FIRE ECOLOGY
SPECIES: Picea mariana | Black Spruce 



FIRE ECOLOGY OR ADAPTATIONS : 
Plant adaptations to fire:  Black spruce produces seed at an early age,
produces good seed crops regularly, and has persistent, semi-serotinous
cones that release seed slowly over a period of years.  Thus, trees
older than 30 years virtually always contain large amounts of seed.
Following fire this large seed supply is released onto burned areas,
allowing rapid seedling establishment.  Black spruce seeds are usually
not destroyed by fire because the cones are located in the upper part of
the crown where they are least likely to burn.  Thus, even when trees
are killed by fire, cones usually retain viable seed.  Furthermore, the
cones are small and occur in tightly compacted clusters, so that some
seeds usually remain viable even after intense crown fires [71].

Immediately following fire large quantities of seeds are released.  In
fact, striking recently fire-killed black spruce trees with an axe
causes seeds to fall from scorched cones [40].  Within 60 days of a fire
in an upland black spruce stand in Newfoundland which had an average
tree height of 40 feet (12 m) and basal area of 188 square feet,
1,500,000 seeds per acre (3,705,000/ha) fell [68].

Delayed seedfall and delayed germination are additional postfire
adaptations which ensure that some seed is always available to germinate
and establish during postfire years with favorable growing conditions
[57].  Although large amounts of seed do fall within the 1st postfire
year, small amounts of seed will continue to be released for several
years after fire.  Seedfall continued for 8 years following fire in a
70-year-old black spruce stand in interior Alaska [61].  Not all seed
released immediately after fire germinates during the 1st postfire year.
In New Brunswick, only 19 percent of black spruce seed artifically sown
on burned areas germinated in the 1st postfire year, while 25 percent
germinated in the 2nd postfire year [57].

Fire regime:  Wildfires are frequent and extensive in black spruce
forests and usually prevent the development of uneven-aged stands [65].
Throughout much of the boreal region of Canada, spruce stands burn at
50- to 150-year intervals [34].  In interior Alaska, most black spruce
stands burn before reaching 100 years in age [25].  Open black spruce
woodlands (also called subarctic woodlands, open boreal forests, or
lichen woodlands) in the Northwest Territories and in northern Quebec
have fire intervals of 100 years or less [9,44,50].  Moving away from
the relatively dry continental boreal forests toward the Atlantic
seaboard, fire intervals become longer.  The longest fire-free intervals
for spruce stands probably occur in southern Labrador, where the fire
rotation for black spruce forests is estimated at 500 years [26].  Black
spruce stands occurring in bogs and muskegs experience longer fire-free
intervals than those in nearby upland stands do, and sometimes become
uneven-aged [65].


POSTFIRE REGENERATION STRATEGY : 
   crown-stored residual colonizer; long-viability seed in on-site cones

Related categories for Species: Picea mariana | Black Spruce