Timing of fire relative to seed development controls availability of non-serotinous aerial seed banks

Abstract

The existence of non-serotinous, non-sprouting species in fire regimes where serotiny confers an adaptive advantage is puzzling, particularly when these species recruit poorly from soil seed banks or from burn edges. In this paper, white spruce (Picea 5 glauca (Moench) Voss) was used to show that the timing of fire relative to seed develop- ment can control aerial seed bank availability for non-serotinous species. To estimate seed survival in closed cones during crown fires, cone heating was simulated using a one-dimensional conduction model implemented in a computational fluid dynamics (Navier–Stokes) fire spread model. To quantify the area burned when germinable seed 10 would be contained in closed cones, empirical fire occurrence and seed development (germinability and cone opening) data were compared for multiple locations across the white spruce range. Approximately 12% of cones contained viable seed following crown fire simulations (0.072ms−1 mean spread rate; 9147kWm−1 mean intensity), and roughly half of the historical area burned resulted from fires that occurred when 15 closed cones would contain germinable seed. Post-fire recruitment from in situ aerial seed banks can occur for non-serotinous species, and may be an important cause of their existence in fire regimes to which they otherwise seem poorly suited.