AOBPreview originally published online on June 23, 2009
Annals of Botany 2009 104(4):715-724; doi:10.1093/aob/mcp148
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The seed bank longevity index revisited: limited reliability evident from a burial experiment and database analyses
1 Institut Méditerranéen d'Écologie et de Paléoécologie IMEP IRD UMR CNRS 6116, Université d'Aix-Marseille III, FST Saint-Jérôme, case 462, F-13397 Marseille Cedex 20, France
2 Institut Méditerranéen d'Écologie et de Paléoécologie IMEP IRD UMR CNRS 6116, IUT Université d'Avignon, Site Agroparc BP 1207, Domaine Saint-Paul France, F-84914 Avignon, France
3 Institut für Botanik, Universität Regensburg, Germany
* For correspondence. E-mail arnesaatkamp{at}gmx.de
Received: 19 February 2009 Returned for revision: 3 March 2009 Accepted: 19 May 2009 Published electronically: 23 June 2009
Background and Aims: Seed survival in the soil contributes to population persistence and community diversity, creating a need for reliable measures of soil seed bank persistence. Several methods estimate soil seed bank persistence, most of which count seedlings emerging from soil samples. Seasonality, depth distribution and presence (or absence) in vegetation are then used to classify a species' soil seed bank into persistent or transient, often synthesized into a longevity index. This study aims to determine if counts of seedlings from soil samples yield reliable seed bank persistence estimates and if this is correlated to seed production.
Methods: Seeds of 38 annual weeds taken from arable fields were buried in the field and their viability tested by germination and tetrazolium tests at 6 month intervals for 2·5 years. This direct measure of soil seed survival was compared with indirect estimates from the literature, which use seedling emergence from soil samples to determine seed bank persistence. Published databases were used to explore the generality of the influence of reproductive capacity on seed bank persistence estimates from seedling emergence data.
Key Results: There was no relationship between a species' soil seed survival in the burial experiment and its seed bank persistence estimate from published data using seedling emergence from soil samples. The analysis of complementary data from published databases revealed that while seed bank persistence estimates based on seedling emergence from soil samples are generally correlated with seed production, estimates of seed banks from burial experiments are not.
Conclusions: The results can be explained in terms of the seed size–seed number trade-off, which suggests that the higher number of smaller seeds is compensated after germination. Soil seed bank persistence estimates correlated to seed production are therefore not useful for studies on population persistence or community diversity. Confusion of soil seed survival and seed production can be avoided by separate use of soil seed abundance and experimental soil seed survival.
Key words: Arable weeds, Bifora testiculata, Carthamus lanatus, Centaurea solstitialis, longevity index, seed bank persistence, soil seed bank