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  • Fath, B  (27)
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  • 1
    Language: English
    In: Emergence: Complexity and Organization, July, 2012, Vol.14(3), p.44(45)
    Description: We present a conceptual synthesis to address the global ecological crisis. The current paradigm underlying life science appears insufficient to enable a solution to the crisis and may be part of the cause of the crisis. We develop a distinct "sustained life" to complement the current paradigm based solely on "discrete life". We present a three-model, multi-scale characterization of the original and fundamental nature of life. The multi-model, expressed as a hyperset formalism, is: life= {environment{ecosystems{organisms{environment}}}} This self-referential, closed loop hierarchy explicitly prohibits fragmentation of sub-units of life and prohibits separation of life from its essential environmental life support context. We integrate work of 1) Ulanowicz and Patten, 2) Rosen amd Kercel and 3) Lovelock and Vernadsky who developed holistic characterizations of life at ecosystemic, organismic and biospheric organization levels, respectively. This paradigm could enable actualization of a mutualistic win-win relation between humans and environment and long-term environmental sustainability.
    Keywords: Carrying Capacity (Ecology) ; Ecosystems
    ISSN: 1521-3250
    E-ISSN: 15327000
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Ecological Modelling, 2007, Vol.208(1), pp.56-67
    Description: Empirically observable energy and matter transfers in ecosystems create network structures commonly called food webs. The relation or interaction type associated with each link between pair-wise objects can be classified as (+, −) or (−, +) depending on the net gain or loss experienced by each object. If objects are not adjacent in the food web, then their observed direct interaction is neutralism (0, 0). From this perspective, a zero-sum balance exists between the number of positive and negative relations in the ecosystem. However, community-level relations arise from observable direct and unobservable indirect pathways within a food web, giving rise to indirectly mediated relations, mutualism (+, +) and competition (−, −). Determination of community-level relations requires a systemic or holistic approach. measures from in the broader frame of ecological network analysis (ENA) provide such a methodology to investigate the relations resulting from all observed and indirect transfers. This research demonstrates the methodology and shows three important results from the analysis. First, all objects in ecological networks are related either through their input and output environs, and therefore all objects interact with and influence the others in the web: there are no null community-level relations. Second, the community-level relations can and do differ from direct relations: what you see is not always what you get. Third, due to the web of trophic and non-trophic interactions, community-level relations usually have a greater occurrence of mutualism than competition making them more positive than the direct relations that produced them: this is the property called network mutualism.
    Keywords: Community Interactions ; Competition ; Food Webs ; Ecological Network Analysis ; Mutualism ; Synergism ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 3
    Language: English
    In: Ecological Modelling, 2009, Vol.220(22), pp.3210-3218
    Description: This research compares two existing methodologies, mixed trophic impact analysis and utility analysis, which use network analysis to evaluate the direct, pair-wise, and indirect, holistic, ecological relations between ecosystem compartments. The two approaches have many similarities, but differ in some key assumptions which affect both the final results and interpretations. Here, we briefly introduce both methodologies through a series of two simple examples; a 3-compartment competition model and a 3-compartment food chain model, and then apply the methodologies to a 15-compartment ecosystem model of the Chesapeake Bay. This example demonstrates how implementing the various conceptual and methodological assumptions lead to differing results. Notably, the overall number of positive relations is greatly affected by the treatment of the self-interactions and the handling of detritus compartments lead to a distinction between ecological or trophic relations. We recommend slight changes to both methodologies, not necessarily in order to bring them completely together, but because each has some points which are stronger and better defensible.
    Keywords: Ecological Network Analysis ; Flow Analysis ; Mutualism ; Competition ; Indirect Effects ; Food Webs ; Ecological Relations ; Trophic Relations ; Predator–Prey Relations ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 4
    Language: English
    In: Ecological Modelling, 2007, Vol.208(1), pp.17-24
    Description: Standard ecology textbooks typically maintain that nutrients cycle, but energy flows in unidirectional chains. However, here we use a new metric that allows for the identification and quantification of cyclic energy pathways. Some of these important pathways occur due to the contribution of dead organic matter to detrital pools and those organisms that feed on them, reintroducing some of that energy back into the food web. Recognition of these cyclic energy pathways profoundly impacts many aspects of ecology such as trophic levels, control, and the importance of indirect effects. Network analysis, specifically the maximum eigenvalue of the connectance matrix, is used to identify both the presence and strength of these structural cycles.
    Keywords: Cycling ; Detritus ; Energy Flow ; Food Webs ; Network Analysis ; Trophic Dynamics ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 5
    Language: English
    In: Ecological Modelling, 2007, Vol.208(1), pp.9-16
    Description: Food webs are constructed as structural directed graphs that describe “who eats whom,” but it is common to interpret them as energy flow diagrams where predation represents an energy transfer from the prey to the predator. It is the aim of this work to demonstrate that food webs are incomplete as energy flow diagrams if they ignore passive flows to detritus (dead organic material). While many ecologists do include detritus in conceptual and mathematical models, the detrital omission is still commonly found. Often detritus is either ignored or treated as an unlimited energy source, yet all organisms contribute to the detritus pool, which can be an energy source for other species in the system. This feedback loop is of high importance, since it increases the number of pathways available for energy flows, revealing the significance of indirect effects, and making the functional role of the top predators less clear. In this work we propose the by adding a detritus compartment to the . We demonstrate the effect of structural loops that result from feeding on detritus, by comparing empirical data sets to five different assembly models: (1) , (2) , (3) , (4) (original in this work), and (5) . Of these models, only the last two explicitly include detritus. We show that when passive flows to detritus are included in the food web structure, the structure becomes more robust to the removal of individual nodes or connections. In addition, we show that food web models that include the detritus feedback loop perform better with respect to several structural network metrics.
    Keywords: Niche Model ; Detritus ; Food Webs ; Energy Cycles ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 6
    Article
    Article
    Language: English
    In: Ecological Modelling, 2007, Vol.208(2), pp.391-394
    Description: Ecological network analysis allows for an investigation of the structural and functional interconnectedness in ecosystems. Typically, these interactions are seen to comprise a food web of “who eats whom”, but more generally applies to the transfer of energy-matter within the biotic and abiotic ecosphere. This web of transactions can be depicted as a digraph or an adjacency matrix in which the presence of direct transactions are represented as a 1 and no transactions as 0. Each transaction between system components leads to an overall network structural pattern. These structures cluster into different categories or regimes based on their cyclic nature. This paper demonstrates threshold effects of the placement or removal of links, such that certain changes essentially keep the structure in the same regime whereas others shift it to another regime in a non-linear manner.
    Keywords: Network Analysis ; Regime Changes ; Food Webs ; Cycling ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 7
    Language: English
    In: Ecological Modelling, 2004, Vol.171(4), pp.329-337
    Description: Network analysis is an important methodology that has been applied in systems ecology. Many theoretical insights have arisen from this approach, primarily the importance of indirect relations in ecosystems and the holistic determination of ecological relations. This approach, adopted from economic input–output analysis, treats systems as interconnected nodes and arcs of material or energy transfer. Due to the difficulty in quantifying large-scale, complex models, most ecological network models are aggregated or lumped models of a few general characteristics. Therefore, the resultant theory was tested using small-scale models with only a small number of compartments. Here, I present a way to develop large-scale cyber-models in order to test four of the main hypotheses of network analysis using models with a large number of compartments. The results show that the hypotheses are affected by model size.
    Keywords: Ecological Models ; Food Webs ; Scale ; Network Analysis ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 8
    Language: English
    In: Ecological Modelling, 2004, Vol.179(2), pp.151-152
    Keywords: Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 9
    Language: English
    In: Ecological Modelling, 2004, Vol.179(2), pp.235-245
    Description: Understanding how 'control' is exercised in ecological systems, even giving a more appropriate definition or meaning to the word 'control' in this context, is an important theoretical issue and would increase our ability to manage ecosystems. Conventionally, in food web ecology, the distinction is drawn between bottom-up and top-down control. In that literature, the bottom-up hypothesis asserts that the primary producers are the source of system regulation and the top-down hypothesis states that keystone species at a higher trophic level can regulate the system. However, we know that in reality control of system behavior is much more complex and distributed than this dichotomy would suggest. Indeed, there is an urgent need for a succinct, yet more complete and comprehensive conceptual framework for thinking about control and for deriving insights into what governs ecosystem organization. In an ecosystem, each element contributes to the overall flow-storage pattern observed in the system through its interactions with the other elements; in this sense, control is distributed among the system elements. Those pair-wise system interactions can be identified and quantified using network analysis. Since the network analysis methodology accounts for both the input (recipient-oriented) and output (donor-oriented) influences from each element, it is possible to use this methodology to move beyond the simple top-down and bottom-up perspective of control. Here, I connect the network analysis methodology to traditional control theory, reintroduce a network-based control parameter using flow analysis and extend the methodology to network storage analysis. Model ecosystems are constructed and used to investigate these properties.
    Keywords: Control Theory ; Distributed Control ; Ecosystem Ecology ; Network Analysis ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 10
    Language: English
    In: Ecological Modelling, 2007, Vol.208(1), pp.49-55
    Description: Ecological network analysis (ENA) is a systems-oriented methodology to analyze within system interactions used to identify holistic properties that are otherwise not evident from the direct observations. Like any analysis technique, the accuracy of the results is as good as the data available, but the additional challenge is that the data need to characterize an entire ecosystem's flows and storages. Thus, data requirements are substantial. As a result, there have, in fact, not been a significant number of network models constructed and development of the network analysis methodology has progressed largely within the purview of a few established models. In this paper, we outline the steps for one approach to construct network models. Lastly, we also provide a brief overview of the algorithmic methods used to construct food web typologies when empirical data are not available. It is our aim that such an effort aids other researchers to consider the construction of such models as well as encourages further refinement of this procedure.
    Keywords: Ascendency ; Ecological Network Analysis ; Food Webs ; Systems Analysis ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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