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The presence of the golden mussel in Brazil is a matter of great concern and causes harm to the country, particularly affecting the power generation sector. Infestation control represents a challenge, and there is a need to mathematically describe the dynamics of the problem. This work proposes to analyze a mathematical model based on differential equations that relate the populations of larvae, mussels, and algae. For this model, the critical points and stationary states are determined, seeking steady-state conditions stability, through the basic reproduction rate. In addition, it presents the sensitivity analysis of the parameters involved. The paper results are relevant as they allow mathematical interpretation of the golden mussel infestation potential through the basic reproduction rate. Furthermore, the sensitivity analysis suggests how important the parameters are for this potential. For that matter, this work can provide baseline information to guide future control strategies as it provides quantification of the species involved over time as well as a condition for infestation. • Mussel-algae interaction model. • Stability analysis of stationary solutions of the model. • Basal reproduction rate for the golden mussel model. [ABSTRACT FROM AUTHOR]

Emergy is becoming an important sustainability ratio. Emergy analysis of real systems cannot be summarized to the trivial analysis of systems with several sources and one product. In such case only the application of the first rule of emergy algebra (all sources of emergy to a process are assigned to the process output) is required and the result can be stored in a simple table. But real systems of interest (ecosystems, complex chemical production systems, etc) are interconnected systems with feedbacks, splits and by-products. As a consequence mathematical foundations for exact emergy analysis appear to be necessary. Indeed, emergy computation within an energy system diagram is based on four rules, the use of which is sometimes confusing. The complexity of the computation of emergy within interconnected system comes also from the fact that it does not obey Kirchoff-like circuit law. Thus, linear algebra approach fails. Emergy computation follows a logic of memorization, thus the evaluation principles deal with pathways. An emergy pathway is a pathway from a source of emergy to a product which represents the sequel of assignations of the emergy source by the processes of the interconnected system. Looking at pathways in ecosystems analysis is not a new subject. Because of the rules of emergy computation (specifically the no double counting rule) among an abundant classification of pathways in ecosystems the emergy pathways appear to be particular elements of only two classes of pathways: the class of simple pathways and the class of terminal non-feedback cycle pathways. This paper is the companion paper of a previous paper written by the same authors. In the previous paper it is explained how to compute emergy flowing on a given arc of an emergy graph assuming all emergy pathways ending by this arc known. As explained in this paper an emergy graph is a transformed graph from an energy system diagram. The aims of this paper are as follows. (i) Explain how to transform an energy system diagram into an emergy graph. (ii) Provide a clear and new algorithm easily programmable to compute emergy pathways. (iii) Insert this new algorithm in the whole procedure for computing an emergy flowing between two processes. (iv) Apply the whole procedure on a real world example. This example shows that the emergy content from meadowland-sun can either carry out by the milk or by the electricity (when considering the biogas and the CHP plant). In the general case, this emergy amount is lesser than the total meadowland-sun emergy. [ABSTRACT FROM AUTHOR]

Abstract: Ecological expert knowledge is often based on qualitative rules consisting of linguistic terms such as ‘low’, ‘moderate’ or ‘high’. Since fuzzy systems transform these rules and terms into a mathematical framework, they allow implementing this expert knowledge in ecological models. However, the development of a reliable knowledge base is complex and time consuming. Recent research has shown that complementing fuzzy systems by data-driven techniques can solve this knowledge acquisition bottleneck. In this paper, a heuristic nearest ascent hill-climbing algorithm for rule base optimisation is applied to construct a fuzzy rule-based habitat suitability model for spawning European grayling (Thymallus thymallus L.) in the Aare river (Bern, Switzerland). Optimisation of the fuzzy rule-based model was based on two different training criteria, the weighted correctly classified instances and Cohen''s Kappa. The ecological relevance of the results was assessed by comparing the optimised rule bases with a rule base derived from ecological expert knowledge. Optimisation based on Kappa appeared to generate acceptable results (CCI=0.70; Kappa=0.32) and was more practical than optimisation based on since the latter required fine tuning of a weight parameter, which accounted for the species prevalence. The optimal rules showed 74% similarity with the rules derived from expert knowledge, while 84% of all model errors was due to false positive predictions of the model. These errors might be due to the impact of variables, which were not included in this study on grayling presence and thus are not necessarily a model error. The habitat suitability model optimised in this paper is able to predict the effect of different impacts on the river system and to select the optimal restoration option. Hence, it could be a valuable decision support tool for river managers and ease the discussion between stakeholders. [Copyright &y& Elsevier]

Litterbag is a standard apparatus used in plant litter decomposition studies. Decreasing bag mesh size hampers litter decomposition due to exclusion of large-bodied consumers and interferences with agents of litter fragmentation. The combined use of coarse and fine mesh bags in field studies is thus relevant for assessing the contribution of macrodetritivores and microbial decomposers to litter decomposition. The present paper examines methods for analyzing the effect of litterbag mesh size on decomposition. I present here a new approach derived from a mathematical analysis of the first-order decay model (i.e. the Olson’s model) and use it to reanalyze a large dataset of litter decay rates in two different mesh size litterbags. The presented calculation method for the extent and rate of litter fragmentation overcomes several shortcomings of previously used indices. I also highlight potential pitfalls associated with using the Olson’s model to analyze the effect of litterbag mesh size on decomposition. [ABSTRACT FROM AUTHOR]

Modeling could be summed up as the task of reproducing the structure and imitating the behavior of complex real-life systems with components interacting with one another at different scales. In many disciplines of ecology, System Dynamics and more recently Individual-Based modeling have emerged as the major tools to support this task. These techniques have usually been considered until now as exclusive alternatives instead of synergistic tools. The present paper starts by presenting the two approaches, and compares them to identify their strong and weak points depending on the type of components constituting the system under consideration. Then we isolate a class of systems difficult or in some cases impossible to model dynamically using any of these approaches alone, because of conceptual limitations. We further point out the usefulness of merging the two paradigms inside of a hybrid modeling framework to handle this class of systems, and present what we consider as the elementary combination patterns of System Dynamics and Individual-Based modeling. Since the power of this promising approach has been unexplored in most fields of ecology, we suggest some possible applications illustrating its usefulness. [Copyright &y& Elsevier]

Abstract: Modeling and simulation is essential for understanding complex ecological systems. However, knowledge of the structure and behavior of these systems is limited, and models must be revised frequently as our understanding of a system improves. Moreover, the dynamic, spatial distribution of activity in very large systems necessitates mapping natural mechanisms as logically as possible onto computer structures. This paper describes theoretical and algorithmic tools for building component-based models and simulations of dynamic spatial phenomena. These methods focus attention on and exploit the irregular distribution of activity in ecological processes. We use the DEVS formalism as the basis for a component-based approach to modeling spatially distributed systems. DEVS is a mathematical theory of discrete-event systems that is well suited for describing large systems that are described by small parts with irregular, short-range interactions. This event-based approach to modeling leads naturally to efficient simulations algorithms which focus on the active parts of a large model. Ecological modeling benefits from these efficient the simulation algorithms and the reusability of the model’s basic components. Our event-based method is demonstrated with a physics-based model of fire spread. [Copyright &y& Elsevier]

Abstract: The traditional oasis is considered as an ecosystem with a particular properties. It consists of growing several crops such date palms, fruit trees and market gardening simultaneously on the same field. Although the nature of transport in oasis canopies is not fully understood, it is still possible to develop mathematical models, which generate realistic canopy microclimates. Throughout this paper, simple electrical analogues (Ohm''s law) and empirical formulas are used to describe Dawn-to-dusk evolution of sensible and latent heat flux and to quantify biomass production inside a traditional oasis in the south of Tunisia. Temperature in and above the canopy also humidity, wind velocity, net, global and photosynthetic active radiation and sap flow within the xylem of date palm and fruit trees are included in the mathematical treatment. Those parameters were measured at different heights and the thermal budget was deduced. For validating our model, we have compared latent heat flux, sensible heat flux and biomass production predicted to, respectively, sap flow data, thermal budget and photosynthetic active radiation measured inside the oasis. We can signal a good behaviour of our calculus. The values simulated can be ameliorated to fit better those measured and the model can be used in general circulation models that require estimates of energy fluxes at a large scale if we can sweep more space by mobile sensors and if we use more sophisticated method to determine the geometrical structure of the trees inside the oasis and their stomata resistances. [Copyright &y& Elsevier]

Abstract: Materials and energy flow analysis (MEFA) has been widely utilized in ecology and economics, occupying unique positions in both disciplines. The various approaches to materials and energy flow analysis in ecology are reviewed, the focus being on the linear network system introduced from input–output economics. After its introduction in the early 1970s, the calculus and system definition for materials and energy flow analysis have been diversified, causing problems in comparing the results of different studies. This paper uses a materials and energy flow analysis framework that is a generalization of the major approaches in ecology and economics to illuminate the differences and similarities between the approaches on the basis of a set of consistent principles. The analysis often shows that seemingly different calculus and interpretations employed by different approaches eventually lead to the same outcome. Some issues of interpretations that conflict or require cautious interpretation are further elaborated. A numerical example is presented to test the generalized framework, applying major analytical tools developed by other approaches. Finally, some parallels, convergents, and divergents of the perspectives of ecology and economics and their implications for endogenized resources economy are discussed as they are reflected in the materials and energy flow analysis frameworks. [Copyright &y& Elsevier]