Desertification Transition in Semi-arid Ecosystems and Directed Percolation

Regime shifts in ecosystems caused by climatic or anthropogenic factors can happen on a relatively short timescale with relevant economic and social effects, a consideration which motivates the large interest in the literature to this topic. A special case of regime shift is given by desertification transitions in semi-arid ecosystems. One desertification model, recently proposed, seems particularly effective in describing several ecological landscapes, taking into account different ecological mechanisms. This model simulates an ecosystem undergoing a desertification transition in term of a stochastic cellular automaton (SCA) subjected to a damage spreading (DS) transition. On the other hand, it is well known that many DS transitions belong to the directed percolation (DP) universality class under certain rather general conditions. Here we investigate the universality class of the SCA model and we identify the region of parameters space inside which it belongs to the DP class.