Thesis (MScFor)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Nine species in ten different seed source trials were evaluated with the aim of understanding their potential as exotics in improving plantation forestry in Rwanda. Assessment was based on tree growth and stem quality, juvenile-mature and trait-trait phenotypic correlations as well as the relationship of seed source performance and the locational variables of seed origin. Eucalyptus saligna, E. urophylla, Pinus maximinoi and P. tecunumanii proved to be very promising as plantation species and are highly recommended. P. patuia and Grevillea robusta are also recommended for plantation and agroforestry purposes respectively. P. caribaea and P. kesiya proved to be very poorly adapted under local conditions and should be retested if resources were available. All trials except E. urophylla, and P. maximinoi (the two had very few degrees of freedom) showed significant differences of varying degrees in different traits between seed sources indicating their potential for genetic improvement through selection and breeding. Similarly, all trials except E. urophylla, and P. maximinoi indicated significant juvenile-mature phenotypic correlations of varying degrees in different traits, with height showing strongest relationships. On average, trait-trait relationship was observed to be strongest between diameter and volume, followed by height and volume, height and branching pattern, stem form and branching pattern, stem form and height, branching pattern and volume, and diameter (and volume) and stem form in that order. Based on juvenile-mature phenotypic correlations, tree height at 15 and 16 years can be predicted as early as at three years for E. tereticornis (r :::0;.4680) and P. kesiya (r:::;0.5530) respectively, while that at 14 and 16 years in P. tecunumanii (r:::;0.4820) and P. patuia (r:::;0.5562) can be predicted using height at four years. This however may only be true where genetic and phenotypic relations are strong (as may be the case in E. tereticornis since high heritability estimates were obtained). The following additional recommendations are made under this study: To study the effect of growth rate on wood properties of very fast growing pine species; to introduce other tropical species such as E. deglupta and P. oocarpa so as to diversify species; carry out studies to better understand the effect of altitude on the adaptability of the exotic tree species in the tropical and sub tropical environments and lastly, carry out genetic tests in future so as to ascertain the obtained results on age-age and trait-trait correlations in this study. / AFRIKAANSE OPSOMMING: Nege spesies in tien verskillende saadbronproewe is geëvalueer met die doeI om hulle potensiaal as eksotiese spesies te verstaan sodat plantasie-bosbou in Rwanda verbeter kan word. Die evaluering is gebaseer op boomgroei en stamkwaliteit, jongeling-volwasse en eienskap-eienskap fenotipiese korrelasies, sowel as die verhouding tussen saadbronprestasie en die omgewingveranderlikes van saadoorsprong. Eucalyptus saligna, E. urophylla, Pinus maximinoi en P. tecunumanii blyk baie belowend te wees as plantasiespesies en word sterk aanbeveel. P. patuia en Grevillea robusta word ook aanbeveel vir die doeleindes van plantasie- en agrobosbou onderskeidelik. P. caribaea en P. kesiya blyk baie swak aangepas te wees onder plaaslike omstandighede en moes weer getoets te word, sou die hulpmiddele beskikbaar wees. Alle proewe (behalwe E. urophylla en P. maximinoi - dié twee het baie min vryheidsgrade gehad) het beduidende verskille van afwisselende grade getoon tussen saadbronne in verskillende eienskappe. Dit dui aan dat hulle potensiaal het vir genetiese verbetering deur seleksie en teling. Eweneens het alle proewe behalwe E. urophylla en P. maximinoi beduidende jongeling-volwasse fenotipiese korrelasies van afwisselende grade in verskillende eienskappe getoon, met hoogte wat die sterkste verhoudings getoon het. Oor die algemeen was die eienskap-eienskap verhouding die sterkste tussen deursnee en volume, gevolg deur hoogte en volume, hoogte en vertakkingspatroon, stamvorm en vertakkingspatroon, stamvorm en hoogte, vertakkingspatroon en volume, en deursnee Cen volume) en stamvorm, in daardie volgorde. Op grond van jongelingvolwasse fenotipiese korrelasies kan boomhoogte op 15 en 16 jaar op so vroeg as drie jaar voorspel word vir E. tereticornis Cr 0 0.4680) en P. kesiya Cr 0 0.5530) onderskeidelik, terwyl boomhoogte vir P. tecunumanii Cr 00.4820) en P. patuia Cr 0 0.5562) op 14 en 16 jaar voorspel kan word op vier jaar. Dit kan egter net juis wees waar genetiese en fenotipiese verhoudings sterk is (soos die geval kan wees met E. teretiornis, aangesien hoë erflikheidskattings verkry is). Die volgende addisionele aanbevelings word in hierdie studie gemaak: om die effek te bestudeer van die groeitempo op die houteienskappe van denspesies wat baie vinnig groei, te bestudeer; om ander tropiese spesies soos E. deglupta en P. oocarpa ook te betrek ten einde die spesies te diversifiseer; om studies uit te voer ten einde die effek van hoogte op die aanpasbaarheid van die eksotiese boomspesies in die tropiese en subtropiese omgewing beter te verstaan; en laastens, om in die toekoms genetiese toetse uit te voer ten einde die resultate wat in hierdie studie op ouderdom-ouderdom en eienskap-eienskap korrelasies verkry is, te bevestig.

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.