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- Volume 2005, Issue 204, 2005
Southern African Forestry Journal - Volume 2005, Issue 204, 2005
Volume 2005, Issue 204, 2005
Author Mary ScholesSource: Southern African Forestry Journal 2005, pp 1 –2 (2005)More Less
Extracted from text ... Southern African Forestry Journal - No. 204, July 2005 1 Guest Editorial Scientific excellence: A decent legacy Citations still remain the key tool for analyses of scientific impact. South Africa produces only 0.5% of the global publications (1997-2001), trailing way behind Brazil, Taiwan, and Greece (King, 2004). Sustainable economic development in competitive global markets requires a direct engagement in the generation of knowledge. Constructive engagement between the North and the South and between partners in the South requires recognition of scientific capacity and delivery. As King points out, citation statistics can also mask a great deal. We want to improve ..
Prescribed under-canopy burning in Pinus patula plantations of the Mpumalanga highveld : the effects of fire on tree growth : scientific paperSource: Southern African Forestry Journal 2005, pp 3 –13 (2005)More Less
The effect of controlled undercanopy burning on tree growth has been studied under 16-year-old <I>Pinus patula</I> trees in Mpumalanga. Three fire intensity treatments and a control "no-burn" treatment, were applied to 1 ha plots. Average fuel depth was 42cm with a mean fuel load of 14.3 tons/ha. Fuel load was reduced by 15%, 30% and 60% in the three intensity burns. Fire intensity parameters were calculated using the BEHAVE fire behaviour prediction and fuel modeling system. Fireline intensity was predicted to be 134, 277 and 761kW/m for low, medium and high intensity experimental burns, respectively. Bark scorch height was found to be significantly greater in the plots under the high intensity burn treatment than in the low and medium intensity treatments. Most trees experienced scorch damage to between 0 and 40% of the crown volume. There was a significant negative effect on tree growth after a period of 36 months in the high intensity burn treatment. A low level (3 dead trees in sample of 360) of mortality occurred. This study showed clearly that undercanopy burning, at a low intensity, could significantly reduce fuel loads without resulting in decreased tree growth. It is recommended that this approach should be explored at an operational scale.
Root volume and raising period affect field performance of Pinus patula cuttings in South Africa : scientific paperSource: Southern African Forestry Journal 2005, pp 15 –21 (2005)More Less
The propagation of pines through cuttings has become a commercial means of rapidly multiplying improved genetic material for operational use in forestry companies. Cuttings of pines are produced entirely in containers in South Africa. Containers, however, can negatively affect plant growth and postplanting field performance if plants are allowed to grow beyond the constraints of the root cavity. The aim of this study was to determine the effects of tray type and plant age on the field performance of <I>Pinus patula</I> rooted cuttings. Field assessments indicate that the combination of greater root mass at planting and increased media volumes improved field growth with the most significant response observed in stem diameter. Factors responsible for producing greater root dry mass at planting were increased media volume and a longer raising period in the nursery. Seven years after planting, cuttings with the largest root mass at planting (0.560 g) were 27% larger in individual tree volume than trees produced from cuttings having the smallest root mass at planting (0.159 g). Field survival was exceptionally good and did not differ among nursery treatments.
Production speed effects on log-making error rates and value recovery for a mechanized processing operation in radiata pine in New Zealand : management paperSource: Southern African Forestry Journal 2005, pp 23 –35 (2005)More Less
Mechanized processing operations are complex "man-machine" systems. The impacts of changes to work practices are, therefore, dependent on the effects the changes have on both the machine and the man. A mechanized processor, delimbing and cutting tree length stems into logs on a landing, was studied in two <I>Pinus radiata</I> plantation forest stands in New Zealand in early 2004 to determine the effect that production speed had on operator decision making and on the machine measurement accuracy and precision. The processor operator was experienced and had a reputation for high value recovery performance. The operator was asked on four occasions to process stems at different production speeds; slow, normal, fast and very fast. Over 150 stems were processed into 849 logs during the four trials. Value recovery, log-making error rates and productivity were assessed during each of the trials. It was found that production speeds ranging from 430 to 610 m3 per day had no impact on gross value recovery, the types of logs cut, or log-making error rates. It was also found that, while length measurement accuracy was not affected by production speed, length measurement precision decreased with higher speeds. Diameter measurement accuracy and precision were both affected by production speed, but there was no obvious trend. Net value recovery increased at higher production speeds as a result of lower production costs.
Application of a 'stem number guide curve' for sustainable harvest control in the dry woodland savanna of northern Namibia : research noteSource: Southern African Forestry Journal 2005, pp 37 –44 (2005)More Less
The savanna woodlands of north-eastern Namibia are a significant source of essential resources for the rural population. Thus far, however, there is little or no growth data available to predict future timber supplies and current yield regulation is limited to the issuing of harvesting permits based on the assessment of available tree sizes, rather than a tree population as a whole. This paper presents the negative exponential function for the development of a guide curve. The curve defines an optimum stand structure based on desired timber yields for specific tree sizes, the intrinsic mortality rates of individual species and the total desirable stocking of a stand. The application of the approach is assessed using the size class distributions of two prominent tree species of the Kanovlei area in north-eastern Namibia. While the function models the development of the populations of the species well, timber and non-timber trees will need to be modelled separately. In the coming years it will be an important priority to establish a system of sample plots to obtain growth data that may support or augment the system.