Pub Date : 1998-02-06DOI: 10.1080/10295925.1998.9631186
F. Malan
SYNOPSIS A study on the incidence and severity of resin-filled shakes was carried out on 36 open-pollinated families established at four different sites. The objectives were to study the distribution of shakes within and between trees, and how it is affected by genetics and environment. In general a clear pattern in the variation among families was observed suggesting that there is some genetic influence. However, between the four different sites the among-family patterns of variation in resin shake propensity, differences between trees within families, and the distribution within tree stems, were extremely variable and inconsistent. From this it is evident that some genotypes seem to respond differently to the influences of environment. Resin shakes often occurred in the basal part of the tree stem, often extending into the stump, but the frequency of occurrence varied considerably between sites. Shakes occurring higher up in the stem were often associated with large knots, knot clusters and forks. The t...
{"title":"Variation in the Incidence of Resin-filled Shakes and Wood Density among Open-pollinated Families of Pinus elliottii Planted at Four Different Sites","authors":"F. Malan","doi":"10.1080/10295925.1998.9631186","DOIUrl":"https://doi.org/10.1080/10295925.1998.9631186","url":null,"abstract":"SYNOPSIS A study on the incidence and severity of resin-filled shakes was carried out on 36 open-pollinated families established at four different sites. The objectives were to study the distribution of shakes within and between trees, and how it is affected by genetics and environment. In general a clear pattern in the variation among families was observed suggesting that there is some genetic influence. However, between the four different sites the among-family patterns of variation in resin shake propensity, differences between trees within families, and the distribution within tree stems, were extremely variable and inconsistent. From this it is evident that some genotypes seem to respond differently to the influences of environment. Resin shakes often occurred in the basal part of the tree stem, often extending into the stump, but the frequency of occurrence varied considerably between sites. Shakes occurring higher up in the stem were often associated with large knots, knot clusters and forks. The t...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129448717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631162
J. Louw
SYNOPSIS A site-growth study was conducted on Eucalyptus grandis on the granitic soils of the Mpumalanga escarpment area. The objectives were twofold, namely to identify those site factors that can be related to the growth of the species, as well as the development of a statistical site-growth model for the quantitative evaluation of sites for tree growth performance. An integrated approach was followed using multiple regression analysis, incorporating attributes on topography, climate and physical and chemical soil characteristics, with Site Index at 20 years (SI20) as the dependent variable. The study revealed that the growth of E. grandis is mainly influenced by factors controlling available soil moisture, together with the organic carbon content of the topsoil. A statistically significant site-growth model was developed, although the model showed bias by overpredicting at low potential sites and underpredicting at high potential sites. This could be ascribed to the use of a growth model (for standardi...
{"title":"A Site-growth Study of Eucalyptus grandis in the Mpumalanga Escarpment Area","authors":"J. Louw","doi":"10.1080/10295925.1997.9631162","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631162","url":null,"abstract":"SYNOPSIS A site-growth study was conducted on Eucalyptus grandis on the granitic soils of the Mpumalanga escarpment area. The objectives were twofold, namely to identify those site factors that can be related to the growth of the species, as well as the development of a statistical site-growth model for the quantitative evaluation of sites for tree growth performance. An integrated approach was followed using multiple regression analysis, incorporating attributes on topography, climate and physical and chemical soil characteristics, with Site Index at 20 years (SI20) as the dependent variable. The study revealed that the growth of E. grandis is mainly influenced by factors controlling available soil moisture, together with the organic carbon content of the topsoil. A statistically significant site-growth model was developed, although the model showed bias by overpredicting at low potential sites and underpredicting at high potential sites. This could be ascribed to the use of a growth model (for standardi...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133164245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631168
E. Govere
SYNOPSIS The socio-economic lifeline of Southern African Development Community (SADC) countries (Angola, Botswana, Lesotho, Malawi, Mauritius, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia and Zimbabwe) is anchored on agriculture and agricultural related enterprises. There is a growing realisation that the lifeline can collapse unless sustainable land-use systems that harmonise land-derived benefits with environmental components (soil, fauna, flora, water and air) are adopted. Among the land-use systems practiced in SADC, agroforestry has the potential to become one of the key strategies in SADC's endeavour to provide multiple benefits with minimum degradation to the environmental components. However, the introduction and implementation of agroforestry activities and the degree of success depend on a clear awareness of the agroforestry development needs. This paper presents agroforestry research, extension and training needs as identified at an international workshop held at the Universit...
{"title":"Research, Extension and Training Needs for Agroforestry Development in Southern Africa","authors":"E. Govere","doi":"10.1080/10295925.1997.9631168","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631168","url":null,"abstract":"SYNOPSIS The socio-economic lifeline of Southern African Development Community (SADC) countries (Angola, Botswana, Lesotho, Malawi, Mauritius, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia and Zimbabwe) is anchored on agriculture and agricultural related enterprises. There is a growing realisation that the lifeline can collapse unless sustainable land-use systems that harmonise land-derived benefits with environmental components (soil, fauna, flora, water and air) are adopted. Among the land-use systems practiced in SADC, agroforestry has the potential to become one of the key strategies in SADC's endeavour to provide multiple benefits with minimum degradation to the environmental components. However, the introduction and implementation of agroforestry activities and the degree of success depend on a clear awareness of the agroforestry development needs. This paper presents agroforestry research, extension and training needs as identified at an international workshop held at the Universit...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"80 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123221157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631164
F. Malan, R. Retief, J. Male
SYNOPSIS Material was sampled from a 60-year-old Pinus patula CCT trial established at the Weza forest, Southern Kwazulu-Natal, to study the effect of planting espacement on wood density, its within-tree variation, and the pulping properties of the wood. Results indicated that differences in growth rate, caused by differences in planting espacement, appear to have a very pronounced effect on overall wood density as well as its within-tree variability. It is important to bear in mind, however, that this result reflects the wood properties of trees grown under conditions that are very different from those created by current management and silvicultural practices. Within the range of normal spacing variation, the effect of spacing on wood density and pulp and paper properties seems to be minimal, suggesting that the enhancement of growth rate by the manipulation of the growing space, has no adverse effect on wood density, and by implication, on any of the factors related to density. The results obtained sugg...
{"title":"The Influence of Planting Espacement on the Wood Density and Pulping Properties of Pinus patula","authors":"F. Malan, R. Retief, J. Male","doi":"10.1080/10295925.1997.9631164","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631164","url":null,"abstract":"SYNOPSIS Material was sampled from a 60-year-old Pinus patula CCT trial established at the Weza forest, Southern Kwazulu-Natal, to study the effect of planting espacement on wood density, its within-tree variation, and the pulping properties of the wood. Results indicated that differences in growth rate, caused by differences in planting espacement, appear to have a very pronounced effect on overall wood density as well as its within-tree variability. It is important to bear in mind, however, that this result reflects the wood properties of trees grown under conditions that are very different from those created by current management and silvicultural practices. Within the range of normal spacing variation, the effect of spacing on wood density and pulp and paper properties seems to be minimal, suggesting that the enhancement of growth rate by the manipulation of the growing space, has no adverse effect on wood density, and by implication, on any of the factors related to density. The results obtained sugg...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"2675 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116519146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631163
P. Pieterse, C. Boucher
SYNOPSIS Acacia mearnsii is an important invasive plant in most of the higher rainfall areas in South Africa. The production of long-lived water-impermeable seeds results in the establishment of large soil-stored seed banks. One way of controlling these seed banks is by felling the plants and burning them to destroy or to stimulate seeds to germinate, so that the resulting seedlings may be controlled. In order to save costs, the hypothesis that the plant population can be burned without felling beforehand, was investigated. A wildfire that swept through a standing population of A. mearnsii plants provided an opportunity to investigate the effects on the population. The mortality of the pre-fire population, the subsequent establishment of seedlings, mortality of seedlings and the spread of the population after the fire were investigated. It was found that the above-ground population increased by a factor of ca. 21,8 due to coppicing of young plants and the mean distance of spread from the edge of an infest...
{"title":"Is Burning a Standing Population of Invasive Legumes a Viable Control Method? Effects of a Wildfire on an Acacia mearnsii Population","authors":"P. Pieterse, C. Boucher","doi":"10.1080/10295925.1997.9631163","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631163","url":null,"abstract":"SYNOPSIS Acacia mearnsii is an important invasive plant in most of the higher rainfall areas in South Africa. The production of long-lived water-impermeable seeds results in the establishment of large soil-stored seed banks. One way of controlling these seed banks is by felling the plants and burning them to destroy or to stimulate seeds to germinate, so that the resulting seedlings may be controlled. In order to save costs, the hypothesis that the plant population can be burned without felling beforehand, was investigated. A wildfire that swept through a standing population of A. mearnsii plants provided an opportunity to investigate the effects on the population. The mortality of the pre-fire population, the subsequent establishment of seedlings, mortality of seedlings and the spread of the population after the fire were investigated. It was found that the above-ground population increased by a factor of ca. 21,8 due to coppicing of young plants and the mean distance of spread from the edge of an infest...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127763777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631167
R. Pott
SYNOPSIS It is apparent that much of the criticism of plantation forestry as a form of land-use is based on emotional bias rather than on hard evidence. The results of a perception survey are presented to support this supposition. Two accusations that are commonly levelled against forestry—namely that it leads to a serious reduction in biodiversity, and secondly that it uses a disproportionate amount of water—are debated and more reasoned views are presented. The need for research and monitoring to provide the factual evidence that decision makers need for the wise management of land-use options—including forestry—is highlighted.
{"title":"Plantation Forestry in South Africa and its Impact on Biodiversity and Water","authors":"R. Pott","doi":"10.1080/10295925.1997.9631167","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631167","url":null,"abstract":"SYNOPSIS It is apparent that much of the criticism of plantation forestry as a form of land-use is based on emotional bias rather than on hard evidence. The results of a perception survey are presented to support this supposition. Two accusations that are commonly levelled against forestry—namely that it leads to a serious reduction in biodiversity, and secondly that it uses a disproportionate amount of water—are debated and more reasoned views are presented. The need for research and monitoring to provide the factual evidence that decision makers need for the wise management of land-use options—including forestry—is highlighted.","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125236387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631165
M. Thomas, D. Everard, G. Wyk
SYNOPSIS An evaluation of a two-metre ground resolution Sputnik satellite image was made for use in woodland management. The Sputnik image was provided as a georeferenced hardcopy image at a scale of 1: 20 000, and covered a woodland project area located inside the Makuya National Park, Northern Province. The evaluation found that the Sputnik image provided insufficient detail for detailed woodland mapping. This was due to reduced ground resolution and poor contrast found in the image. A comparison of 1:50 000 scale black and white aerial photographs showed these to be more suited for detailed woodland mapping in the project area. However, the Sputnik image offered imagery at an ideal scale for field work and was a valuable asset in project orientation/navigation. This was because of the image's capability to provide a single-look of the whole of the study area within the single image.
{"title":"An Evaluation of a Two-metre Resolution Black and White Satellite Image for Woodland Remote Sensing Applications","authors":"M. Thomas, D. Everard, G. Wyk","doi":"10.1080/10295925.1997.9631165","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631165","url":null,"abstract":"SYNOPSIS An evaluation of a two-metre ground resolution Sputnik satellite image was made for use in woodland management. The Sputnik image was provided as a georeferenced hardcopy image at a scale of 1: 20 000, and covered a woodland project area located inside the Makuya National Park, Northern Province. The evaluation found that the Sputnik image provided insufficient detail for detailed woodland mapping. This was due to reduced ground resolution and poor contrast found in the image. A comparison of 1:50 000 scale black and white aerial photographs showed these to be more suited for detailed woodland mapping in the project area. However, the Sputnik image offered imagery at an ideal scale for field work and was a valuable asset in project orientation/navigation. This was because of the image's capability to provide a single-look of the whole of the study area within the single image.","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131486836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631171
D. V. D. Zel
{"title":"Sustainability of Water Resources under Increasing Uncertainty","authors":"D. V. D. Zel","doi":"10.1080/10295925.1997.9631171","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631171","url":null,"abstract":"","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"25 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123325562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-01DOI: 10.1080/10295925.1997.9631166
P. Pieterse, C. Boucher
SYNOPSIS In 1977, Stubbings presented a paper titled “A.C.A.C.I.A. (A Case Against Controlling Introduced Acacias)” at the Second National Weeds Conference. The paper dealt with the merits of introducing biological control agents against introduced acacias, but concentrated mainly on Acacia mearnsii and the conflict of interest caused by the intended release of biological control agents against it. In the same year Luckhoff commented on the paper and challenged some of the statements made by Stubbings. In this paper the arguments of both Stubbings and Luckhoff are reviewed in the context of developments in this field since 1977. Points that are considered include classification of plants as weeds, luxurious water consumption by invaders, necessary actions to be executed before introducing biological control agents, effectiveness of seed-eating insects and integrated control including alternative control measures. Acacia mearnsii and A. saligna are used as case studies to illustrate some of the points made...
{"title":"A.C.A.C.I.A. (A Case Against Controlling Introduced Acacias)—19 years later","authors":"P. Pieterse, C. Boucher","doi":"10.1080/10295925.1997.9631166","DOIUrl":"https://doi.org/10.1080/10295925.1997.9631166","url":null,"abstract":"SYNOPSIS In 1977, Stubbings presented a paper titled “A.C.A.C.I.A. (A Case Against Controlling Introduced Acacias)” at the Second National Weeds Conference. The paper dealt with the merits of introducing biological control agents against introduced acacias, but concentrated mainly on Acacia mearnsii and the conflict of interest caused by the intended release of biological control agents against it. In the same year Luckhoff commented on the paper and challenged some of the statements made by Stubbings. In this paper the arguments of both Stubbings and Luckhoff are reviewed in the context of developments in this field since 1977. Points that are considered include classification of plants as weeds, luxurious water consumption by invaders, necessary actions to be executed before introducing biological control agents, effectiveness of seed-eating insects and integrated control including alternative control measures. Acacia mearnsii and A. saligna are used as case studies to illustrate some of the points made...","PeriodicalId":228456,"journal":{"name":"The Southern African Forestry Journal","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122172678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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