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- Volume 2002, Issue 193, 2002
Southern African Forestry Journal - Volume 2002, Issue 193, 2002
Volume 2002, Issue 193, 2002
Author Lael BethlehemSource: Southern African Forestry Journal 2002, pp 1 –4 (2002)More Less
The Government is committed to the sustainable management of South Africa's forests. In 1998 the Government published the National Forests Act, 1998 (Act No. 84 of 1998). Section 3 of the National Forests Act (NFA) recommends the development of a set of Principles, Criteria, Indicators and Standards (P, C, I & S's) for Sustainable Forest Management (SFM). The Government will use the PCI&S to monitor progress towards sustainable forest management and may set minimum regulatory standards for forestry.
Measuring total economic benefits from water in plantation forestry : application of quasi I-O framework to the Crocodile catchment in South Africa : scientific paperSource: Southern African Forestry Journal 2002, pp 5 –14 (2002)More Less
A quasi input-output framework was applied to measuring direct and indirect economic benefits from water use in plantation forestry in the Crocodile river catchment of South Africa. The study accounted for indirect economic benefits generated in downstream timber processing activities and input supply sectors linked with timber plantations as part of the total economic benefits from water use in forestry. The derived measure of total economic benefits from water use was 9 to 16 fold higher than the estimate of direct benefits (in terms of value added and employment) generated at the primary gum and pine production activities (plantation gate), respectively. The study results showed the importance of considering indirect economic benefits realised in forward and backward sectors linked with the primary production activity in evaluating water allocation strategies and policy regimes.
Acacia mearnsii sensitivity to the application of pre-emergent herbicides applied at planting : scientific paperAuthor Keith M. LittleSource: Southern African Forestry Journal 2002, pp 15 –24 (2002)More Less
Five pre-emergent herbicides were applied either on their own or in various combinations to commercially planted <i>Acacia mearnsii</i> De Wild. seedlings in the KwaZulu-Natal Midlands. <i>Acacia mearnsii</i> growth responses to the protected or unprotected application of these herbicides were compared to a weedfree and weedy control. Compared to the weedfree control, suppression from weed competition only caused a significant reduction in tree growth from 92 days after planting, by which stage most of the residual capabilities of the herbicides tested had been reduced. The herbicides which did give good control of both grasses and volunteer wattle regeneration relative to the weedy treatment were oxyfluorfen alone, or when combined with thiazopyr or thiazopyr + metazachlor. When applied as an unprotected spray, only the herbicide combinations of simazine / terbuthylazine and metazachlor did not cause a significant reduction in tree growth. Although only significant at <i>p</i> < 0,1 the herbicides of oxyfluorfen and glyphosate / simazine / terbuthylazine, when applied as an unprotected spray, caused a reduction in tree survival (arcsine transformed) when compared to the weedfree control. Tree variability was found to be a function of the presence or absence of weed growth and the method of herbicide application. Lower tree variability was exhibited in those treatments for which no pre-emergent herbicides were applied or where the seedlings were protected during spraying.
Source: Southern African Forestry Journal 2002, pp 25 –30 (2002)More Less
We have screened 11 microsatellite markers developed in other <i>Pinus</i> species for their ability to produce fingerprints in the <i>Pinus elliottii x Pinus caribaea</i> hybrid as well as their ability to determine gene flow and parental contribution in this hybrid. We found that cross-species amplification was possible with two thirds of the microsatellite markers screened and that by pooling information from several microsatellite loci it was possible to determine gene flow and parental contribution in the hybrid.
Source: Southern African Forestry Journal 2002, pp 31 –38 (2002)More Less
In order to determine factors which could have a positive influence on the coppicing potential of <i>Eucalyptus nitens</i> , a field survey was carried out at Draycott, near Estcourt in the KwaZulu-Natal Midlands. Five measures of the ability to coppice (stump survival, height of coppice, number of dominant shoots, coppicing potential and coppice vigour) were assessed in seven recently felled compartments. Within these compartments 50 sample and 200 sub-sample sites were selected to provide a range of explanatory variables against which the ability to coppice could be assessed. The explanatory variables included factors related to the previous stand of trees as well as various physiographic factors. The data were analysed using correlation and multiple linear regression techniques. Of the explanatory variables, bark damage, stump volume and landscape aspect were able to account for 73 % of the total variation associated with the response variate of coppicing potential. Despite the amount of variance accounted for, aspect and stump volume may prove to be surrogates for factors not assessed, for example soil moisture or tree size when felled respectively. This field survey provides a basis for future studies in this area of research.
Evaluation of methods for estimating the metabolic rate according to ISO 8996 in forestry work in Zimbabwe : scientific paperAuthor Dianne Staal WasterlundSource: Southern African Forestry Journal 2002, pp 39 –46 (2002)More Less
Forestry activities in Southern Africa may expose forest workers to uncompensable heat stress risk when the climate conditions are such that the body experiences difficulties to dissipate its excess heat to the environment. A study was made in North Eastern Zimbabwe during the hot season to evaluate ISO standard methods for heat stress risk determination in manual forestry work. The differences between the metabolic rate assessments by three methods of ISO 8996 were evaluated, as well as the effects of these variations in the assessments on the heat stress risk determination by ISO 7243 and 7933. The results showed significant differences between the metabolic rate assessment methods, with variations of up to 36% for the same observation period. It was also found that the methods responded inconsistently for different activities. ISO 7243 and 7933 gave contradictory assessments of the heat stress risk in the prevailing climate conditions and the differences in the recommended allowable exposure times by ISO 7933 were up to 265 minutes. It is therefore questionable whether the ISO heat stress standard methods in their present versions are applicable to all work situations in forestry.
The influence of site factors on nitrogen mineralization in forest soils of the Mpumalanga escarpment area : South Africa : scientific paperSource: Southern African Forestry Journal 2002, pp 47 –64 (2002)More Less
The complex biophysical environmental conditions that occur in South African forestry plantations prompt appropriate guidelines for nutrient management applications. Nutrient budget studies in plantation ecosystems indicated a negative nitrogen (N) balance on many sites. Empirical fertilizer trails have shown that, although responses are highly variable, the application of inorganic fertilizers remain an efficient means of improving tree growth. This study was carried out to investigate the influence of variable site conditions on N mineralization, as well as the effect of N mineralization on forest productivity. Data were collected from 31 sample plots, covering a wide range of site conditions in the study area. N mineralization was monitored using multi-week <i>in situ</i> incubations, and compared to a wide spectrum of site factors recorded at each sample plot. The phase of plantation canopy closure (age 6-10 years) was used as the reference age. <br> A significant positive correlation was found between NH <sub>4</sub> <sup>+</sup> mineralization during summer and the growth of <i>Pinus patula</i> (r = 0,77, p < 0,001). This process of the N cycle can therefore be considered as the rate limiting step influencing tree growth. N mineralization is controlled by a complex interaction of various site factors, and numerous correlations and interactions between NH<sub>4</sub> <sup>+</sup> mineralization (summer) and site factors are discussed. Statistical models were developed through multiple regression techniques, to predict N mineralization from independent site variables. The <i>in situ</i> rates of N mineralization could be predicted with an acceptable degree of accuracy by making use of the natural log of mean annual temperature, geological substrate and total N levels in the topsoil (r<sup>2</sup> = 0,71). These models are suitable for incorporation into existing plantation decision support systems. The significance of the response in tree growth, following fertilization with N in existing mid-rotation forest nutrition trials, was evaluated against the predictions of N mineralization using the proposed models. An inverse linear model ( r<sup>2</sup>= 0,89, p < 0,0001) was found to best describe this relationship. Additional research on the process of N mineralization in South African plantations is required to provide accurate recommendations on nutrient management for the various forest management practices currently in use.
The effect of a soil-amended hydrogel on the establishment of a Eucalyptus grandis clone on a sandy clay loam soil in Zululand during winter : scientific paperSource: Southern African Forestry Journal 2002, pp 65 –76 (2002)More Less
To ensure acceptable survival and growth of <i>Eucalyptus grandis</i> clonal material planted in the sandy clay loam soils of the Zululand interior of South Africa, the current planting season is limited to the summer rainfall period. A field trial was initiated with the primary objective of being able to successfully extend the planting period (May to September) within which <i>Eucalyptus grandis</i> clones could be planted. This was done by testing tree growth and survival by the addition of a soil-amended hydrogel (Stockosorb 400K) and comparing it to traditional water planting methods. Five levels of water (0 ml, 500 ml, 1000 ml, 2000 ml and 4000 ml) were combined with five levels of hydrogel (0 g, 3 g, 6 g, 9 g, and 12 g) and applied to the pit at planting in a 5x5 factorial design. The tree variates of mortality, height, groundline diameter, crown diameter, corrected leaf surface index (<i>LSI<sub>C</sub></i>) and corrected biomass index (<i>BI<sub>C</sub></i>) were assessed at 7, 47, 86 and 118 days after planting. <br> There was a highly significant (<i>p<0,01</i>) interaction between hydrogel and water which had a positive impact on both transplant survival and growth. There were significant differences between water only treatments when compared with all levels of hydrogel, with the hydrogel treatments performing significantly better. Optimum survival for water only treatments was achieved at the 4000 ml application level (50 %) while optimum survival for hydrogel and water was achieved for 6 g / 1000 ml and 12 g / 2000 ml of hydrogel and water (100 %). There were no significant differences for survival within all but one of the hydrogel treatments over all applications of water. Both the variates <i>LSI<sub>C</sub></i> and <i>BI<sub>C</sub></i> indicated that tree growth was significantly enhanced by the addition of hydrogel over all applications of water. Optimum tree performance was found to occur at 2000 ml water and 12 g hydrogel. <br> The results from this trial indicate the possibility of using a soil-amended hydrogel (Stockosorb 400K) to : <br> i successfully establish a <i>Eucalyptus grandis</i> clone in the Ntonjaneni area during winter, thereby successfully extending the planting season (between May and September) ;<br> ii significantly reduce water volumes used at planting without negatively affecting current silvicultural standards.
Post-establishment vegetation control in a Eucalyptus grandis x E. camaldulensis stand : research noteSource: Southern African Forestry Journal 2002, pp 77 –80 (2002)More Less
In eucalypt plantations, the effect of shading following canopy closure reduces the growth of competing vegetation. In some eucalypt stands full canopy closure is not achieved and the important characteristic of complete shading is lost. This results in stands with the potential to support competitive levels of postestablishment vegetation. A trial was established on a two year old <i>Eucalyptus grandis x E. camaldulensis</i> stand to determine the competitive effect of post-establishment vegetation on tree growth. A weedfree treatment was implemented annually over a period of five years and compared to a weedy control to determine the time period for the post-establishment vegetation to reach competitive levels. There was no significant tree growth or survival response to competition from post-establishment vegetation for the duration of the trial.
Author Dennis L. OwenSource: Southern African Forestry Journal 2002, pp 81 –82 (2002)More Less
Extracted from text ... Southern African Forestry Journal - No. 193, March 2002 81 Information Note Southern African Forestry Journal - It's History Dennis L Owen Editor SA Forestry Journal There is no doubt that our newer readers will be unfamiliar with the origins of our Journal, while it is probable that some of our more seasoned readers may also have forgotten the history of the Journal you have before you to-day. It all commenced in 1937 when the South African Forestry Association (SAFA) was founded by a group of professionals concerned about the welfare of South African forestry. This Association had five objectives, ..
Source: Southern African Forestry Journal 2002, pp 86 –89 (2002)More Less
Extracted from text ... 86 Southern African Forestry Journal No. 193, March 2002 SAFJ Index 2001 SA Forestry Journals: Index No 190, No 191, No 192 Note: This is an abbreviated Index Article Title shown under name of Main Author only. 191/43 (9pp) means - Journal No 191 Page 43 (9 pages) Author Title Journal E-mail address Aalbaek A Farmers tree planting and access to germplasm (Tanzania) 191/75(13pp) firstname.lastname@example.org Alborough D 190/105 Allan R 191/29 Arbuthnot A 192/9 Ballance A et al Valuing SA savannas: Methological 191/43(9pp) email@example.com Baonza V 190/99 Barnes R.D African Acacias: - Thorny Subject 190/9(10pp) firstname.lastname@example.org Barnes R.D. Forest genetics for the Next Millennium Conference Summing up 190/115(4pp) email@example.com Bauer K 192/73 Burgess T et al Exotic pine forestry in South. Hemi.: Quarantine Practices 192/79(5pp) firstname.lastname@example.org Bux ..