Adaptive advantages of aerial seed banks

Abstract

AbstractProlonged storage of seeds on the plant is called serotiny. It is well represented in fire‐prone, nutrient‐poor and seasonally dry, woody vegetation in Australia, South Africa and North America. Serotiny maximizes the number of seeds available for the next generation by storing successive seed crops and protecting them from granivores, agents of decay and fire heat. It is an advantage when annual seed production is insufficient for self‐replacement in any single year and greatly increases the range of fire frequencies tolerated. While serotiny is a form of environmentally enforced dormancy, it has little in common with soil storage of seeds in terms of its ecology and trade‐offs. Our models have shown that optimal levels of serotiny depend on fire frequency in relation to lifespan of the species, probability of interfire recruitment and the extent of fluctuations in fire intervals. Serotiny is adaptive when the cue for seed release, usually fire, also creates superior conditions for seedling establishment. For serotiny to be an advantage over soil storage, it is essential that any fire is followed by reliable recruitment conditions. Intermediate levels of serotiny are favored as fire intervals approach the lifespan of the species, or if there is a substantial resource cost at short intervals. As the probability of interfire recruitment increases, maximum population growth shifts from strong serotiny under short fire intervals to no serotiny at long fire intervals. As variation about the mean fire interval increases, the optimal level of serotiny declines slightly.