The necessity and utility of a hierarchical approach to model building in ecology is discussed. Some of the basic properties of hierarchies are described and criteria to discern subsystems are shown. A new approach of measuring the resilience in terms of natural probability of occurrence of a certain perturbation has been suggested, together with a stochastic definition of stability.

An apparatus for uniaxial compression testing has been developed to simulate isothermal forging conditions. The system is capable of applying 100-kN loads at temperatures up to 1200 ± 3°C in a controlled environment and at constant true strain rates between 10−5/s and 1/s. The apparatus is described and its performance discussed. To illustrate its use, results on the flow behavior of nickelbase superalloy compacts and composites are presented that demonstrate the importance of proper control of the testing parameters. The difference in flow strength of the two materials under identical testing conditions is discussed.

The application of the modelling process in ecology is outlined. Aspects of modelling as structure-function, systemic attributes and simulation language are examined. The different levels of model evaluation, its ramifications and implications are traced. The model depends on the process concerned and the sources of the most common errors are mentioned.