Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 189-203).

Thesis (Ph. D.)--University of Melbourne, 1985. / Typescript (photocopy). Includes bibliographical references (leaves 332-350).

Thesis (Ph. D.)--University of Adelaide, Dept. of Environmental Science and Rangeland Management, 1997. / Includes bibliographical references (leaves 227-244).

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 137-148).

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "May, 2008." Includes bibliographical references). Online version available on the World Wide Web.

The grassland bird-community has declined significantly in abundance and diversity in Illinois over the past century. Reclamation of surface coal-mines in southern Illinois has created ca. 50,000 ha of grassland habitat that offers surrogate habitat for grassland and shrubland birds. Much of the grassland habitat created by reclamation of mine lands has not been managed and has succeeded to shrubland habitat dominated by both native and non-native shrubs. The purposes of this research were to identify the bird community utilizing reclaimed surface-mines in southern Illinois, and to examine the habitat-associations of the bird community and compare those to previously reported habitat-associations. I examined bird communities, plant structure and composition, and invertebrate communities at grasslands and shrublands at 3 reclaimed surface-mines in southern Illinois. I used 100-m wide strip-transects to survey the bird community and measured habitat characteristics including: vegetation height and density, litter depth and cover, shrub density and height, and plant composition. I observed 57 bird species over 126 surveys in 2008 and 2009. I used Generalized Linear Models and Akaike's Information Criteria to develop habitat-association models for 7 bird species: Henslow's sparrow (Ammodramus henslowii), grasshopper sparrow (Ammodramus savannarum), eastern meadowlark (Sturnella magna), dickcissel (Spiza americana), indigo bunting (Passerina cyanea), field sparrow (Spizella pusilla), and Bell's vireo (Vireo belli). Of these 7 species, dependable models were found for the Henslow's sparrow, grasshopper sparrow, eastern meadowlark, and field sparrow. The best habitat model for Henslow's sparrows indicated a positive association with % litter cover and a negative association with large variations in grass cover. The best habitat model for grasshopper sparrows indicated a negative association with both litter cover and depth and a positive association with grassland area. The best habitat model for the eastern meadowlark indicated a negative association with visual obstruction and shrub density. The best habitat model for the field sparrow indicated a curvilinear association with shrub density and visual obstruction. The habitat-association model for Henslow's sparrows differed from previous research in that neither vegetation height nor density were indicated as important habitat characteristics. To identify the habitat characteristics that have the greatest effect on the overall bird-community composition, I generated graphical ordinations using non-metric multidimensional scaling. The habitat factors most affecting the bird community composition were: vegetation density, vegetation height, litter depth, shrub density, shrub height, warm-season grass cover, and the ratio of habitat area to perimeter. Invertebrate biomass at a site was positively correlated to forb cover and plant richness and negatively correlated to grass cover. Grassland bird species have distinct habitat-associations that allow them to reduce interspecific competition through niche partitioning and would be best managed with a diverse set of successional stages.

Early-successional habitats have become rare in much of the eastern United States, largely due to landuse change, forest maturation and the disruption of natural disturbance regimes. In addition to providing nesting habitat for shrubland species of high conservation concern, wildlife openings may be an important habitat for mature-forest birds during the postfledging period – a critical phase in the avian lifecycle with the potential for high mortality. The habitat requirements of birds during this time period are poorly understood. In this study I examined the relationship between habitat and landscape characteristics on; 1) the abundance of forest nesting birds in shrubland habitat during the postfledging season, and 2) the reproductive success of shrubland bird species. And lastly, I also examined the relationship between avian body condition and seed dispersal, with a focus on comparing native and invasive species. I found that the abundance of forest birds was strongly influenced by landscape characteristics, as well as food abundance and structurally complex vegetation. Shrubland birds varied in their response to habitat variables, but overall productivity was positively related to taller vegetation structure, and was negatively related to lower-dense vegetation. Frugivore diets were generalized, yet they selected native fruit more often than invasive fruit, and invasive fruit negatively affected condition. My findings are consistent with the results of previous studies of habitat use among postfledging birds, and suggest that, like for forest birds, habitat requirements for shrubland birds during the postfledging period differ from those during the nesting season. Hopefully these results will encourage other studies of this important, but poorly understood stage of the avian lifecycle.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Thesis presented for the Degree of Doctor of Philosophy at the University of the Witwatersrand / Successional changes in the vegetation after fire were studied in several fynbos communities of the south-western Cape Province of South Africa. The study sites were located in the mountains, at altitudes between 300 and 1000 m a.s.l., in areas with winter rainfall regimes -1 and annual precipitation of about 900 to 1000 mm. yr Soils are highly leached, derived principally from quartzites. The two main sites were Zachariashoek near Paarl, where summers tend to be rather dry, and Jakkalsrivier east of Grabouw, where summer drought is ameliorated by fog precipitation and cloudiness. Successional changes were followed for intervals of up to 10 yr between fires, as well as for similar periods in vegetation that had been unburnt for 25 yr. Vegetational changes were analysed by means of repeated floristic assessments on permanent quadrats and point-quadrat sampling of canopy cover composition on these and on larger plots. At Jakkalsrivier, recently burnt and long unburnt vegetation were also compared by paired samples. Demographic trends in populations of prominent shrub species were followed by repeated censuses of tagged samples in unburnt and recently burnt vegetation. Also at Jakkalsrivier, the effects of fire on resources available to plants were examined by sampling soil moisture and soil mineral nutrients, as well as by following trends in xylem pressure potentials in selected species of plants and analysing their foliar nutrient concentrations. Effects of fire on microclimate were tested by comparative studies on burnt and unburnt sites. All fynbos communities sampled proved to be highly stable in the face of fire. Essentially, the pre-fire species composition was regained in 2-3 yr in every case. Species were added after fire, partly because of the appearance of ephemerals with life histories tied to fire, but also because of the reappearance of longer-lived plants as well as through the readier detection of species in vigorous vegetative form. The species richness of the regenerating corrununities tended to be quadratically related to pre-fire biomass, as predicted from current succession theory. Most species in any corrununity (about 70% on average) regenerated vegetatively by sprouting after fire. The relative numbers of species that regenerated germinatively, i.e. the seeders, did not vary in a manner predictively related to corrununity biomass. There were relatively few species with specialised life histories based on reseeding, such as those with canopy-stored seed and ephemerals with presumably specialised requirements for germination. Virtually no recruitment could be found among plants in the older (about 25 yr) vegetation, in contrast with lowland fynbos sites, where recruitment of herbaceous species occurs, and some mountain fynbos sites on more fertile soils, where forest precursors may sometimes colonise. Canopy redevelopment after fire indicated similar resilience among the different corrununities, despite variation in regrowth rates. Pre-fire growth-form composition was restored within around 10 yr. Maximum leaf-area indices ranged from about 1,5 to 2,5, although corrununi ties on phreatic sites had leaf-area indices exceeding 3,0. There was no evidence for a suppression of the understoreys by overstorey layers, mainly because the latter were sparse despite the abundance of tall broad-sclerophyllous shrubs in certain habitats. This was because the taller shrubs had sparse or slender crowns, or both, and because mortality tended to thin the populations before dense canopies developed. Trends in the composition of the canopy varied among corrununities. corrununities in productive habitats, i.e. in this case on phreatic sites, were dominated in the early stages by a relatively luxurious growth of ephemeral herbs and soft shrubs which declined within around 3-4 yr. Other sites had very sparse ephemeral cover, the early stages being dominated mainly by Restionaceae, Cyperaceae, and other sprouting herbs, and sprouting and seeding shrubs, which were constituents of the pre-fire canopies. In this respect, the fynbos is clearly distinguished from the California chaparral, for example, where ephemerals tend to dominate the post-fire stages on most sites. There was no evidence that fire had any effect on the water relations of regenerating vegetation, although stream discharge is known to be increased by fire in these environments. There was tentative evidence, in enhanced foliar concentrations of some mineral nutrients, that regenerating species of climax plants exploited nutrients released in fire. However, any such responses were small, especially in comparsion with responses observed in chaparral, for example. Ephemeral shrubs had much higher concentrations of foliar nutrients overall than climax species, tending to confirm the correlations found in Australian heathlands between plant life-history and nutrient economy. The effects of fire on microclimate were pronounced, especially on the thermal and water vapour regimes experienced by seedlings and sprouts. These extremes did not, however, appear as water stress in regenerating plants. Despite relatively sparse canopies, mature vegetation did reduce light at the ground to levels likely to affect seedling recruitment and survival. Preliminary experiments with a local dominant shrub, Leucadendron xanthoconus, showed a pronounced intolerance of shading and hence that light attenuation by canopies must be implicated in successional processes. The demographic studies indicated that density-dependent effects were not important in survival of plants. Two species of fire ephemeral shrubs effectively died out within four years, being characterised by markedly higher growth rates than climax species and brief and early fecundities. Climax shrubs had more or less constant rates of mortality over time, though populations in unburnt vegetation tended to have slightly higher rates of mortality than young populations. Densities of seedling populations were very high, but mortality rates were extremely low. In summary, it may be said that the fynbos communi ties studied here are very stable under a given fire regime. Recovery is rather rapid, being apparently achieved within 10 yr. Not much change occurs in older vegetation, but there was a gradual attrition of populations of dominant shrubs, without recruitment, with rare exceptions. Summer droughts in these montane environments are evidently not sufficiently marked for water deficits to play a primary role in succession, so that fire has no effect on plant water relations. Nutrient responses are relatively weak, and masked in the plants by the low rates of metabolism in climax species. Succession after fire is distinguished by the recovery of pre-fire communities, and subsequent inhibition of recruitment. This inhibition is probably through the effects of canopies on microclimate, although the interactions between especially plants and animals have been implicated in succession in other studies. / AC2017

Bibliography: leaves 227-244. This study is conceived to address various aspects of western myall (Acacia papyrocarpa Benth) recruitment, lifespan, distribution and the effects of major vertebrates on the species' ecology over the major part of its range in South Australia. A study of the population dynamics of the species is done to assess the adequacy of net recruitment. Population structure is examined across the woodlands. The new concept of "fossil paddocks" is adopted to investigate the historical impact of introduced herbivores on the landscape.