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This thesis set out to examine the soils, plants, lichens, invertebrates and common skinks along a gradient of habitat modification. This gradient was represented by ten study sites, of varying management histories, in a mid altitude tall tussock (Chionochloa spp.) grassland in eastern Central Otago. One extreme of the gradient was represented by intact tall tussock plants with a high density of inter tussock vegetation. The other extreme was represented by intensively managed exotic pasture. Native plants, invertebrates and reptiles were present along the entire gradient of modification and there was a clear threshold in the diversity of native plants along the gradient. This threshold was reached after the management practice of ploughing was applied to a site. Sites that had not been ploughed were found to be similar in their native plant diversity, and all unploughed sites had significantly higher native plant diversity than unploughed sites. There was considerable variation in the abundance of individual plant and Coleoptera species along the modification gradient. The most intensively modified sites had the lowest plant diversity, the lowest abundance and diversity of Orthoptera, as well as the lowest abundance of common skinks. Sites with low levels of modification contained a higher abundance of common skinks, and, native forbs, lichens and bryophytes than the more intensively modified sites. With regard to individual plant and Coleoptera species recorded, there were generally not clear thresholds for their presence and absence along the modification gradient. Rather, there was a gradual turnover for most species along the gradient such that the plant and Coleoptera community at opposing ends of the gradient had less species in common sites of similar modification levels. A high proportion of the Coleoptera species observed were present in all sites, suggesting that disturbance has selected for an adaptive generalist life trait, and that the species remaining comprise the resilient portion of the Coleoptera fauna. The relationship between Coleoptera communities and the gradient of modification was scale dependent, with the strongest relationship being observed at the largest scale measured. The hypothesis that faunal diversity and abundance would be best predicted by the structural diversity of the vegetation rather than by plant species diversity was tested. Structural diversity was strongly correlated (p < 0.01) with Coleoptera diversity, and Coleoptera abundance whereas plant species diversity was not. However, plant species diversity was a stronger correlate of common skink abundance than plant structural diversity. The structural diversity of the vegetation has the potential to be measured remotely and could be a correlate for faunal diversity and abundance when undertaking landscape scale studies. This thesis demonstrates that native biota exists within the agricultural environment of the mid-altitude tall tussock (Chionochloa rigida) grasslands of eastern Central Otago despite intensive modification in some areas. The findings suggest that it is possible to integrate the objectives of agriculture and the conservation of some faunal groups especially for the more resilient species. However, this study also indicates that relatively unmodified sites are valuable reservoirs of biodiversity in the mid altitude zone and it is recommended that the limited number of lightly modified sites that remain in the mid altitude zone be conserved.

Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to pre-treatment data from 1987 through 1990. Sixty nine pool-forming, and 59 channel-stabilizing log structures were constructed by the U.S. Forest Service in a 3.7 km reach in 1990. A 20-year flood caused extensive modifications to the instream structures in May 1991. Pool habitat and large wood volume increased in the treatment and the two reference reaches but pool development was greater in the treatment reach compared to the two reference reaches. Summer rearing densities of juvenile steelhead were similar for the treatment and the two reference reaches at the reach scale. Summer rearing densities were lower in the post-treatment period compared to the pre-treatment period for the treatment and two reference reaches. Mean density of juvenile steelhead was higher in complex pools compared to non-complex pools throughout the study area. Mean density of juvenile steelhead was higher in pools associated with large wood from washed-out structures compared to pools associated with intact structures in the treatment reach. Changes in smolt production from the treatment reach following the rehabilitation project could not be determined due to trapping difficulties. Only three percent of the smolts emigrating from the basin overwintered in the treatment reach in 1992. Four life history patterns of juvenile steelhead were identified. Only one of the four life history patterns rears in the Meadow Creek basin until smolting. From these findings I conclude that the instream habitat rehabilitation project did not increase the abundance of juvenile steelhead or smolt production during the first two years after treatment. An extended drought and a 20-year flood may have been the dominant factors controlling abundance of juvenile steelhead over the study period. The Meadow Creek rehabilitation project may have limited success at increasing smolt production because it influences only one of four life history patterns of juvenile steelhead during the entire freshwater rearing phase. / Graduation date: 1997

Riparian zones provide habitat for breeding birds in the semiarid western United States; however, there are few data available that address the effects of livestock grazing strategies on riparian habitats and avian communities. Documenting avian community composition in different riparian vegetation communities and relating vegetation communities to livestock grazing strategies may identify management alternatives that are sustainable from a wildlife habitat perspective, and may permit constructive coalitions between agricultural industry and environmental groups. I compared diurnal breeding bird abundance, individual species abundance, and species richness, and vegetation composition and structure among 12 streamside riparian areas of Bear and Silvies valleys in eastern Oregon during 1993 and 1994. Bird and vegetation data were collected along four replicate transects within each of three riparian vegetation communities characterized by vegetation structure: herbaceous, discontinuous willow (Salix spp.), and continuous willow. These riparian vegetation communities were grazed under summer season-long, summer short-duration, and fall short-duration livestock grazing strategies, respectively, >5 years before the study. Differences in riparian vegetation among communities were primarily related to shrub structure by experimental design. The continuous willow community had more shrub cover overall (P<0.001) and within each 1-m height interval from 0-4 m (P<0.013) than the herbaceous and discontinuous willow communities. The herbaceous community had no shrub cover >1 m in height. Willows extended farther (P=0.031) from the steam edge in the continuous willow community than in the discontinuous willow community. No willows were detected in the herbaceous community. I detected 4,016 birds representing 56 species along the transects. Total bird abundance was greater (P<0.001) in the continuous willow community than in the herbaceous and discontinuous willow communities. Species richness was inconsistent (P=0.034) between years within communities; it was greatest (P<0.037) in the continuous and discontinuous willow communities in 1993, and greatest (P<0.003) in the continuous willow community in 1994. Total bird abundance and species richness in 1994 increased with willow volume (r��>0.707, P<0.001). Of 23 bird species with >20 individual detections over both years, 13 species were most abundant in one or two vegetation communities (P<0.088). Seven species (yellow warbler [Dendroica petechia], song sparrow [Melospiza melodia], willow flycatcher [Empidonax traillii], American robin [Turdus migratorius], common snipe [Gallinago gallinago], bobolink [Dolichonyx oryzivorus], and Vaux's swift [Chaetura vauxi]) were most abundant in the continuous willow community. Three species (savannah sparrow [Passerculus sandwichensis], black tern [Chlidonias niger], and American wigeon [Anas americana]) were most abundant in the herbaceous community. Willets (Catoptrophorus semipalmatus) were most abundant in the herbaceous and discontinuous willow communities whereas cinnamon teal (A. cyanoptera) were most abundant in the herbaceous and continuous willow communities. Red-winged blackbirds (Ageliaus phoeniceus) were inconsistent (P=0.032) between years within communities: they were most abundant in the continuous willow community in 1993, and most abundant in the continuous willow and herbaceous communities in 1994. Hydrophytic woody vegetation within semiarid rangeland environments increases structural complexity and is associated with avian abundance and diversity. Yellow warblers, willow flycatchers, and song sparrows, which depend on hydrophytic shrubs for nesting almost exclusively in the semiarid West, are especially threatened by the elimination or simplification of woody riparian vegetation. I suggest that riparian vegetation structure and composition, which is associated with avian abundance, species richness, riparian associate bird species, and landscape-level biological diversity, be maintained where possible. Seasonal light (<30% use) fall short-duration grazing seemed to be compatible with the maintenance of woody riparian vegetation whereas summer season-long and summer short-duration grazing is likely incompatible. / Graduation date: 1995

Birds are one of the best studied animal groups in the world but are also amongst the most endangered. The wealth of ecological information has shown habitat protection to be vital to bird biodiversity, but habitat loss and degradation continue to defeat conservationists. / Community-based biodiversity conservation efforts have been recently recognized as an important option for safeguarding ecosystems while reducing land use conflicts arising from the material, cultural and spiritual needs of local inhabitants. Community involvement is particularly critical for conservation in anthropogenic habitats. Few studies have linked the ecological impacts of community land use practices with the auto-ecological requirements of dependent bird species. In this study I examine the conservation possibilities for the endangered Sierra Madre sparrow (Xenospiza baileyi) by considering three basic elements: the ecological requirements of the bird, the effects of traditional land use practices in shaping the habitat, and the economic and social conditions that influence current and future land use decisions. I draw on ecological field studies, on traditional ecological knowledge systems, and studies of the political ecological context that influences local practices. / The studies were carried out from 2000-2003 and employed a combination of ethnographic, participative and spatial-ecological approaches to address human-land interactions and their impacts on the sparrow habitat. Social data were obtained through nine workshops which included site visits, transect walks, participatory mapping, oral histories and semi-structured interviews. Ecological data were obtained from landscape ecology analysis, vegetation post-disturbance assessments and detailed bird's nest-site selection analysis. / Results indicate that local people, principally herders, hold a rich knowledge of fire use to achieve diverse purposes, including pasture renewal, grassland maintenance and grass species selection, and prevention of dangerous fires. In order to accomplish their goals, herders have established rotational fire and grazing regimes that consider timing, frequency, location and extent of these disturbance-based practices. This rotational system was found to benefit the Sierra Madre sparrow by maintaining the grassland at the scales needed by the sparrow for nesting. Multiscale habitat recommendations for the species' conservation were derived from this socio-ecological interaction and dynamics. / Unfortunately, external conservation perspectives and interests and internal land tenure conflicts have altered this rotational regime and local perspectives on resource management that threaten the resilience of this social-ecological system. Consequently, traditional ecological knowledge on grassland management can be on risk of disappearing and, with it, important native grasses and grasslands are being made vulnerable. The survival of the Sierra Madre sparrow in particular and of associated biodiversity in general, is in peril if these conflicts are not solved in a relatively short time. A community-based fire co-management program is recommended to promote integrative bird conservation-local development scenarios.

The primary aim of this study was to investigate the role of food supply and ground cover on the community structure, population dynamics and demography of terrestrial small mammals in a subtropical grassland. This aim was achieved through a series of food supplementation and cover manipulation experiments conducted at eKundizeni Farm near Matsapha, Swaziland, over a 28 month period. The effects of five different diets on the rodent Mastomys natalensis were investigated in the laboratory, and the results showed that rolled oats and rabbit pellets were suitable for growth and reproduction in this species. The effects of supplementary food were investigated on two supplemented grids and one control over a twelve month period. Small mammal biomass increased significantly on the supplemented grids in relation to the control. This increase in biomass was the result of a twofold increase in the numbers of M natalensis. Food supplementation further affected M. natalensis by: extending the breeding season of females; increasing body weight; increasing survival; and decreasing home range area. Food supplementation had a weak positive effect on the density of another rodent Lemniscomys rosalia, but did not affect any other demographic feature of this species. Food supplementation did not have a demographic effect on any other species of small mammal captured. The effects of vegetative cover were investigated, over a twelve month period, on two control grids and four manipulated grids on which the vegetative cover was mechanically reduced. Supplementary food was added to two of the latter four manipulated grids. The biomass of small mammals, including M. natalensis, was lower on grids with reduced vegetative cover than on the controls. However, food supplementation resulted in a significant increase in the biomass of M. natalensis on one of the manipulated grids. Hence, M. natalensis was induced to shift to a habitat with reduced cover by the provision of supplementary food. Additional information on the population dynamics, age structure, reproduction and diet of M natalensis, L. rosalia, Mus minutoides and Steatomys pratensis is also presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1997.

Global land-use change and industrialisation has driven biodiversity declines and impaired ecosystem functioning. Recently, there have been large-scale efforts to not only halt habitat loss but create and restore habitat on formerly managed (e.g. agricultural) land. However, although the effects of habitat loss and fragmentation on biodiversity are well understood, our understanding of how biodiversity responds to habitat created in a patchy configuration is not. In particular, little is known about the relative importance of local (e.g. patch size) vs landscape scales (e.g. amount of habitat in the landscape) for restoring biodiversity in created habitat. Here, a long-term, large-scale natural experiment (the Woodland Creation and Ecological Networks project) was used to understand how bird species, communities and behaviour respond to woodland created in a patchy configuration on post-agricultural land. I used a combination of direct and indirect survey methods to quantify bird diversity, abundance and vocal behaviour in post-agricultural woodlands of known age in Great Britain. I show that secondary woodlands favour generalist species and older patches contain more individuals and species due to their vegetation structure. In relative terms, local-scale factors such as patch size made the greatest contribution to bird diversity and abundance. Colonisation events drive community assembly in new habitat, and I found that large-scale (km2) habitat patterns were more important than patch-level factors during colonisation of breeding territories by a long distance migrant bird (Willow Warbler Phylloscopus trochilus). Land management practices surrounding a habitat patch can also affect its perceived quality and relative attractiveness to potential colonisers. Using the Eurasian Wren Troglodytes troglodytes as a model species, I found that high proportions of agricultural land at woodland edges caused an increase in perceived predation risk. In conclusion, I suggest that post-agricultural woodlands rapidly provide valuable habitat for generalist woodland birds. Local, patch-level factors (area, vegetation structure) also appear relatively more important than landscape factors for woodland bird communities. Land-managers seeking to maximise the benefits of woodland creation for birds should thus focus on creating large patches with a diverse vegetation structure.

The feeding ecology of a common saltmarsh crab, Armases cinereum (Armases), was investigated to determine how habitat (mangrove vs. ecotone, natural mangrove vs. modified mangrove fringe) influenced this species’ feeding behavior and trophic ecology in its southwestern Florida, USA, distribution. In the laboratory, Armases’ preference for mangrove material was examined using leaves of three mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) and leaves of different degradation levels (fresh, senescent, and partially-decomposed). Leaf material from A. germinans was preferentially consumed over the other taxa at fresh and partially-decomposed levels of leaf decay. When Armases were offered a choice between four common upland vegetation types (Iva frutescens, Borrichia frutescens, Nephrolepis biserrata, and Stenotaphrum secundatum), the preferred mangrove from the previous experiment (A. germinans, partially-decomposed), and an animal prey item (Gryllodes sigillatus, cricket), Armases displayed greatest selectivity for the animal prey item and high selectivity for both I. frutescens and A. germinans plant taxa (Manly-Chesson α selectivity and Chesson ϵ electivity). Field-based stable isotope analysis was used to determine trophic position and reconstruct dietary proportions of Armases across three pairs of natural and heavily-modified sites within Tampa Bay to determine whether Armases feeding behavior is impacted by the presence of upland forest adjacent to mangrove forest habitat. Analysis of trophic position based on δ15N signatures of Armases from each of the six populations revealed that Armases in habitats with modified connectivity had lower trophic variability and significantly higher average trophic position compared to Armases sampled from the three sites with natural connectivity. Stable isotope diet reconstruction using the Bayesian mixing model SIMMR further established Armases preference for animal-derived food material in habitats with natural and modified connectivity. This preference is likely driven by high selectivity for sources rich in Nitrogen (i.e., animal tissue, partially-decomposed A. germinans material, and I. frutescens). I determined that the use of laboratory experiments in conjunction with stable isotope mixing models is important in accurately investigating feeding preferences of Armases in mangrove intertidal regions. Together, my results show that the diet of Armases is broadly omnivorous and populations can be influenced by the heterogeneity of their habitat. Further feeding experiments, dietary analyses and a longer sampling period are needed to more definitively identify the patterns of Armases detritivory in mangrove and ecotonal upland habitats.

Coastal marine ecosystems are among the most impacted globally, attributable to individual and cumulative effects of human disturbance. Anthropogenic nutrient loading is one stressor that commonly affects nearshore ecosystems, including seagrass beds, and has positive and negative effects on the structure and function of coastal systems. An additional, previously unexplored mechanistic pathway through which nutrients may indirectly influence nearshore systems is by driving blooms of benthic jellyfish. My dissertation research, conducted on Abaco Island, Bahamas, focused on elucidating the role that benthic jellyfish have in structuring systems in which they are common (i.e., seagrass beds), and explored mechanistic processes that may drive blooms of this taxa. To establish that human disturbances (e.g., elevated nutrient availability) may drive increased abundance and size of benthic jellyfish, Cassiopea spp., I conducted surveys in human-impacted and unimpacted coastal sites. Jellyfish were more abundant (and larger) from human-impacted areas, positively correlated to elevated nutrient availability. In order to elucidate mechanisms linking Cassiopea spp. with elevated nutrients, I evaluated whether zooxanthellae from Cassiopea were higher from human-disturbed systems, and whether Cassiopea exhibited increased size following nutrient input. I demonstrated that zooxanthellae population densities were elevated in human-impacted sites, and that nutrients led to positive jellyfish growth. As heightened densities of Cassiopea jellyfish may exert top-down and bottom-up controls on flora and fauna in impacted seagrass beds, I sought to examine ecological responses to Cassiopea. I evaluated whether there was a relationship between high Cassiopea densities and lower benthic fauna abundance and diversity in shallow seagrass beds. I found that Cassiopea have subtle effects on benthic fauna. However, through an experiment conducted in a seagrass bed in which nutrients and Cassiopea were added, I demonstrated that Cassiopea can result in seagrass habitat modification, with negative consequences for benthic fauna. My dissertation research demonstrates that increased human-driven benthic jellyfish densities may have indirect and direct effects on flora and fauna of coastal marine systems. This knowledge will advance our understanding of how human disturbances shift species interactions in coastal ecosystems, and will be critical for effective management of jellyfish blooms.

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / Benthic macroinvertebrates (sampled using South African Scoring System, SASS5) and adult male Odonata (sampled with close-focus binoculars) were recorded on two streams and a river of Soutpansberg, with the aim of determining the effect of invasion and removal of alien riparian vegetation on their assemblages. A secondary aim was to establish the importance of dragonflies as indicators of degree of disturbance in rivers. Forty two aquatic macroinvertebrate families and 33 adult Odonata species were recorded at a total of 71 sampling units. Three distinct riparian vegetation types were selected (natural, alien and cleared). Cleared vegetation refers to clearing of invasive alien trees, allowing regrowth of natural vegetation. Natural and cleared vegetation supported more benthic macroinvertebrate families compared to alien vegetation. Certain families that were lost to alien vegetation were recorded from natural vegetation. The highest SASS5 score was recorded from natural vegetation, followed by cleared vegetation, and the lowest was from alien vegetation. The highest number of adult Odonata was recorded at cleared vegetation, with alien and natural vegetation supporting the least number of Odonata species. Vegetation type, stream flow and microhabitats were statistically identified as the most influential variables for benthic macroinvertebrate assemblages. For adult Odonata assemblages, vegetation type, shade and temperature were the most important environmental variables. Species assemblages of adult Odonata can be used as indicators of environmental condition of rivers. The clearing of alien riparian vegetation clearly benefits the indigenous benthic macroinvertebrates as conditions are restored to their natural state. It also benefits dragonfly species richness, but if natural succession proceeds to a shaded tree canopy, the effect becomes similar to that of habitat shaded by alien vegetation. The impact of alien vegetation is to reduce sun-loving invertebrate species, especially dragonflies, with lesser impact on shade-loving species.