The influence of seed age on germinative responseto the effects of fire in Pinus pinaster, Pinus radiataand Eucalyptus globulus

The aim of this study was to understand the germinative response to fire of three species of seeds of different ages. An experiment was designed in which mature seeds of Pinus pinaster, P. radiata and Eucalyptus globulus were matured and stored in four consecutive years (1990, 1991, 1992 and 1993) and then subjected to high temperatures, the addition of ash, and both factors together. A control treatment for the seeds of each age and species was also performed. Significant differences were observed between the species. The germinative behaviour of seeds subjected to different factors involved in forest fires varied according to the age or the year of collection. This variation was more pronounced in some species than in others. For E. globulus the germination rate followed biannual cycles in which a year with low values followed a year with high values. In nearly all the species, sensitivity to factors related to forest fires increased with age.