H. A. van der Sijde

The Potential of Pine Hybrids in South Africa

SYNOPSIS The performance of a variety of pine hybrids in trials in Zululand and the Transvaal is described. Results are compared with earlier assessments of some Zululand trials. The potential of pine hybrids, especially those of Pinus elliottii and P. caribaea var. hondurensis, for commercial planting in the subtropical regions of South Africa is discussed. Pine hybrids, especially of P. elliottii and P caribaea var. hondurensis, appear to be particularly suitable for large scale use in Zululand, with the possibility of increasing timber production by at least 50 %.

Reaction Wood in Pinus taeda—A Preliminary Report

SYNOPSIS Excessive compression wood has been reported from most young Pinus taeda stands in the summer rainfall region. Huge financial losses are predicted and the Forestry Branch of the Department of Environment Affairs has stopped planting the species until the probability of incidence has been markedly reduced. Climate, site and silvicultural practices do not appear to be causative. An inherited susceptibility in certain seed orchard families has been found which usually coincided with susceptibility to black pine aphid (Cinara cronartii) infestation. The most susceptible families have been removed from the seed orchards and attempts are being made to get the black pine aphid under biological control.

Early results of three blackwood (Acacia melanoxylon) provenance trials in South Africa.

SYNOPSIS A statistical analysis of the growth data of three young blackwood provenance trials, consisting of 12 different provenances, is presented. The trials were established in different forest regions in South Africa. The indications are that on all test sites the Mt Sabine (Vic.), Natal (RSA) and Smithton (Tasm.) provenances were among the five best and the Collingwood River (Tasm.), Stawell (Vic.) and Tallaganda (NSW) provenances were the worst. The Orbost (Vic.) provenance was second in the trials in the Cape forest regions, but was below average in the Transvaal trial.

The Economic Benefits of Forest Tree Breeding

SYNOPSIS The application of research results will increase volume production of forestry plantations and improve the quality of the raw material considerably. This paper illustrates that only one aspect of forestry research, namely tree breeding, will result in volume improvement of 5 to 30%. What does this mean to the industry in terms of money? It is shown that the discounted value of tree improvement potentially available to the industry, is more than R30 million per annum for the six major species grown in South Africa. By contrast, the cost of this research to the forest industry is very low. The present total research budget of less than 1,0% of the Industrys total annual turnover could be raised many fold and still leave the industry with vast “research profits”. If we are serious about self-sufficiency in timber production as stated in our national forest policy, then tree breeding must be our starting point because it will provide increased volume and more versatile and adaptable plantation trees.

Results of an Establishment Trial with Pinus elliottii on the Transvaal Highveld

ABSTRACT In a factorial experiment comprising three site preparation treatments, two weed control and two fertiliser treatments it was found that weed control was the only important factor in establishing pine plantations, favourably affecting both survival and tree growth. Ripping and the application of fertiliser had no effect on survival and basal area growth.

Results of a Small Eucalyptus maculata Provenance Trial

SUMMARY The results of a provenance trial with two imported and one local provenance of E. maculata is given. Differences in volume production were significant, but no differences were found between amount of kino rings in the three provenances.

Wood Density and Growth Rate of Pinus elliottii and Pinus taeda Clones Planted on Two Sites in the Eastern Transvaal / HOUTDIGTHEID EN GROEITEMPO VAN PINUS ELLIOTTI- EN PINUS TAEDA-KLONE OP TWEE GROEIPLEKKE IN OOS-TRANSVAAL GEPLANT

ABSTRACT Eleven years old clonal plantings of Pinus elliottii and P. taeda established on two different sites were sampled to study the variation in wood density. For both species clonal differences were highly significant. Wood density at the high altitude site was consistently lower than that of the same clone at the lower altitude site. Wood density was not correlated with growth rate per site. It was further found that site x clone interaction with regard to wood density was absent, but two P. elliottii clones showed a definite site x clone interaction in respect of diameter growth rate. Density gradient differed largely between the two sites and this difference could not be explained.