Alternate Stable States and Threshold Effects in Semi-Arid Grazing Systems

Models that explain the discontinuous behaviour of semi-arid grazing systems usually herbivore feeding characteristics or plant competition as possible mechanisms. studies indicate, however, that plant-soil relations could be more. We show by means of a graphical model that the interactions between infiltration or nutrient retention and plant density potentially give rise to the of alternate stable vegetation states and threshold effects in semi-arid systems, even without the effect of a non-linear herbivore functional response plant competition. These interactions may trigger a positive feedback between plant density and reduced resource availability, and lead to a collapse of the. The model results are in line with well-documented observations of spatial temporal patterns such as two-phase mosaics and stably degraded grasslands.