Effect of cold exposure on seed germination of 58 plant species comprising several functional groups from a mid-mountain Mediterranean area

The effects of cold statification on seed germination of 58 species from a Mediterranean area in central-region Spain were studied. The area is subject to fires and has a very continental climate, with long winters (187 frost days during the year). Differences in germination among species taking into account their phylogeny were studied by dividing them according to their life form (chamaephytes, hemicryptophytes), post-fire regeneration strategy (non-sprouters, sprouters), and geographical distribution range (Iberian Peninsula endemics, Mediterranean, widely distributed species). Treated seeds were stratified at 5 degrees C for 4 weeks, then incubated, along with the control seeds, at 15 degrees C for 6 weeks. Most species were not affected by cold stratification, and in the cases where they were, germination was generally lower after stratification, not higher. In general, germination percentages were low, which shows that stratification by itself was not able to break seed dormancy. Functional groups differing in their post-fire regenerative strategy or distribution range showed differing responses. Sprouters and endemic species from the Iberian Peninsula were negatively affected by stratification treatment. This is interpreted as a mechanism to stop germination after winter, preventing plants from late germination in spring, which would leave them facing summer drought without a deeply developed root system.