No description available.

Forest insect populations, like many other animal populations, are not uniformly distributed throughout an area but are found in various degrees of concentration regionally and locally. Bark-beetles constitute a major group of economically important forest insects and the causes of their variable concentrations are only partially understood. Among the important circumstances with which variable bark-beetle populations are associated are those encountered in forest stands undergoing cutting practices. In such stands, the conditions affecting bark-beetles vary according to different cutting methods which coincidentally produce different quantities of food in the form of slash, and expose that food, as well as the environment generally to altered micro - and meso - climates. The present investigation was undertaken to determine and explain some of the major factors underlying the variability in concentration of certain bark-beetles in a forest stand cut in certain selected ways. An investigation of this nature may be carried out in an area chosen for this purpose alone, or may be coordinated with a programme already designed for silvicultural purposes. There are advantages and disadvantages either way. The requirements for entomological experimentation are not necessarily best provided by the experimental design which is adequate for silvicultural purposes. On the other hand, the results from such a coordinated study carry the weight of authenticity for representing an actual forestry condition, and not merely a hypothetical case. In addition, the use of the materials provided by a silvicultural study make possible an entomological study which would otherwise be too costly of time and effort. Indeed, one of the chief obstacles to this type of study, heretofore, has been the lack of selectively cut stands. In 1952 the Dominion Forest Service initiated studies on selective cutting of lodgepole pine (Plnus contorta Dougl.) in the foothills region of Alberta. The opportunity was here presented for getting the special forestry conditions for the desired entomological study. The entire entomological Investigation, of which this study is a part, had a broad basis. Ultimately, it is desired to know something of the make-up of the insect complex associated with stands selectively cut in different ways, to learn something of the factors responsible for the variation of concentration, and to observe the effect of the insect population on the forest. The present investigation is an initial study to determine the manner in which the bark-beetles disperse within newly logged regions, and to relate their type of dispersal with the factors common to the environment. The insect complex was made up chiefly of Scolytids, Cerambycids, and Buprestids. Among the species, Ips pini Say. formed the most important component and the one which provided the most suitable data for analytical study. Accordingly the data concerning this species form the basis for the conclusions arrived at in this study. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Plants have been used for centuries to treat a wide range of ailments in the history of all civilizations. However, a growing interest in medicinal plants requires appropriate management to prevent over-exploitation of target species. The challenge for scientists is to find equilibrium between resource exploitation and the maintenance of viable populations of target species. Sustainability of use requires an understanding of the ecological, economic and socio-cultural aspects of resource use and the interaction between these factors. This research focuses on the ecological and socio-cultural aspects required to underwrite species-specific sustainable harvesting systems for bark used for traditional medicine. The social survey conducted in the form of structured interviews with traditional healers reported 69 plant species used for medicinal purposes in the southern Cape. The results suggested that resource users are aware of the increase in demand for medicinal plants in general, attributing this to an increasing recognition of traditional medicines and increasing prevalence of diseases. Ocotea bullata (Endangered), Curtisia dentata (Nearly Threatened) and Rapanea melanophloeos (Declining), as well as Siphonochilis aethiopicus (Critically Endangered), Elaeodendron transvaalense (Near Threatened) and Cassipourea flananganii (Endangered) that do not occur in the area naturally, were identified as species in high demand for their medicinal bark properties. Given the high demand and concerns about over-exploitation, a need for further ecological research to develop sustainable harvest systems was identified. Two species, O. bullata and C. dentata, were selected from an earlier study on the response of several species to bark stripping, that was confined to a study period of three years after treatment. With this current study tree response to bark stripping and harvesting impact were assessed over a period of ten years to reveal the intra and inter-specific difference of wound occlusion (wound closure through bark-regrowth) and the anatomical decay consequences of bark stripping. This is, to the knowledge of the author, the first study to evaluate the structural-tree pathogen interaction following bark stripping on medicinal tree species in Africa. The results revealed species-specific differences in terms of both wound closure and efficiency in decay containment. O. bullata had a significantly better wound occlusion rate and a lower extent of decay. The relationship between tree diameter growth and the rate of wound occlusion allowed for the formulation of a preliminary model that will assist forest managers in developing bark harvest systems. Smaller trees showed poor bark regrowth and a significantly higher mortality, which suggest that a minimum tree size for harvesting needs to be stipulated in the harvest prescriptions. In contrast, C. dentata showed a much higher volume of decay within the stem, poor bark regrowth and a significantly higher mortality of bark-stripped trees. In conclusion, the harvesting of bark for C. dentata through bark stripping is not viable, and alternatives should be explored. O. bullata has a much greater potential for strip harvesting, both in terms of bark regrowth and the containment of wood decay following wounding. / AFRIKAANSE OPSOMMING: Beskawings gebruik al vir eeue plante vir die behandeling van ‘n verskeidenheid van kwale. Die toenemende belangstelling in medisinale plante vereis egter oordeelkundige bestuur om die oorbenutting van teikenspesies te voorkom. Die uitdaging vir wetenskaplikes is om 'n balans tussen die benutting van hulpbronne en die handhawing van lewensvatbare populasies van teikenspesies te bewerkstellig. Standhoudende benutting vereis insig in die ekologiese, ekonomiese en sosio-kulturele aspekte van hulpbronbenutting, en die interaksie tussen hierdie faktore. Hierdie navorsing fokus op die ekologiese en sosio-kulturele aspekte wat nodig is om spesie-spesifieke, standhoudende oesstelsels vir bas wat vir tradisionele medisyne gebruik word, te onderskryf. Die sosiale opname, in die vorm van gestruktureerde onderhoude met tradisionele genesers, dui op 'n totaal van 69 plantspesies wat vir medisinale doeleindes in die Tuinroete gebruik word. Gebruikers is oor die algemeen bewus van die toenemende vraag na medisinale plante, en skryf dit toe aan groter erkenning van tradisionele medisyne en ‘n toename in siektes. Ocotea bullata (Bedreig), Curtisia dentata (Byna bedreig) en Rapanea melanophloeos (Afnemend), asook drie spesies wat nie natuurlik in die gebied voorkom nie, Siphonochilis aethiopicus (Kritiek bedreig), Elaeodendron transvaalense (Byna bedreig) en Cassipourea flananganii (Bedreig), is geïdentifiseer as spesies in groot aanvraag weens hul medisinale eienskappe. Die hoë aanvraag en kommer oor oorbenutting het gelei tot die behoefte vir verdere ekologiese navorsing vir die onwikkeling van oesstelsels vir die spesies. Twee spesies, O. bullata en C. dentata, is geselekteer van ‘n vroeëre studie oor die reaksie van verskeie spesies op basstroping wat beperk was tot ‘n studieperiode van drie jaar na behandeling. Die huidige studie was daarop gemik om die reaksie en impak oor ‘n periode van 10 jaar na behandeling te bepaal, en die intra- en inter-verskille van wond sluiting (wond sluiting deur die hergroei van die bas) en anatomiese verrotting na basstroping te beskryf. Dit is, tot die kennis van die outeur, die eerste studie om die struktuur-boompatogeen interaksie na basstroping op medisinale boomsoorte in Afrika te beskryf. Die resultate dui op spesie-spesifieke verskille in beide wond en die beperking van houtverrotting. O. bullata het ‘n betekenisvolle hoër tempo van wondsluiting en effektiwiteit in die beperking van houtverrotting. Die korrelasie tussen boomdeursnee-aanwas en die tempo van wondsluiting het die ontwikkeling van ‘n voorlopige model om bosbestuurders te help met die ontwikkeling van oesvoorskrifte, moontlik gemaak. Kleiner bome toon swak bas-hergroei en betekenisvolle hoër mortaliteit, wat aandui dat ‘n minimum grootte vir oesbome neergelê behoort te word in oesvoorskrifte. In teenstelling toon C. dentata ‘n baie groter mate van houtverrotting, het swak bas-hergroei, en ‘n betekenisvolle hoër mortaliteit van gestroopte bome. Ter afsluiting, die oes van C. dentata deur basstroping is nie lewensvatbaar nie en alternatiewe behoort ondersoek te word. O. bullata het ‘n groter potensiaal vir standhoudende basstroping, beide in terme van bas-hergroei en die beperking van houtverrotting na oes.

No description available.

Thesis (M.S.)--Oregon State University, 1970. / Typescript. Mounted photographs. Includes bibliographical references (leaves 67-73). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1971. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

The impact of a chromium smelter on pollution was evaluated by determining Cr(VI) in topsoil, grass and tree bark by electhrothermal atomic absorption spectrometry (ETAAS). It was found that bark reflected the levels of air pollution better than soil and grass due to its high accumulative ability of Cr(VI). The tree bark was contaminated with Cr(VI) by a factor of 9 than in soil. It is therefore suggested that the bark be used as an indicator of air pollution for long-term exposure. The concentration of Cr(VI) in the bark was always a fraction of the total concentration of Cr and ranges between 1.6 and 3%. The method used in the preparation of samples was validated by the analysis of certified reference materials.

The study evaluates the potential of pine litter for use as a substrate in the propagation of vegetable transplants in trays. Sub-optimum pH and electrical conductivity of pine litter were addressed by incorporating 10 % feedlot manure by volume. The water holding capacities of pine litter and the pine litter-feedlot manure mixture were higher than the minimum required, but their air filled porosities were below optimum. The pine litter-feedlot manure mixture reduced the germination percentages of cabbage seedlings by 17 % and lettuce seedlings by 13 % relative to composted pine bark, but the germination percentage of tomato seedlings was similar in both substrates. There were no significant differences in the growth of vegetable transplants between the two substrates. In both substrates increasing nutrient availability by adding controlled-release fertilizer had similar positive effects on the growth transplants. Substrate-nutrient availability interactions were only observed in dry shoot mass of lettuce seedlings and dry root mass of tomato seedlings. Composting the pine-litter animal manure mixture could possibly improve the observed low germination percentage of vegetable transplants in pine litter.

No description available.