摘要：
Aims Seed bank strongly influences composition and structure of aboveground vegetation. Little attention has been paid to the role of allelopathy driving soil seed bank dynamics, even though allelochemicals released by allelopathic plants might determine whether a species can or cannot germinate from the soil seed bank and, therefore, to co-exist in the neighborhood of the allelopathic species. Hence, the effects of allelopathic plants on community organization through the effects of allelochemicals on soil seed bank remain largely unknown. In this study, we assessed spatial heterogeneities in soil seed bank caused by the presence of allelopathic plants, and evaluated allelopathic effects on seed bank germination and seedling mortality.
Methods We examined the effects of the allelopathic shrub Artemisia herba-alba Asso on the spatial structure (in terms of species richness and seed density) of the soil seed bank of a semi-arid ecosystem in NE Spain. Specifically, we evaluated seed bank richness and density at three microsites: under the canopy of A. herba-alba individuals, under the canopy of Salsola vermiculata L. (a non-allelopathic shrub) individuals, and in bare soil. In addition, we assessed the effects of aqueous extract of A. herba-alba on soil seed bank germination (seedling emergence and emergence timing) and seedling mortality.
Important findings We found that seed bank richness and density were higher under shrub canopy than they were in bare soil. A. herba-alba and S. vermiculata microsites had similar seed bank richness. However, seed bank density was higher under A. herba-alba because of the high abundance of A. herba-alba seeds. Aqueous extract reduced seedling emergence from the seed bank by 50%, and affected mortality of some emerged seedlings. On the other hand, aqueous extract did not influence the emergence timing of seedlings. We conclude that, although the presence of allelopathic plants does not cause relevant changes in seed bank structure relative to similar non-allelopathic shrubs, their presence can actually result in a reduction of seedling emergence from the seed bank, which leads to low plant species richness and density nearby. To our knowledge, this is the first study to examine the effect of an allelopathic plant on the structure and germination in an entire soil seed bank.
