were easier to refine than those with high yield. This has important implications when considering high yield pulping processes. With regard to pulp strength, the younger material could not achieve the high tear strengths obtained by the older material. However, the tear strengths achieved by these younger sites were comparable with, if not higher than, that obtained by hardwood species. The implications of this is that younger P. patula trees could be used for grades of paper where very high tear strength is not essential, but tensile is (e.g. tissue paper) and that older material can be better used for the purpose of providing the high tear strength needed by certain paper grades (e.g. linerboard and sackkraft). The maximum tensile strength achieved by the younger material was higher than that of the older material. When compared at constant freeness or sheet density, longer cooking times had a deleterious effect on strength properties. Strong predictions of pulp strength from basic wood properties were obtained when strength results were compared at constant freeness and sheet density. Because of the great influence of fibre morphology and chemistry on refining rates and on the resultant strength properties, the results of the study suggest that fibres of greatly different chemical and anatomical characteristics should not be refined together, if beating energy and pulp strength are to be optimised. However, further work is required to evaluate if the separation of fibre resources, to improve pulp quality, would be economically viable. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

The mapping of forest age is important for effective forest inventory as age is indicative of a number of plant physiological processes. Field survey techniques have traditionally been used to collect forest inventory data, but these methods are costly and time-consuming. Remote sensing offers an alternative which is time-effective and cost-effective and can cover large areas. The aim of this research was to assess the capabilities of multispectral and hyperspectral remotely sensed image data and the statistical method, random forest, for Pinus patula age prediction. The first section of this study used spatial and spectral data derived from multispectral QuickBird imagery to predict forest age. Five co-occurrence texture measures (variance, contrast, correlation, homogeneity, and dissimilarity) were calculated on QuickBird panchromatic imagery (0.6 m spatial resolution) using 12 moving window sizes. The spectral data was extracted from visible and near infrared (NIR) QuickBird imagery (2.4 m spatial resolution). Using the random forest ensemble, various methods of combining the spectral and texture variables were evaluated. The best model was achieved using backward variable selection which aims to find the fewest number of input bands while maintaining the highest predictive accuracy. Only five of the original 64 variables were used in the final model (R2 = 0.68). The second part of this study examined the utility of the random forest ensemble and AISA Eagle hyperspectral image data to predict P. patula age. Random forest was used to determine the optimal subset of hyperspectral bands that could predict P. patula age. Two sequential variable selection methods were tested: forward and backward variable selection. Although both methods resulted in the same root mean square error (3.097), the backward variable selection method was unable to significantly reduce the large hyperspectral dataset and selected 206 variables for the model. The forward variable selection method successfully reduced the large dataset to only nine optimal bands while maintaining the highest predictive accuracy from the hyperspectral dataset (R2 = 0.6). Overall, we concluded that (i) remotely sensed data can produce accurate models for P. patula age prediction, (ii) random forest is an effective tool for the combination of spectral and spatial multispectral data, (iii) random forest is an effective tool for variable selection of a high dimensional hyperspectral dataset, and (iv), although random forest has mainly been used as a classifier, it is also a very effective tool for prediction. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Thesis (MSc (Forest and Wood Science))—University of Stellenbosch, 2005. / In this study the mechanical pulping characteristics of Solanum mauritianum (Bugweed) were investigated using Thermomechanical (TMP), Chemithermomechanical (CTMP) and Biothermomechanical (BTMP) methods. Results were compared with those obtained from Pinus patula pulps treated under similar conditions. In the TMP pulping trials, the pretreatment of wood chips involved soaking of chips in water overnight prior to refining. The CTMP pulping trials involved first the impregnation of wood chips with 3% sodium sulfite and 2% sodium carbonate solution for 24 hours before refining. Coculture of hemicellulolytic Aspergillus flavipes and ligninolytic Pycnoporus sanguineus were inoculated to the wood chips in BTMP trials, to enhance wood chip breakdown. Solanum mauritianum (Bugweed) wood chips produced the highest pulp yields and less shive content compared to Pinus patula treated under similar pulping conditions. This could be ascribed to easier fibre separation and lesser fibre damage, as well as its lower extractive content. Results showed that the pretreatment of wood chips prior to TMP pulping increased paper strength properties compared to the pulp prepared from the untreated wood chips. Chemically pretreated wood chips consumed a larger amount of refining energy. With regard to brightness levels, handsheets from Pinus patula pulps recorded lower brightness values than those from Bugweed pulps. This was related to the lighter colour of the Bugweed wood chips and the higher extractive content of Pinus patula. The high brightness level of the CTMP pulps could be attributed to a modification of the lignin chromophores and the extractive removal, which contributed to a lower absorption coefficient of the pulp. Handsheets from BTMP pulps showed a reduction in brightness compared to the TMP and CTMP pulps. This was caused by the darkening of the wood chips during the fungal incubation period. Pulp and paper properties of Bugweed compared favourably to those results published for other hardwoods. The results of this study suggest possibilities for using Bugweed in high yield pulping processes.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: A total of 125 trees covering a range of tree diameters were selected from a progeny trial of open pollinated progenies of Pinus patuia for studies on trait assessments and evaluation for branching characteristics. The trees comprised 25 families with each family having five trees. The trial was 36 months old and was located in a relatively high yielding site in Block B at Usutu in Swaziland. The height, diameter, the number of branches and the number of whorls of each tree were recorded. In addition to these objective assessments on individual trees, trees were given scores for branch size, branch angle, stem straightness and crown coarseness. For the detailed branch evaluation study, trees were marked at 20% and 50% of the total tree height and the section between this range was used. On this section the internode length, the internode diameter, the branch diameter and the branch angle were measured. It was observed that the objective assessments correlated strongly with the scoring (subjective) and it was further recommended that a closer look is needed to consider the prospects of employing subjective assessments as a means of reducing costs incurred during objective trait assessments. The branch sampling study revealed that there were prospects of assessing fewer branches on a tree as opposed to assessing all the branches, which could be a major contributor to the high costs in tree breeding. All three methods used to explore this prospect showed some reasonable agreement with each other in this regard. The best sample is to measure all branches in whorl one and two above 20% tree height followed by sampling four branches, two from the first whorl and two from the second whorl. There is a slight difference in these two samples as determined by the coefficents of determination. The study recommends that four branches can be used in the assessment of the branch angle and the branch diameter on the trees when one considered the cost elements. / AFRIKAANSE OPSOMMING: In 'n ondersoek na die evaluering van tak-eienskappe van Pinus patuIa is 125 bome in 'n oop-bestuifde nageslags-proef geselekteer. Hierdie bome is gekies met groottes wat strek oor 'n wye verskeidenheid van borshoogtedeursnee. Die ondersoek het 25 families ingesluit met elke familie wat uit 5 bome bestaan. Die proef is 36 maande oud en is gevestig in'n hoë produksiearea van Blok B, Usutu, in Swaziland. Die hoogte, borshoogtedeurnee, aantal takke en die hoeveelheid takkranse is gemeet en bepaal by elk van die 125 bome. Verder is punte toegeken vir takgrootte, takhoek, graad van stamkromming en kroon grofheid. In die gedetailleerde tak-evaluasie is slegs die stamseksie tussen 200!o en 50% van die totale boomhoogte gebruik. Op hierdie seksie van die boomstam is die internodale afstand, die internodale deursnee, die takdeursnee en die tak-hoek gemeet. Uit die gegewens wat versamel is, het dit geblyk dat daar sterk korrelasie tussen die objektiewe evaluasie en die subjektiewe evaluasie (met gebruik van kwalitatiewe eienskappe op 'n tellingbasis) verkry is. Hieruit word aanbeveel dat meer aandag aan subjektiewe evaluasie (as vereenvoudigde evaluasieprosedure) bestee word om kostes te besnoei. Die gedetailleerde tak-evaluasiestudie het aangedui dat die gebruik van slegs 'n paar takke, in teenstelling met al die takke op die boom, voordelig kan wees om verdere kostes van evaluasie te bespaar. Die beste monster is om al die takke in die eerste twee takkranse bo 20% boomhoogte te meet. Daarnaas is die beste monster die eerste twee grootste takke in die eerste en tweede takkranse. Die gebruik van hierdie kleiner monsters vir evaluering het in sekere opsigte nog beter voorspellings gelewer as in die gevalle waar al die takke in die eerste takkrans gebruik is. Die studie b aan dat In betroubare monster van vier takke (twee uit elke takkrans bo 20% boomhoogte) geneem kan word om die boom se takeienskappe te be-oordeel.

Ectomycorrhizal (ECM) associations are important elements of forest biomes, connecting and transferring nutrients through an intricate and complex system of hyphal networks, ensuring plants of the nutrients they require, in nutrient poor soil. ECM research and particularly investigations into the diversity of the fungal partners has not received much attention in South Africa, hindering the advance of research in this field. This has been attributed to the difficulty of identifying the mycobionts involved in the symbiosis. The objectives of this study were to examine the ECM fungal diversity associating with Pinus patula, in selected forest plantations in Mpumalanga, South Africa. Both morphological and molecular techniques were used to identify specimens of both sporocarp collections and ECM root tip morphotypes. Morphological analysis of the ECM root tips involved characterisation of root morphology such as colour, branching and texture, and anatomical analysis examined hyphal arrangement in the root mantle and rhizomorphs. Molecular analysis involved sequencing of the Internal Transcribed Spacer (ITS) region and comparative BLAST analysis. Twenty-four sporocarp species were identified from 13 genera, namely: Amanita, Boletus, Clavulina, Inocybe, Lactarius, Rhizopogon, Russula, Scleroderma, Suillus, Tricholoma, Thelephora, Tomentella and Xerocomus. ECM root tip analysis led to the characterisation of 7 wild-type morphotypes identified as an Albatrellus sp., 2 Amanita species, a Rhizopogon sp., Thelephora terrestris, a Tomentella sp. and Scleroderma citrinum. A secondary objective was to determine whether fertilisation treatments within the study sites were responsible for differences in fungal species community structure. No evidence of a change in species diversity or shift in species composition was encountered. It is envisaged that these comprehensive ECM descriptions will be used as reference material to stimulate continued research in this field in South Africa.

The main objective of this thesis was the elucidation of the host-pathogen interaction between Pinus patula and Fusarium circinatum. This was accomplished by studying differential gene expression at the molecular level. Therefore, the first chapter reports the use of PCR-based methods in gene discovery and transcriptome analysis. The use of these techniques in the identification of novel transcripts in host-pathogen interactions addressed. These examples illustrate the differences and strong features of each technique. Chitinases are linked to defence responses in plants. In chapter tw0, the induction of chitinases in P. patula was assessed at both the protein and genetic level. Western blot analysis and enzyme activity assays indicate that chitinase enzyme is not detected a part of the defence response by P. patula after infection by F. circinatum. This was further confirmed by the lack of significant induction of two Pinus chitinase genes, LP6 and PSCHI4, as determined by RT-PCR analysis. Partial DNA sequence homologues for the LP6 and PSCH14 genes were determined and compared with a variety of plant chitinases. The low levels of detectable chitinase induction in P. patula might explain the high levels of susceptibility to the pitch canker fungus observed in seedlings of this tree. Pinus patula, the most widely planted species in South Africa, is highly susceptible to infection by F. circinatum. In chapter three, suppression subtractive hybridisation was used to elucidate the changes taking place at the molecular level early on in this interaction. Most of the identified transcripts shared homology to both biotic and abiotic stress in plants. The induction of one fragment, displaying homology to phytocyanin proteins, as followed through RT-PCR. Induction levels for this fragment differed significantly between less and more susceptible plants. Although most of the sequences isolated in this study can be Iiked to stress, most have not been linked with specific plant-pathogen interactions. This raises questions in regard to the function of these genes in host-pathogen interactions. Further research identify the function of these sequences in the defence response will be needed. These sequences can also be tested against a family of Pinus trees to ascertain if they will be useful in marker assisted selection. A molecular analysis of culture degeneration and pathogenicity of F. circinatum was attempted in chapter four. In this chapter, the differential induction of transcripts in F. circinatum was determined against several other Fusarium spp. Several of he identified fragments shared homology with stress related proteins. One transcript shared homology to a polyketide synthase, FUM5, that could be linked to fumonisin production in other Fusarium spp. ELISA detected no fumonisin production, although the FUM5 transcripts were detected. The identification of all the transcripts could provide a basis for more intensive gene discovery studies in F. circinatum and other Fusarium spp. The induction of these sequences in different isolates needs to be studied to prove their function in F. circinatum. This study also complements several other studies that studied the morphological characteristics of culture degeneration. Resistance gene analogues have been reported from a diverge set of plant species. In chapter five, degenerate PCR amplification was used to isolate TI-NBS-LRR like resistance gene analogues from a range of Pinus species. These sequences w re further characterised through comparative analysis with previously reported Pinus resistance gene analogues. Through motif analysis, several of the known conserved motifs found in NBS domains were identified and conservation with other plant NBS motifs is indicated. The P-Ioop and GLPL motifs displayed a high level of conservation on amino acid level with other plant NBS motifs. However, slight differences in several of the conserved regions were observed when the Pinus analogues were compared with Arabidopsis thaliana. The identification of differences between angiosperm and gymnosperm NBS sequences indicates that design of new degenerate probes and primers for the isolation of more ancient NBS sequences is needed. Further, phylogenetic and structural analyses of these sequences will also aid in understanding the relationship between angiosperm and gymnosperm NBS sequences. The knowledge gained from such a study will highlight the similarities between angiosperm and gymnosperm defence responses. This study represents the first detailed report on RGA in Pinus. / Thesis (PhD)--University of Pretoria, 2006. / Genetics / Unrestricted

Woodlots have become the most important investment opportunity among smallholders of Mufindi district in the southern highlands of Tanzania. Smallholder woodlots are also a major source of wood supply contributing to narrow the supply gap which in 2015 was reported to be 19.5 million m3 per year, where the main wood consumption sectors being construction and domestic heating energy. However, inadequate information about smallholder woodlots, supporting organizations, their linkages and impacts on woodlots performance derail its sustainable development and potential contribution for wood supply and poverty alleviation. The present study therefore specifically explored the tree grower’s motivations, knowledge base and challenges to woodlots farming; assessed woodlot tree species, products, and performance; analyzed the linkages of tree growers with support organizations and evaluated their impacts on the performance of woodlots. Both survey and case study approaches were used to collect data in the three villages namely: Igowole, Mninga, and Nundwe, both in Mufindi district, Tanzania. Mufindi district was purposively selected because of advanced smallholder tree growing. In all the three villages, a total of 93 actors were approached, including 72 tree grower households, 24 from each village, 14 nursery operators and 9 support organizations by snowball sampling. Then, an in-depth interview was conducted to all 72 sampled households. Of which 48 woodlots, 12 - from organized and the other 12 from unorganized tree growers in each village for Igowole and Nundwe, were assessed by rapid appraisal (RA) approach and their performance compared. While 24 woodlots were assessed from Mninga village, and all were from unorganized tree growers. Quantitative data were analyzed using SPSS version 20 and the results summarized in tables and graphs in excel. Woodlots performance and social network data were analyzed using R – software. Based on the study respondents, the results revealed that tree growers were motivated to plant and manage trees mainly for economic reasons (48%, 45%, and 51%) and land security reasons (37%, 30% and 31%) for Igowole, Mninga and Nundwe respectively. About the knowledge base, most tree growers (75% – 100%) in all the three villages had the knowledge on land preparation, nursery management, planting, weeding, pruning, and fire protection. But in all the villages, respondents did not have knowledge on forest growth principles and dynamics, on objectives for the product of the plantations and influence of tree spacing on such desired products. Again, other analyses revealed that; fire, inadequate knowledge, inadequate capital, lack of improved seeds and low timber/tree prices were the main challenges constraining farmers to plant and manage trees in woodlots in the three study villages. And, the main tree species in the study area were Pinus patula and Eucalyptus sp. Organized tree growers where much more supported by organizations than the non-organized ones. Logistic regression analysis performed in R (P = 0.05) revealed significant difference in woodlots performance among organized farmers based on gaps (P = 0.00216), growth condition (P = 0.04478) and planting space (P = 0.02013) criteria. That means, woodlots from organized farmers were generally performing better than those from unorganized farmers. The better performing woodlots of organized tree growers were contributed by social capital through networks and the role of collective action of the farmers in TGAs. Nursery operator farmers were the main source of tree seedlings for unorganized tree growers, while organized tree growers obtained most of the resources including knowledge, seeds and planting materials as well as funds from tree grower associations (TGAs), which were supported by organizations. Thus, for future planning, nursery operator farmers should be supported for improved seeds and planting materials to benefit the nonorganized farmers. Nursery operator farmers should be encouraged to join TGAs, and TGAs should generally be adopted as an effective smallholder tree grower’s support platform in the study area.