Probability of germination after heat treatment of native Spanish pines

Abstract

Spanish pine forests exhibit a high degree of resilience to frequent wildfires. For this reason, they have been considered as active pyrophytes. However, the primary evidence of the fire response of some of the seven Spanish pines suggests that they are not real pyrophytes because germination enhancement has not been detected. In order to investigate the germination response of the Spanish pine seeds after heating, seeds were submitted to different treatments at varying temperatures (50-130°C) and exposure times (1-15 min) to simulate responses to different fire regimes and situations. The probability of germination after heating was modelled by means of multiple logistic regressions using temperature, time and their interaction as predictors. Very predictive models were found for all the pines, except for Pinus pinea. Seeds germinate readily without treatment, losing their viability within a short time and showing a slight protection from fire. The results suggest that, despite the fact that these pines all occur in fire-prone environments, their germination behaviour has clearly not evolved in relation to fire alone. Furthermore, seed behaviour is not related to the general syndromes described as typical of fire-evolved plants. Whereas most of the Mediterranean seeders base their efficient recruitment after wildfires on the presence of hard-coated seeds, most of the Mediterranean pines have attempted other strategies with some variants related to prolific seed production. Only P. pinea regeneration after wildfires depends on the existence of fire-resistant and hard-coated seeds. (© Inra/Elsevier, Paris.).