FLORISTICS OF A CHRONOSEQUENCE CORRESPONDING TO OLD FIELD DECIDUOUS FOREST SUCCESSION IN SOUTHWESTERN OHIO .4. INTRA-STAND AND INTER-STAND COMPARISONS AND THEIR IMPLICATIONS FOR SUCCESSION MECHANISMS

Vegetation, seed banks, and post-disturbance vegetation were compared for a chronosequence of five stands in order to interpret succession mechanisms. With increasing stand age, the species composition of vegetation, seed banks, and post-disturbance vegetation generally diverged. Also, vegetation was more similar with post-disturbance vegetation than with seed banks in the forest stages. These findings are related to changes in the proportions of life-history types during succession, which, as noted in other studies, are accompanied by decreases in seed production and viability and increases in vegetative reproduction. No successional stage had a seed bank or post-disturbance vegetation with most of the common species from the undisturbed vegetation of all stages. This and reanalysis of other studies on similar seres document that the "initial floristic composition" model of succession cannot account for all major stages of a successional sequence. Rather, the seeds and vegetative propagules present in old-field communities may be capable of regenerating stages from the pioneer through the age of the community disturbed but not older stages, and forests cannot regenerate a series of old-field stages but are capable of directly regenerating themselves through vegetative reproduction.