Bibliography: leaves 100-114. / Human-induced land management practices are key factors which influence the dynamics of landscapes, land elements and biotic communities in Xeric Succulent Thicket, a notoriously fragile and low resilience ecosystem in the Eastern Cape, South Africa. In its natural state this vegetation type is characterized by a continuous mosaic of clumps of diverse woody shrubs in a matrix of grass, hardy dwarf shrubs and bare ground. When indigenous herbivores are replaced by domestic livestock at unsustainable stocking rates, the ratio of clump to interclump areas decreases. This has impacts on biodiversity at the landscape level, and affects the composition and species richness of plant, arthropod and reptile communities and fungal symbionts. The study has two main objectives: 1) to detennine the local-level effects of different types of land use on biodiversity in Xeric Succulent Thicket; and 2) to better understand the factors which affect biodiversity in different taxonomic groups and at different spatial scales, so that the preservation function of protected areas could be enhanced. The key questions which are addressed in the thesis are what does 'biodiversity' mean, and what are its different dimensions in Xeric Succulent Thicket; what roles do protected areas and other lands play in preserving biodiversity, how are different taxonomic groups affected by different types of land use; and how can biodiversity be monitored and measured? . The regional 'conservation landscape' is seen as the protected area plus the land immediately adjoining it, and is viewed as an integrated mosaic of anthropogenic landscapes (land management units), land elements (patches within landscapes). producer communities (assemblages of interacting plant species), consumer communities (assemblages of interacting herbivores and predators) and soil microorganisms. From a process point of view, the research relates the intensity of disturbance, mainly as a result of herbivory, to landscape complexity, the structure of land elements, and the species richness of producers and consumers within land elements. The patterns which emerge are interpreted in the context of ecosystem functioning, from the point of view of a practicing conservation biologist.

Water-use efficiency (WUE) as reflected in the leaf carbon stable isotope ratio was compared between co-occurring indigenous fynbos proteoids and invasive Australian hakeas H. sericea, H. gibbosa and H. suaveolens. At the driest site, H. suaveolens was slightly more WUE than several co-occurring proteoids; there was no significant difference between hakeas and proteas at the other sites. Transpiration rates of shoots and of whole trees were compared between Hakea sericea and Protea repens growing on Stellenboschberg northeast of Cape Town. Both measurements showed no real difference between the species and it is concluded that differences in water relations are not responsible for the highly competitive growth rates of hakeas in fynbos. It is hypothesised that hakeas may be able to vegetatively outcompete proteoids as a consequence of monopodial architecture and some ability to prevent shade-limitation of photosynthesis. A rough estimate of water loss due to transpiration and interception by H. sericea stands indicates that this species may have a significant effect on catchment water loss relative to open-canopy proteoid fynbos. This effect would be due not to transpiration rates of individual trees but to consistently high densities of mature hakea stands.

Morphometrics was used to study variation in Schizeae pectinata as previous study showed that material originating from the summer rainfall area of South Africa differ in several aspects from that originating from the winter rainfall area. The plant has a simple structure and consequently spore, stoma and sporangia sizes, as well as the number per lamina was studied to determine if the species can be subdivided into two groups, e summer and e winter rainfall group, as was previously hypothesised. Univariate and bivariate methods were used to display the extent of variation within the species. Univariate analysis reflect variability of spore and stomata size, and the number of pinna pairs per lamina. Statistical analyses showed that interpopulation variation for these characters are often highly significant. Phonetic methods were used in the analyses of the data set and shows continuous variation in this species. This continuous variation in Schizaea pectinata could be linked to a phenotypic response to environmental differences between the two regions.

No description available.

No description available.

Six days following the application of 1.5 and 3.0 lb/A of 2- methoxy-4-sec.-butylamino-6-ethylamino-s-triazine (GS-14254) to established plots of alfalfa, water samples were collected at several distances from the plots and analyzed for herbicide residues with a Beckman DB-G grating spectrophotometer. The data indicate that GS-14254 is transported in small amounts but that the concentrations in the runoff water decline rapidly with increased distance from the treated areas and time. S-14254 produced no visual injury symptoms of leaf chlorosis or plant stunting on alfalfa at the two rates used. However, some initial injury has been reported by other workers. This study indicates that oats are very sensitive to GS-14254 and that they would be a good bioassay for detecting different concentrations of this chemical in soil. The data indicate that the green alga, Chlorella, is a very sensitive test organism. However, all herbicide concentrations and incubation periods examined were found to be algistatic. Indications are that concentrations of this chemical transported in irrigation or precipitation runoff water when used at recommended rates, would likely not be hazardous to plant and animal life.

An integrated management approach for jointed goatgrass control was investigated at two farms in northern Utah using three tillage regimes and tree herbicides. The tillage regimes included no tillage, conservation tillage, and conventional tillage. Each regime was composed of different tillage practices common in the Intermountain West. A preemergence herbicide, clomazone, and two postergance herbicides, 2, 4-D and glyphosate, were investigated. Greenhouse studies were also conducted to investigate clomazone efficacy and depth of planting of winter wheat and jointed goatgrass. Differential sensitivity to clomazone between jointed goatgrass and winter wheat did not occur in the greenhouse for the rates tested. A treatment of 0.11 kg ai ha-1 clomazone reduced wheat and jointed goatgrass fresh weights similarly by 49 and 63% respectively. Jointed goatgrass did not germinate below 6.4 cm and emergence was initially reduced at the 2.5 cm soil depth. Winter wheat emergence was not lowered until the seed was planted 5.0 cm deep or deeper and continued to 8.9 cm deep.

This study was conducted to gain a better understanding of the seasonal changes of Gleason Elberta peach flower buds at the vii cellular level. Peach buds were obtained from the Howell Experiment Station in Ogden, Utah. Samples were collected at weekly intervals from October 25th, 1971 to March 29th, 1972 . When a killing frost precluded further sampling, the buds were preserved by standard electron microscopic techniques . Thin sections (500 to 700 A) of the cells around the ovarious cavity were examined with a Zeiss EM-9S-2A electron microscope. From October 25th, 1971 to January 3rd, 1972, more heterochromatin than euchromatin was in the nucleus . After January 3rd, 1972, no heterochromatin patches were observed. Nucleopores were not observed until March 7th, 1972. Proplastids looked very similar to mitochondria until November 22nd, 1971 when the alignment of the transparent part of proplastids became apparent around the envelope. The number of lipid droplets increased and reached a maximum level near December 6th, viii 1971 then leveled off. A few short cisternae of rough endoplasmic reticulum (RER) were found only in the sample collected on October 25th. From October 25th throush December 27th, short tubular smooth endoplasmic reticulum (SER) was observed near the cell membrane region and only a few Golgi bodies were found, scattered in the cytoplasm. They were in a pre-maturation stage. Starting from December 27th Golgi bodies were in a maturation stage, long sheetlike rough endoplasmic reticulum was noted and lysosomes, presumably pinched from Golgi bodies, were also observed. On February 22nd, the number of mitochondria as well as Golgi bodies and Golgi vesicles had increased . The number of mitochondria was further increased on February 29th. On March 7th, amyloplasts presumably developed from proplastids were observed. The results of this work revealed that polysaccharide metabolism was in progress from October 25th to December 27th as indicated by the presence of SER. The presence of lysosomes starting on December 27th suggested that the cell was undergoing intracellular digestion . The increased number of mitochondria and the Golgi bodies observed on February 22nd revealed an increased rate of respiration and the progression of cell wall metabolism respectively. The presence of nucleopores on March 7th would enhance exchange of information between the nucleus and the cytoplasm.

No description available.

No description available.