A model of Calluna population dynamics; the effects of varying seed and vegetative regeneration

Regeneration of Calluna vulgaris in heathlands occurs from both seed and layering, although the relative importance of these two strategies appears to vary. A population model based on transitions between growth phases has been devised and parameter values obtained from published and original work. The effects of differing amounts of seed and vegetative regeneration on the population changes were then tested.The model predicts that a population with a relatively high occurrence of layering will tend towards a steady state, with little temporal variation in population density and cover. Conversely, low layering capacity increases temporal variation with little effect on mean cover. Increased seed regeneration on the other hand, increases both the amplitude of temporal variation in population density, and the frequency of cycles, whereas low seed regeneration results in a stable age distribution at less than 100% cover.