Prescribed burning of northern heathlands: Calluna vulgaris germination cues and seed-bank dynamics

The European coastal heathlands are important habitats for international conservation. Today, these low-intensity farming systems are threatened by the cessation of traditional management regimes, such as grazing and prescribed burning. In natural systems, the effects of fire on germination responses are often explained by adaptation to fire over extended periods of time. However, Northern heathlands are semi-natural systems with only a limited fire history. We investigated whether and how the keystone species in this system, Calluna vulgaris, responded to prescribed burning, based on previous findings where Calluna germinable seed-bank densities showed a pronounced peak right after fire. Our main findings were (i) an ecophysiological response to smoke; (ii) a potential explanation for this pattern, revealed by a seed-bank experiment where we managed to re-create the germination pattern experimentally by using an aqueous plant-derived smoke solution; and (iii) a history of anthropogenic use of fire and the development of heathlands in the region documented through palaeoecological investigations.