Variation in soil seed bank and relationship with aboveground vegetation across microhabitats in a savanna‐woodland of West Africa

Abstract

Soil seed bank (SSB) characteristics may vary with habitat heterogeneity. We investigated the SSB density in three microhabitats (under canopy, eroded soil and bare soil) in five vegetation types (abandoned farm, dense woodland, gallery forest, grassland and open woodland) at varying soil depths (0–5, 5–10 and 10–15 cm) in a savanna‐woodland in Burkina Faso, West Africa. Total germinable SSB densities varied between 4 and 308 seeds per dm3 of soil. Herbaceous taxa were the major constituent of the germinable SSB across the microhabitats, regardless of vegetation type. Seedlings of 30 species emerged from the SSB, of which 24 were annual species and only 4 woody species, indicating that natural regeneration of woody species via seed dispersal is limited. Both microhabitat and vegetation type contributed to the variation in taxa richness, and germinable seed density and diversity. There was a significant difference in SSB density and richness between microhabitats in the different vegetation types (p < 0.05). The SSB densities were higher under tree canopies than outside tree canopies (eroded soil and bare soil) and highest in the upper soil layers in all vegetation types. The aboveground vegetation (AGV) and flora within the SSB shared many herbaceous species but many woody species present in the AGV were absent in the SSB. Under tree canopies are the ecological niches that favor accumulation of a diversity of seeds, suggesting the preservation and conservation of adult trees in savanna‐woodland ecosystems is critical to facilitating the restoration of these ecosystems.