Soil moisture level and substrate type determine long-term seed lifespan in a soil seed bank

Aims Seeds are usually classified as short- or long-term persistent. It is still hardly understood how environmental conditions influence seed persistence. The study aimed to monitor the long-term effects of different moisture and substrate on seed persistence. Methods Seeds of three Rumex species buried in autumn 2009 in combinations of moisture and substrate were exhumed in spring 2015 and 2021 to test their persistence in the soil after 5.5 and 11.5 years, respectively. Long-term persistence data were compared with data from previous short-term experiment for the same species and environmental conditions reported in Abedi et al. (Plant Soil 374:485-495, 2014). Results No seeds of R. acetosa were found viable after 1.5 years. Seeds of R. acetosella retained viability after 11.5 years mostly in dry-loam (similar to 60%) and moist-sand (similar to 25%) test conditions and moisture levels were identified as the main driver. R. maritimus retained >= 80% viability in moist and wet test conditions and >40% in the dry test conditions. Conclusions For one (R. acetosella) of the three investigated species, the classification of soil seed bank type depended on environmental conditions, emphasizing the need to introduce a more detailed classification scheme for soil seed persistence and to include the information about extrinsic parameters in databases. However, in the other two species with transient (R. acetosa) and long-term persistent (R. maritimus) seed banks, there are rather intrinsic parameters that affect seed viability. Hence, both site-specific environmental factors as well as seed germination traits need full consideration in the classification of future soil seed bank studies.