Fire impact on a maquis soil seed bank in Cabaneros National Park (central Spain)

The direct impact of fire on the soil seed bank and the changes observed one year later were studied by analysis of seed content in sample layers at depths of 0-2 cm and 2-5 cm. Fire had a severe but selective impact on the sail seed bank: species with transient seed reserves accumulating on the soil surface were eliminated, whereas species with persistent buried seed reserves tended to remain in the soil after the passage of fire. Thick seed coats were shown to be an efficient mechanical protection barrier to fire. One year after fire, trade-off between input and output into seed bank produced a conspicuous recovery of seed density and species richness on the soil surface, and a pronounced impoverishment in the 2-5-cm-depth soil layer. In general, seed banks of woody species were severely depleted due to the lack of replacement following fire, with the exception of Erica, which maintained a high seed bank density in the upper soil layer. The post-fire recovery of soil seed populations was mainly due to two clearly differentiated groups of annuals. The first group was of species whose seeds survived fire, germinated, and completed their phenological cycle. They were mainly fire-ephemerals. The second group consisted of wind-dispersed species whose soil seed banks had suffered a very severe (even total) depletion by fire. They were mainly Gramineae and Compositae species which behaved as opportunistic fire-sensitive invaders.