A model for the evolution of vegetation and its application to rangelands of Greece

Range management is traditionally based on the plant succession theory that was developed in the U.S.A. in the beginning of the 20th century. This theory states that vegetation progressively evolves to a final stage called “climax”, which is determined by the climate of each region. Overgrazing is connected with the various degradation stages away from the climax. Climax vegetation corresponds to the “excellent” range condition class, which ensures the maximum desirable vegetation to grazing animals. As a result, grazing management is regulated in relation to the various successional stages of vegetation. This model was questioned by several investigators even in the U.S.A. and it has never been applied in the Mediterranean basin countries. In this region, the climax vegetation is a forest, which is not of interest to range management. Over the last 15 years, an alternative theory was proposed, the state-and-transition model. According to this model, rangelands can be described with a set of distinct states and a set of transitions between states. Factors that cause the transitions may be both natural (e.g. climate, fire, etc.) and management oriented (e.g. grazing, wildfires, fertilization, etc.). In this paper, it is argued that the state-and-transition model is more appropriate to the rangelands of Greece than the one based on range succession and experimental evidence from the Lagadas region is presented to support this suggestion.