In the pursuit of sustainable development, Environmental Impact Assessments (EIA) are acknowledged globally as a tool designed to assist governing authorities by providing the information required to make an informed decision regarding development proposals. South Africa has entrenched this EIA requirement in the presiding environmental legislation: the National Environmental Management Act (Act 107 of 1 998). In the effort to manage the negative impact of development on the rocky ridges of Johannesburg, the Gauteng Department of Agriculture, conservation, Environment and Land Affairs (GDACEL) has introduced a buffer zone requirement in the procedure of the EIA. The Red Data Plant Policy for Environmental Impact Evaluations for GDACEL described a buffer zone as a collar of land that filters out inappropriate influences from surrounding activities. As a tool in the EIA, a buffer zone is a worthwhile concept. However, the determination of the dimension of the buffer zone on rocky ridges, is non-discriminatory between sites, and thus, presents potential contention between decision-making authorities and developers. There is a need for further research to establish a scientifically acceptable method of determining site-specific buffer zones for individual EIA applications. The key objective of this paper is to suggest the possibility of determining a buffer zone that accommodates the unique environmental aspects of each site. This is achieved by determining the distance between the edge of existing developments and the point at which the successional climax community within the adjacent natural vegetation is established. Three suitable study sites, consisting of developed residential estates on ridges adjacent to nature reserves, were identified within the greater Johannesburg metropolis. The three study sites identified for this assessment include Kloofendal (west), Morning Hill (east) and Kliprivier (south). Within each study site field surveys were conducted along transects starting 5m from the development edge and ending 75m within the nature reserve adjacent to each site. Quantitative (species density) and qualitative (Braun-Blanquet cover-abundance values) data analysis was employed to describe and evaluate the identified plant communities. The data in this study provides clear indication that a 25-35m buffer zone would suffice for these specific plant communities to maintain a climax successional status if impacted on by residential development. This paper thus makes a case for permitting the determining of variable buffers zones, based on a gradient analysis of a plant community, as a potential panacea to the problem of resistance and reluctance to accept present standard buffer zones. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2007.

The literature of disturbance ecology reveals that, under present climatic conditions, non-native plants have little or no role in high arctic tundra revegetation. Rather, it has been suggested that indigenous flora, especially long-lived perennial graminoids, are crucial to recovery. However, few long-term data are available on past impacts within productive sedge-meadows in the High Arctic, and none which consider the non-vascular flora. / This thesis combines biogeographical and patch dynamics perspectives to focus on $ geq$21 yr of natural and assisted recovery of vegetation and soils from a wide range of dated anthropogenic surface disturbances at three Canadian Arctic sites. Empirical, experimental and archival investigations were made among climatically similar, but widely disjunct, coastal lowlands of contrasting geologies on Baffin, Devon, and Cornwallis Islands. These data encompass minerotrophic and oligotrophic wetlands in which the vascular floras show minimal differentiation yet the sampled bryofloras share only 31.8% of their total taxa. The occurrences chosen for study are representative of the most widespread, small-scale human impacts in the North, including vehicular, pedestrian, construction, and pollution disturbances. / It was determined that rutting from even a single passage of a tracked vehicle in summer resulted in significant reductions in species richness and biomass. On slopes $ geq$2$ sp circ$, these same small ruts have drained large areas of peatlands, a serious cumulative impact. Long-term effects of drainage include the local extinction of populations of Sphagnum spp. and rhizomatous vascular aquatics, and changes in the chemistry and thermal regime of drained mineral soils. Other effects include significant changes in biomass and the concentrations of macronutrients in the leaves of dominant species. These effects were magnified in peatlands drained where multi-pass vehicle movements occurred. / Species richness displayed an inverse relationship with trampling intensity and the soils of heavily trampled ground remained severely compacted after 21 years. These patches were dominated by dense swards of ruderal grasses. Nutrient concentrations in the leaves of the latter and other colonizing and surviving species tended to increase with trampling intensity. Trampled patches and archaeological sites appeared selectively grazed by several herbivores. Although humans initiated the disturbances within these patches, it is the animals which are responsible for many of the dynamics of patch change over the long-term. / Classification and ordination procedures revealed linkages between the floristic associations of trampled meadows on Baffin Island and archaeological sites on Devon and Cornwallis Islands. One critical implication is that even low levels of human impact may give rise to ruderal plant communities which are extremely persistent. These patches are poor in terms of species richness, but contribute to habitat heterogeneity at the landscape level and comprise preferred forage for local vertebrate herbivores. / Archaeological excavation and restoration revealed that at least some stores of viable seed exist in both mesic and wet tundra soils and point to the importance of initial floristic composition (sensu Egler 1954). From a long-term perspective, the data establish that mesic tundra vegetation and soils are easily disturbed and recover much more slowly than their low arctic counterparts under similar disturbance regimes.

The recent increase in large fires in southwestern forests has prompted concern regarding their ecological consequences. Recognizing the importance of spatial patterns in influencing successional processes, I asked: (1) How do large fires change plant communities?; (2) What are the implications of these changes for ponderosa pine forests?; and (3) What is the relationship of fire severity to gradients of climate, fuels, and topography? To address the first two questions, I studied succession in the woody plant community at two sites that burned in high-severity fire: La Mesa fire in northern New Mexico (1977) and Saddle Mountain in northern Arizona (1960). After large fires, abiotic conditions, associated prefire plant distributions, and spatial patterns of burning interacted to result in particular successional outcomes. Variation in abundance and diversity of species that spread from a refuge of seed sources remaining after the fire followed the model of wave-form succession. I investigated the implications of large fires for ponderosa pine by examining the influence of spatial patterns of burning on regeneration. Tree density corresponded most closely with particular scales of seed dispersal kernel and neighborhood severity metrics. Spatial patterns of burning remained influential even after consideration of variables describing subsequent burning and the physical and biotic environment. Age structure of young forests indicated that populations spread in a moving front and by long-distance dispersal. To explore the relationship between fire severity and climate, I investigated how the spatial heterogeneity of high-severity patches varied among 20 fires across gradients in fire size and climate. The largest fires generally occurred during cool dry La Niña climates, however, several fires deviated from this trend. Some spatial properties of severity did not correspond to fire size or to changes in climate. Characteristics of fuels and topography altered spatial patterns of severity, but interactions with extreme burning conditions may have disrupted these local influences in both La Niña and El Niño fires. Spatial patterns of fire severity are central to understanding ecological dynamics following large fires in southwestern forests. Moreover, simplistic assumptions regarding the relation of fire severity to fire size and climate should be viewed with caution.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 45-51). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2004. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (PhD) University of Montana, 2008. / Title from author supplied metadata. Contents viewed on May 19, 2010. Includes bibliographical references.

No description available.

This study makes use of simple statistical models which may be manipulated for projection of changes in the Kaiparowits Region of Southern Utah. A method of determining habitat preferences of small rodents from capture-recapture trapping data is proposed. It is suggested that some aspects of animal behavior regarding trapping may also be explained. Timing of flowering of Oryzopsis hymenoides and Hilaria jamesii as related to enviromental conditions was investigated, and models of the requisite conditions proposed. It is suggested that similar models may be used to describe the timing of other phenological events. Succession on disturbed sites is considered to determine predictablility of revegetation. It was determined that early stages of succession of three habitat-types are proceeding in a manner similar to that described on other areas of the pinyon-juniper forest.

1. For the first time detailed phytosociological measurements, using objective methods have been made in a large number of lowland successional stands throughout eastern Canada. 2. Soil and soil surface organic matter samples were collected on a volume-weight basis for all stands studied. An increased use of bulk-density sampling methods is advocated as they allow the conversion of all nutrient percentage and parts per million analyses to actual weights par unit area profile depth, as was done in the present work. [...]