Uncertainty in Dynamic Process to Extinction

The investigation of perturbation experiments is important not only to forecast the effect of ecological management but also to know community interactions. So far, uncertainty has been well known for perturbation experiments: many authors has reported that long-term response of ecosystem to applied perturbations has been very difficult to predict. In the present article, however, we report the uncertainty even in short-term response. We carry out a computer experiment of extinction, and explore whether the so-called fluctuation enhancement occurs or not, where the fluctuation enhancement means that there are a variety of processes to the extinction. We apply the contact process (CP) on a two-dimensional lattice in which interaction is restricted between adjacent lattice points. We also apply the mean-field simulation (MFS) of CP, where long-range interaction is aloud between any pair of lattice points. Computer simulation reveals that for both CP and MFS, stationary state exhibits the so-called critical slowing-down which denotes that relaxation time diverges near the extinction. It is also found that the fluctuation enhancement occurs in the case of CP. Because of short-range interaction, there are a variety of different processes to extinction.