Abstract

Here we report the main trends observed in the soil seed bank of some species-rich pastures located near Vic (NE Spain), evaluating the relationship between soil seed bank and standing vegetation in two contrasting communities (xerophilous pasture and mesoxerophilous grassland), and the potential role of the soil bank in community regeneration. We analyzed 140 soil samples via germination tests and direct observation. The total seed pool (including soil seed bank and standing vegetation) was characterized in terms of morpho-functional traits.

The soil seed content was high and showed strong seasonal variation. We found 12,178.8 to 785.7 seeds m-2 in the germination tests, and 6,909.1 to 4,882.5 seeds m-2 through direct observation. The shallow soil horizon contained much higher densities and species richness than the deep horizon, and higher relative frequencies of elongated or appended seeds. In both communities, 35-45% of the species richness in the soil seed bank corresponded to opportunists, which were rarely found in the established vegetation. In contrast, half of the taxa in the aboveground xerophilous pasture and two-thirds in the mesoxerophilous grassland were not found in the soil bank.

The persistent seeds in the soil bank belonged to a few taxa, mainly not found or rare in the established vegetation. Most of the main species of this vegetation, such as dominant grasses and abundant sub-shrubs, were poorly represented in the soil seed bank.

* Corresponding author. Fax: +34 934112842. E-mail address: [email protected]

These trends indicate the limited role of this bank in the regeneration of the communities studied, particularly in the mesoxerophilous grassland. The changes in land use occurred during the last half century have strongly increased the fragmentation of semi-natural plant communities, and impair the conservation of plant diversity of this species-rich landscape.

Keywords: biodiversity decline, community ecology, habitat fragmentation, grasslands, landscape ecology, seed persistence, seed traits, xerophilous pastures

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