- A-Z Publications
- Southern African Forestry Journal
- Previous Issues
- Volume 2004, Issue 202, 2004
Southern African Forestry Journal - Volume 2004, Issue 202, 2004
Volume 2004, Issue 202, 2004
Author D.W. Van der ZelSource: Southern African Forestry Journal 2004, pp 1 –2 (2004)More Less
Extracted from text ... Southern African Forestry Journal - No. 202, November 2004 1 Guest Editorial Plantations, wildfires, silted rivers and streamside forests South Africa has always been a country of contrasts and extremes. Drought and floods both occur at regular and irregular intervals. There is therefore this time nothing new out of Africa when some extreme people equate plantations and silted rivers with each other. Already nearly a century ago the Drought Commission also considered plantations as a factor and commissioned government to carry out research on the effect of plantations on river quantity and quality. The South African Forestry Research Institute ..
Modelling maximum canopy conductance and transpiration in Eucalyptus grandis stands not subjected to soil water deficits : scientific paperSource: Southern African Forestry Journal 2004, pp 3 –11 (2004)More Less
There is much current interest in predicting the maximum amount of water that can be transpired by <I>Eucalyptus</I> trees. It is possible that industrial waste water may be applied as irrigation water to eucalypts and it is important to predict the maximum transpiration rates of these plantations in an attempt to dispose of this contaminated water. It is also useful to have a reference against which to compare evapotranspiration at any <I>Eucalyptus</I> site to estimate the degree of reduction in potential water use caused by soil water deficits. This paper proposes a simple model that can be used to predict maximum rates of daily transpiration by short-rotation <I>Eucalyptus grandis</I> plantations experiencing no significant soil water deficits or fertility limitation. Daily sap flow data recorded in a single average tree in an irrigation and fertilisation trial at Came plantation in the KwaZulu-Natal Midlands were used to estimate mean daily canopy conductance. Analysis of daily and seasonal variation in conductance confirmed that solar radiation and vapour pressure deficit are the dominant factors reducing canopy conductance below potential values, when soil water availability is high. A simple canopy conductance model based on these data was then used with the Penman-Monteith equation to predict daily transpiration rates by <I>E. grandis</I> trees at a second site situated on Frankfort plantation in the vicinity of Sabie, Mpumalanga. These model predictions were compared to a mean daily sap flow rate recorded in four sample trees over a full year. Transpiration estimated using the Penman-Monteith equation and canopy conductance model agreed well with the observed daily sap flow (R<sup>2</sup> = 0.79). The total observed annual sap flow at Frankfort was equivalent to 1320 mm, with a mean daily rate of 46 <I>ℓ</I> tree<sup>-1</sup>. The corresponding modelled annual sap flow was 1226 mm. A seasonal change in the relationship between canopy conductance and vapour pressure deficit, observed in a previous study on E. grandis, was again apparent from the Came plantation data.
The effect of the colonisation extent of arbuscular mycorrhizal fungi on the growth of pot grown Pterocarpus angolensis seedlings : scientific paperSource: Southern African Forestry Journal 2004, pp 13 –20 (2004)More Less
The effect of the level of arbuscular mycorrhizal fungi (AMF) colonisation on the growth of <I>Pterocarpus angolensis</I> was studied. Mycorrhizal infected seedlings, showing either good or poor growth, under the same environmental conditions (temperature, humidity, light level) were analyzed for above and below ground biomass and N and P concentration. The grouping was based on the number of leaves and seedling size. All plants had AMF infection, with poor growth plants having a 75% infection and good growth plants 45%. The highly infected poor growth plants had fewer leaves, smaller total leaf area and total plant mass. The below ground plant component N and P concentration of good growth plants was higher than in poor growth plants. There was however no difference in N and P concentrations of above ground components between the two groups. No nodules were recorded for good growth plants while plants in the poor growth group had nodules. There was no difference in the specific leaf mass and shoot:root ratio of the two groups, although the leaf area ratio was higher in good growth plants. The high AMF infection had a negative effect on the growth and development of plants. This study highlighted the presence of AMF in nursery grown <I>Pterocarpus angolensis</I> and the host benefits from various colonisation levels. A long-term field trial is needed to study the effects of different AMF colonization levels on tree vigour under different environmental conditions.
Grade verification of SA pine - bending, modulus of rupture, modulus of elasticity, tension and compression : scientific paperAuthor W. BurdzikSource: Southern African Forestry Journal 2004, pp 21 –27 (2004)More Less
The last verification of SA pine timber strengths was done in the early 1980s. Uses of the pine logs and the rotation periods have changed. This investigation was undertaken to verify the visual grade 5 grading rules of SANS 1783-2 (1997) on 36 x 111 mm specimen sizes. Qualified timber graders identified forestry areas with low-density SA pine. Four sawmills were randomly chosen as being representative of the forestry in those areas. Bending, tension and compression tests were done in accordance with the ISO standard test methods. It was found that only one of the sawmills came close to making the grade strength. The combined strength from all the sawmills indicated that these would only make a grade 4. It is thus suggested that sawmills that do only visual grading, in accordance with SANS 1783-2 (1997), draw random specimens that can be tested in-house for strength or by an independent testing laboratory to ensure that their timber meets the requirements of a grade 5.
The effects of ontogenetic maturation in Pinus patula - part 1 : nursery performance : scientific paperSource: Southern African Forestry Journal 2004, pp 29 –36 (2004)More Less
The age at which parent or donor hedges reach ontogenetic maturity has frequently been cited as a debilitating factor in the production of conifer cuttings. This point varies between species and prevailing environmental conditions. Among other things, a lack of knowledge of the effects of hedge maturation in <I>Pinus patula</I> has resulted in reluctance among South African foresters to plant cuttings of this species. Consequently, several trials were established between 2000 and 2003 to investigate the effects of ontogenetic maturation on the performance of <I>P. patula</I> cuttings in the nursery and field.This paper forms the first component of a three-part series and reports on those effects observed in the nursery. The effects of hedge maturation on field performance and cycling of <I>P. patula</I> hedges as a means of rejuvenation, are reported separately. An analysis of the nursery data indicates that rooting efficiency, root system quality, and stem size and form, all decline with increasing hedge age. A decline in root system quality was particularly apparent and was observed prior to a decline in rooting efficiency.
Source: Southern African Forestry Journal 2004, pp 37 –44 (2004)More Less
Field trips were undertaken as a preliminary exercise, to identify the available rattan species in Western Nigeria and to estimate the quantities available. Information relating to their end-uses was collected from cane furniture makers and other rattan cane users through the use of questionnaires and personal observation. The species in descending order of availability were <I>Calamus deeratus, Eremospatha macrocarpa, Oncocalamus manni</I> and <I>Laccosperma secondiflorum. L. secundiflorum, C. deerratus, E. macrocarpa</I> and <I>O. manni</I> having average stock densities per plot of 100 square metres of 6, 22, 12 and 18 clumps respectively. The diameters of the small-stemmed rattan species (<I>C. deerratus, E. macrocarpa and O. manni</I>) ranged from 7.2 to 17.8mm while that of <I>L. secundiflorum</I>, a large stemmed species, ranged from 12.5 to 38.5mm. Rattan canes were mainly from wild stocks and cane furniture/handicraft weavers form the bulk of cane users. Other uses of cane within the study area include: as cane for flogging, ropes for tying hides to drum frames, fish traps and loop for climbing palm trees. The wastage from harvesting operation of the rattan canes ranged from 20 to 55 percent of the length of the plant. <br>Rattan plants if properly harnessed, and their biological, physical and mechanical properties understood, could contribute significantly to the economy of African nations.
Source: Southern African Forestry Journal 2004, pp 45 –53 (2004)More Less
Factors controlling seedling recruitment of <I>Colophospermum mopane</I> (Kirk ex. Benth) Kirk ex. J. Leonard were investigated on the highveld of Zimbabwe. Seed germination and seedling survival and growth were monitored under canopy and outside canopy microhabitats for a period of 3 years. Seed germination in both microhabitats exceeded 70%. Although there was no significant difference in seed germination between the two microhabitats, seedling survival was significantly lower under canopies than outside canopies. More than 75% of newly emerged seedling losses were attributed to water stress, which suggests that abiotic factors (mainly rainfall) may account for most of the fluctuation in recruitment in this species. Open areas with bare ground or sparse grass cover were favourable sites for seedling recruitment. Seedlings appear to be shade-intolerant and require increased light intensities and temperature for growth. Seedlings grew slowly probably because they initially allocated more biomass to root growth. Shoot growth was also hampered by recurrent dieback mainly caused by fire. Most seedlings resprouted after aboveground organs were killed by fire. It is concluded that seedling recruitment of this species is mainly limited by inconsistent rainfall events that characterize most areas where it grows.
Organic matter fuel briquettes as a forest conservation tool in Lake Malawi National Park : research noteSource: Southern African Forestry Journal 2004, pp 55 –60 (2004)More Less
Environmental degradation including deforestation is of great concern in the whole of sub-Saharan Africa, even in many protected areas. One of them is Lake Malawi National Park (LMNP), which encases the most populated village in Malawi, Chembe. The rise in population has increased the pressure to utilize natural resources in LMNP, and the collection of firewood for domestic use as well as for commercial purposes has led to woodland degradation in the park area. To assist LMNP and its stakeholders in combating deforestation, World Wide Fund for Nature (WWF) Finland has promoted organic matter fuel briquettes as a substitute to firewood since 2001. <br>This article is the result of data collection related to the monitoring of the briquette project and forest management practices in LMNP. Results showed that illegal firewood collection inside park area is widespread and its control inefficient. It was also found that despite interest towards fuel briquettes, cost is the limiting factor when people choose their fuel source. Stronger marketing efforts are needed to increase the viability of the briquette business. Another alternative would be to teach families how to make briquettes for household use. Concentrated efforts to regulate "free" fuelwood collection inside park area are needed to reverse deforestation.
Early growth and survival of Acacia galpinii after planting in a semi-arid environment in Zimbabwe : research noteSource: Southern African Forestry Journal 2004, pp 61 –66 (2004)More Less
<I>Acacia galpinii</I> grows naturally on the riverbanks and smaller drainage lines in semi-arid areas of Southern Africa. Trial planting of the species as a decorative tree commenced in 1993 along urban roads in Bulawayo, Zimbabwe. Early growth and survival of the species after planting was investigated in order to assess its suitability for afforestation in semi-arid environments. Growth and survival of trees were measured 3 to 9 years after planting. A significant positive correlation between crown height and stem diameter was observed in all the trial plantings. Growth rate was fast with trees reaching a mean diameter of 10 cm and height of 3 m over 3 years and a diameter of 16 cm and height of 5 m over 9 years. Such growth rates were reached under frequent drought conditions. Average stem height growth was 0.6 m year-1 and diameter growth (at 30 cm above ground) was 2 cm year-1. Survival of <I>A. galpinii</I> was more than 86 percent. Foliage transparency was in excess of 80% for all age groups while crown dieback and stem damage was below 5%. <I>A. galpinii</I> was found to be suitable for dry-zone afforestation.
Author Kitikidou KyriakiSource: Southern African Forestry Journal 2004, pp 67 –76 (2004)More Less
In order to apply the least squares method in regression analysis, the values of the dependent variable <I>Y</I> should be random. In an example of regression analysis linear and nonlinear taper equations, which estimate the diameter of the tree <I>d</I><sub>h</sub><sub><sub>i</sub></sub> at any height of the tree h<sub>i</sub>, were compared. For each tree the diameter at the breast height of 1.3 m (<I>D</I>), the total tree height (<I>H</I>) and the diameters at heights of 0.3 m, 0.8 m and at 2 m intervals above breast height diameter (that is at 3.3, 5.3, 7.3 ... m) were measured. Two methods were used to fit equations to data: in the first method, all diameter measurements were used, therefore the values of the dependent variables were not random, because obvious autocorrelation exists between the diameters measured on the same tree. In the second method only the last (highest) diameter for each tree was taken, making the dependent variables random. Regression results, for the two methods, were compared using the confidence interval estimates for the regression coefficients, the multicollinearity tests and Fit Index (<I>FI</I>) values as criteria. The comparison of results showed that randomness of the dependent variable (second method) did not improve the estimates, in any of the regression equations.
Author F.S. MalanSource: Southern African Forestry Journal 2004, pp 77 –82 (2004)More Less
The storage of logs under water sprays has proved to be a highly effective method to preserve logs over prolonged periods against drying defects and infestation by staining fungi. Wet-storage has little effect on wood quality apart from some degradation of the thin outer layer of the log, as well as an increase in moisture content. Strength loss seems to be rare and when it occurs it develops slowly. The only changes to the wood of practical significance are caused by the activity of anaerobic bacteria during the storage period. The porosity of the wood tends to increase while the colour of the wood might change towards a darker tinge. While a slight colour change might be problematic in some avenues of utilisation, the increased porosity could either be a friend or a foe. The increased porosity allows chemicals and moisture to diffuse quicker through the wood, making drying and preservative treatment somewhat faster and easier. However, difficulties have been reported which probably relate to differences in porosity caused by differences in bacterial activity within the log during wet-storage. These include differences in drying rates, causing differences in moisture content between and within boards at the end of a drying cycle, and uneven absorbance of surface finishing layers in pine furniture manufacture. <br><I>P. taeda</I> saw logs containing large amounts of abnormal compression wood, which were kept in wetstorage for prolonged periods, yielded boards that were considerably less prone to distortion during processing. The wet-storage of eucalypt logs has proved to be a useful method of reducing growth stressrelated defects such as log splitting and board distortion. <br>Wet-storage was also found to be an effective means of rendering susceptible timber more immune to powder-post beetle (<I>Lyctus</I>) attack. <br>In general it appears that the advantages of wet-storage outweigh the problems associated with it which, in any case, can be dealt with relatively easily in practice.
Cold tolerant Eucalypts in South Africa - growth information for informed site-species matching : technical noteSource: Southern African Forestry Journal 2004, pp 83 –84 (2004)More Less
Site-species matching is very important in managing the various limiting site and climatic factors in the more temperate forestry areas in South Africa. Information has been gathered from ICFR site-species interaction trials and provenance / progeny trials and summarised into a format which should make the siting of species on low productivity sites a more informed process, and will ultimately assist the forest industry in achieving optimum growth performance on all sites, with the least risk of crop failure.