Dynamics in Central European near-natural Abies-Fagus forests: Does the mosaic-cycle approach provide an appropriate model?

Question: The mosaic-cycle concept of forest dynamics dominates in Central Europe. According to this concept intermediate-scale disturbances only accelerate the forest break-up under existing cycles of forest development. Is such an approach correct, or should new developmental cycles be elaborated for intermediate-scale disturbances? Location: Near-natural Abies alba - Fagus sylvatica forests in the Swietokrzyski National Park in Central Poland. In these forests intermediate-scale disturbances occurred between 1970 and 1990. Methods: Data were collected twice in areas surrounding 212 permanent sample points ( in 1994 and 2004). Two increment cores were taken from 259 sample Abies trees. The effect of intermediate-scale disturbances on radial increment of Abies was assessed. Probabilities of stand transition during a 10-year period between individual stages and phases of development of the mixed forest were calculated. The development stages and phases were arranged into hypothetical succession series of successive changes. Results: In 1994 70 stands and in 2004, 47 stands representing stages and phases containing the older generation formed by trees > 100-150 years were found. Also, in 1994 142 and in 2004, 165 stands representing stages and phases containing the younger generations only, formed by trees < 100-150 years, were recorded. Stages and phases containing only younger generations do not occur in the existing forest development cycle which does not consider the influence of intermediate-scale disturbances separately. Two developmental cycles, which take into account the presence of the older generation and the younger generations only ( under conditions of the occurrence of intermediate-scale disturbances), are proposed. Conclusion: The mosaic-cycle concept of forest dynamics can be used to analyse the dynamics of Central European near-natural mixed-species forests, but new developmental cycles should be elaborated for intermediate-scale disturbances.