Thesis (M. Sc. (Botany))--Rhodes University, 2000.

Thesis (M.A.)--Humboldt State University, 2006. / Includes bibliographical references (leaves 36-38). Also available via Humboldt Digital Scholar.

abstract: One of the most economical and viable methods of soil improvement is dynamic compaction. It is a simple process that uses the potential energy of a weight (8 tonne to 36 tonne) dropped from a height of about 1 m to 30 m, depending on the project requirement, on to the soil to be compacted hence densifying it. However, dynamic compaction can only be applied on soil deposits where the degree of saturation is low and the permeability of the soil mass is high to allow for good drainage. Using dynamic compaction on saturated soil is unsuitable because upon application of the energy, a part of the energy is transferred to the pore water. The technique also does not work very well on soils having a large content of fines because of the absence of good drainage. The current research aims to develop a new technology using biogenic gas production to desaturate saturated soils and extend the use of dynamic compaction as a ground improvement technique to saturated soils with higher fines content. To evaluate the feasibility of this technology an experimental program has been performed. Soil columns with varying soil types have been saturated with substrate solution, resulting in the formation of nitrogen gas and the change in soils volume and saturation have been recorded. Cyclic triaxial tests have been performed to evaluate the change in volume and saturation under elevated pressure conditions and evaluate the response of the desaturated soil specimens to dynamic loading. The experimental results showed that soil specimens treated with MIDP under low confinement conditions undergo substantial volume expansion. The amount of expansion is seen to be a factor of their pore size, which is directly related to their grain size. The smaller the grain size, smaller is the pore size and hence greater the volume expansion. Under higher confining pressure conditions, the expansion during gas formation is suppressed. However, no conclusive result about the effect of the desaturation of the soil using biogenic gas on its compactibility could be obtained from the cyclic triaxial tests. / Dissertation/Thesis / Data sheets / Masters Thesis Civil, Environmental and Sustainable Engineering 2018

Many rural communities in arid areas of the world make extensive use of perennial water supplies retained within the sediment of a river channel. This naturally filtered water provides for their basic subsistence. A general term applied to the abstraction of water from river sediment is sand-abstraction. Ephemeral and seasonal rivers primarily drain the dryland regions of the world. These arid regions are typically subject to extensive environmental degradation with a consequent high degree of surface erosion. As a result, many of the rivers have become sand rivers, filled with copious amounts of sediment. Most arid areas are subject to occasional rainstorms and flash floods that immediately drain to waterways and saturate the sediment within the river channel. In larger rivers a perennial supply of water is maintained within the sediment. Despite a perceived potential for this water resource there has been little development of any small-scale technology that is suitable for use at a basic rural level. A research and study programme was instigated to assess fully, the potential of such a resource. Field research was undertaken to characterise typical sand rivers and to assess the water storage and water loss and retention factors within river sediment. A check list for identifying possible sand-abstraction sites was devised. In the process of this study the advantages of storing water in sand was fully appreciated and attention given to the development of initially less suitable sites in serious water deficit areas. Systems for efficient abstraction of water were reviewed and designs formulated for the fabrication of equipment to mechanically draw water from river sediment. A series of well-screens, well-points, infiltration galleries and caissons have been designed and initial tests have been conducted under field conditions. Simple technology handpumps that it was considered could be operated, maintained and repaired by rural communities using locally available materials have been developed in conjunction with the abstraction equipment. In consultation with rural people an analysis was made of the technical and sociological requirements that are considered essential for the sustainability of technology suitable for use by disadvantaged rural communities. Both practical and literature research has indicated the latent possibility of this technology. Interaction has been maintained with four communities throughout the research and development period and contributions and indications received are that there is a need to develop such a water source with an upgraded technology. The conclusion from the work undertaken is that development of the technology is worthwhile and that greater efforts should be made to promote it at a small-scale, rural level. In addition the potential to provide clean water in arid regions from such a lowtechnology application should be drawn to the attention of professional water engineers.

The succession on the dunes of the Mlalazi Nature Reserve represents a classical example of primary succession. The reproductive strategies of eight key species were compared to determine some of the mechanisms affecting the community dynamics, at the population level, in the early stages of succession. There is a temporal separation in the flowering and fruiting phenologies. Passerina rigida, Stipagrostis zeyheri and Imperata cylindrica produced small seeds with a low fruit/seed mass ratio within a short cycle. The seeds are suitable for wind-dispersal. The animal-dispersed species; Eugenia capensis, Mimusops caffra and Scaevola plumieri, produced large fleshy seeds with a high fruit/seed mass ratio within cycles of six months and more. Chrysanthemoides monilifera, also an animal-dispersed species, produced a large quantity of small fleshy seeds throughout the year. The fern, Microsorium scolopendrium produced spores throughout the year. The staggered fruiting and flowering phenology ensures a year-round availability of fruit in the dunefield. The key species formed less than half of the species composition of the soil seed bank. The size and range of the soil seed bank differed between the species. P. rigida and S. plumieri formed a high proportion of the seeds in the soil with a wide distribution along the successional gradient. The other species had low soil seed densities with short distribution ranges, or were not present. P. rigida and S. plumieri are easily dispersed species, whereas the other species may have a more restricted and clumped distribution due to the effect of foragers. A high density of P. rigida and E. capensis seeds were found under the parent trees. Only seeds of P. rigida and S. zeyheri were found in the soil in the open. Seeds of P. rigida, S. zeyheri, E. capensis and M. caffra were found under the canopies of P. rigida, E. capensis and M. caffra. No seeds of C. monilifera and I. cylindrica were found in the soil, possibly due to predation. The period of the study (September 1991 to November 1992) was in a dry or drought cycle with only 56.8% of the mean annual rainfall falling. Seed germination and seedling survival of all the species were affected by these dry, warm climatic conditions. The species had seedling densities of less than 4 seeds/m². The environmental conditions along the successional gradient also had an effect on seed germination and seedling survival. Environmental factors of soil pH, light intensity and surface soil temperatures were higher in the open than under canopy. Soil pH and the understorey cover decreased as the light intensity decreased from under the canopy of P. rigida to M. caffra . Litter cover and plant height increased. E. capensis had measurements intermediate to the two species, but had higher surface soil temperatures and plant height than P. rigida. Seedlings of P. rigida in the open and under the canopy of the parent plants had died by the end of the monitoring period. 50% of the seedlings of S. zeyheri under the canopy of P. rigida and M. caffra died. The mortality rate of the seedlings of E. capensis was lower under M. caffra than under the parent plants. I. cylindrica may be propagated vegetatively. However, the mortality of the propagules was greater under the canopy of E. capensis than under P. rigida. M. caffra only germinated under the canopy of E. capensis with a 100% mortality of the seedlings. M. scolopendrium only produced propagules through vegetative propagation under the canopy of E. capensis and M. caffra. The mortality of the young ferns was less than 50% and less under M. caffra than under E. capensis. No seedlings of C. monilifera or S. plumieri were found. The seed distribution range, seed germination requirements and the effect of the environmental conditions on the germination of the seeds and seedling establishment of the species appear to important factors of the reproductive strategies regulating the size of the species populations along the successional gradient.

There are about 100,000 described fungal species, however, the diversity could be higher because conventional techniques do not allow identification of all groups of fungi and there are still unexplored geographical areas. High-throughput DNA sequencing methods provide the opportunity to resolve the diversity and distribution of mycelia in soil. Soils are the largest pool of terrestrial carbon and macromolecular materials, such as lignin and cellulose, form an important part of this soil carbon. Saprotrophs (decomposers) fungi degrade lignin and cellulose that is important to the global carbon cycle, although lignin is highly resistant to degradation if compared with cellulose. In this work, we investigated the diversity of fungi in sand-dune soils and their involvement in the decomposition of lignin and cellulose. The key findings of this work were:•A comparison of sand-dune ecosystems from two reserves in the UK showed differences in the ion concentrations, pH and total organic carbon in soils, suggesting that there were different environmental conditions that could potentially affect the distribution/presence of microbial communities in soils, e.g. fungal communities.•Fungi from field samples were identified using 454 pyrosequencing. The identified fungal species belong to groups with different ecologies, among which are wood-rotting fungi that are the main agents responsible for the lignin breakdown. The fungal communities were distributed differently across the different sand-dune ecosystems, sampling times and type of bait materials.•Lignin and cellulose can be degraded in field samples over time. Lignin degradation was shown by the shifts in the [Ac/Al]S, [Ac/Al]G and [S/G] relative lignin decomposition state proxies, and cellulose degradation by the shifts in the [cellulose:cellulose+lignin] ratio. Cellulose degradation was faster than lignin, thus confirming previous studies.•The degradation of both lignin and cellulose was different depending on the type of plant material, ecosystem/soil characteristics where the material was buried and fungal communities present on the bait materials.•Lignin breakdown was most likely to be by white-rot fungi that were identified colonising the bait materials.

Der Transport von Sand ist geprägt durch die Ausbildung von Strukturen. Die kleinste Form bezeichnet man als Rippel. Da die Dimension von äolischen Sandrippeln nicht sehr groß ist, existieren nur wenige Messungen welche direkt am Strand oder in der Wüste durchgeführt wurden. In diesem Artikel wird ein Messverfahren vorgestellt, welches eine Vermessung von Höhenunterschieden im Sandfeld in der Größenordnung von Millimetern ermöglicht. Die durch die sogenannte „Schattenwurf-Methode“ erhaltenen Ergebnisse stehen in guter Übereinstimmung mit der Literatur. Außerdem werden Erkenntnisse aus der Untersuchung von Sandkorngrößenverteilungen an verschiedenen Positionen eines Rippels aufgezeigt. Des Weiteren wird in dieser Arbeit eine Methode vorgestellt, welche es ermöglicht, ein durchgängiges Höhenprofil für ein vermessenes Sandrippelfeld zu erstellen. Das Ergebnis erlaubt eine genauere Betrachtung und Analyse des Verlaufs von Rippelbergen und Rippeltälern. / The transport of sand is affected by the development of structures. The smallest kind of them is called ripple. Owing to the fact that the dimension of aeolian sand ripples is not very large there are only a few measurements that were made directly at the beach or in the desert. This article presents a measurement method that provides the possibility of measuring height differences in the dimension of millimetres. The results achieved by the so called “shadow-cast” method are in good agreement with that found in literature. In addition, findings concerning the investigation of the sand grain size distribution at different positions on the ripple are presented. Furthermore, a possibility of producing continuous profiles of a measured sand ripple field, is presented in this work. The result allows a specified observation and analysis of developing ripple crests and ripple troughs.

Diese Studie soll einen näheren Aufschluss über die Ermittlung der mittleren Saltationslänge und somit über den Sandtransport geben. Die Bestimmung der vertikalen und horizontalen Verteilung des Sedimenttransports erfolgte mittels MWAC- und Quaderfallen-Messungen. Das dazugehörige Feldexperiment fand im März 2008 am Zingster Strand (Ostsee/Deutschland) statt. Des Weiteren wurde von Namikas im Juni 1997 in der 'State Vehicular Recreation Area' (SVRA) an der kalifornischen Küste der Transport mithilfe von Vertikal- (VTRAP) und Horizontalfallen (HTRAP) ermittelt (Namikas, 2003). Die Experimente der Quaderfallen und der HTRAP wurden numerisch simuliert und auf Tauglichkeit zur Sprunglängenberechnung geprüft. Die Analyse brachte hervor, dass die vier benutzten Quaderfallen mit unterschiedlicher Länge eine unzureichende Vorhersage für den Massenfluss liefern. Die HTRAP gibt erst durch Differenz der einzelnen Fächer eine nahezu korrekte Prognose. Folglich kann durch eine Korrektur der ermittelten Werte eine zutreffende mittlere Saltationslänge errechnet werden. / This study is giving a near information about ascertaining of mean saltation lenght and consequently about sand transport. The vertical and horizontal distribution of transport of sediment was determined by using MWAC-sampler and cuboid traps measurements. The respective field experiment was processed on the beach of Zingst (Baltic Sea/Germany) in March 2008. Furthermore, the transport was established by using vertical (VTRAP) and horizontal traps (HTRAP) in the 'State Vehicular Recreation Area' (SVRA) on the California coast in July 1997 (Namikas, 2003). The experiments of cuboid traps and HTRAPs have been simulated numerical and checked for efficiency to evaluation of jump lenght. The results generated an insufficient prediction of mass flux by using four cuboid traps with different length. The HTRAP delivered an almost correct prognosis when seperate compartments are subtracted. Consequently a true mean saltation length is calculated by an adjustment of determined values.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第17868号 / 工博第3777号 / 新制||工||1577(附属図書館) / 30688 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 木村 亮, 准教授 立川 康人 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Turfgrass establishment on sand-based rootzones is routinely accomplished by using sod produced on a fine-textured native soil. As a result, soil layering occurs, potentially causing initial reduction in water infiltration, rooting, aeration, and overall turfgrass quality. This research was aimed at determining the feasibility of applying sand over existing native soil to produce hybrid bermudagrass (Cynodon dactylon [L.] Pers. x C. transvaalensis Burtt-Davy) sand-based sod. Factors evaluated were visual quality and scalping. Treatments were harvested and transplanted to a sand-based research green where handle-ability, tensile strength, and infiltration were also evaluated. Results indicate aerify and topdress treatments showed higher quality pre-harvest. Control and 25 mm treatments were best in terms of harvesting, handle-ability, and sod tensile strength. Infiltration data indicated no significant differences between treatments. These outcomes along with further analysis could provide sod producers with a valuable product for use on sand-based rootzones.