Lack of hard-seeded species in pre-fire and post-fire seed banks in the region of Murcia (south-eastern Spain)

Abstract

Permanent seed banks are thought to be of essential importance for the reproductive success of many obligate seeder species during early post-fire succession. To evaluate the role of seed banks for post-fire regeneration in SE Spain, seed bank analyses were carried out on recently burnt sites and in long-unburnt areas in two climatically different regions of the province of Murcia, using the seedling emergence method as well as the physical separation technique. We found great variability in the number of seeds between sites and expositions. Lowest seed numbers were found in the mountains while locally very dense seed banks of > 3500 seeds/m2 in the upper two cm of soil were present at the coast. Species of Poaceae, Asteraceae as well as annual species such as Asterolinum linum- tellatum prevailed whereas hard-seeded species known to occur frequently in post-fire Mediterranean vegetation (e.g. Cistaceae, Fabaceae or Convolvulaceae) were sparse or absent in the seed bank. We conclude that the hard-seeded species are not a self-evident compound of the species composition during post-fire succession of long-unburnt sites in south-eastern Spain