Black spruce seed availability and viability after fire, Northwest Territories, Canada

Context : Black spruce ( Picea mariana ) is an important conifer in boreal North American that develops a semi-serotinous, aerial seedbank and releases a pulse of seeds after fire. Variation in post-fire seed rain has important consequences for black spruce regeneration and stand composition.

Aims : We explore the possible effects of changes in fire regime on the abundance and viability of black spruce seeds following a very large wildfire season in the Northwest Territories, Canada (NWT).

Methods: We measured post-fire seed rain over two years at 25 black sprucedominated sites and evaluated drivers of stand characteristics and environmental conditions on total black spruce seed rain and viability.

Results : We found a positive relationship between black spruce basal area and total seed rain. However, at high basal areas this increasing rate of seed rain was not maintained. Viable seed rain was greater in stands that were older, closer to unburned edges, and where canopy combustion was less severe. Finally, we demonstrated positive relationships between seed rain and seedling establishment, confirming our measures of seed rain were key drivers of post-fire forest regeneration.

Conclusion: These results suggest that black spruce recruitment after fire may be reduced with projected increases in fire activity.