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.