Growth and reproduction of Digitalis purpurea in different stages of succession.

Growth reproduction and regeneration were investigated in populations of Digitalis purpurea present in different stages of secondary forest succession. Interference between D. purpurea and an experimental vegetation emerging from natural seed banks on a natural soil was studied during two successive growth seasons under natural radiation and temperature conditions.Growth and seed production were found to be strongly reduced and germination was inhibited in the early/midsuccessional vegetation. In later successional stages sparse but relatively stable populations were maintained by seed production and germination. However, local extinction seems inevitable. A remarkable shift occurred from fast and repeated flowering of compounded rosettes in the colonization phase to delayed flowering of monocarpic rosettes in later phases.The significance of secondary rosettes allowing for the repeated flowering is discussed. A condensed scheme of the population cycle of D. purpurea is presented.