Life-system analysis is
the examination of interacting ecological processes
affecting population dynamics. The major problem in
application of life-system analysis is in developing
methods for analysis of ecological processes. I use a
non-linear sensitivity analysis of simulation models to
evaluate the role of individual ecological processes and
their interactions in population dynamics. The method is
applied to the problem of population stability.
Coefficients of m- and v-stability
characterize stability of the mean and variance of
population density, respectively. Contributions of
ecological processes and their interactions to m- and v-stability are
represented by non-linear sensitivity coefficients. The
second application is the analysis of common pine sawfly
(Diprion pini
L.) population dynamics in Russia. Process interactions
are shown to be important in outbreak patterns of this
pest.
A generalized, coupled
system of finite-difference equations is used to
describe a population in which one generation depletes
the carrying capacity of a subsequent one. It is shown
through graphical presentation of numerically defined
stability characteristics that the general consequence
of this interaction is severe instability. Potential
evolutionary strategies which restore system stability
are examined by modifying the original set of equations
and repeating the analysis. It is concluded from these
results that there are at least two general types of
stabilizing strategies: refuge and reduction of
intergenerational flow. The latter strategy is further
subdivided into diversion and dispersion tactics. These
strategies may be ranked according to their tendency
toward stable, single-point equilibrium as follows:
Diversion > Refuge > Dispersion. Biological
attributes of species illustrating these methods are
outlined. Finally, the significance of these findings to
other evolutionary strategies (e.g., r and K selection) is
discussed.