A theoretical basis for understanding and managing biological populations with particular reference to the spruce bark beetle

The applicability of qualitative analysis and modelling is discussed with reference to the population dynamics of the spruce bark beetle Ips typographus . On the basis of a set of assumptions and postulates, the structure of the population dynamical interactions is discussed. Dynamic analysis suggest that the Scandinavian spruce bark beetle population is a stable system which may be triggered into boom and bust dynamics. We suggest that qualitative analysis should proceed, explicitly, through four steps: (1) An explicit statement of the biological assumptions and postulates. (2) A structural analysis, wherein the critical interaction network of the system is defined. (3) An equilibrium analysis, wherein the potential equilibrium points of the key organism (e.g., the pest species) are deduced. (4) A dynamic analysis, wherein the multispecies equilibrium points are found and their sensitivity to pertuberation analyzed. This formal approach should expose many and varied population systems to the interpretive and explanatory powers of qualitative analysis.