DYMEX - Software to Model Natural Systems
DYMEX is a modular modeling package that allows the user to develop and run deterministic population models of biological organisms rapidly. Such models help to summarize our understanding of an organismís population dynamics, identify gaps in knowledge, and rapidly evaluate management options. Both the graphical, icon-driven layout and descriptive language used for DYMEX components were designed for ease of use by biologists.
DYMEX models can range in complexity from the simplest model with no age structure or use of environmental inputs, to multi-species models with complex environmental drivers. As the userís understanding of the system grows, the models can be enhanced through modification or addition of components. The parameter values can be tuned at any time without the need to return to the Builder.
The package consists of two major components:
The Builder is used to construct a model. It consists of a user interface that allows the biologist to choose modules or functions from a list and assemble them into a model. The Builder can be used to model the population dynamics of any species, and describe the environments in which a species exists.
It works by creating files that describe the processes that determine population change. Some of the major modules included are:
Timer: Sets the model's timestep and performs timekeeping functions.
Lifecycle: Uses a cohort-based modelling paradigm to describe populations and ecological processes. This module forms the heart of most DYMEX models. It is highly flexible and many different lifecycles can be modelled by adjusting the stage structure and processes.
DataFile: Allows a wide range of user-supplied data to be read into the model. A specialized version of this module that reads and interprets meteorological data is also included.
Event: The user can incorporate significant events such as chemical spraying, fire, frost, etc. These events can be scheduled, or triggered by user defined thresholds.
Other modules included in DYMEX can be used to manipulate model variables in various ways, or to simulate environmental variables such as evaporation or soil moisture changes. Most of the modules can be configured to suit a particular application. The Builder translates the screen representation of a completed model into a file ready for transfer to the second part of the package Ė the Simulator
The Simulator reads the files created in the Builder. It runs the model after the user has defined the required conditions for the particular simulation, and then presents the results in tables or graphs. Additional facilities allow for automatic, multiple runs of models to explore, for example, optimal timing of pesticide applications or to perform sensitivity analyses on parameters. Model results can be saved in standard spreadsheet format for further analyses using other software.