Ecological Modelling 149 (2002) 71 – 83 Modeling competition, dispersal and effects of disturbance in the dynamics of a grassland community using a cellular automaton model Yiannis G. Matsinos *, Andreas Y. Troumbis Biodiersity Conseration Laboratory, Department of Enironmental Sciences, Uniersity of Aegean, Mytilene 81100, Greece Abstract There is an ongoing interest for the mechanisms responsible for the observed patterns of species composition within plant communities. A number of earlier studies on plant competition indicate that resource competition and interspecific differences in seed dispersal may be important factors for the population dynamics in plant communities. Most theoretical work has been focused on either competition for light or nutrients or, on the other hand, seed dispersal using in most cases probabilistic approaches. Both processes are characterized by a pronounced spatial dimension, so in order to be investigated one has to use spatial models. In our study we tried to integrate the two processes, using a cellular automaton model that takes into account both species dispersal and competition characteristics in an effort to understand how natural patterns of plant distributions arise. Our aim was to quantify effects of competition and dispersal in grassland community dynamics, particularly the effect on resilience of the communities to gap creating disturbances that were imposed at different spatial extent. In our simulations we used data from an experimental biological community assembled with five grassland species. Model results showed that longer dispersing plants may have a competitive advantage in their colonization success as compared to the better competitors, especially in the cases of a disturbance-mediated creation of gaps in the landscape. An increase of the species number led to more stable end communities and a higher percent cover of the landscape. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Spatial modeling; Population dynamics; Cellular automata; Biodiversity www.elsevier.com/locate/ecolmodel 1. Introduction The problem of understanding how large-scale community and landscape characteristics emerge from local interactions of individuals has been acknowledged as one of the most important challenges in ecology (O’Neill, 1989; Turner and O’Neill, 1995). It can be considered as a partic- ular case of the general problem of understand- ing evolution of patterns in ecological scale. There is no complete methodology for pointing out which kind of small-scale mechanisms in a complex system affect characteristics of the * Corresponding author. Tel.: +30-251-3622-8; fax: +30- 251-3629-8. E-mail address: gmats@aegean.gr (Y.G. Matsinos). 0304-3800/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0304-3800(01)00515-4