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Dissertations / Theses on the topic 'Biotic communities'

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Published: 4 June 2021
Last updated: 6 September 2023

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1

Henriksson, Anna. "Biotic resistance in freshwater fish communities." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110251.

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Invasions of non-native species cause problems in ecosystems worldwide, and despite the extensive effort that has been put into research about invasions, we still lack a good understanding for why some, but not other, communities resist these invasions. In this doctoral thesis I test hypotheses on biotic resistance using a large dataset of more than 1000 both failed and successful introductions of freshwater fish into Swedish lakes. We have found that the classic species richness hypothesis is a poor descriptor of introduction success because it fails to acknowledge that resident species contribute to the resistance in different ways. We developed a new measure of biotic resistance, the weighted species richness, which takes into account that the resident species contributes to the resistance with different strength and sign. Further, we correlated performance traits of species in their role as an invader and as a resident species to predict how the biotic resistance of these communities would develop over time. We found a positive correlation between performance traits: Some species have high introduction success, they make a large contribution to the resistance, and they cause extinctions when introduced but do not go extinct themselves when other species establishes, whereas other species are weak performers in these respects. Thus, the biotic resistance of these communities should grow stronger as non-native species accumulates. These results give us clues about what type of communities that should be most sensitive to further invasions, i.e., communities harboring species weak performers.  My results show that the biotic resistance of communities is an important factor in determining invasibility of a community. They also show that methods for quantifying resistance must take into account how interactions are structured in nature. What determine the biotic resistance of a community is the type of interactions that the resident species have with the invader and not the species richness of the community.
2

Ricks, Kevin Daniel. "Biotic Filtering in Endophytic Fungal Communities." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6871.

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Plants can be colonized by complex communities of endophytic fungi. This thesis presents two studies, both of which investigate biotic filtering in endophytic fungal communities. Chapter 1. Endophytic fungi can be acquired horizontally via propagules produced in the environment such as in plant litters of various species. Given that litters from different plant species harbor distinct endophytic fungal communities and that endophytic fungi may be dispersal-limited, the structure of the endophytic fungal community of a given plant may be determined by proximity to particular inoculum sources. Community assembly may also be affected by biotic filtering by the plant. Therefore, a plant may be able to select particular fungal taxa from among the available pool. In that case, the structure of the endophytic fungal community in the plant could be somewhat independent of the structure of the inoculum community. We tested the hypothesis that biotic filtering of endophytic fungal communities occurs in Bromus tectorum by exposing it to a variety of inoculum sources including litters from several co-occurring plant species. The inoculum sources differed significantly from each other in the structures of the communities of endophytic fungi they harbored. We characterized the structures of the resulting leaf and root endophytic fungal communities in Bromus tectorum using high-throughput sequencing. All tested inoculum sources successfully produced complex communities of endophytic fungi in Bromus tectorum. There was significantly more variation in the structures of the communities of endophytic fungi among the inoculum sources than in the resultant endophytic fungal communities in the leaves and roots of Bromus tectorum. These results suggest that biotic filtering by Bromus tectorum played a significant role in the assembly of the endophytic fungal communities in tissues of Bromus tectorum. Because endophytic fungi influence plant fitness, it is reasonable to expect there to be selective pressure to develop a uniform, desirable endophytic fungal community even from disparate inoculum sources via a process known as biotic filtering. Chapter 2. Frequently one finds that different plant species harbor communities that are distinct. However, the nature of this interspecific variation is not clear. We characterized the endophytic fungal communities in six plant species from the eastern Great Basin in central Utah. Four of the species are arbuscular mycorrhizal (two in the Poaceae and two in the Asteraceae), while the other two species are nonmycorrhizal (one in the Brassicaceae and one in the Amaranthaceae). Our evidence suggests that both host mycorrhizal status and phylogenic relatedness independently influence endophytic fungal community structure.
3

MacDonald, Arthur Andrew Meahan. "Abiotic and biotic factors creating variation among bromeliad communities." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58954.

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Many ecological communities show variation from place to place; understanding the causes of this variation is the goal of community ecology. Differences in community composition will be the result of both stochastic and deterministic processes. However, it is difficult to know to what degree deterministic processes will shape community composition. In this thesis I combined observational and experimental approaches to quantify deterministic processes within a particular ecological community -- they phytotelmata of bromeliad plants. In my thesis I describe three studies at different scales of organization: 1) do organisms of different size respond equally to changes in their environment 2) how do predators interact to influence prey survival 3) what mechanisms underly the response of similar species to the same environmental gradient, bromeliad size. In Chapter 1, I tested an hypothesis developed from previous observational data -- that smaller organisms respond less than larger ones to the same environmental gradient -- different bromeliad species that occur under different forest canopies. After removing variation caused by dispersal, I found that environmental variation explained little variation for bacteria, more for zooplankton and most of all for macroinvertebrates. In my second chapter, I examined ecological determinism on a smaller scale -- within a single trophic level (macroinvertebrate predators). I found that predators may interfere with each other, reducing predation rates and increasing prey survival. In Chapter 3, I examine macroinvertebrate responses to bromeliad volume. I use both null models and a field experiment to show that for at least one such pair, a difference in abiotic tolerances may be the plausible mechanism. Together these results illustrate when, and to what degree, bromeliad communities respond to deterministic factors. All three chapters first demonstrate a pattern, testing it against a suitable null distribution, before attempting to quantify possible mechanisms with a field experiment. This combination of observation and experiment is an approach which can contribute to our understanding of how ecological systems work.
Science, Faculty of
Graduate
4

Theron, Leon-Jacques. "Distribution and abundance of rodents, millipedes and trees in coastal dune forests in northern KwaZulu-Natal." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/03292006-103859.

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5

Waterhouse, Martin. "On the edge : peripheral communities and marginal anthropology." Thesis, University of South Wales, 2002. https://pure.southwales.ac.uk/en/studentthesis/on-the-edgeperipheral-communities-and-marginal-anthropology(ef955531-baf0-445a-9e41-6720a9874a88).html.

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This is a study of people, place, and cultural "identity" in two small parishes that are geographically on the periphery of the United Kingdom. Both are coastal parishes: one is in South-west Wales overlooking the Irish Sea and the other is one of the islands comprising The Orkney archipelago.' This is also a work of marginal anthropology (Fox, 1975) that discusses both conventional and more experimental "ways of telling" in an attempt to interpret human social behaviour.
6

Karsten, Jennifer. "Teaching about complexity in primary and secondary schools : an exploration of new approaches to ecosystem education." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85174.

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The purpose of this research was to investigate ways in which complexity could be used as the paradigm through which schoolchildren might understand ecosystems in a new way. To that end, new conceptual and practical approaches for learning about ecosystems have been presented, and the effects of these approaches on teachers and other educational stakeholders have been explored. A variety of learning environments were visited and over two hundred educational stakeholders were consulted. This resulted in a number of suggestions on and a discussion of the introduction of complexity, as a lens by which to teach about ecosystems and as a teachable subject, within that context, to pre-university schoolchildren.
The development of the learning and teaching approaches for this age group (primary and secondary school) involved exploring the state of ecosystem studies as they are presently conducted, and seeking the content within the current curricula that had congruity with the content of interest: ecosystem phenomena related to complexity. The insights gained from that investigation led to the creation of two types of approach, an approach to learning about ecosystems through the lens of complexity, and an approach to teaching about ecosystems through the lens of complexity. The Complexity Conceptual Approach deals with the various ways of understanding, or conceptualizing, ecosystem complexity and the Complexity Practical Approach deals with the content, technology, and methodology used for instruction on ecosystem complexity. The two approaches can be used together as part of a "complexity framework" that is flexible enough to be used in a diverse variety of learning situations.
Substantial consideration was given to the foreseeable prospects for these approaches: how implementation might occur, the issues involved, and the anticipated outcomes. Accordingly, topics of discussion include the introduction of the conceptual and practical approaches in terms of their effects on various educational stakeholders (such as teachers, students, parents, and administrators) and on different levels of the educational system. This type of investigation (in which potential impacts are considered) is, itself, reflective of the kind of systems-thinking that the complexity approaches were established to engender in schoolchildren.
7

Fultz, Jessica Erin. "Effects of shelterwood management on flower-visiting insects and their floral resources." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/fultz/FultzJ0805.pdf.

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8

Shanmuganathan, Subana. "Soft systems analysis of ecosystems thesis submitted to Auckland University of Technology in fulfillment of the degree of Doctor of Philosophy, 2004." Full thesis. Abstract, 2004.

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9

Boller, Michael Louis. "Hydrodynamics of marine macroalgae : biotic and physical determinants of drag /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3188836.

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10

Jaeger, Andrea L. "Invasive species impacts on ecosystem structure and function." Diss., Connect to online resource - MSU authorized users, 2006.

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11

Consuegra, Erin Jean Liles Mark Russell. "Characteristics of viral communities in soil, activated sludge, and influent." Auburn, Ala., 2009. http://hdl.handle.net/10415/1791.

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12

FAGORZI, CAMILLA. "The green deal challenge: exploiting biotic interactions from bacterial strains to communities." Doctoral thesis, Università degli studi di Ferrara, 2021. http://hdl.handle.net/11392/2488178.

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One of the main factors behind agricultural sustainability is the effective management of nitrogen (N) inputs, a key element for crop production. Plant growth and agricultural yield is a result of complex interactions between the plant, soil and its microbial communities. An effective way for the management of N inputs resulting in farming practices that are economically viable and environmentally prudent is the use of biologically fixed nitrogen. Symbiotic nitrogen fixing bacteria (rhizobia) represent a promising source of biologically fixed nitrogen, since they provide N inputs directly into the plant (legume). The overarching aim of this thesis is the description, the deciphering and exploitation of the microbial contribution to environmental sustainability. The first chapter of this thesis focuses on the above-mentioned topic, the symbiosis between legumes and rhizobia, ranging from the most recent discoveries on rhizobia to improve agricultural practices in harsh soils to the choice of the best partnership. Although being species-specific, rhizobia in nature exhibit somewhat large variation in the symbiotic efficiency with different varieties of the same host plant species, which may limit their application to crop as inoculants. While the molecular basis for the species-specificity have been well defined, the molecular basis of the specificity between the variety plant and the bacterial strains belonging to the same species are unknown. In this chapter, the evolutions of the partnership along the genus and its pangenome is dissected and the model species for plant-rhizobium symbiosis, Sinorhizobium meliloti (syn. Ensifer) and Medicago sativa (alfalfa) became our model to investigate the host-symbiont recognition during the initial perception. Next to the novel findings on the evolution of symbiotic nitrogen fixation in the genus, taxonomic revision of the Sinorhizobium/Ensifer genus as well indicates some guidelines for genus delineation in Rhizobiaceae. The second chapter focuses on the study of the microbiota and its interaction with the environment, analysing the signatures of microbial life in nature. Environmental microbiology can be defined as the study of microbes, their functions, and interactions in all habitats on Earth (and beyond). The papers presented in this chapter are aimed at exploring three different environments sharing the feature of being “extreme”, that is non-conventional for aerobic, mesophilic microbes. The third chapter reports a systems-biology investigation of metabolic adaptation strategies with a study on the diauxie, showing the metabolic networks of Pseudoalteromonas haloplanktis (a heterotrophic marine bacterium) in complex nutritional conditions encountered in the environment.
Uno dei principali fattori alla base della sostenibilità ambientale è la gestione efficace degli input di azoto (N), un elemento chiave per la produzione agricola. La crescita delle piante e la resa agricola sono il risultato di complesse interazioni tra la pianta, il suolo e le sue comunità microbiche. Un modo efficace per la gestione degli input di azoto, che ha come risultato lo sviluppo di pratiche agricole economicamente valide e rispettose dell'ambiente, è l'uso di azoto fissato biologicamente. I batteri simbionti azoto fissatori (rizobi) rappresentano una preziosa fonte di azoto fissato biologicamente, poiché forniscono alla pianta (legume) questo importante elemento direttamente a livello della radice. Il primo capitolo di questa tesi si concentra sull'argomento appena menzionato, la simbiosi tra piante leguminose e rizobi, spaziando dalle più recenti scoperte sui rizobi, volte a migliorare le pratiche agricole in terreni di difficile coltivazione, alla scelta del miglior partenariato. Sebbene siano specie-specifici, i rizobi in natura mostrano una variabilità piuttosto ampia nell'efficienza simbiotica con diverse varietà della stessa specie di pianta ospite, il che può limitare la loro applicazione come inoculanti per le colture. Mentre le basi molecolari della specie-specificità sono state ben definite, quelle che determinano la specificità tra la varietà vegetale e ceppi batterici appartenenti alla stessa specie sono sconosciute. In questo primo capitolo, vengono sezionate le evoluzioni della partnership simbiotica fra pianta e rizobio. Le specie modello Sinorhizobium meliloti (syn. Ensifer) e Medicago sativa (erba medica) sono diventate il nostro modello per studiare il riconoscimento ospite-simbionte durante la percezione reciproca iniziale. Accanto alle nuove scoperte sull'evoluzione della fissazione dell'azoto simbiotico, la revisione tassonomica del genere Sinorhizobium/Ensifer indica alcune linee guida per la delineazione del genere nelle Rhizobiaceae. Il secondo capitolo si concentra sullo studio del microbiota e della sua interazione con l'ambiente, analizzando le “firme” della vita microbica in natura. La microbiologia ambientale può essere definita come lo studio dei microrganismi, delle loro funzioni e interazioni in tutti gli habitat della Terra (e oltre). Gli articoli presentati in questo capitolo hanno lo scopo di esplorare tre diversi ambienti che condividono la caratteristica di essere “estremi”, non convenzionali, per i microbi aerobici, mesofili. Il terzo capitolo riporta un'indagine di biologia dei sistemi delle strategie di adattamento metabolico con uno studio sulla diauxia, che mostra le reti metaboliche di Pseudoalteromonas haloplanktis (un batterio marino eterotrofico) in complesse condizioni nutrizionali incontrate nell'ambiente.
13

Zhang, Chi Tian Hanqin. "Terrestrial carbon dynamics of southern United States in response to changes in climatic, atmosphere, and land-use/land cover from 1895 to 2005." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Forestry_and_Wildlife_Sciences/Dissertation/Zhang_Chi_13.pdf.

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14

Snyder, Gretchen Beth. "Mechanisms driving increased prey consumption with increasing predator diversity." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Summer2009/G_Snyder_051509.pdf.

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15

Nakamura, Masahiro. "Positive plant-mediated indirect effects of biotic and abiotic factors on arthropod communities." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147855.

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16

Hoopes, Carla. "Influence of native bunchgrass and invasive forb litter on plant growth in a semi-arid bunchgrass prairie." Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/hoopes/HoopesC0506.pdf.

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17

Degerman, Traci Michelle. "The development of landscape design principles based upon ecosystem aesthetics, and their application in rehabilitating Diablo Lake Overlook, Ross Lake National Recreation Area, Washington." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Spring2007/T_Degerman_050307.pdf.

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18

Kaye, Maria Ellen. "The role of functional traits and phylogeny in assembly of tropical forest communities in Danum Valley, Sabah." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231264.

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Tropical forests have been studied by community ecologists since the earliest days of the field because of their diversity and complexity and much of the theory behind community assembly has been developed in the tropics. However, the processes that act to assemble species in tropical forest across a very fine scale are still poorly understood. This study investigates community structure in 20ha area of hyper diverse tropical rainforest in Sabah, Malaysia. In order to examine community phylogenetic structure, I reconstructed a molecular phylogeny for all species in the study site using DNA barcoding loci. From this, I calculated phylogenetic diversity metrics for each community and then used a null model to compare observed phylogenetic diversity with that which would be expected if communities were randomly assembled with respect to phylogeny. The analyses showed that communities are more closely related than predicted by the null model. I also collected species functional trait data and showed that species assemblages and community weighted mean trait values correlate with environmental gradients on the plot. I also compared functional diversity to data simulated from null models. This showed that communities are on average more functionally similar than predicted at random. Finally, I performed a multivariate analysis with environmental, spatial, phylogenetic and trait data from communities across the plot. The analyses recovered an elevational and soil gradient that correlated strongly with community composition. Species occupying different ranges along this gradient had differing trait values and were phylogenetically distinct. These analyses demonstrate that even fine scale environmental variation is influential in assembling communities over a small area of forest. A soil nutrient gradient is consistently recovered that correlates with topography, suggesting that soil nutrient distribution is mediated by the downslope movement of water leaching soils on ridge tops and leading to accumulation of nutrients in valleys. This gradient is associated with species compositional variation and also with community weighted mean functional traits, indicating that the environment is influencing species distributions even over very small areas. Communities were both functionally and phylogenetically clustered, adding further support to this conclusion.
19

Harley, Christopher David Grant. "Environmental modification of biological interactions : a comparison across scales /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5271.

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20

Ciannelli, Lorenzo. "Cross-scale analysis of the Pribilof Archipelago, southeast Bering Sea, with a focus on age-0 walleye pollock (Theragra chalcogramma) /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5292.

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21

Simpson, Roderick F. "EcoSystem-Sim a virtual ecosystem simulator /." [Gainesville, Fla.] : University of Florida, 2001. http://purl.fcla.edu/fcla/etd/UFE0000352.

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Thesis (M.S.)--University of Florida, 2001.
Title from title page of source document. Document formatted into pages; contains x, 60 p.; also contains graphics. Includes vita. Includes bibliographical references.
22

Speckman, Suzann Gail. "Characterizing fish schools in relation to the marine environment and their use by seabirds in lower Cook Inlet, Alaska /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5301.

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23

Turner, Andy W. Rabeni Charles F. "Watershed-sediment-biotic linkages in small streams of Missouri's Osage River Basin." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/5358.

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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on January 19, 2010). Thesis advisor: Dr. Charles F. Rabeni. Includes bibliographical references.
24

Selong, Jason H. "Impacts of aquaculture effluent on water quality and biotic communities in Virginia headwater streams." Thesis, This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-08252008-162223/.

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25

Stolk, Henk. "Emergent models in hierarchical and distributed simulation of complex systems : with applications to ecosystem and genetic network modelling /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19095.pdf.

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26

Hooten, Mevin B. "Hierarchical spatio-temporal models for ecological processes." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4500.

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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 26, 2007) Vita. Includes bibliographical references.
27

Boyd, Eric Stephen. "Biology of acid-sulfate-chloride springs in Yellowstone National Park, Wyoming, United States of America." Diss., Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/boyd/BoydE0807.pdf.

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28

Kathiria, Palak, and University of Lethbridge Faculty of Arts and Science. "Incompatible and compatible plant pathogen interactions." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2006, 2006. http://hdl.handle.net/10133/351.

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Pathogens are one of the prevalent stresses to plants. Resistance mediated by the resistance genes is efficient mechanism for evading the pathogens. To understand the influence of various biotic and abiotic factors on resistance gene promoters, plants having N gene promoter fused with reporter genes were developed. Experiments with tobacco plants revealed that on tobacco mosaic virus infection, the N protein may increase in the cells. Also, extreme temperature may result in decrease in the N protein. The salicylic acid produced during the development of systemic acquired resistance does not hinder the N promoter function. Hence, it can be concluded that the promoter region of resistance genes can be influenced by many biotic and abiotic factors. In the tobacco plants lacking the N gene, infection with tobacco mosaic virus leads to generation of systemic recombination signal. Experiments suggest that this signal can lead to better tolerance of the pathogen in next generation. Also, in the plants which received systemic recombination signal, the resistance gene loci are hypermethylated and the frequency of rearrangement in these loci increases. Hence, the signal results in higher tolerance to pathogen and increased genetic variability in resistance genes.
xvi, 147 leaves : ill. (some col.) ; 29 cm.
29

Sgarzi, Serena. "Environmental and biotic factors influencing the size structure of the aquatic communities in Mediterranean ponds." Doctoral thesis, Universitat de Vic - Universitat Central de Catalunya, 2022. http://hdl.handle.net/10803/673519.

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Les basses mediterrànies són ecosistemes amb un alt valor ecològic, que pateixen una forta regressió per les pressions antròpiques. No obstant això, l'atenció científica rebuda sempre ha estat molt escassa, i la majoria dels estudis ecològics s'han centrat en la seva biodiversitat, més que l'estructura de la mida corporal de les seves comunitats. Les comunitats planctòniques i les poblacions del peix endèmic i amenaçat Aphanius iberus (Valenciennes, 1846) es van analitzar en basses costaneres permanents salobres (Capítol 1 i 2) i en basses temporànies d'aigua dolça (Capítol 3). L'estructura de la mida es va estudiar mitjançant diferents mètriques de mida (índex de diversitat de mida, espectre de mida, longitud corporal mitjana) i es va aplicar a diferents escales ecològiques (grups funcionals, nivell de població, considerant més d'un nivell tròfic a la vegada), per esbrinar els principals factors ambientals i biòtics que determinaven l'estructura de mides de les comunitats i poblacions aquàtiques a les basses mediterrànies.
Mediterranean ponds are ecosystems with a high ecological value, suffering a strong regression due to anthropogenic pressures. Notwithstanding, the received scientific attention has always been far lesser than other larger water bodies. Most ecological studies on Mediterranean ponds have focused on their biodiversity, but only to a lesser extent they have paid attention to the body size structure of their communities. Planktonic communities and populations of the endemic and threatened fish Aphanius iberus (Valenciennes, 1846) were analyzed in brackish permanent coastal ponds (Chapter 1 and 2) and in temporary freshwater ponds (Chapter 3). Size structure was studied using different size metrics (e.g., size diversity index, size spectrum, mean body length, etc.) and applied at different ecological scales (i.e., functional groups, population level, more than one trophic level together), to unravel which were the main environmental and biotic drivers shaping the size structure of aquatic communities and populations in Mediterranean ponds.
30

Corrao, Jason James. "Relationships Between Streamside Management Zone Width and Biotic Communities of Headwater Streams in West Virginia." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/43919.

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The importance of streamside management zones (SMZ) in minimizing the impact of non-point source pollution from silvicultural operations is recognized by the forestry Best Management Practices of most states. However, research concerning the SMZ width and harvesting intensity required to maintain water quality and biotic communities is limited. The goal of this study is to evaluate the efficacy of different SMZ widths and forest harvesting intensities within SMZs, in maintaining the water quality and biotic communities of 22 headwater streams located in the mountains of East-central West Virginia. Streams were organized in four blocks and randomly assigned one of six silvicultural treatments involving variation of SMZ width and harvesting intensity within the SMZ; 30.5 m SMZ with no residual harvest, 30.5 m SMZ with 50% residual harvest, 15.3 m SMZ with no residual harvest, 15.3 m SMZ with a 50% residual harvest, 4.5 m SMZ and control (no harvest within the watershed). Stream water chemistry parameters (in particular, NO3, NH4, Ca, Mg, conductivity and total dissolved solids) as well as aquatic macroinvertebrate communities were monitored from June 2003 through March 2005. Average nitrate concentration in streams harvested with a 4.5 m SMZ was more than 4 times as high as that of control streams. Average summer and fall stream temperatures were inversely related to SMZ width. Mean values for a number of macroinvertebrate community metrics were indicative of poorer water quality in streams harvested with a 4.5 m SMZ. During this short-term study SMZs of at least 15.3 m appeared to be sufficient to maintain water quality. However, harvesting was restricted to one side of the stream and logging induced stream disturbances were observed even with SMZs of 30.5 m. For these reasons SMZs of at least 30.5 m are recommended as a cautionary measure to minimize the potential for impacts to biotic communities. In addition, residual harvest of up to 50% of the basal area within the SMZ did not appear to impact water quality during the temporal scope of the study.
Master of Science
31

McCollum, Donna s. "LANDSCAPE AND LOCAL INFLUENCES ON THE BIOTIC INTEGRITY OF FISH COMMUNITIES IN OHIO HEADWATER STREAMS." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1091819607.

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32

McCliment, Elizabeth. "Phylogenetic and metabolic diversity of microbial communities inhabiting deep-sea hydrothermal ecosystems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 217 p, 2007. http://proquest.umi.com/pqdweb?did=1397900421&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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33

Tornwall, Brett Matthew. "The role of dispersal networks in structuring biotic communities: A tale of streams and metacommunity theory." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/75004.

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Identifying the processes and mechanisms that govern communities of organisms is the main goal of community ecology. Locally operating mechanisms such as environmental filtering, in which the environment determines what species are found in a given location, as well as regional processes such as dispersal have all been identified as potential drivers of community processes. However, the relative importance of these drivers may vary temporally and spatially. In dendritic stream networks, headwater streams are isolated when compared to more centrally located mainstem stream sections. I investigated the potential for stream networks to influence the relative influence of local and regional processes via a survey and field experiment based approaches. I found that headwater streams can influence mainstem stream communities, potentially as a result of the dispersal of organisms or abiotic materials. Additionally, I demonstrated that macroinvertebrate communities in headwater streams respond more strongly to manipulations of local environment than do mainstem streams, both in terms of community composition as determined taxonomically and as functional traits. These results indicate that headwater streams may be affected differently than mainstem streams by anthropogenic activity and as such, management strategies and restorations may need to be specifically tailored to address the relative influences of local and regional processes at varying points within a stream network.
Ph. D.
34

O'Connor, Rory Charles. "Small Mammals Matter? Linking Plant Invasion, Biotic Resistance, and Climate Change in Post-Fire Plant Communities." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5756.

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The introduction and establishment of exotic species can profoundly alter ecosystems. Two exotic species drastically changing the landscape of deserts in western North America are Bromus tectorum L. and Bromus rubens L. Through the buildup of biomass and slow decomposition rates in deserts these two exotic annual grasses can alter fire regimes that change the plant and animal community dynamics in the ecosystems. To better understand the ecological mechanisms that could restrict or alter the patterns of invasive plant establishment we established a replicated full factorial experiment in the Great Basin and Mojave Desert. The combinations of factors being manipulated are burned or intact plant communities, and presence or exclusion of small mammals. Generally invasive species establishment is thought to be a result of competitive superiority or lack of natural enemies, but if that is the case then why do not all invasive species establish and become highly abundant in their new ecosystems? To understand why some invasive species establish and others do not we monitored three dominant exotic species from the Great Basin and the Mojave Desert, B. tectorum, Halogeton glomeratus (M. Bieb.) C.A. Mey., and B. rubens. We observed that the presence of small mammals create a biotic resistance to B. tectorum, H. glomeratus, and B. rubens. This pattern was observed in both intact and burned plant communities; however, it was most prevalent in the burned plant communities. The strength of the biotic resistance on these invasive species varied between species and the years sampled. In deserts both plant and small mammal communities are tightly tied to precipitation. We wanted to understand how invasive species establishment is affected by small mammal presence after a fire disturbance, and manipulating total precipitation. Total precipitation was manipulated through three different treatments: 1) drought or 30% reduction of ambient precipitation; 2) ambient precipitation; 3) water addition or an increase of 30% ambient precipitation. We focused on B. rubens establishment in the Mojave Desert as our model organism by monitoring it beneath rain manipulation shelters nested in burned/intact and small mammal presence/absence full factorial plots. What we observed was that again small mammals created a biotic resistance on the density of B. rubens regardless of the burn or precipitation treatments. This biotic resistance also translated into decreasing B. rubens biomass and seed density. Under the drought and ambient precipitation treatments we found that small mammals kept the density and biomass equal but under increased precipitation the efficacy of biotic resistance on B. rubens density and biomass was lessened by the availability of the added water.
35

Tungittiplakorn, Waranoot. "Highland cash crop development and biodiversity conservation : the Hmong in Northern Thailand." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0027/NQ36650.pdf.

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36

Clark, O. Grant (Osborne Grant). "Characterization of cyborged ecosystems." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36567.

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In this thesis, a philosophy and lexicon for the engineering of biosystems are established. The focus is on a specific class of biosystems ( ecocyborgs) created by combining ecosystems and technological Components. This work is part of the EcoCyborg Project, a highly interdisciplinary research program which concerns the development of a general theory for biosystems engineering, with an emphasis on system autonomy as a design goal. In the short term, the objective is to develop computational models and simulations for use in the study of ecocyborgs as representative instances of substantially autonomous biosystems. Accordingly, in this thesis an explicit conceptual basis is established for the EcoCyborg Project, as well as for biosystems engineering in general.
First, in the body of the thesis, a biosystem is defined as a coherent assemblage of entities that is alive to some degree as a whole. The sole criterion for life is considered to be comportment that is somewhat autopoietic , whereby local interactions among the components combine to Continually renew the overall system. Next, concepts related to autonomy, or the formulation and pursuit of proprietary goals, are elaborated. The degree of autonomy of a system is seen to depend on its consciousness, or ability to reason using a model of itself. Hence, a substantially autonomous system requires an ensemble of information storage and processing devices (mind) of the type and sophistication (intelligence ) appropriate for this. The approach that is taken here to the creation of ecocyborgs with such minds is described, and a specific mental architecture is delineated, comprising functionally semidifferentiated, intermediate-scale components arranged according to a semihierarchical control organization. Finally, the characterization of such systems is scrutinized as an epistemic process in which knowledge is generated by an observer, but in which only a limited degree of objectivity is possible. A paradigm appropriate to the engineering of ecocyborgs is defined as an illustration, and associated archetypal concepts and descriptive procedures (such as measures) are given that are useful in this context. Such tools are required by significantly autonomous ecocyborgs because they must characterize themselves. They are also necessary to observers with scientific and engineering agendas.
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Parrott, Lael. "The EcoCyborg project : a model of an artificial ecosystem." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23696.

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A model of an artificial ecosystem has been formulated for use as a tool to investigate the dynamics of autonomous biosystems. The model is part of a composite model of an EcoCyborg which consists of an ecosystem and its control system, both of which are contained inside a cylindrical space station. The objectives of this project were to design a model of the ecosystem, and to develop a method for its creation and implementation within the overall framework of the EcoCyborg Project.
The modeling approach that has been adopted for the ecosystem model is individual-based and object-oriented. This enables the inclusion of a description of the abiotic environment, as well as of the organisms that inhabit it. A total of 1000 species representing a range of taxonomic groups may be modeled. Individuals in each species are described by their behaviours and phenotypic traits.
The ecosystem model will be linked with the other components of the EcoCyborg model in a multi-process simulation under OS/2 Warp. The behaviour of the system will be studied to elucidate preliminary guidelines for the design, maintenance and control of complex systems.
38

DeWire, Deana Ann. "Assessment and potential adjustments to the snow-related algorithms in BIOME-BGC, v. 4.2." CONNECT TO THIS TITLE ONLINE, 2008. http://etd.lib.umt.edu/theses/available/etd-01262009-124733/.

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39

Unger, Irene M. "A multi-dimensional investigation into the effects of flooding on the physical, chemical and biotic properties of riparian soils." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5582.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed June 17, 2009). Vita. Includes bibliographical references.
40

Manes, Gianluca. "The near-bottom chlorophyll A̲ maximum in Onslow Bay : effects of wave events on benthic microalgae resuspension /." Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/manesg/gianlucamanes.pdf.

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41

Kamffer, Dewald. "Community-level effects of fragmentation of the afromontane grassland in the escarpment region of Mpumalanga, South Africa." Connect to this title online, 2004. http://upetd.up.ac.za/thesis/available/etd-11242004-104932.

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42

Stamp, Jennifer D. "Associations between stream macroinvertebrate communities and surface substrate size distributions." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1103232587.

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43

McLeod, Rebecca Jane, and n/a. "The roles of key species and functional guilds in facilitating fluxes of organic matter across habitat boundaries in Fiordland." University of Otago. Department of Marine Science, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080505.131451.

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The secondary productivity of communities is inherently influenced by the availability and quality of food resources. Movement of organic matter (OM) across landscapes can connect adjacent systems by providing subsidies of carbon and nutrients, implying that alterations of environments from their natural state may affect the productivity of neighboring food webs. The intact terrestrial and marine environments of Fiordland provide a setting to study linkages between the land and the sea. The first general objective of this study was to determine if large but nutritionally poor (nitrogen-poor, carbon-rich) inputs of forest litter support marine secondary production, and to identify pathways for incorporation of this material into upper trophic levels. Pools of marine and terrestrial OM had distinct values of [delta]�⁵N, [delta]��C and [delta]�⁴S, providing high power to estimate the relative use of these sources by the food webs of the fjord-head deltas. Deposit feeding invertebrates (e.g. Echinocardium cordatum, Pectinaria australis) directly assimilated plant detritus. Heterotrophic bacteria on the surface of the sediment assimilated forest litter and provided a potential food source for invertebrates. Chemoautotrophic bacteria fix CO₂ that originates from decomposing forest litter, thus providing an indirect pathway for incorporation of forest litter into the food webs. In the deep basins the strength of the flux of uptake by chemoautotrophic bacteria through the benthic food web into the upper trophic levels was demonstrated by hagfish (Eptatretus cirrhatus) obtaining 38-51% of their nutrition from these bacteria. The ability of a community to utilize discrete sources of OM relies on the presence of specific functional feeding guilds. Marine algae provide a highly nutritive (nitrogen-rich) food source for the fjord communities and fluxes of algae into food webs are facilitated by grazing invertebrates and filter feeders. The second general objective of this study was to determine how the effective loss of filter feeders from inner Doubtful Sound would alter the flux of marine-derived OM to the food webs of the delta communities. The low salinity environment imposed by the hydroelectric power station in Doubtful Sound caused a large reduction in the abundance of the infaunal bivalves Austrovenus stutchburyi and Paphies australis from delta habitats. Clams could tolerate periods of freshwater exposure of [less than or equal to]20 days duration, but the constant freshwater conditions in Doubtful Sound decreased survivorship. In 2004/05 the biomass of these species in inner Doubtful Sound (7.28 tonnes) was 29 times smaller than in Bradshaw Sound (214.12 tonnes). The associated loss of biodeposits (~91 tonnes(DW) yr⁻� in Bradshaw Sound vs. 1 tonne(DW) yr⁻� in inner Doubtful Sound) may have also altered the flux of nutritive OM to the infaunal community. The river delta communities in inner Doubtful Sound appear to have a higher reliance on forest litter than those in Bradshaw Sound, which is apparent as low values of [delta]�⁵N and [delta]��C for estuarine fish (Notolabrus celidotus, Hemerocoetes monopterygius), which act as integrators of the benthic community. This study demonstrates important linkages between terrestrial and coastal marine ecosystems and highlights the role of functional diversity in facilitating fluxes of organic material through food webs.
44

Collis, John Trifon. "The sustainable development of Benoa Bay an ecosystem approach /." Waterloo, Ont. : University Consortium of the Environment, 1993. http://books.google.com/books?id=qUkoAAAAMAAJ.

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45

BROWN, JOEL STEVEN. "COEXISTENCE ON A RESOURCE WHOSE ABUNDANCE VARIES: A TEST WITH DESERT RODENTS (PREDATION RISK, FORAGING BEHAVIOR, COMMUNITY STRUCTURE)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188178.

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Variability is a universal, but poorly understood, property of ecosystems. A common belief that environmental variability has a destabilizing effect on species coexistence is being challenged by a growing body of theoretical research; variance in resource abundances may actually promote species coexistence. Here, I develop three models which give ecological conditions for coexistence on a single resource. The first considers a resource whose abundance varies seasonally. Coexistence may be possible if there is a tradeoff between foraging efficiency and maintenance efficiency. The first species can forage profitably on low resource abundances while the second uses dormancy to "travel" inexpensively between temporal periods of high resource abundance. The second considers a resource whose abundance varies spatially. Coexistence may be possible if there is a tradeoff between foraging efficiency and the cost of travel. The first species forages patches to a lower giving up density while the second can inexpensively travel between patches with high resource abundances. The third considers an environment in which foraging costs change seasonally. Coexistence may be possible if there is a tradeoff between the cost of foraging during different seasons. The species which is the most efficient forager changes seasonally. Because coexisting species often exhibit little apparent diet or habitat separation, seed-eating desert rodents offer a promising community for testing the three aforementioned mechanisms of coexistence. In a community of four granivorous rodents, (Perognathus amplus, Dipodomys merriami, Spermophilus tereticaudus, and Ammospermophilus harrisii), I used artificial seed patches to measure species and habitat specific foraging efficiencies. The third mechanism of coexistence appears to explain the presence of P. amplus, D. merriami, and S. tereticaudus in the community. Each enjoys a season during which it is the most efficient forager. The second mechanism of coexistence explains the presence of A. harrisii in the community. This species preferred to forage a large number of widely spaced patches to a high giving up density rather than foraging a few patches to a low giving up density.
46

MacFarland, Katherine Dana. "Valuation of Ecosystem Services in Trinity County, California." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10830.

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xvii, 141 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
This study considers the role of the forest ecosystem in Trinity County, California's economy. I seek to better understand the natural resource-based economy of a national forest-proximate community by creating a framework that describes the resource flows into and out of Trinity County and guides ecosystem services valuation within the County. Thus, this study examines the monetary benefits that ecosystem functions create through delivery of goods such as water, energy, and timber and also estimates the value of services, such as recreation, carbon sequestration, and amenity value. Finally, this study examines how money is spent to maintain the ecosystem functions that create these goods and services, such as who pays to maintain water collection and filtration capacity or habitat. Ultimately, this study offers insight into opportunities and limitations for ecosystem services valuation at the county level, and considerations for future attempts to value ecosystem services.
Committee in Charge: Cassandra Moseley, Chair; John Bliss; Trudy Cameron
47

Bissett, Spencer N. "CONSEQUENCES OF VINE INFESTATION: LINKING ABIOTIC INFLUENCES AND BIOTIC INTERACTIONS TO SUCCESSIONAL AND STRUCTURAL CHANGES IN COASTAL COMMUNITIES." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/4018.

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Located at the interfaces of terrestrial and marine environments, coastal habitats are inherently vulnerable to the effects of global change. Barrier island systems in particular serve not only as protective buffers against storm events, but also as sentinel ecosystems for observation of the impacts of sea level rise, and of increasing storm frequency and intensity. In the mid-Atlantic region, shrub thickets of Morella species compose the dominant forest community. The often monospecific nature of these plant community assemblages is advantageous to ecological studies and cross-scale applications; the relatively low diversity facilitates transitions between scales. My objective was to investigate the distribution and community roles of lianas in mid-Atlantic barrier island forest communities. I quantified environmental variables at two barrier habitats with differing site management histories and corresponding topography, and found that abiotic factors affected distributions of woody species, which subsequently affected vine species distributions. Some association of prevalent vine species with the common woody plants Prunus serotina and Morella cerifera was observed, though neither vines nor woody species demonstrated significant species-specific phytosociological associations. Vines demonstrated a long-lasting effect of arresting or delaying succession, and are potentially responsible for the lack of redevelopment of mature maritime forest at these sites. At Hog Island, Virginia, remotely-sensed data were utilized to determine the three-dimensional structural effects of vine infiltration in woody canopies. Vines were found to reduce canopy height and depth, and increase density, short-term diversity, and light-intercepting biomass. Significant vine infiltration can accelerate senescence of shrub thickets, but often results in persistent tangled masses of vegetation which reduce recruitment of later-successional species. These effects may represent long-term, lasting impacts of vine establishment and expansion in these habitats, affecting community succession towards diverse and stable maritime forest, and significantly altering resource dynamics in these sensitive ecosystems.
48

Christian, James Robert. "Modelling studies on a marine plankton community : biological, temporal and spatial structure." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27859.

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The SELECT model (Frost, 1982) is analyzed, criticized, and extended to embrace new information about the feeding behaviour of copepods and the structure of the planktonic food web in a series of alternative models. Diel variations in photosynthesis, grazing, and predation on copepods (temporal structure) and patchiness of zooplankton and their predators (spatial structure) are modelled in other variants. It is observed that the vertical, temporal, and (horizontal) spatial structure of the planktonic ecosystem are important components of ecosystem models that can not safely be ignored. It is further observed that a convincing mechanism for the termination of diatom blooms is lacking and should be a subject of intensive research, and that the status of chlorophyll-containing microflagellates as phototrophs is questionable and should be reconsidered.
Science, Faculty of
Zoology, Department of
Graduate
49

Shinneman, Douglas J. "Determining restoration needs for piñon-juniper woodlands and adjacent ecosystems on the Uncompahgre Plateau, western Colorado." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1212779251&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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50

Cordova, Vicente D. "Evaluation of simulation-derived data for estimating biogeochemical processes in a secondary forest biome in southern Indiana." Virtual Press, 2003. http://liblink.bsu.edu/uhtbin/catkey/1265099.

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