Mechanisms of succession on fallow lands

Vegetation changes during succession can be regarded as plant-to-plant replacement processes. For deeper insight into the nature of these process we need to investigate the mechanisms involved. Therefore two experiments with herbaceous plant communities were analyzed. The data confirm the view that all three types of interaction: competition, coexistence by niche separation, and cooperation, act together. Likewise it can be concluded that the three models of succession proposed by Connell & Slatyer (1977) are not exclusive but describe mechanisms acting together in the same succession process. Evidence is given that seasonal events can act like a switch and influence the successional trend at a later time. It is, therefore, not meaningful to differentiate between fluctuations in the sense of yearly oscillations and the successional trend itself.Dedicated to Prof. Dr Dr h.c. Heinrich Walter on the occasion of the 90th anniversary of his birthday.