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- Volume 2001, Issue 192, 2001
Southern African Forestry Journal - Volume 2001, Issue 192, 2001
Volume 2001, Issue 192, 2001
Source: Southern African Forestry Journal 2001, pp 1 –2 (2001)More Less
Extracted from text ... Southern African Forestry Journal - No. 192, November 2001 1 Guest Editorial Review of sustainable forest management - Criteria and indicators Sustainability should be viewed as a long-term goal, the establishment of which is fundamentally a social decision about the desirability of a survivable ecological and economic system. The real problem is thus not so much defining the goal, but predicting what policies will lead to its achievement (Constanza, 1996). During the past two decades, there have been a number of intergovernmental, international nongovernmental and country-level initiatives to address sustainable forest management issues. One of the most important products to ..
Author S.F. HagedornSource: Southern African Forestry Journal 2001, pp 3 –8 (2001)More Less
Cone and seed production studies in Pinus patula were conducted by the Institute for Commercial Forestry Research (ICFR) in KwaZulu-Natal as part of the improvement programme of the species. The optimum altitude for female strobilus and seed production is approximately 1450 m in KwaZulu-Natal. At four years after establishment of the Breeding Seedling Orchards (BSOs), male and female flowering is high enough to make a commercial cone collection two years later worthwhile. The seed potential is between 120 and 140 seeds per cone and seed efficiency about 50 percent.
The effects of remedial fertilizer treatments on growth and pulp properties of Eucalyptus grandis stands established on infertile soils of the Zululand coastal plain : scientific paperSource: Southern African Forestry Journal 2001, pp 9 –18 (2001)More Less
Remedial fertilizer applications were applied to nutrient-poor stands of <i>Eucalyptus grandis</i> growing on infertile (ex-agricultural) land of the Zululand coastal plain. Two nitrogen-rich fertilizer mixtures were applied in one year-old stands at rates ranging from zero to 160 kg N ha<sup>-1</sup> . Foliar nitrogen levels increased highly significantly at the higher levels of fertilization. A highly significant response to height, diameter and basal area growth was observed within 6 months of treatment initiation which was sustained until clear felling (8.3 years). A comparison of the unfertilized control with the optimum treatment (i.e. a single fertilizer dose equivalent to 80 kg N ha<sup>-1</sup> ) yielded the following results: Utilizable wood volume increased from 136.7 to 264.3 m<sup>3</sup> ha<sup>-1</sup> . The wood density showed a weakly significant increase from 448 to 472 kg m<sup>-3</sup>. The pulpability factor (defined as the pulp yield / kappa number) decreased significantly from 2.63 to 2.32. The net effect of fertilization on pulping properties is a non- significant increase in pulp yield per unit volume of timber (chiefly due to increases in wood density). The combined effects of fertilization on both volume growth and pulping properties resulted in an increase in the pulp yield on a plantation area basis from 32.03 to 63.43 t pulp ha<sup>-1</sup> in the 8.3 year-old stand.
Quantifying the geographic range of Pinus patula var. longipedunculata in Southern Mexico using morphologic and RAPD marker data : scientific paperSource: Southern African Forestry Journal 2001, pp 19 –30 (2001)More Less
<i>Pinus patula</i> var. <i>longipedunculata</i> occurs in southern Mexico, but the extent of its geographic range is poorly defined. Trees from some populations are morphologically similar to <i>P. tecunumanii</i> , which adds to the confusion over the variety's geographic range. Recent field explorations have identified six new populations of supposed <i>P. patula</i> var. <i>longipedunculata</i> in the Sierra Madre del Sur of Oaxaca and Guerrero. In an effort to determine the validity of these sightings, botanical samples were collected from 79 trees in these six populations and were assessed for ten cone and needle morphology traits. Random Amplified Polymorphic DNA (RAPD) analyses were conducted on 73 trees from the six populations, 38 of which were in common to 79 trees used in the botanical study. Species control lots for both the botanical and RAPD studies were <i>P. herrerae</i>, <i>P. oocarpa</i>, <i>P. patula</i>, <i>P. pringlei</i> and <i>P. tecunumanii</i>. Morphologic assessment indicated trees in the Manzanal population were predominantly <i>patula</i> -related, but trees in the other five populations grouped into two clusters that were significantly different from <i>P. patula</i> and <i>P. tecunumanii</i> and not strongly related to the other control species. Conversely, molecular marker results indicated that four of the populations, Manzanal, San Mateo, Tlacuache (Oaxaca) and Yextla (Guerrero) were genetically indistinguishable or closely related to <i>P. patula</i>. The remaining two populations, Juquila (Oaxaca) and Palo Blanco (Guerrero), were closely related genetically to <i>P. herrerae / P. pringlei</i>. The morphologic study indicated that 5% of the trees in the six populations were indistinguishable from <i>P. tecunumanii</i>, but marker analyses indicated that the trees in question were of either <i>P. patula</i> or <i>P. herrerae / P. pringlei</i> origin. <i>Pinus tecunumanii</i> does not appear to occur in the Sierra Madre del Sur of Oaxaca and Guerrero, but a four-needle type of <i>P. herrerae</i> that can be very easily confused with <i>P. patula</i> var. <i>longipedunculata</i> does. The geographic range of <i>P. patula</i> var. <i>longipedunculata</i> is defined as occurring from northeastern Oaxaca to central Guerrero. The existence of populations of the variety in Chiapas needs to be verified using molecular techniques. The genetic relationship between <i>P. pringlei</i> and <i>P. herrerae</i> is much closer than heretofore thought, even though the morphology of each species is very distinctive.
The impact of vegetation control on the establishment of pine at four sites in the summer rainfall region of South Africa : scientific paperSource: Southern African Forestry Journal 2001, pp 31 –40 (2001)More Less
Four trials designed to study the impact of intensive, selective and commercial vegetation control (operational) practices on pine establishment were implemented across an altitudinal and climatic range of sites in the summer rainfall region of South Africa. The trial sites incorporated one high altitude (1650 m a.s.l.) cool temperate site, two mid-altitude (1000 m a.s.l.) warm temperate sites and a low altitude (60 m a.s.l.) sub-tropical site. Treatments implemented at each trial included a weedy and a weedfree control, operational weed control, selective control of herbaceous or woody vegetation types as well as a ringweeding treatment at three sites. The results indicate that the abundance and type of vegetation at a site varies as a function of the local physiographic and environmental conditions as well as historical land-use. At the high altitude site the competitive vegetation was less abundant than at the mid-low altitude sites where vigorous woody vegetation dominated. Due to the differential growth of vegetation across the sites, tree growth responses to intensive and selective vegetation control were site dependent. There were no significant tree growth responses to vegetation management at the high altitude site. Relative to the weedfree control, tree growth suppression was highest on the weedy and woody treatment plots at the warmer, mid-low altitude sites. No significant suppression of tree growth occurred where the vegetation was kept away from the trees, on the ring-weeded and operational treatment plots. Herbaceous vegetation caused significant tree growth suppression only where climatic conditions were conducive to extended seasonal growth.
A comparison of the impacts of winter versus summer burning of slash fuel in alien-invaded fynbos areas in the Western Cape : scientific paperAuthor Patricia HolmesSource: Southern African Forestry Journal 2001, pp 41 –50 (2001)More Less
Dense slash from cleared stands of invasive alien trees in mountain catchment areas poses a hazard to fynbos recovery and soil stability, if it burns under extreme summer weather conditions. Experimental burning of alien slash fuel was done to investigate whether winter burning of fuel may be used as a practical alternative to risking a summer wild fire. Fire intensity, heat release at the soil surface and indigenous post-fire plant recruitment were compared between different blocks of the same felled alien stand, which burnt during a controlled winter burn and a summer wild fire. Both fires consumed nearly all the fuel, but fire intensity and heat penetration into the soil were much greater for the summer wild fire than the winter control burn. Fynbos plant recruitment following the main winter establishment season was extremely low in the summer burn, and indicated that propagules in the upper soil had been killed in the fire. Species that emerged following the summer burn were predominantly resprouters or species with larger seeds that could emerge from deeper in the soil. Plant recruitment, species richness and cover were much higher following the winter burn. Half the species (mainly forbs, resprouters and legumes) appeared during the summer after the fire, but the remainder appeared only after the main winter establishment season. Small-seeded species were few and indicated that all germination cues were not optimized by burning in winter. Alternatively, soil-heating during the winter burn was sufficient to kill small seeds located close to the surface. Comparisons between summer slash fires on granite versus sandstone parent materials suggest that the impacts are much greater on the granite. The impacts were also greater where fuel loads are high. It is recommended that summer burning of slash fuel be avoided in all areas supporting old (>8 yr), dense (>75% cover) alien stands. Furthermore, summer slash fires also should be avoided for moderately dense (>50%) alien stands on shale bands or granite-derived soils. As an interim strategy in these areas, winter burning of fuel should be considered to prevent excessive soil and propagule damage during a summer wild fire. However, future alternatives, such as the immediate targeting of low-density stands and the implementation of biological control agents, urgently should be sought.
The wood quality of Pinus chiapensis (Mart.) Andresen grown in the Mpumalanga forest region : scientific paperAuthor F.S. MalanSource: Southern African Forestry Journal 2001, pp 51 –58 (2001)More Less
The ten best performing families selected in a <i>Pinus chiapensis</i> trial at Tweefontein forest near Sabie have been evaluated for wood and saw timber properties. The wood was found to be soft, remarkably uniform both within and between annual rings, stable, with a well-defined heartwood zone. The latewood proportion of the annual rings was extremely small, resulting in a poorly defined ring structure.<br> The fifty trees studied had an average air-dry density of 0,420 g / cm<sup>3</sup> (extracted and at 12 % moisture content) with individual tree densities varying from 0,380 to 0,465 g / cm<sup>3</sup> at 0,8 m height level. Differences between families were highly significant, suggesting that there is a strong potential to increase the density of the wood through tree breeding.<br> Knots were relatively small and well shaped, and normally occurred in small clusters. Knot occlusions following pruning were accompanied by little grain distortion. When present, the amounts of included resin, pieces of bark and other debris at the occluded pruning cuts, were small and of little practical significance.<br> The wood machined without any difficulty in the wet and dry condition. Boards dried without any significant drying degrade, but moisture loss during drying from the heartwood zone was markedly slower compared to what is normally experienced with the pith zone of other South African commercial pines.<br> Some sawn pieces may not be suitable for some structural purposes where strength is important, while tests on Colombian and Brazilian grown <i>P. chiapensis</i> have shown that the species may not be acceptable for pulp production because of low pulp yields and high alkali consumption. Owing to its high degree of uniformity it might be well suited for special products such as for internal construction purposes, panelling and other decorative work, woodcarving and some applications in the furniture manufacturing industry. It might also be suitable for the manufacturing of items such as match sticks, toothpicks, clothes-pegs and other small wooden objects.
Mechanical Feller-buncher felling : an example study on timber value recovery in South Africa : management paperSource: Southern African Forestry Journal 2001, pp 59 –64 (2001)More Less
Timber breakage during felling reduced the value of timber harvested from a stand. This is especially evident in the larger saw timber stands where large trees are being harvested. A field study was completed with the objective of quantifying and comparing the timber value recovery between conventional chainsaw felling, and mechanical feller-buncher felling, using two pine species - <i>Pinus elliottii</i> and <i>Pinus taeda</i>.<br> Although there was no significant difference in mean volume recovery, felling with the feller-buncher yielded a 2.4% higher volume recovery than chainsaw felling. Mean value recovery, however, for felling with the feller-buncher was significantly higher than chainsaw felling. Study results showed that feller-buncher felling had a 6.8% lower tree value recovery than chainsaw felling. The difference is attributed to a decrease in breakage and improved sawlog recovery when felling with the feller-buncher.
Source: Southern African Forestry Journal 2001, pp 65 –72 (2001)More Less
The savanna woodlands are the largest biome in the country, constituting one-third of South Africa. They are also home to one-quarter of the population, with 70 % of the former homelands being in the savanna biome. Consequently, they have the potential to make a marked contribution to the national economy, both in the formal and informal sector. They are also valuable on a national scale in terms of the ecosystem services they provide, such as carbon storage, biodiversity and water yield. Until recently the real and potential values attached to South Africa's savannas have not been recognised in policy fora and government institutions. Recent policy changes, especially the National Forestry Action Programme and the National Forest Act, have attempted to remedy this situation. These policies have not filtered down to land owners and managers, nor have they resulted in a redirection of government resources. Thus, large areas remain subject to unsustainable use. It is necessary that the true value of woodlands be determined and acknowledged as a stimulus to government agencies, the private sector and local users to use this valuable resource sustainably.
Source: Southern African Forestry Journal 2001, pp 73 –78 (2001)More Less
The production of high quality timber from hardwood requires a gentle and controlled drying to a low wood moisture content. While ambient air drying depends on the weather conditions, conventional hightemperature dryers cause high investments and energy costs. Up to now, solar dryers could not be established in industrial timber production, due to their insufficient drying capacity and the lack of an adequate control of the drying conditions.<br> Therefore, a new solar dryer was developed, which allows a controlled drying of up to 250 m<sup>3</sup> of timber per load. The frame of the dryer is covered with a transparent, highly UV-stabilised and well isolating air bubble foil. A specially developed microprocessor control regulates air flow, temperature, humidity and a back up wood chip furnace, which provides the heat during night and unfavourable weather conditions. The drying regime is adjusted automatically according to the type of wood, the board thickness and the ambient air temperature.<br> The paper presents the experiences gained during the operation of the two worlds largest solar timber dryers, drying up to 35000 m<sup>3</sup> of eucalypt annually. The investigations showed, that investments, drying costs and energy consumption could be reduced by 50 % compared to conventional high-temperature drying systems. At the same time the quality of the timber was improved considerably.
Exotic pine forestry in the Southern Hemisphere : a brief history of establishment and quarantine practices : review paperSource: Southern African Forestry Journal 2001, pp 79 –84 (2001)More Less
Afforestation with exotic softwoods commenced in the Southern Hemisphere at the end of the 19th century. Initially the areas under afforestation were small, but today, exotic plantation species are the basis of huge forestry industries, forming a crucial component of the economies of many countries. Early plantations were relatively free of pests and diseases. However, as the industry expanded, so did pest and disease problems. Initially, quarantine regulations were non-existent or poorly enforced, but in the later part of the 20th century rigorous quarantine regulations were implemented. More recently, the opening of global markets and the increase in trade has increased the risk of introducing new pests and pathogens. The potential losses to the forestry industry are immeasurable and vigilance is required from importers, exporters and even tree breeders moving germplasm, to prevent the spread of pathogens around the world. This review considers the history of softwood forestry and quarantine in some of the most important producers of forest products in the Southern Hemisphere, namely South Africa, Australia and New Zealand.
Author D.P. GwazeSource: Southern African Forestry Journal 2001, pp 85 –92 (2001)More Less
Several F1 eucalypt and pine interspecific hybrids have been tested in Zimbabwe. The first hybrids tests were of pine species, and these were established in 1973. The results from these early tests were not spectacular and interest in hybrids was lost until the 1990's when impressive eucalypt and pine hybrid performances were reported in South Africa and Australia, respectively. During the period 1990-1993 pine hybrids were imported from Australia and eucalypt hybrids from South Africa, and tested on various sites around Zimbabwe. Detailed analyses in 1999 / 2000 showed that many of the tested hybrids outperformed the pure species on specific sites. The reports based on these analyses highlighted the need to test local hybrids, the need to determine wood qualities and the need to determine cost-effective methods to mass-produce the most promising hybrids. Currently, local pine and eucalypt hybrids are being developed for field-testing. These developments and further research needed to realise the full economic potential of hybrids are discussed.