Effect of high temperatures on seed germination of Pinus sylvestris and Pinus halepensis

Fire is one of the most important ecological factors in the Mediterranean forest ecosystems. Most Mediterranean conifers are obligate seeders after fire. Seeds of two conifers species (Pinus sylvestris and Pinus halepensis) were heated to a range of temperatures similar to those registered on surface soil during natural fires (from 70 degrees to 190 degrees C) and a range of exposure times (from 1 to 5 min). Temperatures above 150 degrees C have a negative effect on the germination of both species. With a temperature range from 70 degrees to 130 degrees C there is no difference between this treatment and the control. The increase in temperature and, of course, the longer exposure, generally decrease germination percentages in comparison with the control and this is much more marked in the case of Pinus sylvestris. (C) 2000 Elsevier Science B.V. All rights reserved.