Vegetation, Fire and Herbivore Interactions in Heathland

Studies on heathlands in N.W. Europe have provided a remarkably detailed picture of interactions between the heath vegetation, the major herbivores, and disturbance by fire. Low nutrient status and disturbances such as fire and herbivory are identified as the main factors controlling the dynamics of heath systems. The classical idea of the “Calluna cycle” should be interpreted as one of a larger set of possible pathways for heath vegetation development. Production, shoot nutrient content, and species composition are all greatly affected by the age of the dominant, Calluna vulgaris. Stand age also affects the outcome of fire. Variations in the regenerative capacity of the dominant and associated species in stands of different ages determine the post-fire vegetation response. The effects of disturbance on the vegetation vary with disturbance intensity and scale. Light-moderate grazing or fires at certain frequencies may maintain heathland communities in a relatively productive state and with Calluna as the dominant. More intense grazing or frequent fires may lead to the replacement of Calluna by graminaceous species. Phytophagous insects have similar effects but on a smaller scale. For conservation purposes, traditional management practices may require to be continued or restored, although variations may be necessary to promote biotic diversity.