Persistence and Changes in Morphological Traits of Herbaceous Seeds Due to Burial in Soil

Seeds in soil banks can survive for many years before conditions become more suitable for germination. Meanwhile, seeds undergo changes in morphology and viability. In this study, we launched an artificial seed bank experiment that included 26 species of seeds. We excavated cohorts for 6–8 consecutive years after burial (YAB) in order to determine changes in the morphology (mass, volume, density, seed form) and proportion of fresh (thus persistent) seeds using a crush test as a measure of persistence. The change in seed morphology was fitted by linear and logistic regression, and the proportion of persistent seeds was fitted by logistic regression (effectively by the binomial GLM), which enabled estimation of 50 and 5% persistence times (PT50 and PT05). We found that in most species, seed mass, volume and proportion of persistent seeds declined with YAB, while other morphological traits were less variable, and the decline in these traits with YAB was best fitted with logistic regression. The decline in the proportion of persistent seeds was better fitted by the change in mass than by YAB in some species. Among the species included in this study, PT50 ranged from 1.2 to 10.5 years, and PT05 ranged from 2.1 to 24.3 years. These results can contribute to better understanding of the ecology of weed seed bank persistence in soil. Describing the morphological changes that the seeds undergo in the soil bank may improve our understanding of the biology of seed persistence and facilitate the identification of seeds from the soil bank.