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  • 1
    Language: English
    In: Ecological Modelling, March 10, 2013, Vol.252, p.214(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ecolmodel.2012.06.010 Byline: Brian D. Fath (a)(b), Ursula M. Scharler (c), Dan Baird (d) Keywords: Ecological network analysis; Environ Analysis; EcoPath; Cycling; Model aggregation; Sylt-Romo Bight Ecosystem Abstract: a* The Finn Cycling Index values published in EcoPath are not true FCI values. a* Total system throughputtotal system throughflow. a* Model aggregation affects connectivity measures and homogenization. a* Cycling, indirectness, and synergism are invariant to network size. Author Affiliation: (a) Biology Department, Towson University, USA (b) Advanced Systems Analysis Program, IIASA, Austria (c) School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa (d) Department of Botany & Zoology, University of Stellenbosch, Stellenbosch, South Africa
    Keywords: Ecosystems -- Models
    ISSN: 0304-3800
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Science of the Total Environment, 15 February 2016, Vol.544, pp.103-113
    Description: In this paper, we construct a spatially explicit model of carbon metabolism for the flows of carbon among the components of an urban area. We used the model to identify spatial heterogeneity in the ecological relationships within a carbon metabolic network. We combined land-use and cover type maps for Beijing from 1990 to 2010 with empirical coefficients and socioeconomic data to quantify the flows. We used utility analysis to determine the ecological relationships between the components of the system and analyzed their changes during urban development. We used ArcGIS to analyze their spatial variation. We found that the positive utilities in Beijing decreased over time and that negative relationships mostly outweighed positive relationships after 2000. The main ecological relationships were distributed throughout the entire urban area before 2000; subsequently, exploitation, control, and mutualism relationships became concentrated in the southeast, leaving competition relationships to dominate the northwest. Mutualism relationships were most common for natural components, but were not stable because they were easily disturbed by urban expansion. Transportation and industrial land and urban land were the most important contributors to exploitation and control relationships and may be important indicators of spatial adjustment. Increasing competition relationships unbalanced the carbon metabolism, and limitations on the area of land available for development and on the water resources led to increasingly serious competition. The results provide an objective basis for planning adjustments to Beijing's land-use patterns to improve its carbon metabolism and reduce carbon emission.
    Keywords: Urban Metabolism ; Ecological Relationships ; Ecological Network Analysis ; Spatial Analysis ; Land-Use and Cover Change ; Carbon Emission ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Ecological Modelling, 10 March 2013, Vol.252, pp.214-219
    Description: ► The Finn Cycling Index values published in EcoPath are not true FCI values. ► Total system throughput 〉 total system throughflow. ► Model aggregation affects connectivity measures and homogenization. ► Cycling, indirectness, and synergism are invariant to network size. In this paper, we use data gathered from the Sylt–Rømø Bight Ecosystem in Germany to conduct an ecological network analysis. Specifically, we perform Network Environ Analysis to compare with results already published using EcoPath, which incorporates the ecological network analysis package NETWRK. We focus on the issue of model aggregation in that the Sylt–Rømø Bight Ecosystem has data sets representing nine subsystems. We find that the network properties total system throughflow, cycling, indirect effects ratio, and path proliferation are not affected by aggregation whereas connectivity, homogenization, and synergism are affected. The most interesting result to emerge from this analysis is that careful attention is needed to the different use of total system throughflow and total system throughput (both of which are called TST in the literature). As a result of this difference, the calculations for the Finn Cycling Index differ between the various ecological network analysis packages. Noting that Finn based his index on the total system throughflow approach, a consistent method should be adopted if the metrics are reported as FCI. Further work is needed to determine if a simple correction factor can be applied to the NETWRK and EcoPath values or if the coding algorithms should be changed to reflect the FCI approach.
    Keywords: Ecological Network Analysis ; Environ Analysis ; Ecopath ; Cycling ; Model Aggregation ; Sylt–Rømø Bight Ecosystem ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 4
    Language: English
    In: Ecological Modelling, June 24, 2015, Vol.306, p.160(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ecolmodel.2014.10.027 Byline: Joyita Mukherjee, Ursula M. Scharler, Brian D. Fath, Santanu Ray Abstract: * Robustness in estuarine ecosystem is investigated through ENA. * Mdloti, a temporarily open or close estuary in South Africa is considered as study site. * Different ENA indices are calculated and analyzed for original and perturbed networks. * Change in robustness is not significant for change in the autotrophic biomass scenario but is significant for the other two scenarios. * Robustness is proved to be a good measurement for ecosystem health in this study. Author Affiliation: (a) Ecological Modelling Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India (b) School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4041, South Africa (c) Department of Biological Sciences, Towson University, Towson, MD, USA (d) Advanced Systems Analysis Program, International Institute for Applied Systems Analysis, Laxenburg, Austria
    Keywords: Estuaries – Measurement ; Ecosystems – Measurement
    ISSN: 0304-3800
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Ecological Modelling, 24 June 2015, Vol.306, pp.160-173
    Description: Robustness is a universal feature of ecological systems which promotes sustainability over time. Robustness of an aquatic ecosystem, specifically an estuarine system, is investigated here using indicators derived from ecological network analysis. Estuaries provide us with many ecosystem services and these are consequently prone to face anthropogenic stresses. In South Africa, temporarily open/closed estuaries occupy a significant percentage of coastal boundaries. One of the South African estuaries, namely Mdloti, is studied here using network-based, Ecopath software. The estuarine energy flow networks are perturbed following different scenarios, which are assumed to be a result of selected anthropogenic stresses (eutrophication, overfishing) to the system. Several network indices such as total system throughput (TST), redundancy ( ), Finn’s Cycling Index (FCI) and ascendency over development capacity ratio ( / ) are calculated and analyzed for the original field-based network and three perturbed networks under different scenarios (change of autotrophic biomass, fish yield, and detritus import). The change of ecosystem robustness from the unperturbed network is more pronounced in the perturbed networks of fish biomass change and detritus import than change in autotrophic biomass scenario. These indicators reliably reflected the relative change of flow pattern if any changes occur and magnitude in the networks in different scenarios. From the present study, we show that certain common network indices as mentioned above provide a measure of robustness and can be used for the assessment of ecosystem organization and function. ENA properties and also robustness change depending on the type and magnitude of stress imposed on the system.
    Keywords: Network Analysis ; Ascendency ; Development Capacity ; Redundancy ; Perturbation ; Mdloti Estuary ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 6
    Language: English
    In: Ecological Modelling, 10 November 2017, Vol.363, pp.207-220
    Description: Anthropogenic intervention along with natural variability can both influence and compromise continued ecosystem functioning. Ecological network analysis (ENA) was used to explore ecosystem functioning following disturbances to food web networks of a South African estuary, Mdloti, under different seasons. Keystone species, in particular, play an important structural role in spite of having low levels of presence in terms of biomass. From networks of carbon exchanges, the keystone species are identified which include high trophic level carnivorous fish species like Argyrosomus japonicus, Caranx sexfasciatus and Monodactylus falciformis. It is observed that keystone species differed between seasons, according to changing conditions of the estuary. The positive and negative direct and indirect effects that the keystone species have on the different components of the system are evaluated by a Mixed Trophic Impacts (MTI) analysis and results of the direct-indirect impacts analysis are not consistent across seasons.Results reinforce the fact that the keystone species are context dependent as they show variation over the different networks following species composition change following alteration of the estuaries physical status and season. To simulate disturbance, the keystone species biomass in the initial five networks was changed by 10% in stepwise intervals up to ± 99% and it was observed that the system is somewhat resistant to the perturbation effects of the keystone species.
    Keywords: Food Web ; Ecological Network Analysis ; Mixed Trophic Impacts ; Keystoneness Index ; Mdloti Estuary ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 7
    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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  • 8
    Language: English
    In: Ecological Indicators, Dec, 2014, Vol.47, p.80(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ecolind.2014.04.046 Byline: Delin Fang, Brian D. Fath, Bin Chen, Ursula M. Scharler Abstract: Embodied water in a socio-economic system refers to the hidden water contained in products traded from one region or one sector to another and has been the center of concern for water management in recent years. However, most models developed for water system analysis ignore cycling and indirect flows, making it difficult to explain the effects of structure on these factors among sectors. Therefore, those models fail to examine the water utilization efficiency from an integral view. In this study, we investigate an embodied socio-economic water system using network analysis developed originally for ecological systems. In this manner, we identify structural and throughflow indicators, such as Finn Cycling Index, Indirect effects ratio, and aggradation, to show the efficiency of water utilization. The three indicators show different perspectives of the system's efficiency change over time, indicating that only the combination of these three indicators can provide a holistic portray about efficiency. Results showed that the structure influenced the cycling and indirect flows, and from a throughflow perspective, the system depends on large boundary inputs of fresh water. Furthermore, the values of Cycling Index and Indirect effect ratio are much lower than for natural food webs, implying that the policies that led to the structural change and reduction of boundary fresh water inputs do not lead to positive water utilization seen in natural systems. This study provides a novel perspective and methodology for assessing the structure and efficiency of water utilization system with a whole perspective. Author Affiliation: (a) State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China (b) Department of Biological Sciences, Towson University, Towson, MD 21252, USA (c) Advanced Systems Analysis, International Institute for Applied Systems Analysis, Laxenburg, Austria (d) School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban, South Africa Article History: Received 1 February 2014; Revised 22 April 2014; Accepted 28 April 2014
    Keywords: Water ; Water Use
    ISSN: 1470-160X
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: Ecological Indicators, December 2014, Vol.47, pp.80-88
    Description: Embodied water in a socio-economic system refers to the hidden water contained in products traded from one region or one sector to another and has been the center of concern for water management in recent years. However, most models developed for water system analysis ignore cycling and indirect flows, making it difficult to explain the effects of structure on these factors among sectors. Therefore, those models fail to examine the water utilization efficiency from an integral view. In this study, we investigate an embodied socio-economic water system using network analysis developed originally for ecological systems. In this manner, we identify structural and throughflow indicators, such as Finn Cycling Index, Indirect effects ratio, and aggradation, to show the efficiency of water utilization. The three indicators show different perspectives of the system's efficiency change over time, indicating that only the combination of these three indicators can provide a holistic portray about efficiency. Results showed that the structure influenced the cycling and indirect flows, and from a throughflow perspective, the system depends on large boundary inputs of fresh water. Furthermore, the values of Cycling Index and Indirect effect ratio are much lower than for natural food webs, implying that the policies that led to the structural change and reduction of boundary fresh water inputs do not lead to positive water utilization seen in natural systems. This study provides a novel perspective and methodology for assessing the structure and efficiency of water utilization system with a whole perspective.
    Keywords: Network Environ Analysis ; Water System ; Embodied Water ; Structural Analysis ; Throughflow Analysis ; Utilization Efficiency ; Environmental Sciences
    ISSN: 1470-160X
    E-ISSN: 1872-7034
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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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