Predicting straw decomposition by a four-species fungal community: a cellular automaton model.
A cellular automaton model based on the measured and inferred properties of the fungal saprophytes, Mucor hiemalis (MH), Agrocybe gibberosa (AG), Chaetomium globosum (CG) and Sphaerobolus stellatus (SS) was developed. The model was used to investigate the rate of breakdown of litter, assumed to be made up of sugar and cellulose, and the associated persistence of the 4 model mycelia. The persistence times of the fungi and the degree of breakdown of the resources was examined. This model reproduced most of the results of competition experiments on malt extract agar medium between different fungi. Perfect reproduction of observations was not possible since real fungi showed a variety of responses under similar conditions. The model predicted a number of phenomena seen in other experimental situations. The model expects coexistence between species to continue for longer when spatial effects are important. Persistence of each species was be greatest for some intermediate level of resource patchiness. The model also exhibited the phenomenon of secondary colonization, obligate sugar users could re-colonize through the release of sugars from the breakdown of cellulose by other fungi. The model predicts that, when the resources are patchy, decomposition will take much longer to complete. If the resources are sufficiently patchy, all species die before breakdown of resources is complete.