Effect of Soil Depth on Seedling Emergence in Tropical Soil Seed-Bank Investigations

1. Investigations of tropical soil seed banks have reported large differences in apparent seed densities based on seedling emergence from soil set out under gap conditions. To examine to what extent these differences might reflect different methodologies rather than actual differences in seed density, soil samples of different depths were laid out in germination trays. 2. There was a marked effect of soil depth on total seedling emergence. Germination trays containing soil layers of \geq 10 mm markedly underestimated total seed density. Relative abundance of species in the samples did not alter with depth. Almost all seedling emergence occurred within the first 6 weeks for all soil depths. 3. It is recommended that future tropical soil seed-bank investigations should spread soil to \leq 5 mm. This should not restrict the sample sizes used in seed-bank investigations as rapid germination from shallow soils allows rapid turnover of samples.