Evidence for the dominance of indirect effects in 50 trophic ecosystem networks

Salas, Andria K.; Borrett, Stuart R.

doi:10.1016/j.ecolmodel.2010.12.002

Cited by 45 publications

(35 citation statements)

References 79 publications

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“…Further, as the realized formulation considers both the internal system organization and the external environmental connection, it characterizes the complete system as it was initially described by the model builders. Thus, the realized metric is most appropriate for testing the generality of systems ecology hypotheses like the dominance of indirect effects (Salas and Borrett, 2011), applying ENA insights back to the original system (Zhang et al, 2010a,b), and comparing ecosystem organization (Baird et al, 1991;Whipple et al, 2007;Ray, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…We applied Allesina and Bondavalli's (2003) AVG2 balancing algorithm to 15 models that were not initially at steady state because this technique tends to generate the least distortion of network properties. This is the same set of models used in several recent network studies (Borrett and Salas, 2010;Borrett and Freeze, 2011;Salas and Borrett, 2011), and the model data are available from http://people.uncw.edu/borretts/research.html.…”

Section: Model Inputmentioning

confidence: 99%

“…We then provide a mathematical proof for why this relationship will generally hold when the models are at steady state. We conclude this paper by arguing that this identity bolsters the utility of the realized metric for (1) testing the generality of network hypotheses like the dominance of indirect effects (Salas and Borrett, 2011), (2) applying the ecological insights of this type of ENA to the original system, and (3) comparing ecosystems' organization (Baird et al, 1991Borrett et al, 2006;Borrett and Osidele, 2007;Whipple et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Equivalence of the realized input and output oriented indirect effects metrics in Ecological Network Analysis

Borrett¹,

Freeze²,

Salas³

2011

Ecological Modelling

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A new understanding of the consequences of how ecosystem elements are interconnected is emerging from the development and application of Ecological Network Analysis. The relative importance of indirect effects is central to this understanding, and the ratio of indirect flow to direct flow (I/D) is one indicator of their importance. Two methods have been proposed for calculating this indicator. The unit approach shows what would happen if each system member had a unit input or output, while the realized technique determines the ratio using the observed system inputs or outputs. When using the unit method, the input oriented and output oriented ratios can be different, potentially leading to conflicting results. However, we show that the input and output oriented I/D ratios are identical using the realized method when the system is at steady state. This work is a step in the maturation of Ecological Network Analysis that will let it be more readily testable empirically and ultimately more useful for environmental assessment and management.

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Section: Discussionmentioning

confidence: 99%

Section: Model Inputmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Equivalence of the realized input and output oriented indirect effects metrics in Ecological Network Analysis

Borrett¹,

Freeze²,

Salas³

2011

Ecological Modelling

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“…When the ratio is greater than one, then dominance of indirect effects is said to occur. Analysis of many different models has shown that this ratio is often greater than one, revealing the non-intuitive result that indirect effects have greater contribution than direct effects (Salas & Borrett 2011). Thus, each compartment influences each other, often significantly, by many indirect, non-obvious pathways.…”

Section: Dominance Of Indirect Effectsmentioning

confidence: 99%

Analyzing Ecological Systems Using Network Analysis

Fath

2012

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Abstract. Network Environ Analysis, based on network theory, reveals the quantitative and qualitative relations between ecological objects interacting with each other in a system. The primary result from the method provides input and output "environs", which are internal partitions of the objects within system flows. In addition, application of Network Environ Analysis on empirical datasets and ecosystem models has revealed several important and non-intuitive results that have been identified and summarized in the literature as network environ properties. Network Environ Analysis requires data including the inter-compartmental flows, compartmental storages, and boundary input and output flows. Software is available to perform this analysis on the collected data. This article reviews the theoretical underpinning of the analysis and briefly introduces some the main properties such as indirect effects ratio, network homogenization, and network mutualism.

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“…They are considered by some ecologists to be dominant in ecosystem causality (Patten, 1984;Higashi and Patten, 1989). They have influential impacts on ecosystem structure and function (Salas and Borrett, 2011). They maintain species diversity (Bever, 1999(Bever, , 2002(Bever, , 2003, and stabilize multi-species assemblages (Bergstrom et al, 2009;van Veen et al, 2005;Wootton, 1994Wootton, , 2002.…”

Section: Introductionmentioning

confidence: 99%