Implications of interacting microscale habitat heterogeneity and disturbance events on Folsomia candida (Collembola) population dynamics: A modeling approach

The authors implemented a fractal algorithm in a spatially explicit individual-based model to generate landscapes with different microscale patterns of habitat fragmentation and disturbance events and studied their effects on population dynamics of the collembolan Folsomia candida. Among human activities that may cause habitat destruction, the present study focused on agricultural practices. Soil organisms living in a cultivated field are subjected to habitat loss and fragmentation as well as disturbance events generated by the application of agrochemicals and related activities. In addition, they are exposed to natural stressors, which might influence the effects of chemicals on populations. The authors designed simulation experiments that incorporate these 3 factors and investigated their effects on populations of F. candida in the presence or absence of behavioral avoidance of contaminated habitat. Simulation results show that spatial autocorrelation of contamination has different effects on population growth and equilibrium size according to the percentage of clean habitat. This pattern changes when avoidance behavior is excluded from the model, as does population recovery after a series of disturbance events. The model suggests that a combination of heterogeneous contamination and multiple stressors can lead to unexpected effects of toxicants at the population level. Individual-based models can help to understand these effects and therefore add ecological realism to environmental risk assessment of chemicals and can help to explore the effects of different risk management options.