Canadian Forest Service Publications

Seed abscission schedules and the timing of post-fire salvage of Picea mariana and Pinus banksiana. 2013. Greene, D.F.; Splawinski, T.B.; Gauthier, S.; Bergeron, Y. For. Ecol. Manag. 303:20-24.

Year: 2013

Issued by: Laurentian Forestry Centre

Catalog ID: 34815

Language: English

Availability: PDF (request by e-mail)

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For aerial seedbank species, the seed abscission schedule following fire is of practical interest as it affects the optimal timing of post-fire salvage operations designed to maximize natural regeneration. It is also of theoretical interest as we would expect that the rapid deterioration of the better (very thin duff or exposed mineral soil) post-fire seedbeds due to leaf-fall from regenerating plants ought to select for rapid dissemination of seeds following burning. Nonetheless, there are no published reports of the abscission schedule of an aerial seedbank species that include the full temporal range from the fire date to several years after. In northwestern Quebec, we used eight burnt, non-salvaged stands, four dominated by black spruce (Picea mariana) and four dominated by jack pine (Pinus banksiana), in three different fires to examine the seed abscission schedule of these aerial seedbank species for the first 3 years after fire. We found that (1) the abscission schedules of populations of each species differed between fires and (2) black spruce dispersed seeds from the cones at a significantly slower rate than jack pine at all fires. Extrapolating from the regressions (all fires lumped), we conclude that approximately 90% of jack pine and black spruce seeds will have been dispersed by 1 and 5 years, respectively, after a fire. Further, we argue that due to its protracted abscission schedule, early post-fire salvage will invariably require that black spruce be planted. The approach adopted here should be useful for optimizing post-fire salvage timing for all commercially valuable species with aerial seedbanks.

Plain Language Summary

After a forest fire, salvage harvesting must be performed as quickly as possible in order to prevent degradation, in particular by wood-eating insects. However, regeneration of burned stands may be affected by harvesting too quickly if seed dispersal has not yet taken place.

This study focused on post-fire seed dispersal in black spruce and jack pine. The results indicate that 90% of the seeds in both species were released in the 5-year period following a fire.

However, in the case of jack pine, this rate of dispersal is attained during the first year, while it is only attained in the fifth year in the case of black spruce.

Salvage harvesting in the short term will have a lesser impact on jack pine regeneration, but will reduce the number of seeds available for regeneration in black spruce.

This study will help to determine the ideal timeframe for salvage harvesting in order to promote both wood quality and regeneration quality.