Fire and daily temperatures as germination cues

Brief but high soil temperatures caused by fire are followed by a more prolonged shift in the range of daily soil temperatures as a result of the removal of vegetation. Santana et al. use experimental fires and mechanical removal of vegetation to study germination of three fire-adapted Mediterranean species, Ulex parviflorus, Cistus albidus and Rosmarinus officinalis. They find that the mean daily maxima for soil temperature in fire-induced gaps is at least 20 °C higher than in soil under vegetation at the sites studied, and these higher fluctuations in daily temperature are the most significant factor in determining both seedling emergence and the amount of ungerminated seeds remaining in the soil. They conclude that seeding capacity in Mediterranean Basin obligate seeders may have evolved as a response to a wide range of disturbances, and not exclusively to fire.