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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52130 |
| Date | 12 1900 |
| Creators | Gwebu, Simosabo Bhekinkhosi |
| Contributors | Van Wyk, G., 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 | English |
| Type | Thesis |
| Format | 124 p. : ill. |
| Rights | Stellenbosch University |
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