Dissertations / Theses on the topic 'Effect of habitat modification on'
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1
Rangeley, Robert W. (Robert William). "Habitat selection in juvenile pollock, Pollachius virens : behavioural responses to changing habitat availability." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28648.
Abstract:
This thesis demonstrates how tidal changes in the availability of intertidal zone habitats can affect the distribution and behaviour of juvenile pollock (Pollachius virens). Schools of pollock moved from the subtidal zone to the open habitat in the intertidal zone. On rising tides, pollock switched from the open habitat at low tidal stages to the dense algal habitat at high tidal stages. On falling tides, pollock rapidly schooled downshore in the open habitat. Pollock were rarely solitary in the open habitat and usually formed large schools. In the algal habitats, pollock were usually dispersed and preferred the dense algae over the sparse algae. Predation risk from birds was widely distributed among depths, habitats and stages of the tide, during the day. In a mesocosm experiment, pollock increased their use of the algal habitat and were more difficult to detect following a simulated bird predator threat. Preference for the algal habitat was density-dependent when either pollock abundance or algal habitat area were manipulated. Pollock responded to their potentially high density in the algae by schooling in the open habitat.
2
Maran, Audrey Marie. "The effect of anthropogenic habitat modification on insect-mediated ecosystem services." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1594488419133855.
3
Groshens, Thomas P. "An assessment of the transferability of habitat suitability criteria for smallmouth bass, Micropterus dolomieu." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/44601.
Abstract:
The purpose of this study was to determine if habitat suitability criteria developed in the summer months for sma11mouth bass were transferable among streams representing different eco regions.
Habitat suitability criteria were developed for depth, mean column velocity, cover and substrate for two size classes of sma1lmouth bass, 100-199mm and >200mm, in the North Anna River and Craig Creek, Virginia.
Criteria that accurately describe habitat selection by a species or guild in a system different from where the criteria were developed are said to be transferable to that system. The transferability of suitability criteria between the North Anna River and Craig Creek, as well as depth and velocity criteria from Minnesota, the Huron River, Michigan and the Upper James River, Virginia, to the North Anna River and Craig Creek were tested using a 2x2 contingency table analysis.
Depth criteria for the smaller sizes of sma1lmouth bass did not transfer well between regions; 4 of the 8 transferability tests (50%) failed. Depth criteria for larger sma1lmouth bass transferred to the North Anna River and Craig Creek in all cases.
Velocity criteria developed for the smaller size classes did not transfer well among regions; only 3 of the 8 transferability tests were positive. Likewise, velocity criteria for larger sizes of smallmouth bass did not transfer well; only 1 of 8 tests were positive.
General criteria were developed for depth and mean column velocity by averaging the suitability values reported from this and 3 other studies. General depth and velocity criteria transferred well to the North Anna River and Craig Creek for both the larger and smaller size classes of smallmouth bass; all depth tests were positive and 3 of 4 velocity tests were positive. The improved success of transferability warrants investigation of developing general criteria for smallmouth bass.
Cover criteria for both size classes of smallmouth bass were transferable from the North Anna River to Craig Creek but not vice versa. Substrate heterogeneity criteria were not transferable between the North Anna River and Craig Creek for either size class of smallmouth bass. Criteria developed for the percentage of substrate particles >15cm (smallmouth bass >200mm only) were transferable from Craig Creek to the North Anna River but not vice versa.
The transferability of habitat suitability criteria among regions was inconsistent and it is recommended that site-specific criteria be developed for each stream to which habitat assessments are applied. Additionally, nose velocities used were more consistent between the North Anna River and Craig Creek than were mean column velocities used. Hence, it is recommended that information on nose (focal point) velocities be incorporated into habitat studies to more accurately describe smallmouth bass velocity requirements.
Master of Science
4
Gonsalves, Sydney Marie. "Green Roofs and Urban Biodiversity: Their Role as Invertebrate Habitat and the Effect of Design on Beetle Community." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2997.
Abstract:
With over half the world's population now living in cities, urban areas represent one of earth's few ecosystems that are increasing in extent, and are sites of altered biogeochemical cycles, habitat fragmentation, and changes in biodiversity. However, urban green spaces, including green roofs, can also provide important pools of biodiversity and contribute to regional gamma diversity, while novel species assemblages can enhance some ecosystem services. Green roofs may also mitigate species loss in urban areas and have been shown to support a surprising diversity of invertebrates, including rare and endangered species. In the first part of this study I reviewed the literature on urban invertebrate communities and diversity to better understand the role of green roofs in providing habitat in the context of the larger urban mosaic. My review concluded that, while other factors such as surrounding land use and connectivity are also important to specific invertebrate taxa, local habitat variables contribute substantially to the structure and diversity of urban invertebrate communities. The importance of local habitat variables in urban green spaces and strong support for the habitat complexity hypothesis in a number of other ecosystems has led to proposals that "biodiverse" roofs--those intentionally designed with varied substrate depth, greater plant diversity, or added elements such as logs or stones--would support greater invertebrate diversity, but there is currently limited peer reviewed data to support this. In order to address the habitat complexity hypothesis in the context of green roofs, in the second part of this study I surveyed three roofs designed primarily for stormwater management, three biodiverse roofs, and five ground-level green spaces, from March until September of 2014 in the Portland metropolitan area. Beetles (Coleoptera) were sampled bi-weekly as representatives of total species diversity. Biodiverse roofs had greater richness, abundance, and diversity of beetle species compared to stormwater roofs, but were not more diverse than ground sites. Both biodiverse roofs and ground sites had approximately 20% native beetle species while stormwater roofs had only 5%. Functional diversity was also higher on biodiverse roofs with an average of seven trophic groups represented, while stormwater roofs averaged only three. Ground sites, biodiverse roofs, and stormwater roofs each grouped distinctively in terms of beetle community composition and biodiverse roof communities were found to be positively correlated with roof age, percent plant cover, average plant height, and plant species richness. These results support the findings of previous studies on the importance of local variables in structuring urban invertebrate communities and suggest that biodiverse design can reliably increase greenroof diversity, with the caution that they remain no replacement for ground level conservation.
5
Register, Sarah M. "Breeding biology and habitat associations of cerulean warblers in southern Indiana." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1372052.
Abstract:
The Cerulean Warbler (Dendroica cerulea), a once common summer inhabitant and breeder in southern Indiana, has declined at both local and continental population levels. Effects of specific silvicultural practices on the distribution and abundance of the Cerulean Warbler is unknown. During the summers of 2005 & 2006, Cerulean Warblers were surveyed within the Morgan-Monroe and Yellowwood state forests, as well as the Hoosier National Forest in southern Indiana. Three forest types were surveyed; unharvested reference sites were compared with single tree selection treatments and treatments where a combination of group and single tree selection was used. Mean bird abundance was estimated from bird surveys to determine if a correlation exists between silvicultural regimes and Cerulean Warbler abundance. Cerulean Warblers were located in all treatment types, with no significant differences in abundance between or among treatment types examined. These results suggest that uneven-age management practices, such as single tree and group selection harvesting, provide suitable breeding habitat for Cerulean Warblers.Knowledge of Cerulean Warbler (Dendroica cerulea) male pairing status based on song rates and frequencies, as well as familiarity with non-song vocalizations could be an effective management tool when studying this species. Cerulean Warblers were recorded throughout the breeding season, and 18 song variables were measured and compared between paired and unpaired males using Logistic Regression. Unpaired males had higher song rates and higher minimum frequencies than paired male counterparts. Female and fledgling call notes were also recorded and quantitatively analyzed. These analyses offer further understanding of intraspecific call functions of this species.Department of Biology
6
Tomblin, David Christian. "Ecological niche responses of small mammals to gypsy moth disturbance." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06302009-040517/.
7
Siegel, James Joshua 1956. "An evaluation of the minimum habitat quality standards for birds in old-growth ponderosa pine forests, northern Arizona." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276951.
Abstract:
I studied breeding birds and vegetation in 6 largely pristine old-growth ponderosa pine (Pinus ponderosa) stands and in 3 logged stands that just met the USDA Forest Service's minimum habitat quality standards for old-growth ponderosa pine. Bird populations were similar in all stands. However, brown creepers (Certhia americana) and hermit thrushes (Cattarus guttatus) were low in abundance or absent in 2 of the minimum stands, yet were common in all other stands. Both species preferred cool, moist microenvironments for nesting and/or foraging; conditions that appeared lacking in the more xeric minimum stands. Both species are characteristic of boreal forests, which are cooler and wetter than ponderosa pine forests. I suggest that unlogged old-growth ponderosa pine forests create microhabitats that approximate conditions in more boreal forests. The minimum standards on drier sites appear inadequate in maintaining creeper and thrush habitat. Suggested modifications of the standards include, among others, canopy cover ≥ 50%.
8
Luck, Gary W. "Landscape differences in the ecology of the Rufous Treecreeper Climacteris Rufa." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2000. https://ro.ecu.edu.au/theses/1546.
Abstract:
Anthropogenic habitat modification is a significant threat to the conservation or global biodiversity. The fragmentation and alteration of woodland habitat has resulted in the substantial decline of many woodland bird species in the agricultural regions of southern Australia. The Rufous Treecreeper Climacteris rufaa, a once common woodland resident, has declined in abundance in the wheatbelt of Western Australia and appears to be sensitive to habitat fragmentation. The reasons for this are unclear because our knowledge of the species and the threats posed by fragmentation arc limited. In this study, I compared the social organisation, habitat selection, reproductive success, dispersal and population dynamics of two Rufous Treecreeper populations living in the Western Australian wheatbelt. The first population occupied a large (8,500 ha), relatively undisturbed and unfragmented landscape. The second occurred in an equivalent sized area that had been substantially modified by agriculture. I hypothesised that habitat fragmentation and alteration would adversely affect the viability of the population living in the agricultural landscape. In the unfragmented landscape, treecreepers lived in cooperatively breeding, territorial groups. A group usually comprised a primary (assumed to be breeding) male and female, and philopatric offspring (helpers) from previous breeding seasons. Helpers assisted in the feeding and caring of nestlings and there was a positive relationship between group size and reproductive output. Breeding groups often fanned interactive neighbourhoods whereby resident individuals from one territory would feed nestlings in adjacent territories. A total of 77.7% of 148 nesting attempts produced at least one fledgling. Annual productivity per breeding group (n = 90 group years) was 2.1 ± 0.18 fledglings. Fledgling and juvenile survival rates (0.76 ± 0.04 and 0.46 ± 0.03 respectively) were comparatively high, as was the annual survival rate of primary males (0.77 ± 0.06) and females (0.75 ± 0.05). A multi-scaled analysis of habitat use in the unfragmented landscape identified preferential habitat selection by the species at three spatial scales. At the landscape scale, treecreepers used Wandoo Eucalyptus wandoo woodland at a significantly higher rate than predicted by the availability of this woodland type. Territory selection was positively correlated with the density of hollow bearing logs and nest sites, and tree age. These structural characteristics were also positively correlated with reproductive success und survival in treecreepers, indicating that habitat structure may be a useful measure of territory quality. Nest sites (hollows) were preferentially used if they had a spout angle of ≥ 50° and an entrance size or 5-10 cm, but nest-site selection was not related to nest success. The ecological traits of the treecreeper population living in the agricultural landscape differed from the population in the unfragmented area in a number of ways. Habitat fragmentation in the agricultural landscape disrupted territory contiguity with adverse consequences for social interaction. Nest success and annual productivity were significantly lower in the agricultural landscape, although they varied between different categories of habitat remnants. Reproductive success was lowest in grazed remnants supporting comparatively high population densities. Landscape differences in success did not appear to be a result of a disparity in nest predation levels, but may be related to variation in food availability and habitat quality. The spatial structure and dynamics of the subdivided population in the agricultural landscape were consistent with certain aspects of metapopulation theory. Treecreepers lived in spatially discrete local populations that were unlikely to persist without immigration owing to low reproductive and survival rates. However, movement between habitat remnants appeared to be sufficient to rescue these local populations from extinction. Although declining in numbers during the study, the subdivided population in the agricultural landscape appeared to be fluctuating around equilibrium owing to immigration from outside the study area. The consequences of habitat fragmentation for the Rufous Treecreeper are complex and interactive. A reduction in habitat area and an increase in remnant isolation disrupts the social organisation of the species and results in small localised populations that are susceptible to extinction. Modification of the remaining vegetation may reduce habitat quality leading to poor reproductive success. In addition to increasing habitat area and maintaining landscape connectivity, future management of fragmented landscapes must focus on improving the quality of remnant vegetation by removing degrading process and ensuring the recruitment of endemic plant species.
9
Tatchley, Cerian. "Wildlife impacts of, and public attitudes towards, small wind turbines." Thesis, University of Stirling, 2015. http://hdl.handle.net/1893/22894.
Abstract:
Global wind power generation has grown rapidly in response to targets to reduce greenhouse gas emissions as part of efforts to mitigate climate change, and to increase energy security. While much of the focus in wind energy technology to date has been on wind farms, a relatively recent development is the expansion of the micro-wind sector (turbines generating < 100 kW), and there are now over 870,000 small wind turbines (SWTs) installed globally. However, official planning guidance for SWTs in the UK and elsewhere is lacking. This may be a barrier to SWT installations if there is confusion over the requirements to gain planning permission. One reason for the lack of planning guidance is that our understanding of the wildlife impacts of SWTs is limited and therefore it is difficult to make recommendations for their mitigation. There are a range of potential negative effects wind power can exert on wildlife, in particular on birds and bats, yet to date, there has been very little published research into the wildlife impacts of SWTs. Mortality rates of wildlife at SWTs appear to be relatively low, but disturbance of bats, highly protected species, near SWTs has been previously demonstrated. However, the extent (if any) of this disturbance at habitat features of known importance was unclear. Therefore this thesis used acoustic surveys of bat activity to quantify disturbance of use of linear features (e.g. hedgerows, treelines), habitat important to bats for commuting and foraging, caused by SWTs. Firstly, bat activity did decline after experimental installation of SWTs 5m away from linear features. This decline was species-specific with Pipistrellus pygmaeus showing declines in activity in close proximity to the SWT associated with SWT operation, while P. pipistrellus activity declined in response to installation both at the SWT site and 30m away. Secondly, bat use of linear features is lower when SWTs are located nearby. In particular, P. pygmaeus activity at linear features is lower the closer a SWT is to the feature, and at high wind speeds Myotis spp. use of linear features is similarly lower where SWTs are located nearby. This disturbance did not dissipate along the linear features away from the SWT for at least 60m. This is much further than previously documented disturbance of bats by SWTs, which appeared fairly localised, and may be due to the importance of linear features specifically for commuting between habitat fragments. If so, the cumulative impacts of such disturbance will be important in areas where suitable foraging and roosting habitats is limited and fragmented, and linear features suitable for commuting between habitat fragments are already rare. These results offer support for recommendations that SWTs should be subject to siting restrictions that create a buffer distance between them and important bat habitats such as linear features. Specifically, this thesis recommends that in landscapes with few alternative commuting routes or where particularly rare bat species are present SWT installations require buffer distances to ensure they are a minimum of 60m away from linear features. There has also been a lack of research into public attitudes towards SWTs, despite local attitudes towards wind farm developments having been linked to planning outcomes, implying attitudes can be a barrier to installations. This thesis presents the results of the first survey of public attitudes specifically towards SWTs. Generally attitudes towards SWTs were positive, with over half of respondents rating SWTs as acceptable across a range of landscape settings. However, as for wind power where public attitudes in general are positive but local wind farm developments may still face opposition, only 35% of respondents were in favour of having a SWT installed in sight of their home. A key finding of this survey was that acceptance of SWTs significantly differed between landscape settings, with those in hedgerows and gardens being less well accepted compared to those on road signs, buildings and fields. Respondent comments highlighted visual impacts, efficient use of technology, noise impacts, wildlife impacts and educational value as important factors in their decisions regarding SWT acceptability. Public concern about wildlife impacts appears to be responsive to context, being important to the lower acceptance of SWTs in hedgerows, which were perceived to be particularly risky for wildlife. Potential SWT owners are also shown to be concerned about wildlife impacts from SWTs. Using a choice experiment methodology, an economics technique that allows valuation of non-market goods, farmers (a group most likely to own SWTs in the UK) were found to be willing-to-pay, through loss of SWT earnings from electricity generation, to avoid disturbance of birds and bats or collision mortality of bats. These findings also support the recommendation of the use of buffer distances for SWTs. Buffer distances between SWTs and linear features will help to alleviate public and SWT owner concerns about wildlife impacts, and also increase public acceptance of SWTs by encouraging their installation away from some of the least accepted landscape settings such as hedgerows. Further, potential SWT owners were also found to have no significant preference for avoiding siting restrictions of SWT installations, suggesting they are open to the use of buffer distances, although the suggested distances were substantially smaller than those this thesis ultimately recommends. The findings presented in this thesis have implications for planning guidance, policy makers and developers, but also raise many questions that will require further study. A list of planning guidance recommendations and a list of recommendations for future SWT research are presented in the final section.
10
Smith, Scott M. "The influence of submerged aquatic vegetation on trophic relationships of largemouth bass." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/74542.
Abstract:
Aquatic vegetation is considered a nuisance in many lakes and reservoirs supporting largemouth bass populations, and control (eradication) of vegetation is often undertaken. Yet, the relationship between submerged aquatic vegetation and adult largemouth bass, from a trophic standpoint, is poorly understood. I attempted to quantify this relationship by comparing available prey with consumption from the perspective of individual largemouth bass and the largemouth bass population in Flat Top Lake, West Virginia in 1986 and 1987.
The abundance of largemouth bass ≥200 mm long was positively associated with vegetation density, although no relationship was apparent between the length and relative weight of adult largemouth bass and vegetation. Forage fish abundance was also positively related to vegetation density. Vegetation was heavily utilized by most fish species in the reservoir. Consumption (quantity and diet composition) of individual largemouth bass did not differ among the vegetation densities considered. However, the increased abundance of available prey associated with increased vegetation densities led to increased overall consumption by the largemouth bass population. Thus, largemouth bass production potential was positively related to vegetation density. Increases in the vegetation/open water interface had no short-term (one month). Evidence from this study indicates that aquatic vegetation could be managed to increase the productivity of largemouth bass in Flat Top Lake. The benefits to largemouth bass provided by aquatic vegetation in Flat Top Lake and similar systems should be considered prior to initiating vegetation control activities.Master of Science
11
Ricciardi, Anthony. "The role of the zebra mussel (Dreissena polymorpha) in structuring benthic macroinvertebrate communities in the St. Lawrence River /." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34438.
Abstract:
This research examined how an invasive macrofouling organism, the Eurasian zebra mussel (Dreissena polymorpha), alters benthic communities in a riverine ecosystem. Controlled field experiments using artificial substrates showed that macroinvertebrate abundance is significantly enhanced within Dreissena beds, and that the physical habitat provided by mussel shells has a greater impact on macroinvertebrate abundance than biological factors (e.g., food provided by mussel biodeposits). Data collected at field sites before and after the establishment of dense Dreissena colonies suggested that these colonies alter macroinvertebrate communities on hard substrates primarily by enhancing populations of deposit-feeding organisms (e.g., amphipod crustaceans) and predators (e.g., flatworms), and by displacing fauna that are poorly adapted to interstitial substrate (e.g., large gastropods, net-spinning caddisfly larvae). Freshwater sponges were the only organisms found to compete successfully with Dreissena for hard substrate; sponge overgrowth caused significant local mortality of zebra mussels at all sites where sponges were abundant.The capacity for Dreissena to displace native freshwater mussels (Family Unionidae) in the St. Lawrence River was examined over a four year period by quadrat sampling at selected sites. Dreissena preferentially colonized unionid mussels in the river. Mean infestation loads (number of zebra mussels per unionid mussel) in the St. Lawrence were 10-100 times lower than in the Great Lakes,.but resulted in similar high mortality. Severe declines in unionid species richness and abundance occurred in areas of the river that supported dense Dreissena populations ($>$4,000 mussels/m$ sp2).$ Analysis of data from the Great Lakes-St. Lawrence River system suggests that mass mortality and extirpation of unionid populations typically occurs within 4-5 years following initial colonization of unionids by Dreissena, and that Dreissena infestation will increase the future tate of extinction of North American unionids by nearly 10-fold.
12
Bank, Michael S. "Mercury Bioaccumulation and Habitat Relations of Lotic and Lentic Amphibians from Acadia National Park, Maine, USA." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/BankMS2005.pdf.
13
Breitfuss, Mark, and n/a. "The Effects of Physical Habitat Modification for Mosquito Control, Runnelling, on Selected Non-Target Saltmarsh Resources." Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20031126.074304.
Abstract:
Runnelling is a popular method of physical habitat modification employed on saltmarshes to control pest mosquito populations. The runnelling method involves linking the tidal source to isolated mosquito breeding pools via shallow channels that enable slow water movement of low amplitude tides. Increased tidal flushing inhibits mosquito development. The range of organisms which inhabit saltmarsh are likely to be influenced by altered tidal conditions as they exhibit specific physicochemical requirements for feeding, burrowing or growth. The dynamic nature of saltmarsh may mean that changes to the tidal frequency of a particular region of the saltmarsh promotes extension of marine-like conditions. Because runnels increase the frequency of flooding tidal events in specific regions of the saltmarsh this study predicted that resulting changes would be evident in the physical conditions of saltmarsh substrate, in the transport of buoyant vegetative propagules, in the population characteristics of surface grazing snails and in the density and aperture of crab burrows after flooding and non-flooding tidal events. The physical impacts of runnelling were determined at three marshes which appeared similar in terms of topography, substrate and tidal conditions. Soil water content and consolidation were measured using two sampling protocols: a) comparisons between modified and unmodified shores; and, b) comparisons with increasing lateral distance across the shore from the runnel edge. At one marsh, moisture levels were significantly higher at runnelled than at unrunnelled sites when tides filled the runnels, but this pattern was not found at the other marshes. Soil consolidation was greater at higher shore heights, but was not different between runnelled and unrunnelled shores. Measurements at different lateral distances from runnels demonstrated higher moisture levels and lower consolidation up to 5 m from the edge but not further away. Groups of marked Avicennia marina propagules were released at the three runnelled saltmarshes during flooding and non-flooding tidal events. Groups of propagules released within 10 m of a runnel were always transported significantly further from the starting position and further up the saltmarsh shore after both flooding and non-flooding tides than any other groups. In addition, the pattern of stranding on saltmarsh for significantly different groups was closely associated with the path of runnel construction so that propagules were located either in the runnel or in depressions linked to the runnel that had been isolated mosquito-breeding pools prior to runnelling. It is likely that altered physical soil conditions significantly affected the distribution and size structures of Salinator solida and Ophicardelus spp. snails recorded at the three saltmarshes. The interaction of tidal period and the presence of a runnel contributed to patterns with significant differences between runnelled and unrunnelled regions of the marsh. Generally, the runnel population of snails exhibited flood-like features even during non-flood periods. The distribution and size classes of snails did not differ with lateral distance from runnels. The burrow characteristics of the crab Helograpsus haswellianus were compared to increase the accuracy of estimating abundance from burrow counts. Including only those burrows which were obviously maintained by resident crabs significantly increased the confidence limits of estimating crab abundance using only burrow density counts. This method was applied to runnelled and unrunnelled sites to assess any changes in the density of burrows associated with the presence of runnels. Again, it is likely that physical soil conditions resulting from increased tidal frequency at the runnel did influence crab burrowing with fewer small burrows being found at the runnelled site, low on the shore. In addition, mid- and large-sized burrows tended to dominate close to the runnel edge. Site-specific soil characteristics may help to explain the lack of continuity in patterns associated with runnel effects on non-target saltmarsh resources. While the runnel may increase the soil water content of clayey substrates at some sites it could also result in de-watering of porous sandy soils at other shores. This was evident in the structure of the snail population and distribution of crab burrows which appeared to reflect altered soil physical characteristics associated with the runnel. Runnelling does affect non-target organisms in saltmarsh. However, the scale of impact was usually locally restricted (< 10 m from the runnel edge). The fact that patterns were not recorded at all sites suggests that the influence of runnels is variable and limited by substrate and some biological conditions. Given the efficiency and popularity of runnelling as a physical control method for reducing pest vector mosquito habitat, this study found no evidence to suggest that its use should be discontinued on any ecological basis measured.
14
Breitfuss, Mark. "The Effects of Physical Habitat Modification for Mosquito Control, Runnelling, on Selected Non-Target Saltmarsh Resources." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/367526.
Abstract:
Runnelling is a popular method of physical habitat modification employed on saltmarshes to control pest mosquito populations. The runnelling method involves linking the tidal source to isolated mosquito breeding pools via shallow channels that enable slow water movement of low amplitude tides. Increased tidal flushing inhibits mosquito development. The range of organisms which inhabit saltmarsh are likely to be influenced by altered tidal conditions as they exhibit specific physicochemical requirements for feeding, burrowing or growth. The dynamic nature of saltmarsh may mean that changes to the tidal frequency of a particular region of the saltmarsh promotes extension of marine-like conditions. Because runnels increase the frequency of flooding tidal events in specific regions of the saltmarsh this study predicted that resulting changes would be evident in the physical conditions of saltmarsh substrate, in the transport of buoyant vegetative propagules, in the population characteristics of surface grazing snails and in the density and aperture of crab burrows after flooding and non-flooding tidal events. The physical impacts of runnelling were determined at three marshes which appeared similar in terms of topography, substrate and tidal conditions. Soil water content and consolidation were measured using two sampling protocols: a) comparisons between modified and unmodified shores; and, b) comparisons with increasing lateral distance across the shore from the runnel edge. At one marsh, moisture levels were significantly higher at runnelled than at unrunnelled sites when tides filled the runnels, but this pattern was not found at the other marshes. Soil consolidation was greater at higher shore heights, but was not different between runnelled and unrunnelled shores. Measurements at different lateral distances from runnels demonstrated higher moisture levels and lower consolidation up to 5 m from the edge but not further away. Groups of marked Avicennia marina propagules were released at the three runnelled saltmarshes during flooding and non-flooding tidal events. Groups of propagules released within 10 m of a runnel were always transported significantly further from the starting position and further up the saltmarsh shore after both flooding and non-flooding tides than any other groups. In addition, the pattern of stranding on saltmarsh for significantly different groups was closely associated with the path of runnel construction so that propagules were located either in the runnel or in depressions linked to the runnel that had been isolated mosquito-breeding pools prior to runnelling. It is likely that altered physical soil conditions significantly affected the distribution and size structures of Salinator solida and Ophicardelus spp. snails recorded at the three saltmarshes. The interaction of tidal period and the presence of a runnel contributed to patterns with significant differences between runnelled and unrunnelled regions of the marsh. Generally, the runnel population of snails exhibited flood-like features even during non-flood periods. The distribution and size classes of snails did not differ with lateral distance from runnels. The burrow characteristics of the crab Helograpsus haswellianus were compared to increase the accuracy of estimating abundance from burrow counts. Including only those burrows which were obviously maintained by resident crabs significantly increased the confidence limits of estimating crab abundance using only burrow density counts. This method was applied to runnelled and unrunnelled sites to assess any changes in the density of burrows associated with the presence of runnels. Again, it is likely that physical soil conditions resulting from increased tidal frequency at the runnel did influence crab burrowing with fewer small burrows being found at the runnelled site, low on the shore. In addition, mid- and large-sized burrows tended to dominate close to the runnel edge. Site-specific soil characteristics may help to explain the lack of continuity in patterns associated with runnel effects on non-target saltmarsh resources. While the runnel may increase the soil water content of clayey substrates at some sites it could also result in de-watering of porous sandy soils at other shores. This was evident in the structure of the snail population and distribution of crab burrows which appeared to reflect altered soil physical characteristics associated with the runnel. Runnelling does affect non-target organisms in saltmarsh. However, the scale of impact was usually locally restricted (< 10 m from the runnel edge). The fact that patterns were not recorded at all sites suggests that the influence of runnels is variable and limited by substrate and some biological conditions. Given the efficiency and popularity of runnelling as a physical control method for reducing pest vector mosquito habitat, this study found no evidence to suggest that its use should be discontinued on any ecological basis measured.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text
15
Whytock, Robin C. "Optimising habitat creation for woodland birds : the relative importance of local vs landscape scales." Thesis, University of Stirling, 2018. http://hdl.handle.net/1893/27298.
Abstract:
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.
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Magoba, Rembuluwani Norman Nicholas. "Effect of invasion and clearing of alien riparian vegetation on benthic macroinvertebrate and adult odonata assemblages in Soutpansberg rivers." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1800.
Abstract:
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.
17
Devoucoux, Pierrick. "Conséquences et impacts prévisibles d'une perte d'habitat majeure sur une espèce menacée aux exigences écologiques complexes : effets de la mise en place du contournement ferroviaire à grande vitesse Nîmes-Montpellier sur la dynamique de la population d'Outarde canepetière des Costières de Nîmes." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2285/document.
Abstract:
L'urbanisation et la construction d'infrastructures de transports sont aujourd'hui la première cause de baisse de diversité. De par la perte d'habitat et la fragmentation du paysage qu'ils engendrent, ces ouvrages impactent les populations. Notre travail a cherché à évaluer, sur une espèce aux exigences écologiques complexes, les impacts prévisibles de la mise en place d'une Ligne à Grande Vitesse (LGV) et leurs conséquences. Nous avons étudiés la population d'Outarde canepetière Tetrax tetrax des Costières de Nîmes. A l'échelle de son aire de répartition, cette population fait figure d'exception : elle atteint localement des densités-records et développe des patterns de distributions jusqu'alors jamais rencontrés chez l'espèce. Nous avons cherché à identifier les variations locales de distribution et leur corrélation avec les paramètres d'habitat selon une grande gamme d'échelle spatiale, afin de modéliser les patterns de distribution attendus et les impacts prévisibles de la future infrastructureUrbanization and increasing transport infrastructure construction are known as the main cause of biodiversity loss. By habitat loss and landscape fragmentation they cause, these structures impact populations. Our work sought to assess, on a case of complex ecological requirements, foreseeable impacts of the establishment of a High Speed Line (HSL) and their consequences. We studied the population of Little Bustard Tetrax Tetrax of the Costières nîmoise area. Within its own range scale, this population is an exception: it reaches locally unusually high densities and develops distributions patterns never met previously. We sought to identify local variations in distribution and their correlation with habitat parameters in a wide range of spatial scales, to model the expected distribution patterns and expected impacts of future infrastructure
18
Lewis, Cassandra Kasun. "The effects of habitat fragmentation on Amorpha canescens, a prairie forb, and its associated herbivores." Thesis, University of Iowa, 1999. https://ir.uiowa.edu/etd/5396.
19
Onken, Kai Sven. "Effects of native freshwater mussels and leaf debris on benthic macroinvertebrate abundance and diversity : A field experiment with Margaritifera margaritifera in Vasslabäcken, Örebro county." Thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-84485.
Abstract:
Organisms that are part of complex ecosystems interact not only with other organisms but also with their environment, affecting ecosystem functions. In aquatic ecosystems filter feeders affect ecosystem functioning by transferring energy and nutrients from the water to the benthos. The filter-feeding unionoid mussels can have strong effects on nutrient release and biodeposition in streams, affecting primary and secondary production. In a 90-day field cage experiment during winter 2019-2020, effects of the critically endangered freshwater pearl mussel (Margaritifera margaritifera) and leaf litter on benthic macroinvertebrate communities were tested using a factorial study design. Benthic macroinvertebrates were collected from the cages and examined in the lab. No significant effects of mussels, leaf litter or their interaction on the abundance and diversity of invertebrates were found for most groups. The abundance of Simulidae was however lower in cages with mussels compared to cages without mussels. The presence of mussels in streams may therefore affect ecosystem function, here shown as a possible effect on the interspecific competition for food sources between filter feeders.Organismer i komplexa ekosystem interagerar inte bara med andra organismer utan också med sin miljö, samt påverkar ekosystemfunktioner. I akvatiska ekosystem påverkar filtrerare ekosystemfunktioner genom att överföra energi och näringsämnen från vattnet till det bentiska samhället. De filtrerande unionoida musslorna kan ha stora effekter på närsalter och biodeposition i vattendrag, vilket påverkar primär- och sekundärproduktionen. I ett 90-dagars fältbursförsök under vintern 2019-2020 testades effekterna av den starkt hotade sötvattenspärlemusslan (Margaritifera margaritifera) och löv på bentiska samhällen. Makroevertebrater provtogs i burarna och undersöktes på lab. Det fanns inga signifikanta effekter av musslor, löv eller deras interaktion på makroevertebraters tätheter och diversitet för de flesta grupper. Tätheter av Simulidae var dock lägre i burar med musslor jämfört med burar utan musslor. Förekomsten av musslor i vattendrag kan därför påverka ekosystemets funktion, här visat som en möjlig effekt på mellanartskonkurrens mellan filtrerare.
20
Lau, Jamie K. "Impacts of channelization on stream habitats and associated fish assemblages in east central Indiana." Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1319547.
Abstract:
The objective of this study was to determine the relationship between fish assemblage structure and habitat in streams dominated by an agricultural landscape. Fishes from 20 natural and 20 channelized streams were sampled using electrofishing gear in East Central Indiana. Streams that had been channelized had a lower quality fish assemblage when compared to natural streams as measured by the Indiana V. Eastern Corn Belt Plain Index of Biotic Integrity (IBI). Stream habitat was evaluated using the Qualitative Habitat Evaluation Index (QHEI), which indicated that channelized streams had lower quality primarily due to a loss of heterogeneous habitat. Pearson correlation analysis relating ECB IBI and QHEI was positive and significant, and demonstrated that a reduction in riffle and pool areas associated with channelization was the most significant factor influencing the fish community. Furthermore, species lost when streams are channelized were predictable, and often represented environmentally sensitive species. The results of this study suggested that stream channel alterations have a negative and lasting influence on the fish assemblage which should be recognized prior to any stream development.Department of Biology
21
Hugo, Christine Denise. "The influence of fire and plantation management on Wetlands on the Tsitsikamma plateau." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1464.
Abstract:
Wetlands on the extensively afforested Tsitsikamma Plateau are prone to fire and according to foresters, they behave as fire channels that under bergwind conditions rapidly carry fire into plantations. The destruction of plantations causes great economic loss and MTO would therefore prefer to afforest some smaller wetlands to limit the fire hazard. This study was carried out in the middle of a drought period and sought to determine the influence of fire, plantation management and the environment on wetlands and its component species. This study of palustrine wetlands on the Tsitsikamma Plateau identified five wetland vegetation communities, in which plant species richness was relatively low. Plant compositional structure of wetlands is influenced by wetland location, the height of the adjacent plantation and fire frequency. This study found a pronounced plant species turnover from west to east and soil coarseness increased along the same gradient. Re-sprouters dominated the wetland communities in the Tsitsikamma but a few populations of the obligate re-seeding ‘Near threatened’ Leucadendron conicum rely on fire for rejuvenation purposes. Regarding dragonflies in wetlands, abundance was found to be low, while species richness was relatively high considering the absence of surface water. The study found that fire indirectly influenced dragonfly abundance and species composition by altering vegetation structure. Dragonfly abundance and species richness was generally higher in wetlands with older vegetation (≥ 9 years). Further, most dragonflies frequenting the palustrine wetland habitats were females. Seeing that female dragonflies spend most of their time away from prime breeding habitats to escape male harassment, the study indicated these wetlands as important refuge habitats for them. Dragonfly abundance is expected to increase once the drought ends; however, the overall patterns observed are likely to remain unchanged under wetter conditions. Narrow wetlands (< 10 m) are few on the plateau and it is not advisable to sacrifice wider wetlands in the Tsitsikamma. Further, with regards to ecological processes and wetlands’ influence on the surrounding Tsitsikamma matrix, more research is needed before wetlands may be sacrificed. To deal with the fire risk the Tsitsikamma environment poses to plantations, it is strongly recommended to establish and maintain a cleared buffer area between plantations and wetlands. Further, for vegetation rejuvenation purposes, it is important to burn wetlands at irregular intervals but not more frequently than every nine years and not less frequently than every 25-30 years.
22
Mercado, Alida. "Ground beetle (Coleoptera:Carabidae) communities along a successional gradient in southwestern Quebec and notes on the range expansion of introduced species." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97966.
Abstract:
Species diversity is influenced by disturbance in the environment. Ground beetles (Coleoptera: Carabidae) were used as a model taxon to study the effects of disturbance (i.e., time since disturbance) in different habitats along a successional gradient (agricultural fields, old fields, young forests and old forests). Seventy-three species (5139 individuals) were collected during both years of sampling, of which 9 species are introduced species and compose 64.8% of the total catch. In contrast to the predictions of the Intermediate Disturbance Hypothesis, diversity of ground beetles was higher in the agricultural fields and lowest in the old forests. The community composition, as seen with Nonmetric Multidimensional Scaling ordination, in the agricultural fields was the most distinct, while the difference between and among other habitats was less clear, possibly influenced by the introduced species present in the area. The introduced species collected had a significant influence in the total catch as they represented more than half of the total individuals collected and in the ground beetle community composition. The distribution of seven introduced species in Quebec was studied and compared to what was reported in 1975. Five species have a similar distribution, while the distribution range of Harpalus rufipes DeGeer has expanded south and Bembidion obtusum Audinet-Serville might have been dispersing northeast since its introduction.
23
Goodman, James R. "Artificial avian nest predation in a Kansas tallgrass prairie." Virtual Press, 1999. http://liblink.bsu.edu/uhtbin/catkey/1129624.
Abstract:
Several species of Neotropical migrant songbirds are experiencing declining population numbers. One of many proposed reasons for these declines is the dramatic loss of suitable prairie and grassland nesting habitat in the central United States. The Konza Prairie - a native tallgrass prairie preserve in central Kansas - was used to study possible edge-effect predation of artificial avian ground nests. Two Japanese quail eggs were placed in created artificial nests along transect lines from a wooded edge, a recently burned edge, and a control area. The rate of nest predation after seven days was 16.1 (±12.9%) for the control area. This was taken to represent the typical base level of artificial nest predation for the Konza Prairie. The predation rates for the wooded edge and burned edge were 21.9% (±7.4%) and 18.0% (±6.0%), respectively. These rates were not statistically different from each other or the base level rate of predation. The data suggests that no edge-effect predation occurs for artificial avian ground nests along wooded or burned edges in the Konza Prairie. Predation rates of natural bird nests may be different than these results suggest. It is recommended that future studies identify nest predators and study their foraging behavior near edge habitat.Department of Natural Resources and Environmental Management
24
Neef, Götz-Georg. "Comparative phylogeography of five swallowtail butterfly species (Lepidoptera: Papilionidae) in South Africa : ecological and taxonomic implications." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013574.
Abstract:
With current biota under constant threat of extinction, it is important to ascertain where and how biological diversity is generated and partitioned. Phylogeographic studies can assist in the identification of places and processes that indicate the origin and maintenance of biodiversity. Forest fragmentation has a big effect on local extinction and loss of genetic diversity of forest-restricted taxa, along with divergence and speciation of forest biota. This study aims to understand the effects of these processes on a number of forest-dwelling butterflies using a comparative phylogeographic approach. Mitochondrial DNA of five different Papilio species with different degrees of forest specificity was analysed using phylogenetic methods. In addition, the subspecific taxonomy of P. ophidicephalus was investigated using morphometrics of discal spots on the wings and nuclear DNA analysis along with mitochondrial DNA analysis. The results show that the forest-restricted species (P. ophidicephalus and P. echerioides) have more genetic structure and less genetic diversity than the more generalist species (P. dardanus, P. demodocus and P. nireus). This could be due to inbreeding depression and bottlenecks caused by forest fragmentation. As forest patches become smaller, the population size is affected and that causes a loss in genetic diversity, and increasing habitat fragmentation disrupts gene flow. The intraspecific taxonomy of P. ophidicephalus is far from revealed. However, this study shows there is evidence for the different subspecies when comparing morphological results and genetic results. From the evidence provided here it is suggested that P. ophidicephalus should be divided into two separate species rather than five subspecies.
25
Stephenson, Thomas Robert. "Mule deer response to military activity in southeast Colorado." Thesis, This resource online, 1989. http://scholar.lib.vt.edu/theses/available/etd-07292009-090244/.
26
Shacks, Vincent. "Habitat vulnerability for the Nile crocodile (Crocodylus niloticus) in the Okavango Delta, Botswana." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1651.
27
Cabrera-García, Leonardo. "Linking social and ecological dynamics for bird conservation : protecting the endangered Sierra Madre sparrow in Chichinautzin, Mexico." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102793.
Abstract:
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.
28
Mangachena, Joy Rumbidzai. "Response of bird assemblages to the invasion and clearing of alien trees in the Western Cape, South Africa." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2583.
Abstract:
Thesis (MTech (Conservation and Marine Sciences))--Cape Peninsula University of Technology, 2016.Invasive alien plant species pose a major threat to global biodiversity by displacing native vegetation and transforming habitats. In South Africa, invasive alien plants have become a major component of most habitats. River systems are particularly affected owing to their dynamic nature and to anthropogenic activities. This has resulted in fynbos riparian scrub vegetation being replaced mainly by Acacia and Eucalyptus species, with serious ecological and economic impacts. The presence of alien trees along river banks leads to a reduction in native plant species richness and their high water consumption adds on to the existing water challenges in an already dry country. However, with regards to native fauna, it largely remains unknown both at small or large spatial scale, whether alien trees provide additional habitat which increases biodiversity, or if their presence leads to a reduction of native biodiversity. Impacts on water supply have led to large-scale clearing of invasive alien trees from riparian zones by the government through the Working for Water (WfW) programme. Monitoring and evaluation studies carried out after clearing are not well-rounded and mostly focus on vegetation response to clearing. Although some of these studies have reported successful restoration through passive methods, ecosystem recovery remains partial. There is evidently a lack of information regarding the response of animal communities to invasive alien plant clearing. Therefore, the main objective of this thesis was to investigate bird assemblage response to alien tree invasion and clearing. As a study system, I used the riparian area of the Berg River within the fynbos biome of the Cape Floristic Region, South Africa. The area historically consisted of renosterveld vegetation characterised by a matrix of shrubs and a high diversity of geophytes but relatively poor avifaunal diversity. This area is heavily affected by invasive alien trees and shrubs including Eucalyptus camaldulensis. I employed bird assemblages as an indicator, and used fixed-point bird counts to compare bird species richness and bird abundance between invaded and near-pristine habitats. Invasion by E. camaldulensis significantly reduced bird species richness and abundance. In particular, nectarivores and frugivores, which play important mutualistic roles in the fynbos, were reduced and unexpectedly; there were fewer raptors in invaded areas. I proceeded to carry out a space for time substitution, comparing plant and bird assemblages in invaded sites, near-pristine sites and in sites cleared in 2005, 2007, 2008 and 2014. A general increase in bird species richness and bird abundance with time since clearing exists with bird assemblages in cleared sites being similar to those in near-pristine sites. However, bird assemblages in cleared sites have not yet fully recovered a decade after clearing and four native plant species are still absent. In the third part of my thesis I assessed the impacts of invasive alien plants on bird assemblages at a larger spatial scale. The different responses shown by bird assemblages to invasive alien plant cover depended on the intensity of invasion, spatial scale and other land uses. From a bird’s eye view, this study supports the current clearing by WfW given the significant negative effects of invasive alien plants on bird diversity both at plot and large spatial scales. However, passive restoration is unsuccessful in restoring the full complement of plants and birds, therefore, active restoration should be considered. To limit the cost, I suggest a focused restoration approach of selected keystone tree species which can assist to establish a functional native ecosystem.
29
Mbande, Sekiwe. "Fishes in the Mngazi and Mngazana estuaries, with particular emphasis on the community structure and primary carbon sources." Thesis, Rhodes University, 2004. http://hdl.handle.net/10962/d1005386.
Abstract:
The fish community structure of two contrasting estuaries, one with a well developed mangrove forest (Mngazana) and the other without mangroves (Mngazi) was compared. Both the Mngazi and Mngazana estuary fish communities were dominated by marine species, reflecting the importance of these systems as nursery areas for marine fishes. The Mngazi Estuary contained 18% more estuarine fishes in terms of catch per unit effort (CPUE) than the Mngazana Estuary. The reduced tidal influence due to the narrow mouth opening is a possible reason for the heightened CPUE of estuarine species in the Mngazi estuary. The recorded higher diversity of fish species in the Mngazana Estuary when compared with the Mngazi Estuary was attributed to the greater influence of the marine environment due to the wide permanently open mouth, as well as the presence of a variety of habitats in this system. In both estuaries tropical and temperate species were captured, confirming the transitional nature of their biogeographic location which is situated close to the boundary between the subtropical and warm temperate regions of the Southern African coastline. Contrary to previous studies, which recorded seasonal changes in the proportions of tropical and temperate species, the proportions of tropical species remained unchanged at approximately 70% during the January and June sampling occasions. Global warming as a possible reason for the increased dominance of tropical species is discussed. Although several studies in southern Africa have investigated estuarine food web structure, none have compared mangrove and non-mangrove estuaries. In this study, the primary sources of carbon utilised by the fish fauna in the Mngazi and Mngazana estuaries was investigated. The carbon isotopic values of fishes in both estuaries displayed a continuum rather than a tight clustering around particular energy sources. Most detritus feeders of the family Mugilidae (mullets) from both estuaries were relatively more enriched than other fish taxa. The isotopic values of the mullet species suggest a diet derived from relatively enriched carbon sources such as benthic microalgae, the eelgrass Zostera capensis and associated epiphytes. Based on the isotopic values, piscivorous fishes from both estuaries could not be linked to specific prey fish taxa, but clearly the mullet species were not their main food source. The invertebrate feeders that were found in both estuaries showed greater isotopic variations in the Mngazana Estuary than in the Mngazi Estuary, probably reflecting the higher diversity of habitats (carbon sources) and invertebrate prey species in the Mngazana system. Generally the isotopic signatures of fishes from the Mngazi Estuary were more enriched than those from the Mngazana Estuary, thus indicating the possible effect of δ¹³C depleted mangrove derived carbon in the latter system.
30
Sharratt, Norma. "Response of aquatic macroinvertebrate and aerial odonate assemblages to the removal of invasive alien trees in the Western Cape." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50440.
Abstract:
Thesis (MSc)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Invasive alien trees, especially Acacia species, are a great threat to biodiversity in South African rivers. The national Working for Water Programme is addressing the alien problem by removing alien trees from river margins. The concern is that this may be creating even further disturbance by affecting water quality and habitats. In particular, how is this affecting rare and endemic species? Benthic macro invertebrates and aerial odonates were assessed along five Western Cape rivers in alien-invaded, cleared and natural sites between December and March. The aim was to assess the effect of both alien invasion and alien clearing on aquatic invertebrates. Odonata, being easily sampled, were also assessed as they are severely affected by the lack of understorey plants in shaded, alien-invaded sites. Odonata and benthic macroinvertebrates were treated as two separate studies and no attempt was made to correlate the results obtained from both studies. SASS5, a qualitative, rapid bioassessment technique, based on the sensitivity of the families present, was used as a measure of river health and, indirectly, of water quality. SASS indicated a decline in water quality conditions after alien clearing, a likely response to the greater insolation as well as erosion of cleared banks, resulting in elevated temperatures and suspended solids and lowered oxygen levels. Community responses to alien disturbance and other environmental factors were analysed using PRIMER and CANOCO software. Assemblages of Odonata were found to provide a rapid, cost-effective means of assessment and monitoring. Potential indicator and detector species were also identified using the lndicator Value method. Assemblage patterns of aquatic invertebrates, however, were dominated by between-river and seasonal effects. Therefore, while SASS detected overall changes in river health, without identifying the cause, potential aquatic detector taxa were identified that may be useful for linking general disturbance to alien invasion or clearing. All indicator and detector taxa identified in both studies can be used for long-term monitoring and for identifying biodiverse areas for clearing or protection. In both studies, sensitive, endemic taxa were lost after clearing, being replaced by more tolerant, widespread taxa. Recovery of the biota appears to follow the recovery succession of the vegetation, with most sensitive or endemic taxa only appearing after the recovery of indigenous plants. A number of recommendations are made regarding the restoration of both water quality (particularly with respect to shade and soil erosion) and biotope availability (particularly in terms of the recultivation of indigenous plants) in order to achieve biodiversity objectives. The role of catchment management, prioritisation procedures and long-term monitoring are also discussed.
AFRIKAANSE OPSOMMING: Uitheemse, indringerbome, veral Acacia spesies, is 'n groot bedreiging vir biodiversiteit in Suid- Afrikaanse riviere. Die nasionale Werk vir Water-projek spreek hierdie probleem aan deur uitheemse bome van rivieroewers te verwyder. Die kommer is dat water kwaliteit en habitatte sodoende verder versteur kan word. Byvoorbeeld, hoe word endemiese en bedreigde spesies geraak? Akwatiese makroinvertebrate en volwasse Odonata in vyf Wes-Kaapse riviere is tussen Desember en Maart bestudeer en gemonster in natuurlike gebiede, in gebiede waar indringerbome teenwoordig is, en in gebiede waar hulle verwyder is. Die doel was om die effek van indringerverwante impakte op akwatiese invertebrate vas te stel. Odonata is ook bestudeer omdat hulle maklik gemonster kan word en omdat hulle ernstig geraak word deur indringers. Die uitheemse plantegroei oorskadu die oewers en verhoed die groei van inheemse oewerplante. Die bentiese makro-invertebrate en Odonata is as twee aparte studies behandel en geen poging is gemaak om die resultate van die twee te vergelyk nie. SASSS, 'n kwalitatiewe, bioasseseringsmetode wat op die sensitiwiteit van die aanwesige families baseer word, is gebruik om waterkwaliteit op 'n indirekte manier te bepaal. SASS het aangedui dat daar 'n afname in waterkwaliteit is nadat indringerplante verwyder is. Dit is moontlik as 'n gevolg van groter blootstelling aan sonskyn en erosie van rivieroewers wat veroorsaak dat temperature en die hoeveelheid gesuspendeerde materiaal verhoog word, en dat suurstof konsentrasies verminder word. Die gevolge van indringerplante en ander omgewingsfaktore op akwatiese gemeenskappe is met PRlMER en CANOCO sagteware ontleed. Groepering van Odonata kan gebruik word om op 'n maklike en koste-effektiewe manier om die impak van indringerplante en hul verwydering te bepaal en te monitor. Aanwyserspesies is ook deur middel van die 'Indicator Value' metode geïdentifiseer. Die verspreidingspatrone van invertebraatspesies word deur geografiese en seisoenale effekte oorheers. Dus, terwyl SASS veranderinge in waterkwaliteit kan aantoon, sonder om die oorsaak daarvan te identifiseer, kan aanwyserspesies gebruik word om meer spesifieke impakte deur indringerplantegroei, of indringerverwydering, te bepaal en te monitor. Hulle kan ook gebruik word om gebiede met hoë biodiversiteit vir bewaring of indringerverwydering te identifiseer. Beide studies dui aan dat sensitiewe en endemiese taksa na indringerverwydering verlore gaan, en vervang word met meer geharde, wydverspreide taksa. Herstel van die biota volg op die herstel van die plant gemeenskappe, en die mees sensitiewe of endemiese taksa herstel eers nadat die inheemse plantegroei herstel het. 'n Aantal aanbevelings in verband met die restorasie van waterkwaliteit (veral in terme van die hoeveelheid skaduwee en erosie) en die beskikbaarheid van biotope (veral in terme van inheemse plante) om biodiversiteitsdoelwitte te bereik word gemaak. Die rol van opvanggebied bestuur, voorrang prosedures en lang termyn monitering word ook bespreek.
31
Holgate, Katheryn T., and University of Lethbridge Faculty of Arts and Science. "The effects of cattle grazing on the breeding biology of riparian forest birds." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1999, 1999. http://hdl.handle.net/10133/349.
Abstract:
Cattle grazing in riparian zones can have large impacts on vegetation characteristics and avian biodiversity. To assess these impacts in southern Alberta, vegetation and bird surveys were conducted in twelve riparian sites (four each in heavily grazed, moderately grazed, and ungrazed habitats) along the Oldman River. The shrub understory and bird species diversity and abundance declined significantly as grazing intensity increased. Settlement patterns, territory sizes, and food provisioning rates of some bird species were examined to assess the mechanisms behind this reduction. Five out of seven species settled earlier in ungrazed habitats, whereas two species did not show any discernable settlement pattern. The territory sizes of three species examined increased as grazing intensity increased. House wrens (Troglodytes aedon) brought more food and more food biomass to their nests in ungrazed habitats. These results indicate that available food biomass decreased as grazing intensity increased, and is an important factor in population dynamics of some species.29 cm.
32
Holl, Karen D. "Vegetational and lepidopteran conservation in rehabilitated ecosystems." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40121.
Abstract:
Coal surface mining and associated reclamation practices have had an immense impact on the landscape of the Appalachian region of the United States. However, their effect on floral and faunal conservation has been poorly documented. Lepidopteran communities, vegetation, and nectar resources were studied on 19 mine sites reclaimed 0-30 years previously and five sites in the surrounding hardwoods in southwestern Virginia. The goals of this work were to characterize vegetational and lepidopteran communities of these sites; to understand the relationships between the two; and to assess the role of mine reclamation in regional conservation efforts.
Vegetational community composition of the reclaimed sites appeared to be approaching that of the hardwood sites as time since reclamation increased. However, it will take a number of years, if ever, before the vegetational community composition and structure approximate that of the hardwoods. Between-site variation in vegetational communities was greater in the hardwoods, than the reclaimed sites.
Recently reclaimed mined sites hosted a large number of both individuals and species of diurnal lepidoptera, comprising mostly widespread, generalist species. Multivariate analysis suggested that lepidopteran community composition of reclaimed sites was approaching that of the hardwoods and that lepidopteran communities of later successional reclaimed sites were fairly similar to those of the surrounding hardwoods. Moth community composition closely reflected vegetational community composition and species richness, while butterflies were poor indicators of vegetational communities.
Reclaimed sites provided much more abundant and diverse nectar resources than hardwood forests. Results of nectar studies and butterfly behavioral observations suggested that adult butterfly community composition was strongly influenced by nectar abundance, but that nectar was not a limiting resource.
While reclaimed sites hosted a number of the more common plant and lepidopteran species, it remains questionable whether reclaimed areas will ever host the entire complement of the biota present prior to disturbance. In order to further conservation efforts, rehabilitation projects must be designed and monitored over larger spatial and longer temporal scales.Ph. D.
33
Ivande, Samuel T. "Distribution ecology of Palearctic migrants in the humid Guinea savannah in West Africa." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7446.
Abstract:
Declines in breeding populations of most migrants across much of the Palearctic have been linked to environmental conditions in their African non-breeding grounds. Studying winter distribution dynamics for these species is necessary to understand how factors in these areas may influence their overall population dynamics. This thesis explored in detail the distribution ecology of migrants in the Guinea savannah, the region from where wintering migrants currently show the greatest breeding population declines. In particular, I investigated some prevailing but hitherto little tested ecological hypothesis concerning impacts of geographical, vegetation and anthropogenic characteristics on the densities and winter distribution of migrants in Africa. Migrant distribution seemed to fit a pattern where decisions leading to winter habitat choice and association were hierarchical and jointly influenced by factors extrinsic and intrinsic to the habitats at large and finer scales respectively. Migrants were distributed in reasonable densities across a wide range of habitats. There was also evidence for an independent effect of latitude on densities and distribution, even after controlling for habitat characteristics. There was no evidence of large changes in latitudinal density patterns within a given winter season and site density patterns were generally consistent over the study duration. Migrants and taxonomically-related/ecologically similar Afrotropical residents showed similarities in habitat requirements and utilization, although migrants utilized habitats over a wider latitudinal range. Some migrants tended to show correspondence in site occurrence between consecutive winters but less so within a given winter season and there was an overall low transferability of habitat models for Palearctic migrants between sites in Nigeria. Collectively, the results describe distribution mechanisms typical for ecologically flexible species that can best be described as habitat generalists. As generalists, migrants are expected to show some resilience, especially in dealing with local and small scale changes on their wintering grounds such that these are unlikely to be the primary limiting factor in their population dynamics. However, the scale of ongoing habitat change across much of Africa is perhaps contributing to overcome the resilience engendered by their generalism. Conservation efforts for these mainly generalists species may therefore aim to preserve habitat on a large scale, perhaps through the promotion of sustainable land use practices.
34
Crowther, Amy E. "The restoration of intertidal habitats for non-breeding waterbirds through breached managed realignment." Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/334.
Abstract:
Conservation of intertidal habitats in the UK is vital in order to continue to support nationally and internationally important populations of non-breeding waterbirds. Historic reclamation for agriculture and industry has resulted in the loss and degradation of large areas of these intertidal habitats in estuaries and they continue to be threatened by sea-level rise. Managed realignment is one method which is increasingly being used to restore intertidal habitats. As managed realignment is a relatively new restoration technique, the extent to which knowledge of the biology of estuaries is applicable to managed realignment sites is unclear. Habitat restoration is often unsuccessful or incomplete, so a detailed knowledge of both the natural system and the characteristics of restored systems will usually be necessary to recreate fully-functional estuarine habitats. This thesis focuses on Nigg Bay Managed Realignment Site (Nigg Bay MRS), the first managed realignment site in Scotland, and follows the first four years of ecological development to gain an understanding of how breached realignment can be used to restore intertidal habitats to support non-breeding waterbirds. This thesis has six major aims: (i) to describe the development of saltmarsh, (ii) to describe the development of intertidal flat, (iii) to describe the colonisation by non-breeding waterbirds (iv) to determine how tidal cycle and weather affect patterns of waterbird use, (v) to determine which factors affect the spatial distribution of waders and finally (vi) to determine the patterns of use by individual birds. Four summers after the re-establishment of tidal conditions, almost all of the saltmarsh species recorded on the nearby saltmarsh had colonised Nigg Bay MRS, although recognisable communities had yet to establish. Three winters after the re- establishment of tidal conditions in Nigg Bay MRS, the sediments had a significantly smaller particle size and higher organic matter content compared to the fine sands of the adjacent intertidal flats. The intertidal invertebrate community also differed from the adjacent intertidal flats. Nigg Bay MRS attracted large numbers of non-breeding waterbirds and supported each of the most common wader and wildfowl species present in the wider estuary. Nigg Bay MRS performs a number of important functions for non-breeding waterbirds by: (i) providing a foraging and resting habitat when the tide is absent and intertidal sediments in Nigg Bay are exposed; (ii) providing a foraging resource as the tide passes over the intertidal sediments within the site once the intertidal flats in Nigg Bay are inundated; and (iii) providing a high tide roosting site. On days with low temperatures and high wind speeds, more waterbirds use Nigg Bay MRS, suggesting that it is likely to be providing sheltering benefits. Nigg Bay MRS also provides top-up feeding habitat. The factors that often influence the spatial distributions of waders in estuaries appear to be operating within Nigg Bay MRS. Wader densities are greater on the intertidal flats when they are accessible than on the saltmarsh. Wader densities are also greatest close to creeks and drainage channels, possibly due to higher invertebrate densities, more accessible prey or sheltering benefits. Colour-ringing and radio-tracking of Common Redshank established that Nigg Bay MRS has a subset of regular users, including both adults and juveniles, and the wader assemblage at night may differ from the assemblage during the day. These findings are discussed in terms of the implications for locating, designing and managing future managed realignment projects.
35
Bredenhand, Emile. "Evaluation of macro-invertebrates as bio-indicators of water quality and the assessment of the impact of the Klein Plaas dam on the Eerste River." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/2630.
Abstract:
Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005.A semi-arid country, like South Africa, with unpredictable seasonal rainfall, is subject to great scarcity in water and an ever-increasing demand from the rising human population. Therefore, efficient reservoirs as well as monitoring methods are needed to manage the South African water supply. This study was undertaken on the Eerste River in the Western Cape, South Africa, focusing on the impact of the Klein Plaas dam system on the benthic macroinvertebrates. The study also examined the use of benthic macroinvertebrates as bioindicators of water quality with special reference to the South African Scoring System Version 5(SASS5) that is currently being used nationally. The impoundment of the water, as well as the inter-basin transfer programme and the experimental cage-culture trout farm, all play a significant role in the disturbance impact of the dam on the Eerste River system. The disturbance is manifested as a drop in water quality that can be seen in the distribution of keystone species, changes in the riparian vegetation, as well as in physical-, chemical-, and biomonitoring evaluations. The study also indicated that the SASS5 is effective, but needs some adjustments, such as inclusion of a prediction phase, finer spatial-scale methodologies and greater consideration of the rarity of species.
36
Andrus, Wonnita, and University of Lethbridge Faculty of Arts and Science. "Ecology and conservation of prairie rattlesnakes (Crotalus viridis viridis) in relation to movement in a fragmented urban environment." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological, c2010, 2010. http://hdl.handle.net/10133/2620.
Abstract:
Eighteen prairie rattlesnakes (Crotalus viridis viridis) were tracked using radio-telemetry and 82
snakes were PIT-tagged over a 2-year period in Lethbridge, AB to determine population size,
movement patterns, and habitat utilization, and to predict fragmentation effects on the species
within an urban locale. Population size was estimated using closed population models at 374
snakes (295 adults) and open population models at 204 snakes (161 adults), greater than an
estimate of <50 adults in 2003 (Ernst, 2003) and 2006 (Ernst & Quinlan, 2006).
Mean home range sizes, based on 95% minimum convex polygon analysis, differed significantly
between years (31.51 ha in 2005, 3.72 ha in 2006). Calculated movement parameters, such as
mean distance moved per day, total distance moved over the course of the active season, and
frequency of movement varied between years and individuals. Greater-than-expected (under
hypotheses of even habitat choice) utilization was observed in habitat types located within coulee
and flood plain areas, with apparent preference towards unbroken parcels of grassland or
cottonwoods, whereas less-than-predicted utilization of agricultural habitat type was observed.
Fragmentation effects on prairie rattlesnake movement and occurrence were examined through
modeling and were found to coincide with observed species’ locations, suggesting that prairie
rattlesnakes are undergoing modification of movement patterns to avoid highly concentrated
human density or use. Influence of weather on the use of vegetative ground cover was observed,
as it was accessed more by prairie rattlesnakes at higher temperatures.
Recommendations towards future management of the prairie rattlesnake population in Lethbridge
are given, including protection of the Bridge View Drive site and inclusion of varied habitat types
and terrain when planning habitat and wildlife corridors. Management decisions that ensure
remaining habitat parcels and connective areas near rattlesnake foraging or movement corridors
are also advocated. Identification of future research focuses include studies on juvenile
survivorship, genetic structure, and vehicle-related mortality.xii, 83 leaves : col. ill., col. maps ; 29 cm
37
Braulik, Gillian T. "Conservation ecology and phylogenetics of the Indus River dolphin (Platanista gangetica minor)." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3036.
Abstract:
The historical range of the Indus River dolphin has declined by 80% since the 19th century and has been fragmented into 17 river sections by construction of irrigation barrages. Dolphin sighting and interview surveys showed that river dolphins persist in six river sections, have been extirpated from ten, and are of unknown status in the remaining section. Logistic regression and survival modelling showed that low dry season river discharge was the primary factor responsible for the Indus dolphins range decline. Abundance of the three largest Indus dolphin subpopulations was estimated using tandem vessel-based direct counts, corrected for missed animals using conditional likelihood capture-recapture models. The entire subspecies was estimated to number between 1550-1750 in 2006. Dolphin encounter rates within the Guddu-Sukkur subpopulation (10.35/km) were the highest reported for any river dolphin and direct counts suggest that this subpopulation may have been increasing in abundance since the 1970s when hunting was banned. The dry season habitat selection of Indus dolphins was explored using Generalised Linear Models of dolphin distribution and abundance in relation to river geomorphology, and channel geometry in cross-section. Channel cross-sectional area was shown to be the most important factor determining dolphin presence. Indus dolphins avoided channels with small cross-sectional area <700m2, presumably due to the risk of entrapment and reduced foraging opportunities. The phylogenetics of Indus and Ganges River dolphins was explored using Mitochondrial control region sequences. Genetic diversity was low, and all 20 Indus River dolphin samples were identical. There were no haplotypes shared by Indus and Ganges River dolphins, phylogenetic trees demonstrated reciprocal monophyletic separation and Bayesian modelling suggested that the two dolphin populations diverged approximately 0.66 million years ago. Declining river flows threaten Indus dolphins especially at the upstream end of their range, and it is important to determine how much water is required to sustain a dolphin population through the dry season. Fisheries interactions are an increasing problem that will be best addressed through localised, community-based conservation activities.
38
Tweddle, Gavin Paul. "The influence of overwash and breaching events on the spatial and temporal patterns in ichthyofauna community composition in a temporarily open/closed southern African estuary." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1002957.
Abstract:
This study assessed the importance of overwash and breaching events on the ichthyofaunal community structure in the medium-sized temporarily open/closed Mpekweni Estuary located on the southeast coastline of southern Africa. The fish in the littoral zone of the estuary were sampled using a 5m seine net while the channel region was sampled using two nets, a smaller meshed 30m seine net to target the estuarine spawning species and the juvenile estuarine-dependant marine spawners, and a larger meshed 50m seine net to target the larger marine and freshwater spawning species. Intensive monthly sampling over two years provided data on selected physico-chemical and biological parameters. During the two year sampling period from November 2005 to October 2007 the estuary breached in late July 2006 and remained open till the sandbar re-formed across the mouth in late December 2006. Thus, sampling encompassed three open/closed phases 1) initial closed period, 2) open period and 3) re-closed period after the berm was re-formed. The open period was divided into two phases 1) the out-flow phase and 2) the tidal phase. A total of 36 fish species representing 19 families were sampled using the various seine nets employed during the investigation. In the littoral zone, the estuarine spawners (Estuarine Utilisation Category, [EUC] I), mainly the Gobiidae, Glossogobius callidus, dominated the samples numerically and by biomass. The smaller estuarine spawning species sampled in the channel were numerically dominated by Gilchristella aestuaria in conjunction with two other EUC I species, Atherina breviceps and G. callidus. The estuarine-dependant marine spawners (EUC II), however, dominated the ichthyofaunal biomass of the channel. The abundance and biomass of the larger species targeted were dominated by estuarine-dependant marine spawning species (EUC II), principally Rhabdosargus holubi. During the closed periods of the estuary, total fish abundance and biomass displayed weak seasonal patterns. The breaching event and subsequent open period was associated with a decrease in the total abundances of fish in the littoral zone and channel of the estuary, reflecting the out-flow of estuarine biomass-rich water into the marine environment. The breaching event coincided with a shift in the community composition of the ichthyofauna, reflecting the recruitment of marine spawning species into the estuary. Numerical analysis identified two distinct spatial fish communities within the estuary, a community associated with the mouth region and one comprising the rest of the estuary. The absence of any further spatial patterns in the ichthyofaunal community structure within the Mpekweni Estuary appear to be ascribed to the virtual absence of horizontal patterns in physico-chemical and biological parameters recorded in the system. Cohort analyses were employed to determine possible recruitment events for selected estuarine and marine spawning species. The estuarine spawning species displayed continuous recruitment patterns throughout the study, which appeared to be unaffected by the breaching event. Conversely, the larger marine spawning species displayed multiple cohorts, indicating non-continuous recruitment. Subsequent retrospective analysis of cohorts for the different species identified summer recruitment peaks that coincided with the breaching event and open period. Minor recruitment of marine spawning species also occurred during overwash events. The recruitment of ichthyofauna into the estuary was quantified during three distinct hydrological events: overwash, out-flow phase immediately after breaching and tidal phase during the period when the mouth was open. Estimates of fish recruitment were highest during the outflow phase immediately after the estuary breached and declined as the estuary became tidally inundated with marine water. Although not as high as the outflow and tidal phases, recruitment was evident during overwash events. Results of the current study highlight the importance of both breaching and overwashing events in structuring the ichthyofaunal community composition in a medium-sized southern African temporarily open/closed estuary. These results are broadly in agreement with similar studies conducted both locally and in other regions of the world.
39
Mataruse, Gamuchirai. "Phylogeography and conservation of a newly identified galaxiid from the Joubertina area, South Africa." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1003050.
Abstract:
The dispersal of freshwater fishes in the Cape Floristic Region of South Africa has been attributed to river capture events and confluence of rivers during sea level regression. The role of low drainage divides and inter-basin water transfers have received less attention. A unique lineage of Galaxias zebratus (hereafter the Joubertina galaxias) occurs in two currently isolated river systems, the Gamtoos and Krom. The present study mapped the distribution of the Joubertina galaxias and used mitochondrial and nuclear DNA sequences to assess the processes that could have influenced its current distribution pattern. Analyses of both mitochondrial cytochrome ♭ and nuclear (S7) sequences revealed that observed genetic differentiation cannot be explained by isolation between the Gamtoos and Krom River systems. No genetic differentiation was found between the Krom River System and the Twee River (a tributary of the Gamtoos River System). Shallow genetic differentiation (0.4% for cytochrome ♭ and 0.3% for S7) was found between the Krom and the remaining populations in the Gamtoos River System. High levels of genetic structuring were observed within the Gamtoos River System with most tributaries having one or more unique alleles. Inter-basin dispersal during pluvial periods or recent human mediated translocation seems to be the most plausible explanations for presence of the Joubertina galaxias in the Krom River System. The present study also assessed the threats and habitat preferences of the Joubertina galaxias, and an evaluation of the conservation status of this lineage was done. The Joubertina galaxias is threatened mainly by alien fish invasion, habitat loss and loss of genetic diversity due to fragmentation of its populations. Due to its very restricted geographic range, small known population sizes and the intensity of threats to this lineage’s survival, this lineage has been assessed as Endangered. The lineage has a restricted Area of Occupancy (AOO) and Extent of Occurrence (EOO). The extent of occurrence has declined in all tributaries and is continuing to decline in all except two tributaries that are secure. The lineage may have had natural fragmentation among its populations, but recent threats have completely isolated the populations. The threats affect the lineage’s survival potential in the four tributaries which have small populations that are not presently viable. The densities observed for the Joubertina galaxias ranged from 0.16 - 1.3 fish /m² and the number of mature individuals for the whole population seems to be less than 2500 mature individuals. There is therefore a need for specific conservation actions to ensure the long-term survival of this unique lineage.
40
Junkuhn, Kyle Peter. "The role of seasonality, environmental correlates and edge effects on the diversity and abundance of small mammals in Afromontane forest patches, Eastern Cape, South Africa." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018188.
Abstract:
The Eastern Cape contains the majority of the remaining forested areas in South Africa (95.8 percent Coastal forests and 47.6 percent Afromontane forests), however these occur in fragments. Due to the rapid rise in the human population and its needs, conversion of forests to agricultural land and the extraction of timber increases, natural vegetation are lost and this therefore leads to forests becoming fragmented into small forest patches. One of the main consequences of forest fragmentation is loss of contiguous habitat, which is the dominant threat to species globally as it negatively affects both species richness and genetic diversity. This research investigates the effects that forest fragmentation has on small mammal diversity and abundance. The study sampled small mammals in Southern Mistbelt Afromontane forest patches in the Eastern Cape. The first aim of this study was to identify which environmental variable, or combinations of variables, affect the diversity and abundance of small mammals in fragmented forest patches in the Eastern Cape during the austral summer. The second aim was to compare seasonal changes in small mammal diversity and abundance at a forest edge compared to the forest core at Beggars Bush, an Afromontane forest in the Eastern Cape, South Africa. To identify the environmental impacts that different forests have on small mammals, nine different forests were chosen in the Eastern Cape and sampled during the summer in 2013. These nine forests were: Fort Fordyce Forest, Thaba Ndoda Forest, Hogsback Forest, Dassie Kraans Forest, Langeni Forest, Burchell’s Reserve Forest, Maiden Dam Forest and Kagaberg Forest. At each site, three transects of 30 Sherman Traps each were used. Trapping periods within each forest patch lasted between three to five consecutive nights and traps were inspected once a day in the morning. Nine environmental variables were initially identified and after being tested for normality and colinearity, five variables were chosen. These variables were Altitude, Mean Annual Temperature, Gradient, Patch Size and Mean annual potential evaporation. The number of individuals captures and species richness were then incorporated as dependent variables for best subset multiple regression model selection using the Akaike Information Criterion (AIC). For the second aim, the same trapping methods were used when comparing seasonal changes to diversity and abundance within the forest core. However at the forest edge, due to the small size of the forest, only 20 Sherman traps were used in each transect with five traps (25 percent) placed in the grassland and 15 (75 percent) placed in the forest along each transect. This study was one of few to survey small mammal diversity and abundance in fragmented forests in the Eastern Cape. Gradient, patch size and mean annual potential evaporation were the variables that best predicted the individual number of small mammal captures while only gradient best explained species richness. It does however, need to be noted that capture rates and species richness were very low and this would therefore effect the analysis of environmental variables. Future studies should have a larger sample size of forest patches and include more microhabitat environmental variables to determine their effects on small mammal diversity and abundance. However, it should be noted that through climatic extinction filtering, forest mammals are resilient generalists that can tolerate fragmentation effects. Furthermore, it was found that forest edges appear to play a significant role in small mammal diversity and abundance in the Beggars Bush Afromontane forest. Some species were habitat specialists such as Rhabdomys pumilio preferring the grassland habitat and Graphiurus murinus and Aethomys namaquensis the forest habitat, while Myosorex varius was the only species that was not habitat dependant. It was found that there was a greater diversity and abundance at the forest edge compared to within the forest core throughout most of the seasons. One possible flaw was that the sampling methods were different at the edge and within the forest and therefore future studies should ensure that the method stays uniform throughout the study.
41
Gray, Michael Andrew. "The ecological impacts of habitat modification on tropical biodiversity." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440791.
42
Brush, Janell Marie. "Wetland avifauna usage of littoral habitat prior to extreme habitat modification in Lake Tohopekaliga, Florida." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014260.
43
Muench, Ann Marie. "Aquatic vertebrate usage of littoral habitat prior to extreme habitat modification in Lake Tohopekaliga, Florida." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008580.
44
Wesenbeeck, Bregje Karien van. "Thresholds and shifts : consequences of habitat modification in salt-marsh pioneer zones /." PURL, 2007. http://www.arlis.org/docs/vol1/A/433191982.pdf.
45
Twitchell, Sara Erin. "Evaluating the Effects of Road Crossing Structures on Stream-Associated Amphibians in the Wilson River Watershed, Tillamook State Forest, Oregon." Thesis, Portland State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1535858.
Abstract:
As replacement and removal of undersized culverts gains momentum as an effective technique for restoring natural stream flows and removing fish passage barriers, it is important to evaluate the benefits of these efforts on the in-stream and adjacent riparian habitat for other species of potential concern. This study compares stream-associated amphibian (SAA) occurrence in streams adjacent to different road crossing structures on unpaved forest roads in the Wilson River watershed located within the Tillamook State Forest, Oregon. Surveys were conducted at road crossing structures for three taxa of SAA; Pacific giant salamander (Dicamptodon tenebrosus), coastal tailed frog (Ascaphus truei), and Columbia torrent salamander (Rhyacotriton kezeri). Statistical models were created to analyze the effect of habitat variables on SAA occupancy, and determine whether those variables changed relative to road crossing structures.
Results showed that coastal tailed frog occupancy was positively associated with dissolved oxygen and crayfish presence, negatively associated with longitude, and had a slight quadratic relationship to channel confinement. Because all sites were highly saturated with oxygen, percent dissolved oxygen was likely a surrogate for one or more other covariates, such as in-stream habitat or substrate size. Detection rates of Pacific giant salamander were too high and detection rates of Columbia torrent salamander were too low to provide reliable models, but they did provide some insight into the factors affecting occupancy in the study area, including information about their interactions with road crossing structures. Occupancy rates of Pacific giant salamanders in the study area appear to be unaffected by road crossings, fish passable or otherwise. Conversely, torrent salamanders seemed to be mostly absent from the study sites altogether, but based on the one stream where they were detected, they are not excluded from occupying fish barrier culvert sites.
Top weighted habitat covariates, including dissolved oxygen, channel confinement, crayfish and fish presence, and flow constriction are all indicators of disturbance that can be linked to road crossings. Although the size and structure of road crossings did not prove to significantly influence SAA occupancy, indicators of stream disturbance that can be related to road crossings were included in the best models for predicting occupancy, demonstrating the importance of reducing disturbance related to road crossings on streams.
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Pereboom, Vincent. "Mode d'utilisation du milieu fragmenté par une espèce forestière aux habitudes discrètes." Angers, 2006. http://www.theses.fr/2006ANGE0032.
Abstract:
La biologie de la conservation est une discipline de crise qui se trouve constamment confrontée au manque de données concrètes sur l’éco-éthologie des espèces. La destruction du milieu forestier est la cause majeure de la disparition des espèces dans le monde alors qu’en Europe et Amérique du nord, c’est surtout la destruction des bosquets, des arbres isolés et des haies qui met la survie des populations en danger. Afin d’obtenir des nouvelles connaissances sur l’impact de cette fragmentation de l’habitat, j’ai choisi comme modèle d’étude une espèce considérée comme inféodée aux forêts et reconnue vulnérable à la dégradation des forets, la martre des pins, Martes martes. J’ai étudié, par le radio-pistage de 24 martres, l’utilisation de l’habitat et des corridors forestiers sur deux sites différents. La martre s’avère être une espèce non pas inféodée aux grands massifs forestiers mais par contre dépendante de la présence d’arbres, que ce soit des bosquets ou des haiesThe destruction of forests, a main issue in biological conservation, is one of the greatest threat in biodiversity worldwide. In Europe and North America, however, the maintenance of populations is put in jeopardy by the destruction of trees outside of forests and hedgerows. In order to acquire new insights in the impact of habitat fragmentation, I chose a species regarded as forest specialist and recognised as vulnerable to forest degradation, the Pine marten Martes martes, as a model. I studied habitat and corridor use by Pine martens by radio-tracking 24 martens in France on two different sites. The marten was shown as being a species not dependant on old growth forest, as was previously considered, but instead on the presence of trees in the close vicinity, be they forest groves or hedgerows
47
Clarke, Matthew John. "The effect of habitat fragmentation on ecosystem processes." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364922.
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Axisa, Benedict. "The effect of doxycycline on carotid plaque modification." Thesis, University of Leicester, 2002. http://hdl.handle.net/2381/29400.
49
Watson, Nicholas. "Habitat preferences and the effect of habitat reduction on the quenda (Isoodon fusciventer) in an urban environment." Thesis, Watson, Nicholas (2018) Habitat preferences and the effect of habitat reduction on the quenda (Isoodon fusciventer) in an urban environment. Honours thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/43141/.
Abstract:
Habitat loss has been a large contributing factor in the decline in abundance of many fauna species in Australia. Ground-dwelling mammals are particularly susceptible to this threat and with the increase in urbanisation, there is a pressing need to conserve species that remain in these environments. The quenda (Isoodon fusciventer) is one of the remaining native mammals that persists in the metropolitan area of Western Australia. With the quenda’s recent upgrade to species level, existing information on this species is often extrapolated from eastern sub-species of the southern brown bandicoot. The metapopulation at Murdoch University has declined over recent years and the lack of research on the quenda inhibits conservation efforts.
This thesis studies the habitat preferences of the quenda population at Murdoch University and monitors the effect of vegetation removal, from fire mitigation that is currently ongoing on campus, on quenda activity. It was predicted that the vegetation removal from fire mitigation would have a negative impact on quenda activity. Also of interest was trialling different GPS attachment positions to achieve the longest consistent attachment time when using adhesive. To address these aims, a combination of camera trapping, GPS tracking and quenda diggings were used to determine micro and macrohabitat preferences of quenda. Two sites were targeted for vegetation clearing and camera traps were used to determine any change in quenda activity. Three other sites were monitored as a control.
The study found that at the microhabitat scale, quendas avoided grass, litter and canopy cover. At the macrohabitat scale, quendas preferred shrub cover with higher levels of vegetation density from 48 to 144 cm. Foraging occurred closer to grass trees and in denser vegetated areas. A decrease in quenda activity was observed in areas that experienced vegetation clearing from fire mitigation with the control areas showing an increase in activity. GPS tag positioning showed to have a small influence on attachment time with only the upper back showing a significant increase compared to the mid-flank position.
The findings suggest that dense vegetation and grass trees are vital for the quendas at Murdoch University and is similar to that of other bandicoots from the same genus. Careful management is crucial during fire mitigation to ensure that there is adequate suitable habitat during this process and into the future.
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Osinubi, Samuel Temidayo. "Habitat Effect on the Behaviour and Condition of the Yellow-breasted Boubou (Laniarius atroflavus)." Thesis, University of Canterbury. Biological Sciences, 2012. http://hdl.handle.net/10092/6495.
Abstract:
This project was aimed at investigating behaviour and condition of the Yellow-breasted Boubou, Laniarius atroflavus, in response to habitat differences across core, edge and riparian Afro-montane forest habitats at the Ngel Nyaki Forest Reserve, Nigeria. This species is little known and conservation effort will require direction in identifying the habitat of best quality for their survival. The determination of habitat association using correspondence analysis of census data suggested strongest association with the riparian habitat, even though this habitat held the least overall avian biodiversity as determined from a modified Shannon index. L. atroflavus appeared not to hold territories in the core habitat. Territoriality, vocalisation and time budget showed trends indicating L. atroflavus were more abundant and fared better in the riparian habitat. In this habitat, there was a greater density of territories and a smaller mean territory size, better call quality in frequency bandwidth and duration, and increased displaying and foraging time in the riparian habitat. Difference in size, colour and growth-based measures of condition showed difference between sexes, but did not show a strong habitat effect – males were larger than females, yet females appeared to have better quality of yellow breast feathers for equal carotenoid concentration. The effect of nest predation risk as a predictor of habitat quality revealed nests in the riparian habitat had the greatest daily survival probability, and within this habitat nests established at lower heights survived longest. While the evidence pointed towards the riparian habitat being most suitable for L. atroflavus, this habitat sadly continues to suffer anthropogenic disturbance and this species’ IUCN listing as Least Concern was suspected be an over-estimation.