Surface coal-mining is a source of selenium (Se) contamination in streams of the Appalachian coalfields. Selenium dynamics in aquatic systems are complex and largely controlled by site-specific factors, but have been understudied in Appalachian headwater streams. In this study, we evaluated the degree and dynamics of Se enrichment and bioaccumulation in headwater streams influenced by coal-mining. Based on Se concentrations in macroinvertebrates collected from 23 headwater streams, nine sites were selected for further study: three reference streams with no history of coal-mining, and six streams influenced by coal mining. Mining-influenced streams were further separated into high-Se and low-Sestreams based on macroinvertebrate tissue Se concentrations. Water-column, sediment, biofilm, leaf detritus, and prey and predator macroinvertebrates were collected and analyzed for Se concentration during two sample periods, Sept. - Oct. 2015 and Feb.-March 2016. Selenium concentrations in all media were found to be elevated in mining-influenced over reference streams and in high-Se over low-Se streams. Selenium dynamics, enrichment in particulate media (sediment, biofilm and leaf detritus) and trophic transfer of Se to prey from particulate media and to predators from prey, did not exhibit major differences among streams of differing Se levels. Water column Se concentrations were predicative of Se concentrations in macroinvertebrate tissues. Findings from this study indicate headwater streams influenced by coal-mining are capable of a high degree of Se bioaccumulation in macroinvertebrate populations. / Master of Science / Surface coal-mining is a source of selenium (Se) contamination in streams of the Appalachian coalfields. Selenium dynamics in aquatic systems are complex and largely controlled by sitespecific factors, but have been understudied in Appalachian headwater streams. In this study, we evaluated the degree and dynamics of Se enrichment and bioaccumulation in headwater streams influenced by coal-mining. Based on Se concentrations in macroinvertebrates collected from 23 headwater streams, nine sites were selected for further study: three reference streams with no history of coal-mining, and six streams influenced by coal mining. Mining-influenced streams were further separated into “high-Se” and “low-Se” streams based on macroinvertebrate tissue Se concentrations. Water-column, sediment, biofilm, leaf detritus, and prey and predator macroinvertebrates were collected and analyzed for Se concentration during two sample periods, Sept. - Oct. 2015 and Feb.- March 2016. Selenium concentrations in all media were found to be elevated in mining-influenced over reference streams and in high-Se over low-Se streams. Selenium dynamics, enrichment in particulate media (sediment, biofilm and leaf detritus) and trophic transfer of Se to prey from particulate media and to predators from prey, did not exhibit major differences among streams of differing Se levels. Water column Se concentrations were predicative of Se concentrations in macroinvertebrate tissues. Findings from this study indicate headwater streams influenced by coal-mining are capable of a high degree of Se bioaccumulation in macroinvertebrate populations.

Sea levels are rising due to global warming, which is induced by anthropogenic activities increasing the concentration of greenhouse gas emissions in the atmosphere. Sea level rise is already causing a severe impact on coastal wetland ecosystems, and the influence will intensify in the future. One of these coastal ecosystems is mangrove forests, which grow in intertidal zones and are therefore subject to tidal water level fluctuations. Mangrove forests provide essential ecosystem services to coastal environments and societies, and their exposure to sea level rise is a significant concern. The consequences of sea level rise, such as inundation, erosion, and lack of accommodation space, will increase the extent of mangrove loss. It is therefore essential to fully understand how sea level rise is influencing mangrove ecosystems in different geographical locations, and how likely they are to adapt and survive under different scenarios. This research used a systematic literature review to assess scientific articles from various regions, investigating the current knowledge regarding the impacts of sea level rise on mangrove ecosystems. The information was collected from 40 articles, which covered studies from five continents. The findings affirmed that the negative effects of sea level rise on mangrove ecosystems are recognized globally. It is well understood that, by the second half of the century, mangrove ecosystems will face severe issues if the highest IPCC emissions scenarios are reached. It is further well acknowledged that mangrove forests provide important ecosystem services, for example, by protecting the coastal areas under extreme weather events, benefiting natural resources sectors and recreation, and further delivering crucial climate change mitigation services by sequestering and storing blue carbon. It is therefore essential to recognize mangroves as an important ecosystem and treat them adequately. Mangrove ecosystems’ resilience under sea level rise was commonly found to be dependent on their hydro-geomorphological environment. Under sea level rise, one of the most significant factors contributing to mangroves’ survival and resilience was the availability of accommodation space, which they need to be able to migrate inland as the sea levels rise, along with their ability to adapt to changes in sediment elevation rates. To secure the needed accommodation space and to further help mangrove ecosystems grow and live under the sea level rise scenarios, adequate climate change adaptation strategies must be planned and adopted. These strategies include prioritizing high-priority areas for vegetation growth, estimating areal habitat suitability, strengthening the understanding of land use impacts on mangrove forests, and implementing hybrid solutions for coastal protection. Although the issue of sea level rise influencing mangrove ecosystems is well recognized globally, there was an observed lack of adequate research. Further research and improved understanding are needed to ensure that preparation for all emission scenarios, even for the worst ones, is possible and that climate change adaptation strategies will be well implemented.

No description available.

Phytoplankton are single celled organisms capable of phytosynthesis, and are present in all the major oceans and lakes in the world. Phytoplankton contribute to 50% of the total primary production on Earth, and are the dominating primary producer in most aquatic ecosystems. This thesis is based on the 1D deterministic model by Jäger et. al. (2010) which models phytoplankton dynamics in freshwater lakes, where phytoplankton growth is limited by the availability of light and phosphorus. The original model is here extended to two dimensions to include a horizontal dimension as well as a vertical dimension, in order to simulate phytoplankton dynamics under varying lake bottom topographies. The model was solved numerically using a grid transform and a finite volume method in MATLAB. Using the same parameter settings as the 1D case studied by Jäger et. al. (2010), an initial study of plankton dynamics was done by varying the horizontal and vertical diffusion coefficients independently.

Im Kontext der Energiewende durchlebt die Energiewirtschaft in Deutschland gegenwärtig einen tiefgreifenden Strukturwandel. Der Trend zur Fragmentierung und Dezentralisierung von Marktteilnehmern wird sich in den nächsten Jahren fortsetzen und weiter beschleunigen. Die Komplexität des Energiesystems wird weiter steigen. Gleichzeitig ergeben sich im Zuge dieser Entwicklung für energiewirtschaftliche Akteure (Erzeuger, Verbraucher, Netze, Energiemärkte und IuK-Technologien) vielfältige wirtschaftliche Herausforderungen und Entwicklungsperspektiven. Das Konzept "Ecosystems" eröffnet innovative Perspektiven auf die zu erwartenden energiewirtschaftlichen Entwicklungen. Es strukturiert das komplexe Zusammenspiel der einzelnen Akteure und Teilsysteme mit der Zielsetzung, das Gesamtsystem sicherer, effizienter und umweltverträglicher zu gestalten. Im Fokus der Energy EcoSystems Conference 2013 stehen hierbei vier Betrachtungsebenen – die physikalische Ebene, die IKT-Ebene, die ökonomische Ebene und die soziokulturelle Ebene – sowie deren ebenenübergreifenden Wechselwirkungen. Mit den Sessions "Energy EcoSystems heute und morgen", "Technische Informationsbedarfe im Energy EcoSystem", "Vermarktung und Verbrauch im Energy EcoSystem\\\", \\\"Erneuerbare Energien im Energy EcoSystem", "Innovationen im Energy EcoSystem" und "Quo vadis Energy EcoSystems?" liegen die Schwerpunkte der Konferenz in der Systemintegration von Erneuerbare-Energie-Anlagen, der Flexibilisierung des Verbrauchs auf physikalischer und ökonomischer Ebene, der Standardisierung von Datenformaten und Kommunikationsprotokollen, der Umsetzung steigender informationstechnischer Anforderungen sowie in Ansätzen zur Optimierung des Gesamtsystems. Dieser Tagungsband beinhaltet die wissenschaftlichen Beiträge der Scientific Tracks sowie ausgewählte Präsentationen der Industrie Tracks der Konferenz. Dr. Gerd Arnold, Dr. Stefan Kühne, Johannes Schmidt und Dr. Andrej Werner – das Konferenzkomitee – danken den Teilnehmern für die hochwertigen wissenschaftlichen sowie praxisrelevanten Beiträge und Diskussionen. Weiterhin möchte sich das Konferenzkomitee bei den Projektförderern Sächsische Aufbaubank (SAB), Bundesministerium für Bildung und Forschung (BMBF) sowie Bundesministerium für Wirtschaft und Technologie (BMWi) bedanken, welche durch unterschiedliche Förderprogramme die anstehenden Herausforderungen in der Energiewirtschaft und die Entwicklung hin zu einer erfolgreichen und exportierbaren Energiewende unterstützen. Besonderer Dank gilt den Sponsoren perdata Gesellschaft für Informationsverarbeitung mbH und GETEC net AG, durch deren Unterstützung viele Teilnehmer ihre Ergebnisse und Erkenntnisse auf der EcoSystems Conference 2013 vorstellen konnten. Das Konferenzkomitee dankt auch den Mitgliedern des Organisationskomitees –- Axel Hummel, Stefan Sprick und Robert Wehlitz –- für ihr persönliches Engagement und ihre tatkräftige operative Unterstützung. Weitere Informationen zur Energy EcoSystems Conference 2013 sowie die Folien der ReferentInnen finden Sie unter http://ees2013.infai.org. Alle Informationen zur nächsten Energy EcoSystems Conference werden unter http://ees.infai.org bekannt gegeben.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-05-18T12:18:30Z No. of bitstreams: 1 taisanascimentodesouza.pdf: 1060861 bytes, checksum: 18f51d80da3fa7e5ec8e564e3b85452a (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:03:47Z (GMT) No. of bitstreams: 1 taisanascimentodesouza.pdf: 1060861 bytes, checksum: 18f51d80da3fa7e5ec8e564e3b85452a (MD5) / Made available in DSpace on 2018-09-03T16:03:47Z (GMT). No. of bitstreams: 1 taisanascimentodesouza.pdf: 1060861 bytes, checksum: 18f51d80da3fa7e5ec8e564e3b85452a (MD5) Previous issue date: 2018-02-19 / A dominância de espécies exóticas é uma das principais características de florestas secundárias e dos chamados Novel Ecosystems. Apesar de estudos avaliarem os padrões destas comunidades em florestas tropicais úmidas, pouco ainda é conhecido sobre esses padrões em florestas tropicais. A espécie Pinus elliotti possui alto potencial invasor em florestas neotropicais, sendo encontrada em florestas secundárias da Zona da Mata Mineira. O objetivo deste estudo foi analisar a dinâmica (5 anos) da comunidade arbórea de uma floresta secundária urbana dominada por P. elliotti. As mudanças florísticas e estruturais foram analisadas a partir de comparações entre dois inventários realizados em parcelas permanentes (15 parcelas de 20 x 20 m alocadas aleatoriamente na floresta) nos anos de 2011 e 2016. Todos os indivíduos arbóreos com DAP ≥ 5 cm foram amostrados, mensurados, e calculados os parâmetros estruturais, fitossociológicos e diversidade de espécies. Foram calculadas as taxas de dinâmica (recrutamento, mortalidade, ganho e perda de área basal), sendo amostrados 943 indivíduos, 168 recrutas e 151 mortos. A comunidade apresentou forte dominância específica, com grande concentração dos valores de importância (VI) distribuídos nas sete primeiras espécies (Pinus elliottii; Miconia artemisiana; Mimosa artemisiana; Myrcia splendens, Pleroma mutabilis, Piptadenia gonoacantha e Miconia urophyla), que, juntas, somaram 52,2% do VI total. Entre as duas medições, a taxa de mortalidade, de 3,50%.ano-1, foi pouco inferior a de recrutamento, de 3,85%.ano-1. A taxa de ganho em área basal de 5,98%.ano-1, superou a de perda, de 2,90%.ano-1. Apesar da presença das espécies invasoras e da dinâmica acelerada, não foram observadas grandes alterações estruturais no fragmento, com tendência da comunidade de se manter floristicamente estável, a curto e médio prazo, em função da resistência das principais populações. / The dominance of exotic species is a major feature of secondary forests and socalled Novel Ecosystems. Although studies assess the patterns of these communities in tropical rainforests, little is known about these patterns in tropical forests. The species Pinus elliotti have high invasive potential in neotropical forests, and are found in secondary forests of the Zona da Mata at Minas Gerais State. The aim of this study was to analyze the dynamics (5 years) of the tree community of an urban secondary forest dominated by P. elliotti. Floristic and structural changes were analyzed from comparisons between two inventories in permanent plots (15 plots of 20 x 20 m randomly allocated in the forest) in the years 2011 and 2016. All tree individuals with DBH ≥ 5 cm were sampled, measured, and calculated the structural, phytosociological and species diversity parameters. Dynamic rates (recruitment, mortality, gain and loss of basal area) were calculated, being sampled 943 individuals, 168 recruits and 151 deaths. The community showed a strong specific dominance, with a high concentration of importance values (VI) distributed in the first seven species (Pinus elliottii; Miconia artemisiana; Mimosa artemisiana; Myrcia splendens; Pleroma mutabilis; Piptadenia gonoacantha; Miconia urophyla), which accounted for 52.2% of the total VI. Between the two measurements, the mortality rate of 3.50% .year-1 was slightly lower than that of recruitment of 3.85% .year-1. The rate of gain in basal area of 5.98% .year-1 exceeded that of loss of 2.90% .year-1. Despite the presence of invasive species and accelerated dynamics, there were no major structural changes in the fragment, believing that the community is able to remain floristically stable in the short and medium term, due to the resistance of the main populations.

Im Kontext der Energiewende durchlebt die Energiewirtschaft in Deutschland gegenwärtig einen tiefgreifenden Strukturwandel. Der Trend zur Fragmentierung und Dezentralisierung von Marktteilnehmern wird sich in den nächsten Jahren fortsetzen und weiter beschleunigen. Die Komplexität des Energiesystems wird weiter steigen. Gleichzeitig ergeben sich im Zuge dieser Entwicklung für energiewirtschaftliche Akteure (Erzeuger, Verbraucher, Netze, Energiemärkte und IuK-Technologien) vielfältige wirtschaftliche Herausforderungen und Entwicklungsperspektiven. Das Konzept 'Ecosystems' eröffnet innovative Perspektiven auf die zu erwartenden energiewirtschaftlichen Entwicklungen. Es strukturiert das komplexe Zusammenspiel der einzelnen Akteure und Teilsysteme mit der Zielsetzung, das Gesamtsystem sicherer, effizienter und umweltverträglicher zu gestalten. Im Fokus der Energy EcoSystems Conference 2013 stehen hierbei vier Betrachtungsebenen – die physikalische Ebene, die IKT-Ebene, die ökonomische Ebene und die soziokulturelle Ebene – sowie deren ebenenübergreifenden Wechselwirkungen. Mit den Sessions 'Energy EcoSystems heute und morgen', 'Technische Informationsbedarfe im Energy EcoSystem', 'Vermarktung und Verbrauch im Energy EcoSystem\\\', \\\'Erneuerbare Energien im Energy EcoSystem', 'Innovationen im Energy EcoSystem' und 'Quo vadis Energy EcoSystems?' liegen die Schwerpunkte der Konferenz in der Systemintegration von Erneuerbare-Energie-Anlagen, der Flexibilisierung des Verbrauchs auf physikalischer und ökonomischer Ebene, der Standardisierung von Datenformaten und Kommunikationsprotokollen, der Umsetzung steigender informationstechnischer Anforderungen sowie in Ansätzen zur Optimierung des Gesamtsystems. Dieser Tagungsband beinhaltet die wissenschaftlichen Beiträge der Scientific Tracks sowie ausgewählte Präsentationen der Industrie Tracks der Konferenz. Dr. Gerd Arnold, Dr. Stefan Kühne, Johannes Schmidt und Dr. Andrej Werner – das Konferenzkomitee – danken den Teilnehmern für die hochwertigen wissenschaftlichen sowie praxisrelevanten Beiträge und Diskussionen. Weiterhin möchte sich das Konferenzkomitee bei den Projektförderern Sächsische Aufbaubank (SAB), Bundesministerium für Bildung und Forschung (BMBF) sowie Bundesministerium für Wirtschaft und Technologie (BMWi) bedanken, welche durch unterschiedliche Förderprogramme die anstehenden Herausforderungen in der Energiewirtschaft und die Entwicklung hin zu einer erfolgreichen und exportierbaren Energiewende unterstützen. Besonderer Dank gilt den Sponsoren perdata Gesellschaft für Informationsverarbeitung mbH und GETEC net AG, durch deren Unterstützung viele Teilnehmer ihre Ergebnisse und Erkenntnisse auf der EcoSystems Conference 2013 vorstellen konnten. Das Konferenzkomitee dankt auch den Mitgliedern des Organisationskomitees –- Axel Hummel, Stefan Sprick und Robert Wehlitz –- für ihr persönliches Engagement und ihre tatkräftige operative Unterstützung. Weitere Informationen zur Energy EcoSystems Conference 2013 sowie die Folien der ReferentInnen finden Sie unter http://ees2013.infai.org. Alle Informationen zur nächsten Energy EcoSystems Conference werden unter http://ees.infai.org bekannt gegeben.:Sabine Wieland: Informationsarchitektur im Smart Meter Umfeld unter Berücksichtigung der aktuellen Netzsituation; Stefan Saatmann und Sandra Maeding: Energiewende und Regulierung — Wie werden Sonne und Wind im Stromnetz integriert und reguliert; Stefan Sprick, Tino Ryll, Kerstin Wurdinger, Andrej Werner, Bogdan Franczyk, Marcus Grieger, Jan Pfeifer und Robert Wehlitz: Regenerative Energien Management-Cockpit (REMC): Informationstransparenz in Energiewertschöpfungsnetzwerken; Hendrik Kondziella und Thomas Bruckner: Modellbasierte Investitionsentscheidungen in dezentralen Energiesystemen; Diana Böttger, Philipp Hanemann und Thomas Bruckner: Wirtschaftlichkeitsanalyse eines virtuellen Kraftwerks in Delitzsch innerhalb des EU-Projektes VIS NOVA; Robert Wehlitz, Andrej Werner, Marcus Grieger, Jan Pfeifer, Bogdan Franczyk, Stefan Sprick und Tino Ryll: Smart Meter Installation Management — Prototypgestützte Digitalisierung von Smart Meter Montageprozessen; Marcus Grieger, Andrej Werner, Robert Wehlitz, Jan Pfeifer, Stefan Sprick, Tino Ryll und Bogdan Franczyk: How ICT Could Accelerate the Smart Meter Installation Process — An Assessment of Rollout Experiences; Heiko Mevert: Smart-Metering: Theorie und Praxis; Hartmut Entrup: Anforderungen an IT-Systeme im Zuge der Einführung intelligenter Messsysteme; Martin Winter: Dynamische Anbindung dezentraler Energieanlagen mit IEC 61850; Olaf Krietsch: Verbindungen zwischen SRL-Anbieter und Übertragungsnetzbetreibern gemäß 'Mindestanforderungen an die Informationstechnik für die Erbringung von Sekundärregelleistung'; Sabrina Schlammerl: Innovative Services in der Windenergie: Der Einsatz von RDS-PP und dessen Bedeutung für das Life Cycle Management; Christian Schweitzer: Lebenslaufakte: Ganzheitlicher Ansatz für einen gesicherten Anlagenbetrieb; Rene Baumann: Vermarktungskonzepte für dezentrale Anlagen; Heike Diebler und Lutz Maicher: Energiekosten sparen durch Energetische Transparenz in der verarbeitenden Industrie – ein Praxisbericht; Philipp Guttenberg, Heinrich Hördegen: Betriebsoptimierung für Energiespeicher durch Energieflussmodellierung; Winfried Damm: Regenerative Energieversorgung einer Großstadt, Stadtwerke Leipzig; Uwe Härling: Herausforderungen der Energiewende für das Verteilnetz der MITNETZ STROM; Matthias Müller-Mienack: Integration Erneuerbarer Energien — Notwendige Werkzeuge für den ÜNB; Martin Jarosch-Mitko: Eine Integrationsplattform für Erneuerbare-Energie-Anlagen; Stephan Witt: Energiesysteme als Business Ecosystems – Bedeutung für die strategische Planung und das Innovationsmanagement am Beispiel dezentraler Netzsteuerungsparadigmen; Thomas Bruckner: Die Energiewende in Deutschland – Technologische Lösungen und energiewirtschaftliche Herausforderungen

Master of Landscape Architecture / Department of Landscape Architecture/Regional and Community Planning / Timothy D. Keane / The International Ecotourism Society (TIES), the world’s first ecotourism organization, coined what has become the most succinct definition of ecotourism: “Responsible travel to natural areas that conserves the environment and improves the wellbeing of local people (Honey 2008, p. 6).” Ecolodges are accommodation facilities within ecotourism destinations which must satisfy specific principles, while reflecting the definition of ecotourism. Ecolodge principles include water conservation, preservation of flora and fauna, design to create a small footprint, and interpretive programs to educate both employees and tourists about the surrounding natural and cultural environments, to name just a few. (Mehta 2002, p. 5) Tropical locations, where ecolodges are often found, are comprised of unique ecosystems. With tropical locales, there are specific considerations that could determine the success of a proposed ecolodge development. As a designer, one must understand the biophysical characteristics on site, to inform design decisions of the ecolodge development. In addition, a designer must understand how the indigenous populations utilize the site culturally, physically and spiritually to fully understand the importance of the ecolodge development. (Mehta 2002, p. 12) When proper analysis of cultural and biophysical factors is completed, an ecolodge development is able to conform to the ecotourism definition and satisfy ecolodge principles. Within this manual, a hierarchical list of design principles, guidelines and criteria are communicated to achieve an overall design goal called fitness design. A “fit” design is intended to achieve sustainability and quality of life for the environment and the communities that have daily interaction with the development. As readers navigate through the document, they will be exposed to various considerations of a tropical ecolodge development. The intent of the manual is to provide a structural framework to guide an ecolodge design process.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Designing a mechanistic model that can give rise to realistic architecture of ecological networks is central to the understanding of how species assemble and function in ecosystems. As species are constantly adjusting their diets in an antagonistic network, we here incorporate this adaptive behaviour of diet choice into a bipartite network model, with the effect of antagonistic interactions between species depicted by Holling’s type II functional response. Predictions of this model fit extremely well with the observed levels of nestedness, modularity and node-degree distributions for 61 real host-parasitoid and plant-herbivore networks. We further examined two specific scenarios of our model (species with identical [neutral] demographic parameters and interactions with identical [neutral] benefit in the network) and found that the demography-neutral scenario overestimated observed modularity, whilst the benefit-neutral scenario over-estimate observed nestedness. Relationships between nestedness, modularity and connectance were found strong. Moreover, in contrast to the common belief of the high modularity in antagonistic networks, most real networks (> 80%) are significantly nested, whilst nearly 40% of the real networks are surprisingly less compartmentalized than random networks generated from null models. Regardless of the controversy on whether antagonistic networks are nested or compartmentalized, the proposed model captured the essence of the dynamic nature of structural emergence in antagonistic networks. Due to its predictive power, this model was further used to investigate robustness in antagonistic networks. Predictions showed that the robustness of a network is determined by many factors, such as connectance, resource degree distribution, resource-consumer ratio, diversity, nestedness and compartmentalisation. Surprisingly, the manner of network response to species loss was independent of the sequence followed while removing species from a network. Variations were only noticed in the intensity of the effect resulting from the removals. In addition, we also showed that species extinction procedures which ignore the interaction switch underestimate the effect of any loss of species in these networks. We must therefore value our knowledge of possible adaptive processes in the ecosystem as they may be important for resolving the diversity-stability debate. / AFRIKAANSE OPSOMMING: Die ontwerp van ’n meganistiese model wat aanleiding kan gee tot realistiese argitektuur van ekologiese netwerke is sentraal tot die begrip van hoe spesies bymekaar kom en funksioneer in ekosisteme. Soos spesies voortdurend hul dieet aanpas in ’n antagonistiese netwerk, het ons hierdie aanpasbare gedrag van dieet keuse in ’n bipartiet netwerk model ingewerk, met die effek van antagonistiese interaksies tussen spesies wat uitgebeeld word deur Holling se tipe II funksionele reaksie. Voorspellings van hierdie model pas baie goed met die waargenome vlakke van nestedness, modulariteit en node-graad uitkerings vir 61 ware gasheer-parasiet en plant-herbivoor netwerke. Verder het ons twee spesifieke gevalle van ons model (spesies met identiese [neutrale] demografiese parameters en interaksies met identiese [neutrale] voordeel in die netwerk) ondersoek en gevind dat die demografie-neutrale geval waargenome modulariteit oorskat, terwyl die voordeelneutraal geval waargenome nestedness oorskat. Verhoudings tussen nestedness, modulariteit en konnektiwiteit is sterk bevind. Verder, in teenstelling met die algemene verwagting van hoe modulariteit in antagonistiese netwerke, is oorhoofse werklike netwerke (> 80%) aansienlik geneste, terwyl byna 40% van die werklike netwerke is verbasend minder gekompartimenteerd as ewekansige netwerke gegenereer uit null modelle. Ongeag van die omstredenheid oor of antagonistiese netwerke geneste of gekompartimenteerd is, die voorgestelde model vang die essensie van die dinamiese aard van die strukturele opkoms in antagonistiese netwerke. As gevolg van sy voorspellende krag, is hierdie model verder gebruik om robuustheid te ondersoek in antagonistiese netwerke. Voorspellings het getoon dat die robuustheid van ’n netwerk word bepaal deur verskeie faktore, soos konnektiwiteit, hulpbron-graad verspreiding, hulpbron-verbruiker verhouding, diversiteit, nestedness en kompartementasie. Verrassend, die wyse van die netwerk reaksie op die verlies van spesies was onafhanklik van die reeks wat gevolg het toe die spesies verwyder is uit ’n netwerk. Variasies is slegs opgemerk in die intensiteit van die effek van die verskuiwings. Benewens, ons het ook aangetoon dat die prosedures van spesies se uitsterwing wat die interaksie skakelaar geignoreer het, onderskat die effek van ’n verlies van spesies in hierdie netwerke. Ons moet dus die waarde van ons kennis van die moontlike aanpassing prosesse in die ekosisteem in agneem, aangesien dit belangrik kan wees vir die oplossing van die diversiteit-stabiliteit debat.

Current policy and research have led the field of science education towards a model of "science as practice." In the past decade, several research programs on model-based reasoning practices in education have articulated key dimensions of practice, including constructing and defending models, comparing models to empirical data, using representations to identify patterns in data and use those as inscriptions to buttress arguments. This study presents a detailed case of how the use of a physical microcosm and children's self-directed representations of an ecosystem constrained and afforded student sense-making in an urban elementary classroom. The case analyzed the experiences of a 10-year old fifth grade student, Jorge, and the variation in his expressed understanding of ecosystems as he interacted with academic tasks, along with models and representations, to design, observe and explain an ecological microcosm. The study used a conceptual framework that brings together theories of situated cognition and Doyle's work on academic task to explain how and why Jorge's perception and communication of dimensions of ecosystem structure, function, and behavior appear to "come in and out of focus," influenced by the affordances of the tools and resources available, the academic task as given by the teacher, and Jorge's own experiences and knowledge of phenomena related to ecosystems. Findings from this study suggest that elementary students' ability or inability to address particular ecological concepts in a given task relate less to gaps in their understanding and more to the structure of academic tasks and learning contexts. The process of a student interacting with curriculum follows a dynamic trajectory and leads to emergent outcomes. As a result of the complex interactions of task, tools, and his own interests and agency, Jorge's attunement to the role of water in ecosystems comes in and out of focus throughout the unit. The instructional constraint of needing to integrate the FOSS Water Cycle curriculum into the Bottle Biology Project became an affordance for Jorge to ask questions, observe, and theorize about the role of water and the water cycle in an ecosystem. The practice of modeling a closed ecosystem made salient to Jorge the boundaries of a system and the conservation of water within that system. The closed ecosystem model also presented constraints to students' sense making about the role of interactions when students lack domain knowledge in ecology. Relying on students' own talk, photographs and representations as explanations of phenomena in the Bio Bottle, without establishing norms of representational conventions and communication, resulted in missed opportunities for Jorge to reinforce his sense making during the activity and to develop conventions of scientific representation. Findings from this study can be used to inform the design and implementation of learning environments and curricular activities for elementary and middle school students that address all three dimensions of the Next Generation Science Standards: a) developing conceptual understanding of key concepts in the domain of ecology, b) the cross-cutting concept of systems, and c) multiple practices that ecologists use in developing and evaluating models that explain ecosystem structures, functions, and change over time.