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Wodika, Ben. "EFFECTS OF TIME, SEED SOURCE, AND PLANT COMPOSITION ON MACROINVERTEBRATES IN RESTORED PRAIRIE." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1088.
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Invertebrates influence primary productivity and nutrient cycling in ecosystems. They are also important links between producer and higher trophic levels. Despite their important role in terrestrial ecosystem function, invertebrates are frequently overlooked in ecological restorations. Thus, the objective of this research was to quantify how belowground macroinvertebrate ecosystem engineers and communities change over time following ecological restoration and examine whether the source of dominant plant species and the composition of non-dominant plant species influence aboveground macroinvertebrates community structure in restored prairie. A chronosequence design (space for time substitution) was used to determine the role of restoration age, plant community, and soil structure on the recovery of two belowground macroinvertebrate ecosystem engineers (Chapter 2). Ants and earthworms were sampled from cultivated fields, grasslands restored for 1-21 years, and native prairie. Earthworm abundance increased with time since cessation of cultivation, concomitant with prairie establishment. The abundance and biomass of ants were more related to the structure of restored plant communities than time since restoration. The dominance of exotic earthworms, and a generalist ant species in these restorations, coupled with their known capacity to alter soil properties and processes, may represent novel conditions for grassland development. The same chronosequence of agricultural fields, restored prairies, and prairies that were never cultivated was used to address the second objective of this research, which was to quantify how the belowground macroinvertebrate community composition changed in response to ecological restoration and whether the communities became representative of undisturbed (“target”) communities. Macroinvertebrate communities in the two remnant prairie sampled were distinct from restorations and continuouslycultivated fields. The macroinvertebrate communities in prairie that had never been cultivated were also distince from each other, indicating a “target” community is hard to define. Belowground macroinvertebrates changed in a trajectory that was not representative of either remnant prairie, but was representative of the an average of both remnant prairies. Thus, if you reconstruct prairie from cultivated soil conditions (“build it”), macroinvertebrates will colonize (“come”), but attaining a community representative of a specific target may require introduction from that target. Colonization of macroinvertebrates in restorations aboveground are most likely to be influenced by aspects of the plant community. A third objective of this research was to quantify whether variation in dominant species (cultivars vs. local ecotypes) and composition of subordinate species (local species pools) influence the composition of aboveground macroinvertebrates. Macronvertebrate abundance, richness, diversity, trophic groups and community composition in late summer did not vary between prairie restored with cultivar and local ecotypes of the dominant grasses. This was observed in two field experiments. The species pool treatment did influence the macroinvertebrate community, as one species pool had slightly higher morphospecies diversity and hymenopterans that the other two species pools. This was likely due to the presence of an ant-tended legume, Chamaecrista facsciculata Michx., in one species pool. Overall, this research demonstrates that time since the cessation of disturbance (cultivatation) and plant communities influence macroinvertebrate communities in restored prairie. Restored prairies in the Midwest are likely to be colonized by exotic earthworms and cosmopolitan ants. More research is needed to reveal how they influence ecosystem functioning.Belowground, macroinvertebrate communities may not represent restoration “targets” and these “targets” may be hard to define if remnants are rare or there is a high degree of spatial variation on the landscape. Variation in plant communities above ground appears to influence the structure of aboveground macroinvertebrate communities more than variation within dominant species. Whether this aboveground variation is reflected is reflected belowground deserves further investigation.
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McCaffery, Magnus. "The influence of an ecosystem engineer on nutrient subsidies and fish invasions in Southwestern Montana." Diss., [Missoula, Mont.] : University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-03102010-102211.
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Bush, Laura Elizabeth. "Stability and variability of the ecosystem engineer Sabellaria alveolata on differing temporal and spatial scales." Thesis, Bangor University, 2016. https://research.bangor.ac.uk/portal/en/theses/stability-and-variability-of-the-ecosystem-engineer-sabellaria-alveolata-on-differing-temporal-and-spatial-scales(1deae07d-a12b-4f61-9838-77e1a8bc9cca).html.
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Climate change is directly and indirectly impacting biota, A common prediction is that biogeographic ranges will extend poleward, with increases in abundance near the leading edge. Understanding how marine species will respond is hindered by a scarcity of long-term datasets. However, within the British Isles there is a long history of well-documented intertidal research. Historical data are stored in a variety of forms from grey-literature and national databases to published journals. Sabellaria alveolata is a conservationally important biogenic reef-forming species that reaches its northern range limit within the British Isles. The aim of this thesis was to establish if S. alveolata has responded predictably to climate change, and to investigate abiotic and biotic drivers of observed change. Through comparisons with historical and contemporary collated and collected data on different spatial scales, it was clear that S. alveolata has exhibited persistence in distribution, and stability in abundance and morphology on a long term, broad spatial scale with no significant difference in distribution, abundance or reef-forming morphology exhibited from the 1980s to the 2010s (>50 % stability in all paired data; Bush et al., Chapter 2). Within this, S. alveolata populations have demonstrated change on reduced spatial scales, increasing in response to increased temperature near the northern range edge, with some decreases in response to increased wave exposure well within the range (explaining ~ 50 % of the variance in both instances; Bush et al., Chapter 3). Through long-term monitoring studies, this study demonstrated high within-site variability. Additionally evidence was provided that, within Britain, the intertidal ecosystem engineers S. alveolata and Mytilus edulis are alternative stable state communities on pebble shores, with complete change of state from S. alveolata dominated to M. edulis dominated reef in 1 year (Bush & Davies, Chapter 4). State is partially maintained by settlement success in both instances (R2 ≥ 0.55). Finally, through a combination of traditional monitoring and laboratory techniques with state of the art modelling approaches, this study provided insights into reproductive strategy, larval dispersal and population connectivity patterns of S. alveolata and provided evidence of subpopulations of reef-forming species on British coastlines (e.g. Scotland to North Wales, Mid Wales, and South Wales to Southwest England; Bush et al., Chapter 5).
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Hochhalter, Samuel J. "Patch-Scale Effects of an Invasive Ecosystem Engineer on the Structure and Function of a Eutrophic Stream." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/307.
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Recent theoretical and technological advances in ecosystem science have dramatically expanded the ways in which scientists can pursue and explore ecological questions. For my thesis research, I integrated the recent theoretical concept of organisms as ecosystem engineers with the relatively recent development of stable isotope tracer tests to ask the question: how does the invasive common carp affect stream ecosystem structure and function? To investigate the structuring role of carp, I measured autotroph seasonal distribution and abundance and macroinvertebrate seasonal abundance and diversity within two stream reaches in Spring Creek, Utah, USA; one with low carp biomass (LCB) and one with high carp biomass (HCB). I installed a series of carp exclosures in the HCB reach to examine the response of the stream to carp exclusion. To explore the effects of carp on stream nitrogen dynamics, I performed a three week, continuous injection of 15N as ammonium chloride. The macrophyte and macroinvertebrate community was severely depauperate in the HCB reach compared to the LCB reach. The observed rapid colonization of a relatively abundant and diverse macrophyte and macroinvertebrate community at the carp exclusion sites in the HCB reach not only indicates that carp engineering reduces the abundance and diversity of these communities, but also highlights the importance of the spatial distribution of engineered and non-engineered patches in dictating the temporal scale of re-colonization. Carp engineering had a simplifying effect on stream N dynamics that ultimately limited the uptake and retention capacity of the HCB reach. For example, macrophytes played a dominant role in the N dynamics of the LCB reach by directly assimilating NH4, retaining N rich FBOM, and by providing habitat necessary to support an abundant and relatively diverse macroinvertebrate community that facilitated greater trophic transfer of nitrogen. Conversely, carp reduction of macrophytes in the HCB reach resulted in an overall reduction in areal uptake rates of NH4, reduced trophic transfer of N, and significantly reduced N retention. These results clearly indicate that carp engineering reduces macrophyte and macroinvertebrate abundance and diversity in streams and that N dynamics are simplified in carp engineered patches.
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Vitelli, Frederico. "Herbivory by Parma mccullochi (Pomacentridae) : its role as an ecosystem engineer in temperate algal-dominated reefs." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/583.
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Pomacentridae is one of the most representative families of herbivorous fishes inhabiting both tropical and temperate reefs, yet the vast majority of studies examining feeding within this family have been undertaken in tropical rather than temperate regions. Despite the high abundances of the pomacentrid Parma mccullochi in temperate waters of Western Australia, and their likely importance in removing algae from reefs in the region, there is a lack of information on their diet and their impact on the reef algal community. This study aims to determine the role of Parma mccullochi as an ecosystem engineer on temperate algal-dominated reefs in the metropolitan waters of Perth, Western Australia. To achieve this, the diet of P. mccullochi and any ontogenetic differences, and its impact on the reef in terms of algal composition and algal recruitment were determined. P. mccullochi in the temperate reefs of Western Australia was found to be a strict herbivore, with its diet comprising almost entirely red foliose and filamentous algae such as Hypnea spp., Ceramium sp. and Brongniatrella sp., and showing no ontogenetic shift. Based on electivity indices, P. mccullochi showed a positive selection for specific algal taxa such as Brongniartella sp., Dasyclonium sp., Hypnea spp. and Dictyopteris spp. The species composition of macroalgae differed significantly between inside and outside P. mccullochi territories (P = 0.010), and a caging experiment in P. mccullochi territories indicated a moderate effect on the composition of recruiting algae (P = 0.067). Algal assemblages inside the territories were characterised by Hypnea spp. and Dasyclonium spp., while those outside the territories were characterised by the brown algae Ecklonia radiata and Sargassum spp., the foliose red alga Rhodimenia sonderi and the coralline red alga Amphiroa anceps. Total algal biomass was significantly lower (P = 0.0126) while species richness was higher (P = 0.0114) inside compared to outside territories. This study, therefore, provides the evidence to refute the theory that temperate Pomacentridae have a low impact on the temperate reefs (Jones 1992). P. mccullochi has the capacity to structure the benthic composition of reefs and maintain high biodiversity patches within kelp canopies. This effect is amplified by the high abundances of the species observed in Perth metropolitan waters, and can therefore be considered an ecosystem engineer/landscaper of temperate algal dominated reefs, highlighting its importance in ecosystem processes of temperate reefs in the region.
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James, Alexandra Iona Biological Earth & Environmental Sciences Faculty of Science UNSW. "Development of resource-rich patches by soil-disturbing animals in arid environments." Awarded by:University of New South Wales. Biological, Earth & Environmental Sciences, 2009. http://handle.unsw.edu.au/1959.4/44353.
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In arid landscapes limited resources are concentrated into fertile patches that allow greater productivity than would otherwise be expected. Fertile patches are created and maintained by processes that modify soil topography and interrupt the flow of resources across the landscape. These processes may be abiotic or biotic in origin. Species that modify, maintain or create habitat have been termed ecosystem engineers. One group of soil disturbing ecosystem engineers creates fertile patches by modifying soil microtopography through foraging for food and creating habitat. This thesis examines the effects of soil foraging animals on resource concentration in arid environments and how effects are moderated by species and landscape. Chapter 1 provides an overview of the importance of fertile patches in arid systems and describes previous research on the effects of ecosystem engineers in arid environments. Chapter 2 examines how fertile patch creation by a well-studied arid zone engineer, the ant, varies between ant species and landforms, demonstrating that while we can generalise about the effects of ant nests on water flow and nutrient levels, differences in soil type, nest density and ant species across sites are likely to moderate these effects. Chapters 3, 4 and 5 compare the engineering effects of reintroduced native species, the Greater bilby (Macrotis lagotis) and Burrowing bettong (Bettongia lesueur) with the Sand goanna (Varanus gouldii) and the invasive European rabbit (Oryctolagus cuniculus) across three Australian landforms, revealing differences between reintroduced and invasive engineers at the both patch and landscape scales. At the landscape scale, differences in pit densities and resource concentration in foraging pits between landforms suggest that fertile patch development is not uniform. Chapter 6 examines whether the structure of the pit or the presence of litter per se explains observed increases in plant germination in foraging pits, and compares temperature and soil moisture conditions in bilby and bettong pits to the soil surface. Chapter 7 is a review that builds upon previous chapters, published and unpublished literature of the potential for reintroductions of ecosystem engineers to restore ecosystem function in degraded environments. Chapter 8 summarises the research presented in this thesis and its implications, and suggests directions for future work.
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Martin, Stephanie Ann, and Marietjie Landman. "The Aardvark as an ecological engineer in the Eastern Karoo: dig patterns and emergent processes." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/11952.
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Species which play particularly important roles in ecosystem patterns and processes are recognised as keystone species or ecosystem engineers. The conservation of these species is critical for the maintenance of the ecological role they play in ecosystem function. The aardvark, Orycteropus afer, is known to play a role in biopedturbation through digging for refuges and for prey, and as a consequence of these digging activities is expected to serve the role of an ecosystem engineer and keystone species. This study aimed to describe and quantify the ecological patterns and processes driven by the aardvark through their digging activities, within the eastern Karoo, and thereby evaluate the significance of aardvarks as ecosystem engineers and keystone species in a semi-arid environment. The landscape pattern (dig abundance and distribution) and soil displacement of aardvark forage and refuge digs in a semi-arid Karoo landscape, as well as the ecological processes (generating fertile, seed retention hotspots) driven by aardvark forage digs was measured. Refuge digs occurred in the highest densities in areas characterised by a specific suite of soil, vegetation and elevation features, while forage digs occurred in high abundance in most habitats measured, and were likely driven by prey availability. Forage digs served as litter and seed retention hotspots, with accelerated decomposition rates of litter as a function of increased soil moisture in digs. The functional processes (i.e. resource capture, shelter for plants and animals, germination sites, soil aeration, organic turnover, mineralization rates, fertile soil displacement and transport) driven by aardvark digs are not restricted to refuge digs. Forage digs occurred in most habitats measured and their functional role is unique and perhaps greater across the landscape in comparison to refuge digs. The aardvark has a disproportionate effect in ecosystems, in terms of its refuge and forage digs relative to its abundance and therefore its role as a keystone species and ecosystem engineer is confirmed. Conservation and protection of this species is therefore essential to maintain its important role in ecosystem function.
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Njozela, Cuma. "The role of the sandprawn, Callichirus kraussi, as an ecosystem engineer in a temporarily open/closed Eastern Cape estuary, South Africa." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001539.
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The role of the sandprawn, Callichirus (=Callianassa) kraussi (Stebbing), as an ecosystem engineer was assessed in the lower reach of the temporarily open/closed Kasouga Estuary situated along the Eastern Cape coastline of southern Africa over the period April 2010 to June 2011. The study comprised two distinct components, a field study and a caging experiment. The field study assessed the correlation between sand prawn densities and selected physico-chemical (organic content of the sediment and bioturbation) and biological (microphytobenthic algal concentrations and macrobenthic abundance and biomass) variables in 50 quadrants in the lower reach of the estuary. Densities of the sand prawn within the quadrants ranged from 0 to 156 ind m⁻² (mean = 37 ind m⁻²). There were no significant correlations between the densities of the sandprawn and the estimates of the organic content of the sediment and the abundance and biomass of the macrofauna (P > 0.05 in all cases). Numerical analyses failed to identify any effect of the sandprawn density on the macrofaunal community structure. The rate of bioturbation was, however, strongly correlated to the sand prawn density. Similarly, the microphytobenthic alga concentrations were significantly negatively correlated to the sand prawn densities ((P < 0.05). The absence of any distinct impact of the sandprawn on the macrobenthic community structure appeared to be related to their low densities in the lower reach of the estuary during the study. To better understand the role of the sandprawn as an ecosystem engineer, a caging experiment was conducted using inclusion and exclusion treatments (n= 5 for each treatment). Densities of the sandprawn in the inclusion treatments (80 ind m⁻²) were in the range of the natural densities within the estuary. The experiment was conducted over a period of 18 weeks in the lower reach of the estuary during summer. The presence of the sandprawn, C kraussi, contributed to a significant decrease in the microphytobenthic algal concentrations and the abundance and biomass of the macrofauna (P < 0.05 in all cases). The decrease in the microphytobenthic algal concentrations in the presence of the sandprawn appeared to be related to the res-suspension of the sediments (bioturbation) generated by the burrowing and feeding activities of the sandprawn. The observed decrease in macrofaunal abundances and biomass in the inclusion treatments appeared to be mediated by both the decreased food availability (mainly the microphytobenthic algae) and the burial of organisms within the sediments. Numerical analysis indicated that the sandprawn did, however, not contribute to a change in the species composition of the macrofauna. Results of the current study indicate that C.kraussi plays an important role in structuring the invertebrate community and energy flow within temporarily/open closed Kasouga Estuary.
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Posthumus, Erin Elizabeth. "Do Red Squirrel Middens Promote Vertebrate Species Diversity?" Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/294022.
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The modifications animals make to their environments can be critical to species diversity. Red squirrels (Tamiasciurus hudsonicus) create large piles of conifer cone debris (middens) and are hypothesized to function as a keystone species due to positive associations between middens and other vertebrate species. We assessed vegetation and landscape structure at middens with a resident red squirrel for varying consistencies over the prior 5 years and surveyed mammals and birds at the community and population level. After accounting for vegetation and landscape characteristics, red squirrel-created resources positively influenced species richness of medium and large mammals and ground foraging birds, abundance of deer mice (Peromyscus maniculatus) and ground foraging birds, and activity of cliff chipmunks (Tamias dorsalis). Increased knowledge of the interaction strength of the red squirrel with its environment may be used to inform decisions in forest management and restoration and offer insight on the conservation value of larderhoarding mammals.
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Bancroft, Wesley J. "Environmental response to burrowing seabird colonies : a study in ecosystem engineering." University of Western Australia. School of Animal Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0064.
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[Truncated abstract] Ecosystem engineers are organisms that physically modify habitat in a manner that modulate resource flows and species within ecosystems. Ecosystem engineering is distinct from classical interactions (competition, predation, parasitism and mutualism) in that it does not involve direct trophic exchange between organisms. The term ‘ecosystem engineer’ is a recently adopted one, and we are just beginning to investigate the occurrence and impact of engineers in ecosystems. My thesis explores the ecosystem engineering actions of Wedge-tailed Shearwaters, Puffinus pacificus, in a Mediterranean island, heathland ecosystem. I have approached this by (1) describing and quantifying the physical impact of these engineers, and (2) describing and quantifying the effects that these actions have on three major ecosystem components: the soil, the vascular plants, and the vertebrate fauna. Wedge-tailed Shearwaters are procellariid seabirds that excavate nesting burrows on offshore islands. The birds are colonial nesters, and on Rottnest Island, 17 km off the mainland coast of south-western Western Australia, their colonies have expanded considerably in recent decades. The expansion fits the trend observed in other tropicalorigin seabirds that breed in south-western Australia. In the last ten years, two new colonies have appeared (in a total of six) and the number of burrows on the island has almost doubled, to 11 745 ± 1320SE. In the same period the area occupied by the birds has increased by almost half ...
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Sancomb, Elizabeth J. "Direct and indirect effects of white-tailed deer (Odocoileus virginianus) herbivory on beetle and spider assemblages in Northern Wisconsin." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1408363956.
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Jones, Kevin Christopher. "Ecological effects of the feeding and construction activities of the Eurasian beaver (Castor fiber) in Scotland : implications for reintroduction." Thesis, University of Stirling, 2006. http://hdl.handle.net/1893/211.
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Beavers have been described as a “keystone species” and “ecosystem engineers”, and in this dual role have great potential to physically modify their environment through tree-felling, foraging and construction activities. The resultant change in habitat heterogeneity can affect the flora and fauna that share the habitat with them. There has been recent interest in reintroducing the Eurasian beaver to the United Kingdom after an absence of over 400 years. To date, no research (aside from this thesis) has focussed on beaver ecology and behaviour in Scotland. This study has investigated the ecological effects of a small number of beavers in two enclosed but semi-natural Scottish sites at Bamff in Perthshire. The research conducted over a three-year period, with particular emphasis on the effects of tree-felling, foraging and construction activities. Trees were felled for both dietary and construction purposes, with felling rates being influenced by habitat availability, quality and the degree of habitat modification required. Highest rates were evident during the initial colonisation period of marginal sites (c. >300 trees / beaver / calendar year), and lowest rates in later years of occupation of more optimal sites (c. 55 – 70 trees / beaver / calendar year). Preferences were generally for willow and aspen trees, with conifers almost entirely avoided, and smaller trees preferred over larger ones. Proximity of trees to waterbodies was also an important factor, with nearer trees favoured, and generally most felling occurred within 50 m of water. Such behaviour followed the principles of optimal central place foraging. These preferences were less predictable however when intense construction activity was undertaken, with larger trees preferred and generic preferences for deciduous trees apparently invalid. In such cases, close proximity to the construction site was of prime importance. Increased cover of herbaceous plant species was observed in beaver-created canopy gaps in riparian woodland, whilst macrophyte diversity within waterbodies increased slightly in areas of herbaceous grazing. The diversity of terrestrial ground invertebrates was highest in areas of heavy tree-felling, and invertebrate richness and abundance was greatest in areas of herbaceous grazing under an intact tree-canopy. Furthermore, the abundance, diversity and richness of macroinvertebrate communities were increased by beaver-generated woody debris in ponds and streams. Overall, 30% of all macroinvertebrate species collected were found only in beaver-affected areas, due to the refugia and food supply provided by beaver dams, caches and lodges, as well as hydrological effects of these structures. These results are discussed with reference to future plans to return the beaver to Scotland. The habitat usage and modification of riparian ecosystems in northern Britain is likely to be similar to that found in this study, and the results are believed to be relevant, applicable and transferable to many areas of Scotland.
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Veras, Priscila de Cerqueira. "Papel do peixe Malacanthus Plumieri (Actinopterygii) na estrutura dos bancos de rodolitos do Arquipélago de Fernando de Noronha - Brasil." reponame:Repositório Institucional da UFABC, 2016.
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Orientador: Prof. Dr. Guilherme Henrique Pereira FilhoDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Evolução e Diversidade, 2016.
Engenheiros Ecossistemicos (EE) modulam a disponibilidade de recursos no ambiente. Este e o caso dos rodolitos (i.e. gnodulos de vida livreh compostos por mais de 50% de algas calcarias incrustantes que formam bancos em fundos inconsolidados) que promovem habitats para diversos organismos. Por outro lado, muitos desses organismos modulam condicoes para o crescimento de rodolitos. Esta interacao resulta na criacao de redes altamente dependentes de EEs. O peixe Malacanthus plumieri move rodolitos para a construcao de montes. Esta movimentacao altera o estado fisico de nodulos e, possivelmente, contribua para a diferenciacao das comunidades associadas. Portanto, avaliamos se as comunidades de macrofauna vagil (> 500¿Êm) presentes nos montes sao afetadas de forma positiva, negativa ou neutra em relacao a area controle (i.e. sem interferencia do M. plumieri). Alem disso, procuramos identificar as principais variaveis fisicas, que sao alteradas pelo peixe, que predizem a estrutura da macrofauna associada aos rodolitos. Para tanto, amostramos no Arquipelago de Fernando de Noronha 30 rodolitos na area controle e 30 nos montes. Cada nodulo foi individualmente inserido em sacolas de nylon com malha de 500¿Êm. Os epibiontes foram removidos e identificados. Mensuramos volume e diametros de cada rodolito e quantificamos o peso seco das macroalgas e do sedimento. Observamos que rodolitos da area controle apresentaram maior quantidade de macroalgas epifitas e sedimentos aprisionados quando comparados com rodolitos presentes nos montes (t=-0,04, p<0,001 e t=-0,54, p <0,001; respectivamente). A bioturbacao causada por M. plumieri altera as condicoes para o estabelecimento da macroalgas, reduzindo as taxas de sedimentos aprisionados. Como resultado, ha uma reducao na abundancia, riqueza e densidade de macroinvertebrados (t=-7,42, p<0,001; t=-7,92, p<0,001; t=-2,84, p<0,01; respectivamente). Portanto, M. plumieri afeta indiretamente a comunidade de macroinvertebrados vageis. Em contraste com outros estudos, o efeito da coexistencia destes EEs parece ser antagonico (i.e. positivo para a abundancia e riqueza de ictiofauna e negativo para macroalgas e macroinvertebrados). Assim, mudancas estruturais no sistema, embora promovidas pelo mesmo EE, influenciam comunidades de diferentes maneiras e sao dependentes da escala dos organismos em questao.
Ecosystem engineers (EE), such as rhodoliths, control the availability of resources in the environment, providing habitats for other organisms, as other algae and many animals. Some of these organisms are able to modulate the environmental conditions where rhodoliths grow, thus forming a highly dependent network. The sand tilefish Malacanthus plumieri, for example, moves rhodoliths to build mounds over their burrows. This behavior changes the physical medium in which the nodules are, and therefore, their associated communities¿ structure and composition. We assessed the effect of communities associated with mounds in comparison to non-mounded areas (i.e. rhodolith areas without the interference of the tilefish). Additionally, we seek to identify the main physical variables changed by the action of M. plumieri in predicting the structure of the macrofauna associated with rhodoliths. Rhodoliths from non-mounded areas showed higher amounts of epiphytic macroalgae and sediment trapped on rhodoliths than mounds (t=-0.04, p<0.001 and t=-0.54, p<0.001, respectively). Bioturbation caused by M. plumieri alters the conditions for macroalgae establishment, reducing the trapped sediment. As a result, there is also a reduction in the abundance, richness and density of macroinvertebrates (t=-7.42, p<0.001, t=-7.92, p<0.001, t=-2.84, p<0.01 respectively). The ecosystem role of M. plumieri indirectly affects the vagile macrofauna community. In contrast to other studies, the coexistence of these EEs (i.e. rhodoliths and tilefishes) seems to be antagonistic (i.e. positive for the abundance and richness of ichthyofauna and negative for macroalgae and macroinvertebrates). Thus, structural changes in the system, although promoted by the same EE, influence communities in different ways depending on the scale of the organisms in question.
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Jones, Auriane. "Effect of an engineer species on the diversity and functioning of benthic communities : the Sabellaria Alveolata reef habitat." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0142/document.
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A travers le monde, les zones côtières abritent une grande diversité d’ingénieurs de l’écosystème accomplissant des fonctions clés comme le recyclage de la matière organique et des nutriments. Les habitats résultants de l’activité biologique de ces espèces sont exposés à de nombreuses perturbations comme la surpêche, le piétinement ou via l’aménagement des côtes. Dans ce contexte, il est urgent de comprendre le fonctionnement de ces habitats ingénieurés et comment ils sont affectés par des perturbations croissantes. Pendant ma thèse, j’ai utilisé l’habitat récifal construit par le polychète grégaire tubicole Sabellaria alveolata comme cas d’étude. Tout d’abord, les changements environnementaux et biotiques associés à la mise en place d’un récif à S. alveolata et à sa perturbation croissante ont été évalué, se concentrant sur les paramètres du sédiment (e.g. granulométrie, contenu en matière organique) ainsi que la diversité taxonomique et les assemblages d’espèces. De manière similaire, le troisième article se penche sur le fonctionnement trophique de la communauté récifale et d’une communauté contrôle afin de comprendre les effets de la mise en place de l’espèce ingénieur sur les transferts de carbone, s’intéressant successivement à l’ensemble de la communauté des consommateurs, aux consommateurs primaires et à l’importance des sources de nourriture autochtones (microphytobenthos et Ulva sp.) vs allochtone (phytoplancton). Dans cette partie, j’ai utilisé les isotopes stables du carbone et de l’azote ainsi que différentes approches analytiques telles que des mesures de la niche isotopique et des modèles de mélange. L’article 2 a pour but de comprendre les interactions entre complexité de l’habitat récifal, hétérogénéité des sources de nourriture autochtones et échelles spatiales dans l’explication des variations du rapport isotopique du carbone de S. alveolata et d’un suspensivore associée. Dans les deux derniers chapitres, j’ai traité la question du fonctionnement de l’habitat ingénieuré de manière directe, en utilisant des incubations de carottes benthiques pour mesurer des flux biogéochimiques (e.g. demande en oxygène), ou indirecte, en utilisant des indices de diversité fonctionnelle et isotopique intégratifs. Cette dernière partie révèle l’existence d’un optimum de densité de S. alveolata, utilisée comme proxy des perturbations, où la niche trophique et le fonctionnement biogéochimique du récif sont tous les deux maximauxCoastal zones worldwide are home to a large diversity of ecosystem engineers that perform key functions such as the recycling of organic matter and nutrients. The habitats resulting from the biological activity of these species are exposed to numerous disturbances such as over harvesting and trampling or via coastal modification. In this context, it is becoming key to understand the functioning of these engineered habitats and how they are affected by increasing disturbances. During my PhD, I used the reef habitat built by the gregarious tubiculous polychaete Sabellaria alveolata as a study case. First, the environmental and biotic changes associated with the establishment of a S. alveolata reef and its increasing disturbance were assessed, focusing on sediment characteristics (e.g. grain-size distribution, organic matter content) along with taxonomic diversity and species assemblage. In the same vain, the third article looks into the trophic functioning of the reef community and a control community to understand the effects of the establishment of the engineer species on carbon transfers, successively looking at the whole consumer community, the primary consumers and the importance of autochthonous (microphytobenthos and Ulva sp.) vs allochthone (phytoplankton) food sources. In this part, I used carbon and nitrogen stable isotopes and different analytical approaches such as isotopic niche metrics and mixing models. Article 2 aims towards understanding the interactions between reef habitat complexity, autochthonous food source heterogeneity and spatial scales in explaining the carbon isotopic ratio variations of S. alveolata and an associated suspension-feeder. In the last two chapters, I address the functioning of the engineered habitat either directly, using benthic core incubations to measure biogeochemical fluxes (e.g. oxygen demand) or indirectly, through the use of integrative functional and isotopic diversity indices. This last part reveals the existence of an optimum value of S. alveolata density, used as a disturbance proxy, where the trophic niche and the biogeochemical functioning of the reef are both maximal
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Guerin, Natalia. "Impacto da invasão e mecanismos de regeneração natural do cerradão em áreas ocupadas por Pteridium arachnoideum (kaulf.) Maxon (Dennstaedtiaceae) no sudoeste do Estado de São Paulo." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-06052010-084435/.
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As samambaias do gênero Pteridium caracterizam-se pelas largas frondes e por um sistema de rizomas subterrâneos que possibilita sua rápida expansão. Apresentam elevada produção de biomassa ao longo do ano, que aumenta a incidência de incêndios, e ainda liberam substâncias químicas consideradas alelopáticas. Atualmente, são conhecidas como plantas-problema, pois vêm se expandindo e ocupando grandes áreas em diversas partes do mundo, causando impacto econômico e ecológico. Nesse contexto, este estudo teve por objetivo geral a compreensão do impacto da invasão por Pteridium arachnoideum sobre a vegetação de cerrado e a elucidação dos mecanismos por meio dos quais vem sendo lentamente revertido o processo de invasão na área de estudo. Para tanto, analisamos áreas de cerradão invadidas há mais de quatro décadas na Estação Ecológica de Assis (EEcA), no sudoeste do estado de São Paulo. Analisamos a composição florística e estrutura da comunidade em uma área invadida dentro da EEcA. Avaliamos os componentes do estrato arbóreo e regenerante da comunidade, a fim de verificar quais as espécies que conseguiram ultrapassar as barreiras físicas e químicas impostas pela presença da samambaia. Para tanto, comparamos a vegetação da área invadida com uma área adjacente não invadida, com ambiente e histórico de perturbações semelhantes. Utilizamos 100 pontos quadrantes para amostragem da composição florística e, para caracterização da estrutura da comunidade, alocamos 15 parcelas de 10 m x 30 m para amostrar o estrato superior, dentro das quais foram instaladas sub-parcelas de 2 m x 30 m para o estrato intermediário e de 2 m x 2 m para o estrato inferior. Medimos a cobertura das copas das árvores dentro das parcelas e estimamos a porcentagem de cobertura do solo por Pteridium. As espécies que conseguiram ocupar a área no início da invasão são tolerantes à sombra e com ritmo de crescimento rápido, características que possibilitaram que tais espécies ultrapassassem a barreira de samambaia e se estabelecessem na área. Já as espécies do estrato inferior se assemelham às da área não invadida, indicando que está havendo uma substituição das espécies na comunidade vegetal. A baixa densidade das árvores na área invadida diminui a competição entre os indivíduos, que, por sua vez, investem em aumento de tamanho, sendo consideravelmente maiores do que as árvores do cerradão não invadido. Essas árvores, que formam o estrato arbóreo atualmente, estão facilitando a regeneração natural de espécies arbóreas nativas e, assim, revertendo, lentamente, o processo de invasão. Testamos quais variáveis, relacionadas às funções ecológicas e aspectos estruturais das árvores de grande porte que se estabeleceram nas áreas invadidas, estão favorecendo as plantas em regeneração sob suas copas. Para tanto, amostramos os indivíduos maiores que 50 cm sob a copa de árvores sistematicamente selecionadas, segundo atributos funcionais e estruturais. Verificamos que as árvores que possuem copas mais densas e perenifólias apresentaram mais regenerantes sob suas copas. A resiliência característica do cerrado tem possibilitado que as áreas invadidas consigam se recuperar, podendo se assemelhar futuramente às áreas de cerradão da EEcA, porém muito lentamente. Ações de manejo que almejam a restauração dessas áreas mais rapidamente devem focar seus esforços na eliminação do Pteridium e/ou na introdução de espécies que possuam as características das árvores que atuam como facilitadoras da regeneração.The genus Pteridium comprises bracken species recognized by large fronds and a rhizome system that allows their fast expansion. Bracken presents an elevated biomass production throughout the year, that increases fire occurrence and release chemical compounds that are considered allelopathic. Nowadays, species of the genus Pteridium are well known as problem-species, due to their expansion and occupation of large areas around the world, causing great economic and ecological impacts. Aiming at the comprehension of bracken invasion over cerrado vegetation, we studied its impact over the plant community and, also, the slow natural regeneration process of cerrado recovery after invasion. We analyzed savanna woodland areas that have been invaded for over four decades, at Assis Ecological Station (EEcA), in southwestern São Paulo State. We analyzed the floristic composition and the plant community structure in an invaded area, compared to a non invaded patch of savanna vegetation. Components of the arboreal and regeneration strata were analyzed, in order to verify which species managed to pass by the physical and chemical barrier imposed by bracken. We assessed 100 points to assemble the floristic composition, using the quarter method, and for the community structure we used 15 plots of 10 m x 30 m to assemble the superior strata. The intermediate layer was assessed by sub-plots of 2 m x 30 m and the inferior strata using 2 m x 2 m sub-plots. We measured the canopy cover and also bracken cover inside the plots. The arboreal species first occupying the invaded area are shadow tolerant and fast growing, attributes which allowed them to overtake the bracken layer and establish. Nowadays, the invasive species has been replaced by a high number of arboreal species, the inferior strata being floristically similar to the area not invaded. The low density of adult trees in the invaded area reduce the competition among individuals that end up investing in growth, with greater size compared to those trees in the non invaded area. These large trees function as nurse trees, facilitating other species to establish under their canopies. We tested which variables related to the ecological functions and tree structure are favouring the understory, in order to comprehend the ecological processes and interactions that regulate the assembly rules of the invaded community being recovered. We assembled all individuals from arboreal species over 50 cm high growing under the projection of nurse trees canopy. These nurse trees were systematically selected, for the basis of functional and structural attributes. Understory density and richness were higher under trees with dense and permanent shadow, and that was the attribute better explaining the recovery process. The high resilience of savanna have helped the recovery of invaded areas. This process, however, has been very slow. Interventions whiling to restore those areas should be focused on bracken eradication and/or introduction of those species that can facilitate the natural regeneration.
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DeVanna, Kristen M. "Spatial Correlation and Facilitation Between Dreissena and Hexagenia: Possible Food-Web Disruption?" University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1320935549.
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Queiros, Ana Filipa de Moura. "Ecosystem engineers in diversity and process relationships." Thesis, Bangor University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528333.
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Blanc, Lori A. "Experimental study of an avian cavity-nesting community: nest webs, nesting ecology, and interspecific interactions." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28420.
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Cavity-nesting communities are structured by the creation of and competition for cavities as nest-sites. Viewing these communities as interconnected webs can help identify species interactions that influence community structure. This study examines cavity-nesting bird community interactions within the fire-maintained longleaf pine (Pinus palustris) ecosystem at Eglin Air Force Base, Florida. In chapter 1, I provide a background review of the ecology of my study system. In chapter 2, I use nest webs to depict the flow of cavity-creation and use at Eglin. I identified 2 webs into which most species could be placed. One web contained 6 species associated with pines. The second web contained 5 species associated with hardwoods. Red-cockaded woodpeckers (Picoides borealis) and northern flickers (Colaptes auratus) created most cavities used by other species within this community. In chapter 3, I describe snag densities and nest-site selection of the cavity-nesting bird community at Eglin. Large, mature pine snags were abundant, exceeding other reported densities for southern pine forests. Pine snags were heavily-used, despite the abundance of available red-cockaded woodpecker cavities in living pine. Hardwood snags accounted for 10% of nests found, and were used by 12 of 14 species. Diameters of nest-trees and available snags were below the range of optimal nest-snag diameters reported in other studies, indicating the need for site-specific snag management guidelines. In chapter 4, I combine a study of basic ecological principles with endangered species management to examine interactions within the cavity-nesting bird community at Eglin. I used a nest web to identify a potential indirect interaction between the red-cockaded woodpecker and large secondary cavity-nesters, mediated by the northern flicker. I used structural equation modeling to test a path model of this interaction. By experimentally manipulating cavity availability, I blocked links described in the model, confirming cavity creation and enlargement as mechanisms that influence this indirect relationship. I demonstrated that a red-cockaded woodpecker cavity-management technique could disrupt this indirect relationship by affecting northern flicker behavior, and provided an empirical example of how, in interactive ecological communities, single-species management can have indirect effects on non-target species.Ph. D.
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Ward, Jessica MacKay. "Community-level effects of nonindigenous aquatic ecosystem engineers." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92244.
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Hamani, Vincent. "Vers une meilleure compréhension des écosystèmes portuaires : interactions entre les organismes filtreurs et leur environnement." Thesis, La Rochelle, 2022. http://www.theses.fr/2022LAROS013.
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L’hyper-anthropisation, en particulier le long de nos côtes, a profondément modifié l’environnement. De plus en plus de structures, telles que les ports, forment des écosystèmes à part entière. Parmi la multitude d’espèces qui peuplent le port, un groupe semble particulièrement intéressant à étudier : les Filtreurs (bivalve set tuniciers). Ces organismes, par leurs modes de vie, ont une forte interaction avec l’environnement portuaire. En effet, en restant fixés sur les structures, ils subissent sans cesse les facteurs environnementaux qui caractérisent le port et leur mode d’alimentation, la filtration, les amène à être en contact avec une grande quantité d’eau et donc avec les éléments qui s’y trouvent. L’objectif de ce travail de thèse est d’étudier ce socio écosystème particulier qu’est l’environnement portuaire à travers ce groupe clé : les filtreurs. Ce travail par une approche pluridisciplinaire a permis :-d’étudier et de cartographier les communautés de filtreurs présents dans le port de plaisance de La Rochelle ; montrant ainsi la complexité de leur communauté et le fait qu’elles seraient impactées par des facteurs anthropiques et hydrosédimentaires .-d’analyser l’effet de deux contaminants très présents en milieu portuaire, le cuivre et le zinc, sur un organisme filtreur modèle : le pétoncle (Mimachlamys varia) ; et de montrer leur impact sur plusieurs voies métaboliques impliquées dans de nombreuses fonctions biologiques, telles que l'osmorégulation, le stress oxydatif, métabolisme énergétique, la reproduction et des phénomènes d’apoptose.- de mettre en évidence le fait que les filtreurs interviennent dans la composition des vases en remobilisant les sédiments présents dans la colonne d’eau et en modifiant leurs propriétés physico-chimiques ;que cela est espèce-dépendant et fortement modulé par les conditions environnementales telles que le taux de matière organique.-de développer plusieurs méthodes d’échantillonnage et d’analyse novatrice nécessaires pour appréhender cet environnement particulierThe hyper-anthropization, particularly along our coasts, has profoundly modified the environment. New structures, such as harbors, emerging, forming “true” ecosystems. Among the multitude of species inhabiting the port, one group seems particularly interesting to study: the filter feeders (bivalves and tunicat). These organisms have a strong interaction with the port environment due to their behaviour. Indeed, by remaining anchored to the structures, they are constantly subjected to the environmental factors that characterize the port and their feeding behavior, the filtration, leads them to be in contact with a large quantity of water and therefore with the elements that are in it. The objective of this thesis is to study this particular socio-ecosystem that is the port environment through this key group: the filter feeders. Through a multidisciplinary approach, this work, has allowed :-to study and map the communities of filter feeders present in the marina of La Rochelle; showing the complexity of their community and the fact that they are impacted by anthropogenic and hydrosedimentary factors.-to analyze the effect of two common contaminants in the port environment, copper and zinc, on the metabolism of a model filter-feeder organism : the scallop (Mimachlamys varia); and to show that they impacted several metabolic pathways involved in numerous biological functions, such as osmoregulation, oxidative stress, energetic metabolism, reproduction and apoptosis.- to highlight the fact that filter feeders are involved in the composition of the mud by remobilizing the sediments present in the water column and by modifying their physico-chemical properties; and that is species dependent and is strongly modulated by environmental conditions such as the level of organic matter.- to develop several innovative sampling and analysis methods needed to understand this particular environment
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Catano, Christopher. "Species and habitat interactions of the gopher tortoise: A keystone species?" Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5153.
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Species-species and species-habitat interactions have been demonstrated to be important in influencing diversity across a variety of ecosystems. Despite generalities in the importance of these interactions, appropriate mechanisms to explain them are absent in many systems. In sandhill systems of the southeast U.S., gopher tortoises have been hypothesized to be a crucial species in the maintenance of diversity and function. However, the mechanisms and magnitude in which they influence their communities and habitats have rarely been empirically quantified. I examined how habitat structure influences tortoise abandonment of burrows and how tortoise densities influence non-volant vertebrate community diversity. Tortoise burrow abandonment is directly influenced by canopy closure, with each percent increase in canopy cover relating to a ~2% increase in the probability of burrow abandonment. In addition, tortoise burrow density was positively correlated with diversity and evenness, but not species richness. This influence was directly proportional to burrow density, supporting a dominance role for this species and rejecting the commonly asserted keystone species mechanism. I also quantified the influence of tortoises in influencing diversity relative to other environmental and habitat variables. Through this research, I have demonstrated that disturbance and habitat structure are important, but diversity responds most to density of burrows in the habitat. These findings demonstrate the intricate relationships interacting to maintaining diversity in sandhill systems. In particular, habitat change leading to declines of gopher tortoises may have drastic negative impacts on vertebrate species diversity.M.S.
Masters
Biology
Sciences
Biology
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De, almeida Tania. "Impact d’une espèce ingénieure de l’écosystème et son utilisation en restauration écologique : Le cas de Messor barbarus (L.) dans les pelouses méditerranéennes Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands Harvester ants as ecological engineers for Mediterranean grassland restoration: impacts on soil and vegetation A trait-based approach to promote ants in restoration ecology." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0358.
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L’objectif principal de cette thèse était double : (i) mesurer l’impact d’une espèce de fourmi sur son écosystème, afin (ii) d’en déduire des applications potentielles dans le domaine de la restauration écologique.Les fourmis sont parmi les organismes les plus abondants des écosystèmes terrestres et occupent des zones géographiques très variées. Elles jouent des rôles écologiques clés dans de nombreux écosystèmes comme ingénieurs du sol, prédateurs ou régulateurs de la croissance et de la reproduction des plantes. Cependant les données collectées localement sont souvent parcellaires et ne permettent pas d’avoir une vision complète de l’impact d’une espèce sur son milieu.Messor barbarus (L.), connue pour redistribuer les graines et pour modifier les propriétés physico-chimiques du sol, est largement répandue dans le Sud-Ouest de l’Europe notamment au sein des pelouses méditerranéennes. Elle pourrait donc jouer un rôle majeur dans la composition et structuration de ces pelouses caractérisées par une forte biodiversité mais dont le nombre et la superficie ont drastiquement diminué ces dernières décennies.Dans un premier temps, par une étude multi-compartiments, nous avons confirmé l’hypothèse selon laquelle M. barbarus est une ingénieure de l’écosystème au sein des pelouses méditerranéennes. Elle transforme cet habitat en modifiant, comme attendu, les propriétés physico-chimiques du sol. Ces modifications sont associées à une augmentation de la biomasse et de l’hétérogénéité des communautés végétales ainsi qu’à des changements dans les faunes épigée et endogée (abondance, occurrence et structure des communautés). De plus, M. barbarus modifie profondément les relations trophiques et non trophiques interspécifiques et entre les espèces et leur habitat. L’hétérogénéité créée à l’échelle locale par l’activité de cette fourmi, entraine une diversification des niches écologiques au sein de ces pelouses.Malgré leur rôle souvent majeur sur le fonctionnement des écosystèmes, les fourmis ne sont que très rarement considérées en restauration écologique. Sur notre site d’étude, un chantier de réhabilitation d’une pelouse sèche après une fuite d’hydrocarbures et un transfert de sol, M. barbarus a permis d’accélérer la restauration des propriétés physico-chimiques du sol mais aussi de la banque de graines à moyen terme - sept ans après la réhabilitation du site. Ces résultats font donc de cette espèce une bonne candidate en ingénierie écologique.Afin de généraliser l’utilisation des fourmis en restauration écologique, nous proposons une méthodologie à destination des gestionnaires basée sur l’utilisation de traits fonctionnels et d’histoire de vie. Pour cela nous avons évalué le potentiel des fourmis en écologie de la restauration, puis nous avons listé l’ensemble des traits connus pour affecter les compartiments abiotiques et biotiques et/ou pertinent pour effectuer un suivi du succès de la phase de restauration. La méthodologie proposée permet une première sélection des espèces potentiellement utilisables en fonction des objectifs de restaurationThe main objective of this thesis was double: (i) to assess the impact of an ant species on its ecosystem, in order to (ii) deduce potential applications in the field of ecological restoration.Ants are among the most abundant organisms in terrestrial ecosystems and occupy a wide range of geographical areas. They play key ecological roles in many ecosystems as soil engineers, predators or regulators of plant growth and reproduction. However, the information collected locally is often fragmented and does not provide a complete overview of the impact of a species on its environment.Messor barbarus (L.), known to redistribute seeds and to modify the soil physico-chemical properties, is widespread in South-Western Europe, particularly in Mediterranean grasslands. Therefore, it may play a major role in the composition and structuring of these ecosystems, which are characterised by high biodiversity but whose abundance and surface area have decreased drastically in recent decades.Through a multi-compartment study, we confirmed the hypothesis that M. barbarus is an ecological engineer in Mediterranean grasslands. This species changes this habitat by modifying, as expected, soil physico-chemical properties. These modifications are associated with an increase in both biomass and heterogeneity of plant communities, as well as changes in above- and belowground fauna (abundance, occurrence and structure of communities). Messor barbarus profoundly changes trophic and non-trophic relationships within and between species and their habitat. The heterogeneity created locally by the activity of M. barbarus leads to a diversification of ecological niches within these grasslands.Despite their major role in the functioning of ecosystems, ants are rarely considered in restoration ecology. In our study site, corresponding to a dry grassland rehabilited after an oil leak and a soil transfer, M. barbarus contributed to accelerate the restoration of the soil physico-chemical properties but also of the seed bank in the medium term - seven years after the rehabilitation. These results make this species a good candidate for ecological engineering.In order to generalise the use of ants in restoration ecology, we propose a trait-based methodology for stakeholders. We evaluated the potential of ants in restoration ecology, then listed all the traits known to affect abiotic and biotic compartments and/or relevant to monitor the success of the restoration phase. The proposed methodology provides a first selection of potentially relevant species according to the restoration objectives
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Hortobágyi, Borbála. "Multi-scale interactions between riparian vegetation and hydrogeomorphic processes (the lower Allier River)." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAL001/document.
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Dans les écosystèmes, tels que les rivières, les marais salés, les mangroves, les dunes côtières, qui sont exposés à des flux hydrogéomorphologiques fréquents et réguliers (c’est-à-dire à des perturbations physiques), des rétroactions se mettent en place entre la géomorphologie (eau, sédiments et formes fluviales) et les plantes (par exemple Populus nigra L., Salix alba L., Salix purpurea L. dans les rivières). L’établissement de la végétation est contrôlé par des processus hydrogéomorphologiques qui, en retour, sont modulés par la végétation. De telles rétroactions contrôlent la dynamique des écosystèmes riverains. Dans cette thèse, nous avons abordé deux questions principales afin de mieux comprendre les rétroactions entre la végétation riveraine et les processus hydrogéomorphologiques : (i) comment la végétation riveraine répond-elle aux contraintes hydrogéomorphologiques ? (ii) comment et dans quelle mesure les plantes ingénieures, une fois établies, affectent-elles la géomorphologie fluviale ? Nous avons étudié ces questions sur la rivière Allier (France) à travers une approche emboîtée multi-échelles allant de l’échelle du patron paysager au trait de plante. Nous avons testé l’applicabilité de la méthode de photogrammétrie pour quantifier la réponse et l’effet de la végétation riveraine et des rétroactions biogéomorphologiques à différentes échelles spatio-temporelles (corridor, banc alluvial et individu). À l’échelle du corridor, nous avons recherché la signature topographique de la végétation riveraine dans le paysage, en utilisant des données photogrammétriques et LiDAR. À l’échelle intermédiaire du banc alluvial, nous avons étudié l’aptitude des trois espèces pionnières dominantes riveraines de Salicaceae (P. nigra, S. purpurea, S. alba) à s’établir et à agir comme ingénieurs d’écosystème en piégeant les sédiments fins. À l’échelle la plus fine du trait de plante, nous avons quantifié la relation existante entre les attributs de trait de réponse des jeunes plantes de P. nigra et leur exposition à trois niveaux différents de stress mécanique (tête de banc fortement exposée, queue de banc moins exposée, chute alluviale). Nous avons identifié les difficultés et les erreurs à ne pas commettre pour appliquer correctement la photogrammétrie dans les études des rétroactions biogéomorphologiques. En tout état de cause, la photogrammétrie s’est avérée être un outil performant pour quantifier un ensemble de paramètres pertinents pour répondre à des questions de recherche fondamentale aux trois échelles spatiales considérées. À l’échelle la plus large, la signature topographique de la végétation est particulièrement difficile à identifier en raison de la dynamique complexe des formes fluviales de la rivière Allier. Cependant, en concentrant les observations sur des zones de taille réduite et fortement connectées (bancs alluviaux bordant le chenal), la signature de la végétation a pu être identifiée par cette méthode. Elle semble augmenter avec la croissance de la hauteur végétale (progression temporelle de la succession biogéomorphologique), ce qui est en accord avec le modèle de succession biogéomorphologique fluviale (SBF). À l’échelle intermédiaire du banc alluvial, les rétroactions biogéomorphologiques pouvaient être bien identifiées. La capacité des plantes riveraines à s’établir et à agir comme ingénieurs d’écosystème dépend à la fois des espèces et de leur physionomie, de leur âge et de leur position respective sur les bancs alluviaux. À l’échelle la plus fine de l’individu, nous avons capturé la réponse morphologique et biomécanique contrastée de P. nigra à l’exposition aux différents niveaux de contrainte mécanique d’un point de vue de trait. Dans tous les niveaux hiérarchiques, des rétroactions biogéomorphologiques liées aux échelles ont été détectées et synthétisées dans un modèle conceptuel. [...]N ecosystems, such as rivers, salt marshes, mangroves, coastal dunes which are exposed to frequent and regular hydrogeomorphic fluxes (i.e. physical disturbances), feedbacks between geomorphology (water, sediment and landforms) and plants (e.g. Populus nigra L., Salix alba L., Salix purpurea L. in rivers) can occur. Vegetation esta¬blishment is controlled by hydrogeomorphic processes which in turn are modulated by vegetation. Such feedbacks control riparian ecosystem dynamics. In this thesis, we addressed two main questions in an effort to better understand feedbacks between riparian vegetation and hydrogeomorphic processes: (i) How does riparian vegetation respond to hydrogeomorphic constraints? (ii) How, and to what extent, do established engineer plants affect fluvial geomorphology? We studied these questions through a nested multi-scale approach from landscape pattern to plant trait scales on the dynamic wandering Allier River (France). We tested the applicability of the method of photogrammetry to quantify the response and the effect of riparian vegetation and biogeomorphic feedbacks at different spatio-temporal scales (i.e. corridor, alluvial bar and individual). At the corridor scale, we searched for the topographic signature of riparian vegetation in the landscape, using photogrammetric and LiDAR data. At the intermediate alluvial bar scale, we investigated the aptitude of three dominant pioneer riparian Salicaceae species (P. nigra, S. purpurea and S. alba) to establish and to act as ecosystem engineers by trap¬ping fine sediment. At the finest, plant trait scale, we quantified the relation between response trait attributes of young P. nigra plants and their exposure to three different levels of mechanical stress (a highly exposed bar-head, a less exposed bar-tail, a chute channel). We identified some difficulties or failures to properly apply photogrammetry in biogeomorphic feedback studies. However, photogrammetry appeared as a useful tool to quantify a set of relevant parameters to respond to fundamental research questions concerning biogeomorphic feedbacks at the three nested spatial scales. At the broadest, the topographic signature of vegetation was not easy to capture because of the complex shifting mosaic of landforms of the Allier River. However, by focusing on more connec¬ted, restricted areas (i.e. alluvial bars), the signature of vegetation could be captured. It seems to increase with increasing vegetation height corresponding to the evolutionary phases of the fluvial biogeomorphic succession (FBS) model. At the intermediate, alluvial bar scale, biogeomorphic feedbacks could be well identified. The capacity of riparian plants to establish and act as ecosystem engineers depended both on species and their physiognomy, their age and their location on alluvial bars. At the finest, individual plant scale, we captured the contrasting morphological and biomechanical response of P. nigra to variable mechanical stress exposure from a trait perspective. In all hierarchical levels, scale-related biogeomorphic feedbacks were detected and described in a conceptual model. The three scales were considered as cycles composed of four different phases, which can have a variable temporality. The broadest spatio-temporal scale represents the evolution over several decades of the landscape mosaic resulting from the balance between constructive (vegetation establishment, growth and succession) and destruc¬tive (floods) forces. [...]
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Brown, Joseph K. "Emergent interactions influence functional traits and success of dune building ecosystem engineers." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4111.
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Stability of coastal systems are threatened by oceanic and atmospheric drivers of climate change. Sea-level rise compounded with increased frequency and intensity of storms emphasizes need for protection of inner island systems by dune formations. Dune building processes are affected by interactions between growth of ecosystem engineering dune grasses and environmental factors associated with disturbance such as sand burial and salt spray. Climate change may also cause latitudinal expansion of some species, resulting in emergence of competitive interactions that were previously absent. Topographic structure of coastlines, traditionally influenced by sand burial, could change as a result of competition emergence. My goal was to determine if species functional trait responses to common abiotic factors are altered by novel and current biotic interactions. I performed a multi-factorial greenhouse experiment by planting three common dune grasses (Ammophila breviligulata, Uniola paniculata, and Spartina patens) in different biotic combinations, using sand burial and salt spray as abiotic stressors. I hypothesized that biotic interactions will cause these dune grasses to shift functional trait responses to abiotic factors that are associated with dune building. I found that plants consistently decreased in biomass when buried. I also found that competition between A. breviligulata and U. paniculata negatively affected dune building function traits of A. breviligulata. This indicates that competition with U. paniculata could alter dune structure. In comparison A. breviligulata had a positive interaction with S. patens, which increased functional trait responses to abiotic stress. Last, we found that competitive intransitivity could occur between these species. My results can be used to make predictions on cross-scale consequences of novel competitive events. This experiment also provides evidence that consideration of local biotic interactions is important in understanding connections between plant level dynamics and large-scale landscape patterns in high stress environment.
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Choosai, Chutinan. "Biological activity in paddy fields : the role of soil engineers in ecosystem functioning." Paris 6, 2010. http://www.theses.fr/2010PA066156.
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Les ingénieurs du sol modifient les propriétés physicochimiques des sols à travares la création de structures biogéniques. Ce travail vise à déterminer le rôle respectif de deux types de structures : les buttes termitiques et les turricules de vers de terre. Les buttestermitiques agissent comme des sites de hute activité boilogique. Ils constituent des refuages pour la macrofaune. Ces buttes sont enrichies en C,K,P et argiles par rapport aux sols environnants. Les vers de terre en accumulant leurs turricules au pied du riz favorise l'hétérogénèïté spatiale. Ces structures biogéniques constituent des taches de fertilité dans les rizières avec plus de particules fines et d'éléments minéraux. En conclusion cette étude montre que les structures biogéniques produites par les termites et les vers de terre jouent des rôles clés dans la régulation de certains processus écologiques
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Mitchell, Mark E. "Nutrient Cycling Dynamics and Succession in Green Roof Ecosystems." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin150487303109878.
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Parrott, Lael. "Learning to engineer life, development of a generally configurable model for the simulation of artificial ecosystems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq64489.pdf.
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Speed, James D. M. "Ecosystem engineers of the tundra the impacts and extent of goose herbivory in the high Arctic /." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26470.
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DeVanna, Kristen M. "Role of Dreissena as ecosystem engineers : effects to native bioturbators and benthic community structure and function /." Connect to Online Resource-OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1165420236.
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Thesis (M.S.)--University of Toledo, 2006.Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science Degree in Biology (Ecology-track)." Bibliography: leaves 26-34.
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Sanabria-Blandon, Maria Catalina. "Effects of agricultural Landscape of the Colombian Llanos on Ecosystem Services and assemblages of soil engineers." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066025/document.
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Les savanes tropicales sont très importantes pour la production agricole et de nombreux services écosystémiques. En Colombie, ces savanes ont été traditionnellement gérées par l'élevage extensif et l'agriculture à faible intrants. La conversion actuelle de ces systèmes naturels en agriculture intensive peut avoir des effets dévastateurs sur la biodiversité du sol et au-dessus du sol. La macrofaune du sol représente une part importante de la biodiversité des agroécosystèmes et certains groupes ont reçu une attention considérable en tant qu'ingénieurs des écosystèmes. L'objectif général de la thèse est d'évaluer et d'analyser les impacts des paysages agricoles sur les communautés d'ingénieurs des sols et les services écosystémiques fournis par le sol dans les Llanos colombiens. Trois questions principales ont été abordées: (1) Quel est l'impact de la gestion agricole sur les communautés de fourmis et est-il possible d'identifier des espèces de fourmis qui pourraient servir d'indicateurs des services écosystémiques basés sur le sol? (2) Quel est l'impact de l’usage des sols sur les communautés de fourmis et de termites et cet impact est-il lié aux modifications des propriétés physiques et chimiques des sols? (3) Les traits écologiques et morphologiques des fourmis répondent-ils aux usages du sol et aux propriétés du sol?Les résultats de cette thèse confirment que les communautés de fourmis sont très sensibles aux changements d'usage de sols et constituent de bons indicateurs précoces des services écosystémiques basés sur les sols. Plus précisément, les cultures annuelles se sont révélées le plus préjudiciables aux communautés de fourmis et de termites, et cela est probablement dû à l'application d'intrants chimiques, ainsi qu'au travail du sol et aux pesticides. Tous les usages du sol (savanes, plantation de caoutchouc ou palmiers à huile, pâturages améliorés et cultures annuelles) ont une faune particulière, mais certaines espèces ont des besoins particuliers en termes d’habitat pour leurs nids, leur nourriture, ou des refuges. Certaines espèces sont plus généralistes et particulièrement adaptées aux environnements perturbés. En ce sens, la présence de toutes les utilisations du sol dans un paysage contribue dans une certaine mesure à la diversité totale. On a constaté que les usages des sols avec une couverture arborée permettent le maintien d’espèces rares, discrètes et souvent avec exigences de habitat particulairesTropical savannas are highly important for agricultural production and many other ecosystems services. In Colombia, these savannas have been traditionally managed through extensive livestock production and low-input agriculture. The current conversion of these natural systems to intensified agriculture can have devastating impacts on belowground and aboveground biodiversity. Soil macrofauna represents an important part of agroecosystem biodiversity and some groups have received considerable attention as ecosystem engineers. The general goal of the thesis is to evaluate and analyze the impacts of agricultural landscapes on soil engineer communities and soil ecosystem services in the Colombian Llanos. Three main questions were addressed: (1) What is the impact of agricultural management on ant communities and is it possible to identify ant species that could be used as indicators of soil-based ecosystem services? (2) What is the impact of land uses on ant and termite communities and is this impact associated with modifications of soil physical and chemical properties? (3) Do the ecological and morphological traits of ants respond to land uses and soil properties?The results of this thesis confirm that ant communities are highly sensitive to land use changes and constitute good early indicators of soil-based ecosystem services. More accurately, annual crops have shown to be detrimental to ant and termites communities and this is probably due to the application of chemical inputs, as well as to tillage and pesticides. All land uses (Savannas, rubber or oil palm plantations, improved pastures and annual crops) have a particular soil fauna, but some species have particular habitat requirements for nest sites, food, refugees, etc. Some species are more generalist and are particularly adapted to disturbed environment. The presence of all land uses within a landscape contributes to a certain extent to the total diversity. It was found that sites with a tree cover protect rare, sometimes inconspicuous and perhaps fragile species
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Beltrand, Maeva Mereana Marion. "The effects of the macroalga Gracilaria gracilis and increasing temperatures on the performance of the endemic Cape eelgrass Zostera capensis." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27537.
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Rising temperature caused by global warming alters physiology, phenology and/or distribution in a wide array of plant and animal species, which has dramatic knock-on effects at different levels of organisation. This study investigates the individual and interactive effects of temperature (18ᵒC, 22ᵒC and 30ᵒC) and additions of the macroalga Gracilaria gracilis (high and low) on the performance of the seagrass Zostera capensis, which occurs in Langebaan Lagoon, South Africa over a seven-week period. Results from the laboratory experiment revealed that G. gracilis did not significantly affect the performance of Z. capensis although temperature did result in greater leaf width, fouling and senescent biomass, as well as marginally greater leaf area and lower below-ground biomass at 30ᵒC. Increasing temperature also increased G. gracilis biomass, percent cover and fouling by microalgae. In addition, there was no interaction between temperature and the additions of Gracilaria. The overall findings of this study indicate that Z. capensis abundance is likely to decrease while G. gracilis will conversely increase in abundance in response to warming. Changes in abundance of those two ecosystem engineers highlight the possibility of a phase shift from a seagrass- to macroalgal-dominated state in Langebaan Lagoon.
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Whittington-Jones, Gareth Morgan. "The role of aardvarks (Orycteropus afer) as ecosystem engineers in arid and semi-arid landscapes of South Africa." Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005445.
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Arid and semi arid environments are characterised by extreme fluctuations in temperature and low rainfall which present significant challenges to the animals inhabiting these areas. Mammals, such as aardvarks (Orycteropus afer, Pallas 1766), excavate burrows in order to avoid predators and climatic extremes and are termed “ecosystem engineers” as they physically modify their environment and in doing so create new habitats and alter the availability of resources to other species. In this study I assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark burrows in relation to paired control sites. In addition, I evaluated the use of aardvark burrows by other vertebrate and invertebrate species and investigated the impact of aardvark burrow mounds on landscape scale floristic diversity. Maximum temperatures were significantly lower (p < 0.05) and minimum temperatures and midday humidity were significantly higher (p < 0.05) inside the burrows at the three study sites, Kwandwe Private Game Reserve (Kwandwe), Mountain Zebra National Park (MZNP) and Tswalu Kalahari Reserve (Tswalu). There were no significant differences between the concentration of seeds, the average numbers of unique individual small mammals, trap success or small mammal species richness recorded inside the burrows compared to outside (p > 0.05). At all three sites, small mammal species diversity was higher in the burrows but this result was also not significant (p > 0.05 for all). Trap success and the number of individuals captured was higher at Tswalu than the other two sites (p < 0.05 for both). The different methods used in this study revealed a total of 25 mammal, seven bird, one amphibian and six reptile species utilising aardvark burrows. There were significant differences in insect community assemblages between the burrows and open control areas at Kwandwe and Tswalu (p < 0.05 for both) but not at MZNP (p > 0.05). The parasitic guild was more prominent inside the burrows than outside but their abundance was not as high as anticipated, possibly due to the placement of traps closer to the burrow entrances than the sleeping chambers. The complex structure of the burrows prevented the placement of traps in close proximity to the sleeping chambers. As expected, the amount of bare earth was significantly higher on active and recently abandoned burrow mounds compared to the old burrow mounds and reference plots at all three sites (p < 0.05 for all), with the exception of the active burrows at Tswalu. Overall, the different plot types were characterised by significantly different plant communities during all the seasons at MZNP, during three of the seasons at Kwandwe and only during winter at Tswalu. The total species richness recorded on the reference plots was higher than on the burrow mounds at all three sites. However, species diversity on the reference plots was not significantly higher than the burrows at any of the sites (p > 0.05 for all sites). Although the results were not significant, the overall species diversity at a site level was greater than the reference patches at Kwandwe and Tswalu (p > 0.05 for both). Aardvarks fulfil the criteria of a significant ecosystem engineer and their presence in arid and semi-arid environments is likely to be critical to the survival of other individual organisms and species, particularly when alternative burrowing animals are either absent or restricted in their activities. Thus, aardvark populations should be considered a conservation priority in arid and semi-arid ecosystems.
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Holland, Michael. "An Assessment of the U.S. Army Corps of Engineers' Environmental Plan Evaluation Methods." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/124.
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The U.S. Army Corps of Engineers is a federal agency with a mission to develop water resource projects to benefit the nation. Some of its large scale projects have been built to benefit cities, but through unintended consequences have caused economic and environmental damages. For example, its control of Mississippi River flooding has protected the City of New Orleans, but contributed to land loss in coastal Louisiana, and by some accounts, made the population more susceptible to hurricane damage. The agency has now embarked on a mission to restore some of the damaged environmental areas. This dissertation evaluates whether policies and practices used by the agency to evaluate and select plans to implement is logically flawed and could produce suboptimal project selection. The primary issue is the practice of including only implementation costs in the analysis while excluding other positive and negative economic impacts. A case study is performed using the method to evaluate a traditional economic development project for which optimal project selection has already been determined using widely accepted benefit-cost practices. The results show that the Corps' environmental project evaluation method would cause rejection of the most efficient plan. The loss of welfare that would result from using this technique is measured by comparing the welfare gain of the optimal project to the welfare gain of the suboptimal projects which could be selected using the flawed methodology. In addition, the dissertation evaluates whether suboptimal results could be produced using two other current Corps policies: selecting projects based on production efficiency, and the exclusion of environmental benefits from the discounting process. For the first policy, a simple counter example shows how clearly inferior choices may come from including only supply considerations in investment choices. For the second policy, it is demonstrated mathematically that refraining from discounting benefits while discounting costs causes a bias towards selection of plans that take longer to build, are delayed in their implantation, or a combination of the two.
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Kavanagh, Lydia Jane. "An engineered ecosystem for environmentally sustainable wastewater treatment for remote tourist resorts in tropical/sub-tropical regions /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16958.pdf.
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Perfect, Charles. "From engineered channel to functioning stream ecosystem : rates, patterns and mechanisms of development in a realigned river channel." Thesis, University of Stirling, 2010. http://hdl.handle.net/1893/2431.
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1. Realigning rivers is becoming common as a solution to conflicting needs of land development and ecosystem preservation. Although an increasing number of projects are monitored, exactly how these channels develop as functional stream ecosystems is still poorly understood. Mining in the upper catchment of the River Nith (Scotland) required the realignment of 3km (approx.) of river. The engineered channel was designed around sound geomorphological principles of sediment transport and supply with a sinuous planform and pool-riffle sequences along the installed gravel-bed. 2. A comprehensive survey covering biotic and abiotic development was devised and implemented to test models and hypotheses relating to the development riverine habitats over the first three years. 2. Physical habitat development at the reach scale was investigated using fixed-point photography and differential GPS surveys of the thalweg and of cross-sectional form every 100m. This revealed the development of a relatively diverse streambed habitat in response to both the channel slope and planform. However, other than at meander bends where asymmetry developed over several years, little change was observed to the form of the engineered riverbanks. 3. Kick-net surveys of benthic invertebrate communities at 10 sites showed a negative relationship between specific measures of diversity and downstream distance during the early stages of development. (e.g. Richness with chainage at the 6 month stage) but the relationship degrades rapidly and is likely in part to appear as a result of low population densities. 4. Survey of transects through the riparian zone perpendicular to the river indicated that colonisation by vegetation is also related to distance along the realignment but physical habitat and geographical factors play a more dominant role over development (Canonical correspondence analysis of vegetation data in 2007) 5. Many of the indices of diversity for both biotic and abiotic elements of the ecosystem proved ineffective at detecting development at the reach scale. This may be because significant changes occur at a smaller scale than was detected by the surveys. It is likely that greater resolution is required to detect more ecologically meaningful relationships and patterns. 6. Overall study shows constructed realignments can rapidly develop a diverse streambed community within 24 months. Riparian communities are slower to develop because of the slow development of riverbank habitat diversity. Other ecosystem properties such as resilience and connectivity may take much longer.
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True, Aaron Conway. "Ecological engines: Finescale hydrodynamic and chemical cues, zooplankton behavior, and implications for nearshore marine ecosystems." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54019.
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Ephemeral patches of hydrodynamic and chemical sensory cues at fine scales are fundamentally important to the life success of plankton populations and thus the overall health and vitality of nearshore marine ecosystems. We employed various tools from experimental fluid mechanics to create ecologically-relevant hydrodynamic and chemical conditions in a recirculating flume system for zooplankton behavioral assays. The goal was to quantify and correlate changes in zooplankton behavior with coincident sensory cues. A laminar, planar free jet (the Bickley jet) was used to create finescale, free shear layers with targeted hydrodynamic characteristics as well as finescale, sharp-edged layers of both beneficial and toxic ("red tide") phytoplankton species. Planar particle image velocimetry (PIV) and laser-induced fluorescence (LIF) were used to quantify the flow and concentration fields, respectively.
Behavioral assays with a variety of crustacean zooplankton species including Antarctic krill (Euphausia superba), estuarine crab larvae (Panopeus herbstii), and calanoid copepods (Temora longicornis and Acartia tonsa), each unique in its ecology, morphology, and life history, show clear and statistically-significant behavioral responses to relevant hydrodynamic and chemical cues. Estuarine crab larvae optimize short term and long term behavioral needs (foraging and habitat selection) by sensing and exploiting the information contained in multi-directional free shear flows. In the presence of thin layers of toxic algal exudates (Karenia brevis), T. longicornis and A. tonsa exhibit explicit avoidance behaviors through significant increases in swimming speed and overall behavioral variability resulting in a conspicuous hydrodynamic signature in a risk/benefit behavioral response. Finally, Antarctic krill exploit the hydrodynamic cues contained in a free shear layer to modify swimming behaviors and ultimately graze in a thin phytoplankton layer (Tetraselmis spp.). Each species is able to sense and exploit the information contained in coherent hydrodynamic and chemical sensory cues to change swimming kinematics and alter macroscale trajectory characteristics.
Quantifying changes in zooplankton behavior in response to ecologically-relevant sensory cues is a crucial step towards modeling (e.g. via biophysically-coupled individual-based ecosystem models) and managing sustainable marine fisheries.
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Sandom, Christopher. "Wild boar, wolves and fences : managing ecosystem engineers and keystone species to restore ecological processes, a case study in the Scottish Highlands." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542969.
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Eriksson, Bert. "The zoo-geomorphological impact of fossorial rodents in sub-polar alpine environments." Licentiate thesis, Uppsala universitet, Kulturgeografiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-150807.
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The geomorphological impact of small fossorial mammals (adapted to digging and living underground), such as rodents can be significant, and both their direct and indirect effects may contribute to landscape formation. This thesis is based on empirical field studies of two burrowing rodent species in sub-polar environments, namely invasive House mice (Mus musculus) on sub-Antarctic Marion Island and Norwegian lemmings (Lemmus lemmus) in sub-Arctic Abisko. The spatial distribution, sediment displacements, impact on vegetation and microclimatic effects of the rodents are documented. Invasive mice and rats, introduced on sub-Antarctic Islands during the 19th century, lack natural enemies and are shown to have a significant direct and indirect geomorphic impact by direct sediment displacement, vegetation removal by burrowing, grazing and trampling and thereby exposing the sediments for rain, wind and frost processes. The geomorphic impacts of lemmings are comparatively more limited as they rely on natural hollows and snow cover for protection and do not burrow to the same extent as other fossorial rodents in cold regions. Lemmings are thus suggested to have little impact on landform integrity, but can affect vegetation composition. A comparison of the findings from this study with published data on seven other rodent species and other physical mass transfer mechanisms in sub-polar and alpine environments suggests that fossorial rodents are a significant and sometimes dominant geomorphic force in sub-polar and alpine environments. The geomorphic work by ground squirrels, ice rats, plateau pikas and zokors is shown to be in the same order of magnitude as solifluction and rock falls. In alpine and periglacial environments these rodents are considered to act as key-stone species and ecosystem engineers through the creation of landforms by dislocation and of soil and other impacts on soil properties, vegetation and ecosystem function
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Oliveira, Marina Vasconcelos de. "Efeitos dos ninhos de Atta sexdens (Linnaeus, 1758) (Hymenoptera: Formicidae) sobre a estrutura da comunidade de artr?podes do solo na Mata Atl?ntica." Universidade Federal Rural do Rio de Janeiro, 2017. https://tede.ufrrj.br/jspui/handle/jspui/1925.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Tropical forests support a great vegetal diversity, in part, through an nutrient cycling initiated by the soil arthropod?s fauna, which facilitated the litter decomposers action, propitiating the release of stock nutrients to the soil. Therefore, studies about these fauna and what factors alter it are extremely important to understand the nutrient cycling process in tropical forests. Among epigeic fauna represents, the leaf-cutting ants are considered the Neotropical region dominant herbivores and studies relate their multiple effects on vegetable community and the soil . Nonetheless, there aren?t studies about leaf-cutting ants effects on other arthropods communities, including mirmecofauna. This study aim to investigate the nests effects of the leaf-cutting ant Atta sexdens (Linnaeus, 1758) (Formicidae: Myrmicinae) on a soil arthropod community. The study site was Reserva Ecol?gica de Guapia?u, Cachoeiras de Macacu, Rio de Janeiro, Brazil, where we collected samples at ten A. sexdens nests in period of 2 February to 9 February 2016. Along a linear transect of 32 meters, we collected litter samples from 0,25 m? size at intervals of 8 meters from each nests? edge of A. sexdens, whereby we also measured the air and soil temperature, the light and the air relative humidity. We aim to verify if litter structure and microclimatic conditions alter arthropod community structure and if these effects can be mediated by A. sexdens nests. The hypothesis in question are: 1) Litter Hypothesis, whereby arthropod community structure would be influenced by litter and litter would be altered by A. sexdens; 2) Abiotic Factors Hypothesis, whereby arthropod community structure would be influenced by abiotic factors and these factors would be altered by A. sexdens and 3) Nest Hypothesis, whereby community alterations would happen through intrinsic factors to active nests presence and not explained by alterations in a litter and/or in abiotic factors measured. For the test of the first and the second hypothesis, we did simple regressions and next variance analysis, assessing the litter and abiotic factors effects on arthropod community parameters and if this effects can be mediated by A. sexdens. To test Nest Hypothesis, we did variance analysis and analysis of similarities, assessing direct effects of A. sexdens on other arthropods community. We collected 3074 arthropods, among them Acari and Collembola were the most abundant groups. In relation of the ants, we obtained 63 specimens, in 26 genera and 32 identified species. The Strumigenys genus was one of the most frequent genera and it detained the biggest richness among mirmecofauna predators.We didn?t detect A. sexdens effects on soil arthropod community around its nests. Studies that include sazonality and behavior comparison between different species of leaf-cutting ants can result in new knowledge about the interaction between these organisms and other arthropods
As florestas tropicais sustentam uma grande diversidade vegetal, em parte, devido ? ciclagem de nutrientes iniciada pela fauna de artr?podes do solo, que facilita a a??o dos decompositores da serrapilheira, propiciando a libera??o dos nutrientes estocados para o solo. Logo, estudos sobre essa fauna e que fatores a afetam s?o importantes para a compreens?o dos processos de ciclagem de nutrientes em florestas tropicais. Dentre os representantes da fauna epigeica, as formigas-cortadeiras s?o consideradas os herb?voros dominantes da regi?o Neotropical e estudos relatam seus m?ltiplos efeitos sobre a comunidade vegetal e o solo. Entretanto, n?o h? estudos sobre os efeitos das formigas-cortadeiras sobre a comunidade dos demais artr?podes. Este estudo visa investigar os efeitos dos ninhos de formigas-cortadeiras Atta sexdens (Linnaeus, 1758) (Formicidae: Myrmicinae) sobre a comunidade de artr?podes do solo. A ?rea de estudo foi a Reserva Ecol?gica de Guapia?u, munic?pio de Cachoeiras de Macacu, Rio de Janeiro, Brasil, na qual coletamos amostras em 10 ninhos de A. sexdens no per?odo de 2 a 9 de fevereiro de 2016. Ao longo de um transecto linear de 32 metros, coletamos amostras de serrapilheira de tamanho 0,25m? a intervalos de 8 metros a partir da borda de cada ninho de A. sexdens, nos quais tamb?m medimos as temperaturas do ar e do solo, a luz e a umidade relativa do ar. Objetivamos averiguar se a estrutura da serrapilheira e as condi??es microclim?ticas alteram a estrutura da comunidade de artr?podes e se esses efeitos podem ser mediados pelos ninhos de A. sexdens. As hip?teses em estudo s?o: 1) Hip?tese da Serrapilheira, na qual a estrutura da comunidade de artr?podes seria influenciada pela serrapilheira e a serrapilheira seria alterada por A. sexdens; 2) Hip?tese dos Fatores Abi?ticos, na qual a estrutura da comunidade de artr?podes seria influenciada pelos fatores abi?ticos locais e estes fatores seriam alterados por A. sexdens e 3) Hip?tese do Ninho, em que as altera??es na comunidade se dariam por fatores intr?nsecos ? presen?a dos ninhos ativos e n?o explicados por altera??es na serrapilheira e/ou nos fatores abi?ticos medidos. As duas primeiras hip?teses foram testadas atrav?s de regress?es lineares simples, seguidas de an?lises de vari?ncia, avaliando os efeitos da serrapilheira e dos fatores abi?ticos sobre os par?metros da comunidade de artr?podes e se esses efeitos podem ser mediados por A. sexdens. No teste da hip?tese do Ninho, fizemos an?lises de vari?ncia e an?lises de similaridade, avaliando os efeitos diretos de A. sexdens sobre a comunidade dos demais artr?podes. Coletamos 3074 artr?podes, dentre os quais Acari e Collembola foram os grupos mais abundantes. Em rela??o ?s formigas, obtivemos 63 morfoesp?cies, em 26 g?neros e 32 esp?cies identificadas. O g?nero Strumigenys foi um dos g?neros mais frequentes e deteve a maior riqueza dentre os predadores da mirmecofauna. N?o detectamos efeitos de A. sexdens sobre a comunidade de artr?podes do solo do seu entorno. Estudos que incluam a sazonalidade e que comparem o comportamento entre diferentes esp?cies de formigas-cortadeiras podem resultar em novos conhecimentos a respeito da intera??o desses organismos com os demais artr?podes
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Heuner, Maike [Verfasser], Birgit [Akademischer Betreuer] Kleinschmit, Boris [Akademischer Betreuer] Schröder-Esselbach, Stijn [Akademischer Betreuer] Temmerman, and Reinhard [Gutachter] Hinkelmann. "Key ecosystem engineers in estuarine vegetation : their niches, traits, and services for coping with hydrodynamic stress / Maike Heuner ; Gutachter: Reinhard Hinkelmann ; Birgit Kleinschmit, Boris Schröder-Esselbach, Stijn Temmerman." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156270472/34.
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Vieira, Camila. "Engenheiros dos ecossistemas em plantas : modificações arquiteturais de folhas por largatas de Lepidoptera influenciam a estrutura de comunidades de artrópodes /." São José do Rio Preto : [s.n.], 2010. http://hdl.handle.net/11449/87623.
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Orientador: Gustavo Quevedo RomeroBanca: Martin Francisco Pareja
Banca: Thiago Junqueira Izzo
Resumo: Engenharia dos ecossistemas é um processo em que organismos modificam a distribuição de recursos (i.e, disponibilizando novos habitats) para outras espécies via interação não trófica. Lagartas de Lepidoptera enroladoras de folhas podem atuar como engenheiros dos ecossistemas florestais, uma vez que são capazes de modular interações entre comunidade artrópode - planta fornecendo aos colonizadores secundários diversos tipos de benefícios. Essas lagartas quando engenheiras influenciam o padrão de distribuição e abundância de outras espécies facilitando indiretamente a ocorrência de novas espécies, bem como aumentam a diversidade de artrópodes sobre planta. Apesar de estudos terem demonstrado que lagartas engenheiras ampliam a diversidade de artrópodes sobre folhas (efeito local), apenas um estudo avaliou o efeito na planta por inteiro (efeito regional), mas apenas para guildas específicas (i.e., herbívoros); nenhum estudo até agora avaliou como comunidades diversificadas, de regiões tropicais, respondem aos impactos de lagartas engenheiras. Nesse estudo reportamos a influência das lagartas enroladoras sobre comunidades de artrópodes em grande escala espacial (i.e., efeito local e regional) e temporal (i.e., diferentes períodos sazonais). Especificamente, avaliamos se (i) abrigos foliares favorecem a ocorrência de artrópodes e amplificam diversidade sobre plantas, (ii) se o tipo de abrigo (funil, cilindro com diferentes diâmetros) interfere na colonização por diferentes guildas de artrópodes, (iii) se os efeitos dos abrigos é local (folha) ou estende-se por toda a planta hospedeira (efeito regional), (iv) se plantas com abrigos foliares atraem maior número de artrópodes nos períodos secos, e se (v) plantas com abrigos foliares, por atraírem mais predadores, têm menor taxa de herbivoria foliar. Nossos resultados demonstram que abundância, riqueza... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Ecosystem engineering is a process by which some organisms change the distribution of resources (i.e., creating new habitats) for other species via non-trophic interactions. Shelter-building caterpillars can act as forest ecosystem engineers, because they may modulate interactions, between arthropods-plant communities, by providing the secondary settlers with several kinds of benefits. These caterpillars as ecosystem engineers influence the distribution pattern and abundances of other species facilitating the occurrence of new species indirectly, as well as increasing the diversity of arthropods on the plant. Although some studies have demonstrated that caterpillar leaf shelters amplify the diversity of arthropods on leaves (local effect), only one study evaluated the effect in the whole plant (regional effect), but this study only took into account specific guilds (i.e., herbivores); To date, no evaluated how speciose communities of tropical regions respond to the impacts of engineer caterpillars. In this study we reported, for the first time the influence of the lepidopteran shelter leafs on communities of arthropods in the tropics along both large spatial (i.e., local and regional effects) and temporal scales (i.e., different seasonal periods). Specifically, we evaluated if (i) leaf shelters benefit the occurrence of arthropods and amplify the diversity on plants, (ii) if the shelter architecture (funnel, cylinders with different diameters) interferes with the colonization of differents arthropods guilds, (iii) if the effects of shelters are local (within leafs) or extends to the whole host plant (regional effect), (iv) if plants with leaf shelters attract more arthropods in the dry periods, and if (v) plants with leaf shelters, which likely attract more predators, have lower levels of leaf herbivory. Our results show that the abundance, richness and total biomass of arthropods within... (Complete abstract click electronic access below)
Mestre
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Vieira, Camila [UNESP]. "Engenheiros dos ecossistemas em plantas: modificações arquiteturais de folhas por largatas de Lepidoptera influenciam a estrutura de comunidades de artrópodes." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/87623.
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Engenharia dos ecossistemas é um processo em que organismos modificam a distribuição de recursos (i.e, disponibilizando novos habitats) para outras espécies via interação não trófica. Lagartas de Lepidoptera enroladoras de folhas podem atuar como engenheiros dos ecossistemas florestais, uma vez que são capazes de modular interações entre comunidade artrópode – planta fornecendo aos colonizadores secundários diversos tipos de benefícios. Essas lagartas quando engenheiras influenciam o padrão de distribuição e abundância de outras espécies facilitando indiretamente a ocorrência de novas espécies, bem como aumentam a diversidade de artrópodes sobre planta. Apesar de estudos terem demonstrado que lagartas engenheiras ampliam a diversidade de artrópodes sobre folhas (efeito local), apenas um estudo avaliou o efeito na planta por inteiro (efeito regional), mas apenas para guildas específicas (i.e., herbívoros); nenhum estudo até agora avaliou como comunidades diversificadas, de regiões tropicais, respondem aos impactos de lagartas engenheiras. Nesse estudo reportamos a influência das lagartas enroladoras sobre comunidades de artrópodes em grande escala espacial (i.e., efeito local e regional) e temporal (i.e., diferentes períodos sazonais). Especificamente, avaliamos se (i) abrigos foliares favorecem a ocorrência de artrópodes e amplificam diversidade sobre plantas, (ii) se o tipo de abrigo (funil, cilindro com diferentes diâmetros) interfere na colonização por diferentes guildas de artrópodes, (iii) se os efeitos dos abrigos é local (folha) ou estende-se por toda a planta hospedeira (efeito regional), (iv) se plantas com abrigos foliares atraem maior número de artrópodes nos períodos secos, e se (v) plantas com abrigos foliares, por atraírem mais predadores, têm menor taxa de herbivoria foliar. Nossos resultados demonstram que abundância, riqueza...
Ecosystem engineering is a process by which some organisms change the distribution of resources (i.e., creating new habitats) for other species via non-trophic interactions. Shelter-building caterpillars can act as forest ecosystem engineers, because they may modulate interactions, between arthropods-plant communities, by providing the secondary settlers with several kinds of benefits. These caterpillars as ecosystem engineers influence the distribution pattern and abundances of other species facilitating the occurrence of new species indirectly, as well as increasing the diversity of arthropods on the plant. Although some studies have demonstrated that caterpillar leaf shelters amplify the diversity of arthropods on leaves (local effect), only one study evaluated the effect in the whole plant (regional effect), but this study only took into account specific guilds (i.e., herbivores); To date, no evaluated how speciose communities of tropical regions respond to the impacts of engineer caterpillars. In this study we reported, for the first time the influence of the lepidopteran shelter leafs on communities of arthropods in the tropics along both large spatial (i.e., local and regional effects) and temporal scales (i.e., different seasonal periods). Specifically, we evaluated if (i) leaf shelters benefit the occurrence of arthropods and amplify the diversity on plants, (ii) if the shelter architecture (funnel, cylinders with different diameters) interferes with the colonization of differents arthropods guilds, (iii) if the effects of shelters are local (within leafs) or extends to the whole host plant (regional effect), (iv) if plants with leaf shelters attract more arthropods in the dry periods, and if (v) plants with leaf shelters, which likely attract more predators, have lower levels of leaf herbivory. Our results show that the abundance, richness and total biomass of arthropods within... (Complete abstract click electronic access below)
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Holbrook, David Lee. "Corbicula fluminea Invasion as a Secondary Effect of Hydrilla verticillata Management via Triploid Grass Carp (Ctenopharyngodon idella)." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062823/.
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A study of Asian clam (Corbicula fluminea Müller) colonization in relation to changes in aquatic vegetation community as a result of management of Hydrilla verticillata (L. f.) Royle with grass carp was conducted at the Lewisville Aquatic Ecosystem Research Facility (LAERF), Lewisville, TX, from April 2015 through October 2016. Percent vegetation cover, C. fluminea abundance and water quality metrics (pH, turbidity, conductivity, DO, calcium, chlorophyll a) from 16 experimental subjects were analyzed. Treatments included four replicated grass carp stocking densities; 1-control with no fish stocked (n = 4), 2-low density of 40-43 fish per vegetated ha (n = 4), 3-medium density of 72-81 fish per vegetated ha (n = 4) and 4-high density of 110-129 fish per vegetated ha (n = 4). Data analysis showed statistical significance in the relation of C. fluminea abundance to percent vegetation cover (multiple linear regression, r2 = 0.820), grass carp stocking densities (two-way analysis of variance, p = <0.001) and chlorophyll a (multiple linear regression, r2 = 0.339). Findings of this research indicate the possibility that management of hydrilla had enabled establishment of secondary invasive species.
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Engvall, Cecilia. "A first classification of zoogeomorphological activity and impacts by large mammals in national parks, South Africa." Thesis, Uppsala universitet, Kulturgeografiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-194811.
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Pfeiffer, Birgit Verfasser], Rolf [Akademischer Betreuer] [Daniel, Michael [Akademischer Betreuer] Hoppert, Hermann [Akademischer Betreuer] Jungkunst, Stefanie [Akademischer Betreuer] Pöggeler, Stefan Pd [Akademischer Betreuer] Irniger, and Kai Jun [Akademischer Betreuer] Heimel. "Impact of plant species, N fertilization and ecosystem engineers on the structure and function of soil microbial communities / Birgit Pfeiffer. Gutachter: Michael Hoppert ; Hermann Jungkunst ; Stefanie Pöggeler ; Stefan Pd. Irniger ; Kai Jun.- Heimel. Betreuer: Rolf Daniel." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1047932199/34.
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Dahlsjö, Cecilia A. L. "Termite assemblage structure and function : a study of the importance of termites in lowland equatorial forests." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:28a37283-4013-4c5a-be2e-aac26d97f838.
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Termites are important ecosystem engineers in tropical and sub-tropical terrestrial regions where they influence ecosystem processes by altering the physical and chemical structure of the habitat. Termites affect nutrient availability by decomposition and comminution (shredding) of organic matter and act as agents of bioturbation as they re-work substrates during the construction of nests, tunnels and runways. At present we have a relatively good understanding of termite diversity patterns in the tropics through the extensive use of the standardised transect sampling protocol by Eggleton et al. (1995). These diversity data suggest that there is a functional difference in termite assemblage structure, and potentially in termite abundance and biomass, among comparable habitats across continents. However due to the lack of comparable abundance and biomass data from South America this has not previously been confirmed. In this thesis I, therefore, collected extensive data on termite taxonomic and functional assemblage structure in a South American site in Peru. The data were used to compare termite abundance and biomass from two comparable sites in Africa (Cameroon) and south east Asia (Malaysia) in order to gain better understanding of the role termites play in ecosystem processes. I found that there was an intercontinental difference in the abundance and biomass of termite feeding-groups mainly due to the dominance of soil-feeding termites in Cameroon and the absence of fungus-growing termites from Peru. The impact of certain lineages on the intercontinental differences suggests that the differences may be due to biogeographical evolution. Moreover, Eggleton et al. (1998) show that larger-bodied soil-feeding termites in Cameroon process more energy per unit area than predicted by their body size. Due to the need for an examination of the allometric relationships in termite assemblages outside Africa and the development of a more sophisticated feeding-group classification I explore the findings in Eggleton et al. (1998) further using population density - body mass relationships in three termite feeding-groups among the three continental sites in Cameroon, Peru and Malaysia. I found that large-bodied soil-feeding termites in Cameroon and large-bodied wood-feeding termites in Peru had higher population densities than expected by their body masses. As the population density - body mass relationship is inverse to that of the energy - body mass relationship the results suggest that the two feeding-groups also use more energy than expected by their body masses. Further, we have a relatively good understanding of the role termites play as ecosystem engineers e.g. in nutrient cycling and distribution, however, compared with our understanding of wood and litter decomposition in tropical forests quantitative data on the impact of termites in soil processes is poorly understood. In this thesis I conducted, to our knowledge, the first in situ soil macrofauna exclusion experiment using translocated soil in Peru to examine the impact of termites on soil C and N loss. I found that termites promote soil C and N loss which may be linked to the increase in microbial activity due to the passage of soil through the termite gut as well as the affect termites have on bioturbation and nutrient distribution. To conclude, in this thesis I present the first intercontinental comparison of abundance and biomass as well as the first in situ soil macrofauna exclusion experiment to date. The link between termite ecology, biogeography and evolution is discussed as well as the contribution of this thesis to the field of termite ecology.
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Roman, Alexander Cesar Ferreira. "Rela??es ecologicas entre caranguejos e composi??o arb?rea em bosques de mangue naturais e restaurados no nordeste brasileiro." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/14045.
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This study aimed to compare the development of crab and tree communities of two restored mangrove areas, one planted with Rhizophora mangle and the other naturally recovered, and also to compare the predation of Grapsid crab Goniopsis cruentata and the Ocypodid Ucides cordatus over the propagules of three mangrove trees: Rhizophora mangle, Avicennia schaueriana e Laguncularia racemosa. Specifically, we tested the hypothesis that Goniopsis predation is more important that Ucides predation, and that these consumers have antagonist effects over propagule consumption. In each area, 10 quadrates were selected at random to analyze tree richness, diameter, height, tree biomass and crab richness and density five years after restoration experiment start. Results show that tree height, biomass and crab density were significantly higher in artificially restored area. No significant differences were observed in crab species richness between areas, but higher tree richness was observed in self-recovered area. Results suggest that planting propagules of Rhizophora can significantly increase tree recovering if the aim was increase tree biomass and crab density, which can accelerate return of ecological functionality. Goniopsis is a more important propagule predator than Ucides both in natural and restored areas. The effects of Goniopis were higher in absence of Ucides, due to negative interactions among these two predator species. The preference of Goniopsis by Avicennia and Laguncularia can favor the dominance of Rhizophora observed in Neotropical mangroves. This study suggests that propagule predation by Goniopsis should be controlled in restoration programs, if dominance of Rhizophora is undesirable respect to more rich tree communities
O presente estudo teve como objetivo comparar o desenvolvimento das comunidades de ?rvores e caranguejos de duas ?reas de mangue restauradas, uma plantada com Rhizophora mangle e outra naturalmente recuperada, al?m de comparar a magnitude da preda??o do Graps?deo Goniopsis cruentata e do Ocypod?deo Ucides cordatus sobre os prop?gulos de tr?s esp?cies de mangue: Rhizophora mangle, Avicennia schaueriana e Laguncularia racemosa. Em particular, foi testada a hip?tese de que a preda??o de Goniopsis ? mais importante que a preda??o por Ucides e que esses consumidores possuem efeitos antag?nicos sobre a preda??o de prop?gulos. Em cada ?rea, 10 quadrantes foram aleatoriamente selecionados para analisar a riqueza arb?rea, di?metro, altura, biomassa arb?rea e riqueza e densidade de caranguejos cinco anos ap?s o in?cio do experimento de restaura??o. Os resultados mostraram que tanto a altura e biomassa arb?reas quanto a densidade de caranguejos foram significativamente maiores na ?rea artificialmente restaurada. N?o foram observadas diferen?as significativas na riqueza de esp?cies de caranguejos entre as ?reas, mas houve uma maior riqueza de esp?cies de ?rvores na ?rea auto-recuperada. Estes resultados sugerem que o plantio de prop?gulos de Rhizophora pode aumentar significativamente a recupera??o da cobertura vegetal, se o objetivo for elevar a biomassa arb?rea e a densidade de caranguejos, o qual pode acelerar o retorno da funcionalidade ecossist?mica. Goniopsis foi um predador de prop?gulos mais importante que Ucides tanto em ?reas naturais quanto restauradas. Os efeitos de Goniopsis foram maiores na aus?ncia de Ucides devido a intera??es negativas entre estas esp?cies de predador. A prefer?ncia de Goniopsis por Avicennia e Laguncularia pode favorecer a domin?ncia de Rhizophora observada nos mangues Neotropicais. Este estudo sugere que a preda??o de prop?gulos por Goniopsis em programas de restaura??o de mangue deveria ser controlada se a domin?ncia de Rhizophora ? indesej?vel em rela??o a comunidades com mais esp?cies de ?rvore
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Silva, Rodrigo Pires da. "The The sun coral as an ecosystem engineer." Master's thesis, 2018. http://hdl.handle.net/10451/36493.
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Tese de mestrado, Ecologia Marinha, Universidade de Lisboa, Faculdade de Ciências, 2018As invasões biológicas são uma das maiores ameaças à biodiversidade e aos ecossistemas marinhos nos dias de hoje. A introdução de espécies não-indígenas começou a ser comum no início do século XX devido ao grande aumento do tráfego marítimo decorrente da globalização. Regra-geral, a introdução de novas espécies não é propositada. Grande parte dos indivíduos pioneiros são transportados em águas de lastro ou viajam encrustados em navios transoceânicos. Os indivíduos transportados para fora da sua zona original de distribuição podem assumir um estatuto de espécie invasora se detiverem determinadas características: elevada resiliência a mudanças ambientais, grandes taxas de recrutamento e crescimento, grande variabilidade genética, curto período de gestação, maturidade sexual precoce, grande capacidade reprodutiva e/ou uma dieta muito diversificada. A costa sudeste do Brasil, onde este estudo foi desenvolvido, não apresenta formações recifais de coral, contudo existem algumas espécies de coral na região, como é o caso do coral cérebro endémico Mussismilia hispida e do coral invasor Tubastraea spp. Este trabalho tem como principal objetivo perceber de que forma o coral invasor, Tubastraea spp., influencia a estrutura da comunidade local e o seu impacto na teia trófica. Para tal, foram desenvolvidos dois estudos em paralelo, no verão de 2017. O primeiro visa compreender como a presença de coral-sol influencia a macrofauna associada ao substrato rochoso, tendo em conta três coberturas de coral diferentes (0%, 50%, 100%), em dois locais distintos na Ilha de Búzios, SP, Brasil (capítulo 2). Enquanto que o segundo trabalho pretende caracterizar a teia trófica facilitada pelo coral-sol e elucidar se o bivalve invasor Leiosolenus aristatus recebe alimento do seu anfitrião, Tubastraea spp (capítulo 3). Ambos os estudos focam questões em aberto sobre o efeito do coral-sol como engenheiro ecossistémico na região. O género Tubastraea refere-se a um coral ahermatípico e azooxantelado, pertencente à ordem Scleractinia. É o único género de escleractíneos a invadir o Brasil atualmente, tendo uma alta taxa de invasão que o torna numa das maiores ameaças à biodiversidade marinha local. Coral-sol é a designação em português, devido à disposição dos seus pólipos e coloração amarela/alaranjada. As principais espécies a ocorrerem em águas brasileiras são Tubastraea coccínea e Tubastraea tagusensis. O coral-sol é nativo do Indo-Pacífico tendo uma vasta distribuição geográfica. O seu sucesso como espécie invasora advém da posse de algumas características, tais como o hermafroditismo, uma estratégia reprodutiva diversificada, uma elevada capacidade de fixação em substrato natural e artificial, altas taxas de recrutamento e crescimento, e uma preferência de assentamento em estruturas verticais. No oceano Atlântico, o início da sua invasão ocorreu no mar das Caraíbas (anos 1940) e o primeiro registo no Brasil foi nos anos 1980, numa plataforma petrolífera, na baía de Campos, a norte do estado do Rio de Janeiro. O Capítulo 1 introduz o tema em estudo, apresentando os principais objetivos de trabalho da tese, o Capítulo 2, foca o impacto do coral-sol na fauna bentónica, o Capítulo 3 descreve a teia trófica em que se insere o coral-sol, com recurso a análise de isótopos estáveis, e o Capítulo 4 apresenta as conclusões gerais e perspetivas futuras sobre este tema. O trabalho apresentado no Capítulo 2 contou com a recolha de amostras em dois locais distintos, separados por 3km, ao longo da Ilha de Búzios, São Paulo, Brasil, e duas áreas de amostragem em cada local, distanciadas por algumas dezenas de metros. O trabalho de campo consistiu na raspagem de três réplicas em cada área, em regiões saturadas pelo coral, parcialmente cobertas (aproximadamente 50% de cobertura) e sem presença do invasor. Todo o material recolhido foi lavado e peneirado em 9 crivos de malha com diâmetros decrescentes, onde ficou retida a macrofauna. Após separação, identificação e armazenamento da fauna encontrada, procedeu-se à análise de variáveis univariadas (abundância, biomassa e tamanho médio), à utilização do índice de diversidade e riqueza Shanon-Wiener e à análise multivariada da estrutura da comunidade. Todas as análises referidas seguiram o mesmo modelo, tendo “coral cover” como o principal fator (“no coral, half-coral e full coral”), examinados à escala espacial de dois locais e duas áreas. O coral-sol provou ser um elemento de exclusão de alguns macro-invertebrados (ex. tanaídeos, ostracodes e copépodes) e o responsável pelo declínio da abundância e riqueza na estrutura da comunidade local. É sugerida a existência de um cenário satisfatório, em termos de abundância, biomassa e riqueza, em regiões onde a presença do coral-sol é parcial ou inexistente. Perante os resultados obtidos, pode-se sugerir, também, que o limiar da resiliência do ecossistema estudado está iminente. Este estudo confirma o coral-sol como um importante engenheiro ecossistémico – organismo cuja presença ou atividade altera as características físicas circundantes, criando e modificando habitats e influenciando todas as espécies aí presentes. Medidas terão de ser tomadas rapidamente para evitar perdas permanentes de biodiversidade local. Por outro lado, a análise isotópica do δ13C e δ15N apresentada no Capítulo 3 revelou que a teia trófica associada ao coral é maioritariamente composta por organismos filtradores e que as novas comunidades, após a invasão, são dominadas por seres heterotróficos, em vez de autotróficos (organismos dominantes antes da invasão). Para além da importante expansão do coral-sol, o mitilídeo Leiosolenus aristatus, nativo do mar das Caraíbas, mas com uma distribuição geográfica muito alargada, foi frequentemente encontrado no interior das bases rígidas do coral invasor. Tubastraea spp. e Leiosolenus aristatus são originários de localizações geográficas distintas, portanto a sua associação apenas ocorre em locais onde ambos são alóctones. Os resultados obtidos sugerem que tanto o coral-sol, como o bivalve, são organismos filtradores. Uma das hipóteses para a ocorrência desta associação, seria a de que o bivalve beneficiaria de alimento providenciado pelo coral, mas tal não se verificou. A invasão do mitilídeo é facilitada pelo coral, por este encontrar refúgio nas suas bases calcárias. É expectável que a continuação da invasão pelo coral-sol seja acompanhada pela expansão da distribuição deste bivalve invasor. Conclui-se que a rápida invasão do coral-sol no litoral norte de São Paulo, é uma grave ameaça à biodiversidade local por estar iminente uma importante alteração do ecossistema, juntamente com a facilitação da introdução de um bivalve invasor, competidor com outras espécies nativas. A alteração de habitats, pode vir a ter consequências profundas nas comunidades locais. Ambos os estudos, são pontos de partida para o conhecimento do impacto negativo que o coral-sol pode ter na estrutura da comunidade associada aos fundos rochosos, como engenheiro ecossistémico. Sugere-se a continuação de estudos dentro desta temática, com o intuito de aumentar o conhecimento, contribuindo para a eventual gestão, minimização dos impactos ou erradicação desta espécie invasora.
Invasive species are a serious threat to biodiversity because they displace native species, change community structure and food webs and alter fundamental processes (such as nutrient cycling and sedimentation). Any organism that is outside of its native geographic range that may or has become injurious to animal or human health, the economy and/or natural environment is considered as invasive species. Globalization (i.e. increase of the international ship traffic) is the main driver of invasive species introduction. Tubastraea spp., commonly designated sun coral, is an ahermatypic and azooxanthellate scleractinian coral, the only scleractinian which has been introduced in Brazilian waters and one of the most widespread invaders in the world. The present work aimed to investigate the impact of Tubastraea spp. in the local biological community, examining the rocky shore associated macrofauna, in an area under rapid invasion, at Búzios Island, São Paulo, Brazil, under three different coral coverages (0%, 50% and 100%) (chapter 2) and characterizing the food web associated with Tubastraea spp., using stable isotopes (chapter 3), during the summer of 2017. Chapter 1 introduces the basis for this work and describes the main aims of this thesis. Chapter 2 investigates the impact of the sun coral on the benthic macrofauna, chapter 3 describes the food web where this coral is included, and chapter 4 presents the main conclusions and future perspectives. The alteration of mobile invertebrate assemblages according to the degree of sun-coral space occupation was examined on vertical walls (with 3 different coral cover levels) and the differences found among two study sites and areas, within each study site were examined. It was observed that the sun coral may exclude major invertebrate groups (i.e. tanaids, ostracods and copepods). Abundance, biomass and richness of associated macrofaunal species declined in areas saturated by the sun coral, confirming that this coral is an ecosystem engineer. The structure of the food web associated to the colonies of Tubastraea spp was previously unknwon. At the basis of this coral another invasive species is very often found, the bivalve Leiosolenus aristatus, a borer species that perforates the base of hard corals. Stable isotopic analysis was applied to all organisms occurring at the microhabitat built by Tubastraea spp. to 1) provide the first trophic characterization of the food web facilitated by Tubastraea spp., while also 2) elucidating if L. aristatus receives nutrition from its coral host Tubastraea spp. Stable isotopic analyses showed that the food web that accompanies this invasive coral seems to be mostly composed of suspension feeders, confirming that the new community established after Tubastraea spp. invasion is dominated by heterotrophs. It was also concluded that both Tubastraea spp. and L. aristatus are suspension feeders consuming similar resources. This way, L. aristatus seems to profit from the expansion of Tubastraea spp. because the coral provides it with a structure to live, but not a source of nutrition. As Tubastraea spp. progresses in its invasion of new areas, this borer bivalve should follow. This work describes for the first-time the impact of Tubastraea spp. on the southeast Brazilian rocky bottoms’ associated macrofauna and food webs. The rapid expansion of this ecosystem engineer is leading to the alteration of the native macrofaunal community. This work indicates that this invasion will result in a decline in local biodiversity and in profound alterations to the food web of subtidal rocky shores.
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"Ecosystem Consequences Of Genetic Variation In The Salt Marsh Engineer Spartina Alterniflora." Tulane University, 2015.
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Ecosystem engineers can govern ecosystem dynamics, yet ecosystem consequences of trait variation within engineering species are often overlooked. Combining field and greenhouse experiments with mathematical modelling, this study aimed to assess the relative importance of heritable and non-heritable trait variation within the engineer species Spartina alterniflora in controlling salt marsh erosion. In the field experiment, plots along a devegetated shoreline were restored with wild and cultivated sources to test whether populations exerted different control on erosion. The greenhouse experiment investigated whether genotypic trait differences were conserved when genotypes were exposed to elevated nutrients. A modelling approach was used to extrapolate empirical findings to temporal and spatial scales involved in landform evolution, considering spatial patterns in trait variation. The field experiment revealed that erosion rates were higher in plots planted with a wild, non-local source population as compared to plots planted with cultivars or local genotypes. Differential erosion could not be explained by differences in biomass, suggesting that other traits and resource use are stronger determinants of erosion. In the greenhouse experiment, cultivars and wild genotypes exhibited trait-specific differences in phenotypic plasticity under changing nutrient availability. Nutrient regime and heritable trait differences explained 70% of observed variation in soil shear strength. Soil shear strength increased when plants received more nutrients, but plant genotype had an equal or larger influence on soil characteristics. Model simulations suggested that older marshes (with large clones) and genetically diverse marshes (with high spatial variance in soil shear strength) may experience higher mean erosion rates. However, simulations also showed that average erosion rates are easily underestimated if the observation period is short, as variability of annual erosion rates and the probability of mass failure events were also mediated by clone size and composition. These findings illustrate that heritable and non-heritable trait variation interact with environmental conditions and landform history, together driving geomorphological processes crucial to the persistence of coastal marshes. Consideration of these interacting factors is needed when deploying ecosystem engineers for habitat restoration.1
Brittany Marie Bernik
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Verstege, Jacqueline. "Fox and lemming responses to climate and snow conditions at the Arctic’s edge." 2017. http://hdl.handle.net/1993/31976.
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Low species diversity in the Arctic promotes strong food-web linkages, as changes in abundance of one species may influence many others. Using harvest records, I determined Arctic fox populations are declining in their southern distributional range due to shallower snow potentially limiting density of lemmings, their primary prey, which live and breed beneath snow. Additionally, warm fall and spring temperatures are shortening access to alternative prey, seals on sea ice. Arctic foxes also influence other species through non-trophic interactions, as lemming winter nests were found on 70% of fox dens examined. I determined warmer subnivean temperatures promoted by accumulation of thick snow leeward of tall vegetation on dens attracted lemmings to these dens. Furthermore, lemming reproduction was higher dens compared to traditional lemming habitat. This research highlights the impact of climatic variables on Arctic predator-prey interactions and the importance of understanding impacts of trophic and non-trophic interactions on species demographics.February 2017