Soil seed bank richness, abundance and density across spatial scales and global biomes

Soil seed banks are an important component of plant population and community dynamics. As a functional strategy that has evolved in response to abiotic disturbance regimes, they are likely to play a key role in determining biodiversity responses to global change. However, like all aspects of biodiversity, patterns in soil seed banks are likely to be scale-dependent. Here, we investigate components of diversity in the soil seed bank across global biomes, accounting for sampled soil area and geographic extent. Species richness increases with spatial scale at a similar rate across terrestrial biomes, but with differences in the slope (beta diversity). At small scales (0.01 m2), mediterranean systems exhibited the highest seed bank richness, while at larger scales (15 m2) it was tropical forests. Seed density m-2 in the soil was highest in arable systems, followed by tropical and temperate grasslands. Lower densities were found in both high-diversity tropical biomes that are characterised by short-lived seeds, and low-diversity boreal/tundra biomes with more stable established vegetation. Our synthesis shows how a combination of spatial scale and the environmental conditions of different biomes shape global patterns of the multiple components of biodiversity in the soil seed bank. ### Competing Interest Statement The authors have declared no competing interest.