Spatial-Temporal Dynamics of a Germinable Seed Bank of a Semi-Arid Vegetation in the Brazilian Northeast

Soil seed bank contributes to the maintenance and renewal of the plant community. Species richness and density of the soil seed bank are affected by the temporal and spatial variations occurring in dry environments. Thus, this study aimed to characterize the effect of time (climatic season and annual precipitation) and space (soil depth and microhabitat type) on floristic composition, species richness, and seed density in the soil bank from a Brazilian dry forest over seven consecutive years. During the study period, 0-5 cm soil samples were collected in three types of microhabitats (Flat, Rocky, and Riverside) from the litter and soil, totaling 2940 samples. The seed bank was quantified using the seedling emergence method; each collected sample was monitored for six months. All data on species richness and seedling emergence were analyzed using the GLM and Anosim test for floristic composition. Results show that the floristic composition, species richness, and seed density differ between climatic seasons, between years of study, between soil depths, and between the three types of microhabitats found in the studied area. However, the explanatory power of each variable was low, demonstrating that other variables such as temperature, wind action, and predation may also be influencing seed storage in the soil bank. In summary, this study demonstrated that the richness, species composition, and emergence of seedlings recorded in soil seed banks are influenced by the spatiotemporal variation found in dry environments. Thus, all the tested variables partially explained the behavior observed in the seed bank.