01575nas a2200217 4500008003900000245012600039210006900165300001200234490000800246520073600254653001100990653004101001653001501042653003101057653001801088653003901106653001101145653001101156100006301167856012701230 2006 d00aSpatially-explicit competition indices and the analysis of mixed-species plantings with the Simile modelling environment 0 aSpatiallyexplicit competition indices and the analysis of mixeds a295-3020 v2333 a

Individual-based modelling and analysis of forest experiments has been made more accessible to researchers with the advent of modelling environments like Simile from www.simulistics.com. Individual-based analyses of tree growth data offer insights not possible with plot-based analyses, especially when the original experimental design has been compromised by mortality or other unforeseen events. The paper illustrates how Simile can be used for individual-based analyses of mixed plantings, and how it can be used to explore the consequences of the resulting statistical models. A mixed-species planting of Eucalyptus pellita and Acacia peregrina is used to illustrate possibilities.

10aAcacia10aDistance-dependent competition index10aEucalyptus10aIndividual-based modelling10aMixed-species10aPowersim; Stella; Systems dynamics10aSimile10aVensim1 aInformation, Jerome VanclayCorresponding Author Contact, K u//www.simulistics.com/publications/spatially-explicit-competition-indices-and-analysis-mixed-species-plantings-simile-mode02003nas a2200253 4500008003900000245009500039210006900134260001200203300001400215490000700229520119300236653005301429653001501482653001101497653001901508653001501527653002601542653001101568653001101579653001801590100001501608700001501623856011101638 2005 d00a“It was an artefact not the result”: A note on systems dynamic model development tools0 aIt was an artefact not the result A note on systems dynamic mode c12/2005 a1543-15480 v203 a

Environmental modelling is done more and more by practising ecologists rather than computer scientists or mathematicians. This is because there is a broad spectrum of development tools available that allows graphical coding of complex models of dynamic systems and help to abstract from the mathematical issues of the modelled system and the related numerical problems for estimating solutions. In this contribution, we study how different modelling tools treat a test system, a highly non-linear predator–prey model, and how the numerical solutions vary. We can show that solutions (a) differ if different development tools are chosen but the same numerical procedure is selected; (b) depend on undocumented implementation details; (c) vary even for the same tool but for different versions; and (d) are generated but with no notifications on numerical problems even if these could be identified. We conclude that improved documentation of numeric methods used in the modelling software is essential to make sure that process based models formulated in terms of these modelling packages do not become “black box” models due to uncertainty in integration methods.

10aLotka-Volterra equation; Predator-prey modelling10aMATEMATICA10aMATLAB10aModel analysis10aMODELMAKER10aNumerical ODE solvers10aSimile10aSTELLA10aStiff systems1 aSeppelt, R1 aRichter, O u//www.simulistics.com/publications/it-was-artefact-not-result-note-systems-dynamic-model-development-tools01878nas a2200181 4500008003900000245004500039210004000084300001300124490000700137520137300144653002601517653001401543653002601557653001101583100002201594700001701616856006301633 2003 d00aThe Simile visual modelling environment.0 aSimile visual modelling environment a345-358 0 v183 a

Simile is a visual modelling environment that has been developed to overcome the problems involved in implementing agro-ecological simulation models using conventional programming languages: problems such as the effort and skill needed to program the models, the lack of transparency in models implemented as programs, and the lack of reuseability of models and submodels. It combines the familiar System Dynamics (compartment-flow) paradigm with an object-based paradigm, allowing many forms of disaggregation to be handled, as well as spatial modelling and individual-based modelling. Its visual modelling interface makes it accessible to non-programmers, at the same time allowing models to be largely self-documenting. Models can be run very efficiently as compiled C++ programs, and users can develop new visualisation tools for displaying model results. Simile has been used in international research programmes, including the modelling of Mediterranean vegetation dynamics and modelling the interaction between households and land at the forest margin in developing countries. Simile has been developed in a spirit of open standards for model sharing. Models are saved as a text file in a structured format, with a view to enable model sharing with other modelling environments and to encourage others to develop additional tools for working with models.

10aDeclarative modelling10aModelling10aModelling environment10aSimile1 aMuetzelfeldt, R I1 aMassheder, J uhttp://www.simulistics.com/files/documents/SimilePaper.pdf