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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53045 |
| Date | 04 1900 |
| Creators | Mugunga, Canisius P. |
| Contributors | Van Wyk, Gerrit, Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 128 pages |
| Rights | Stellenbosch University |
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