Qualitative modeling in ecology: loop analysis, signed digraphs, and time averaging

Nature can be overwhelming both in the complexity of interactions and in their measurements. Models reduce complexity through simplification of the interactions, and qualitative models reduce the number of measurements. Qualitative models in ecology have taken the form of signed-digraphs or loop models. These assume that ecological systems are at or near equilibrium. For biotic systems far from equilibrium, the method of time averaging has been developed.