Lotus tenuis (Fabaceae) Seedling Emergence from the Soil Seed Bank Covered with Cattle Dung

This study examined the Lotus tenuis seedling emergence from natural and artificial soil seed banks covered with cattle dung of different thicknesses. We tested the hypothesis that seedling emergence from soil seed banks covered with fresh cattle dung depended on seed weight, its dormancy and dung thickness. Two seed dormancy categories (low and high seed-coat impermeability to water) were obtained from a sample of hard seeds with and without scarification with sandpaper. Natural and artificial soil seed banks of Lotus tenuis were covered with 0.5, 2, 4 and 6 cm thick fresh dung pats; control seed banks were not covered. The results of this study showed that increasing dung thickness affected negatively the seedling emergence in different ways: (1) Seeds germinated under dung pats but seedling emergence was impeded with increasing dung thickness. Seedling emergence from heavy seeds was higher than from the light ones. (2) Moisture contained in the fresh dung was enough to trigger the germination of seeds on dry soil. Seedlings died because of dung desiccation. Seed dormancy prevented the germination under fresh dung. The amount of seeds recovered alive decreased with dung thickness. Seeds with high dormancy categories were more numerous than those with low dormancy categories. Cattle dung deposition on the soil seed bank of L. tenuis can negatively affect the seed survival and seedling emergence.