Thesis (Ph. D.)--School of Biological Sciences, Faculty of Science, University of Sydney, 1999. / Bibliography: leaves 235-260. Also available in print form.

Thesis (Ph. D.)--University of California, Riverside, 2008. / Includes abstract. Title from first page of PDF file (viewed Febrary 3, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references. Also issued in print.

Thesis (M.S.)--Ohio University, November, 2009. / Title from PDF t.p. Includes bibliographical references.

No description available.

No description available.

Stream-flow and storm-flow in four small catchments were analysed by the paired catchment method for a response to fire. Two of the catchments were vegetated with over-mature fynbos (the indigenous scrub vegetation of the south-western Cape Province, South Africa), one was afforested to Pinus radiata and the fourth to Eucalyptus fastigata. One of the fynbos catchments was burned in a prescribed fire in the late dry season. The other catchments burned in wildfires. Neither of the fynbos catchments showed a change in storm-flows. Annual total flow increases of around 16% were in line with predictions, being related to the reductions in transpiration and interception. The manner of stream-flow and storm-flow generation appeared to have remained unaltered despite the fire. The two timber plantation catchments experienced large and significant increases in stormflow and sediment yields, while total flow increased by 12% in the pine catchment and decreased marginally in the eucalypt catchment. After fire, storm hydrographs were higher and steeper though their duration was little changed. These fire effects are considered to be due to changes in storm-flow generation consistent with an increased delivery of overland flow to the stream channel. This was caused, in part, by reduced infiltration resulting from water repellency in the soils of the burned catchments. The inherent wettability of a wide range of soil types and textures from beneath timber plantations and other vegetation types over a broad geographic distribution in South Africa was measured by four methods. Soils with high repellency ratings, unrelated to fire, are common and are most likely to occur beneath plantations of Eucalyptus and Acacia spp. and indigenous forest. Water repellent soils played a role, at two of the three locations, in the generation of overland flow from small plots exposed to simulated rainfall. However, the inherent repellency of the dry soils was extreme, such that fire-induced water repellency was not a factor in the response of the plots. The important role of fire in this experiment was in burning-off of repellency in the surface layer of the soil and in removing ground cover. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

A predictive understanding of plant community response to various environmental influences (e.g. type, timing and frequency of disturbance, site productivity, fertilization, etc.) is a general goal of plant ecology. This study sought to further understanding of mesic grassland dynamics in KwaZulu-Natal using long-term field experiments (> 50 years) and short-term pot and plot competition experiments. The specific objectives were to: 1) examine the effects of long-term burning of grassland on soil organic matter content because of its potential impact on nitrogen cycling and community composition, 2) examine patterns of community composition and species richness in response to different type, timing and frequency of disturbance (burning and mowing) in a long-term grassland burning and mowing experiment and to different type and amounts of fertilizer application in a long-term grassland fertilization experiment, 3) develop hypotheses concerning the response of different species to disturbance and fertilization, and test these hypotheses using pot and plot competition experiments, and 4) provide a general synthesis of the results of the various field, pot and plot experiments that may be used to develop a predictive theoretical framework for mesic grassland dynamics. Total soil nitrogen was lowest in sites burnt annually, intermediate in sites burnt triennially and highest in sites protected from disturbance and sites mown annually in the dormant-period (spring or winter). Winter burning reduced soil organic carbon and total soil nitrogen more than spring burning. Mineralizable nitrogen was reduced by burning. The different effects of type, timing and frequency of disturbance on total soil nitrogen appeared to be an important determinant of community composition and species richness. Short-grass species (Themeda triandra, Eragrostis capensis, Heteropogon contortus, Diheteropogon amplectens and Eragrostis racemosa) were most abundant in annually burnt sites (especially winter burnt sites), whereas medium and tall-grass species (Eragrostis curvula, Cymbopogon spp., Hyparrhenia hirta and Aristida junciformis) were most abundant in triennially burnt sites, sites protected from disturbance and sites mown annually in the dormant-period, all of which had higher total soil nitrogen than annually or biennially burnt sites. Species richness and short-grass species declined with increasing levels of nitrogen fertilization in the fertilizer experiment and declined with increasing productivity and nitrogen availability in both the fertilizer and burning and mowing experiments. Thus, it was hypothesized that the type, timing and frequency of disturbance resulted in different compositional states through different effects on soil resources (especially nitrogen), which affected the competitive balance between short and tall species. The hypothesis that composition was determined by disturbance-mediated soil nitrogen availability was supported by competition experiments, which revealed that shortgrass species were most competitive in low-nutrient/low-productivity treatments and tall-grass species most competitive in high-nutrient/high-productivity treatments. The fertilizer experiment and a competition experiment revealed that tall broad-leaved species were most competitive in sites of highest productivity, fertilized with both nitrogen and phosphorus, whereas tall narrow-leaved species were most competitive in sites of intermediate productivity, fertilized with nitrogen only. It was hypothesized that summer mowing increased the abundance of short-grass species and decreased the abundance of tall-grass species in the burning and mowing experiment by increasing the competitive ability of short-grass relative to tall-grass species, rather than the tall-grass species being less tolerant of mowing. A competition experiment revealed that tall-grass species (Hyparrhenia hirta and Panicum maximum) were as tolerant of cutting as a short-grass species (Themeda triandra). Themeda triandra was shown to become extremely competitive in cutting treatments, reducing the biomass of most other species relative to their monoculture biomass, showing that its dominance of mown sites in the burning and mowing experiment was a result of its superior competitive ability rather than greater tolerance of mowing. However, many tall erect herbaceous dicots appeared to be intolerant of summer mowing, probably because their meristems are aerial and easily removed by mowing, whereas short creeping herbaceous dicots were increased by summer mowing probably because their meristems were below the mowing height. Further, these short species would be vulnerable to shading in unmown sites. Thus, species with basal meristems (hemicryptophytes) or meristems near the soil surface (geophytes) appear to be more tolerant of mowing than species with aerial meristems (phanerophytes), but the tradeoff is that a low meristem height renders them vulnerable to shading in unmown sites. Very high litter accumulation in the sites protected from disturbance appeared to have a direct influence on community composition and species richness. Species that dominated these sites (e.g. Tristachya leucothrix & Aristida junciformis) initiated tillers below-ground and had sharp erect shoots that appeared to be an adaptation for penetrating litter. Species that initiate tillers below-ground are probably less vulnerable to the effects of shading by litter because their tiller initiation is not dependent on high light availability. The fact that Aristida junciformis was shown to have very low competitive ability in two competition experiments, suggests its dominance of protected sites was through tolerance of high litter levels rather than competitive exclusion of other species. Low grass species richness in these sites was probably a result of an inability of many species to tolerate these high litter levels. This study has revealed that inherent site productivity and its interaction with the effect of disturbance on soil resources and litter levels is a major determinant of community composition and species richness. The effect of type, timing and frequency of disturbance on soil nitrogen was able to account for the principal changes in community composition. Thus, the influence of disturbance on soil nitrogen is a unifying principle in plant ecological theory that enables greater understanding of disturbance-composition relationships. However, intolerance of certain forms of disturbance (e.g. mowing) by species with aerial meristems, or intolerance of accumulating litter in the absence of disturbance by species without sharp erect shoots, may also have important influences on composition. In addition, this study has revealed that plant traits (height, leaf width, position of tiller initiation, shoot morphology and position of meristems) were well correlated with the various effects of disturbance and fertilization on community composition, indicating that a plant trait-productivity-disturbance framework has great potential for understanding and predicting species response to disturbance and multiple limiting nutrients. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2003.

No abstract available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Coastal sage scrub (CSS), a lowland plant community native to California, is home to many rare, threatened, or endangered plants and animals. Fire, a natural feature of CSS, is essential for maintaining species diversity. However, the invasion of non-native grasses has altered the fire regime in CSS, increasing fire frequency and fire season length and decreasing fire intensity. Changes in the historical fire regime may in turn cause feedbacks that favor non-native species, resulting in the loss of biodiversity in invaded CSS sites. Numerous studies have examined patterns of post-fire succession in CSS; however, the role that the pre-fire seed bank and the relative abundance of natives to non-natives play in vegetation regrowth and community recovery is unclear. A lack of adequate pre-fire data on community composition makes testing hypotheses about the role of seed banks in post-fire recovery challenging. I propose to study recovery of the plant community in two differentially invaded CSS sites (East and West field) following a fire at the Bernard Field Station in September 2013. Data collected at the two sites from 2009-2013 reveal that non-native grass cover was significantly higher than native cover at both sites, though the West field had slightly higher native forb cover. Furthermore, the invasive grass Bromus diandrus almost entirely dominated the East field. Vegetation cover in the West field was more diverse with the abundance of other non-natives (Bromus hordeaceus, Bromus madritensis, Vulpia myuros) and natives (Amsinckia menziesii, Lupinus spp.) significantly higher than in the East field. To determine the effects of these pre-fire differences on recovery processes, I will carry out a randomized block experiment with four treatments (control, native seed addition, non-native grass removal, and both native seed addition and removal of non-native grasses). Twelve blocks will be evenly divided between the East and West fields. I propose to measure relative seedling abundance for both native and non-native species after each significant rainstorm over a three-year study period. I hypothesize that the composition of seed banks pre-fire will predict vegetation regrowth post-fire. Specifically, I predict that, under control conditions, B. diandrus will dominate the East field post-fire given its high abundance pre-fire. Further, I predict that regrowth in controls plots in the West field will be more variable given its more diverse seed bank pre-fire. Lastly, I predict that native forbs will exhibit the greatest degree of recovery in plots where active restoration methods (seeding and non-native grass removal) are employed; the effects of these restoration methods should be strongest in the East field because the pre-fire vegetation community was more heavily weighed towards non-native species. This study will add crucial knowledge to our understanding of how the pre-fire seed bank in CSS affects its recovery post-fire, which may inform future conservation efforts to ensure the continued health and protection of CSS sites around California.

A stratified sampling method was used to study the effects of two prescribed fires on a 250-acre section at the northwest end of Fork Ridge, Hoosier National Forest, in the spring of 1993 and 1995. An unburned area at the southeast end of Fork Ridge, adjacent to the burned area, and with similar forest communities, was used as a control area. Three growing seasons after the last fire, the burned area exhibited noticeable differences in understory vegetation. Herbaceous species diversity and richness, total herb cover on mesic sites, and mean percent cover and relative frequency for mesic-site, shade-tolerant species were greater on the burned area than on the unburned area. Dry-site, shade-intolerant tree seedlings including scarlet oak (Quercus Coccina), chestnut oak (Quercus prinus), sassafras (Sassafras albi dum), and tulip poplar (Liriodendron tulipifera) had higher relative frequency in the burned area, while shade-tolerant flowering dogwood (Cornus Florida) had lower relative frequency. / Department of Biology