Black ash circles are found under the burned canopies of big dead pine trees up to three years after fires. Similar circles are formed as the result of a spatial pattern of seedling recruitment after fires. It has been suggested that the accumulation of ash around the burned trees, and the differential reaction of seed germination to ash, may be a major cause for the spatial pattern of seedling recruitment after fires. The results of germination experiments in pots prove that thick cover of ash has a negative effect on germination of Pinushalepensis Miller, and on germination and growth of Cistussalviifolius L. Ash solutions in petri dishes had no effect on germination and growth of both species. Pinus seems to be more well adapted than Cistus to germination and growth in sites with high amounts of ash after fire. Our results support the hypothesis that the ash around the burned pine trees, and the differential reaction of plant species to the ash may explain the spatial pattern of seedling recruitment after fire. We suggest that the relatively high resistance of pine seed germination to osmotic stress is an adaptation to post fire germination rather than to germination in arid zones.

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