FIRE ECOLOGY
SPECIES: Betula alleghaniensis | Yellow Birch 



FIRE ECOLOGY OR ADAPTATIONS : 
Yellow birch is susceptible to fire injury due to its thin bark [32];
young yellow birch do not usually survive fire.  Mature trees may
survive because the thin forest floor under large yellow birch does not
usually support severe or persistent surface fire [90].  Yellow birch
germinates readily on early postfire sites [91,92,115].

Forest Type:  Heinselman [52] suggested that the presence of yellow
birch in old mixed forests is hard explain without fire disturbance;
however, other authors describe yellow birch as opportunistic with
respect to fire but not fire dependent [90].  Lorimer [77,78] reported
that the presence of yellow birch (in land survey records) is not a
reliable indicator of previous fire.  In Massachusetts, a beech-hemlock
forest containing yellow birch developed on an island where fire had not
occurred for many years.  The land surrounding the island is occupied by
fire-dependent pitch pine (Pinus rigida) and scrub oak types.  In the
1940's the island forest was broken up by a hurricane, which corresponds
with the age of many yellow birch [30].

Fire Frequency:  Yellow birch typically occurs in forests with fire-free
intervals of at least 150 to 300 years; the fire regime is characterized
by crown and severe surface fires in combination [52].  The
presettlement hemlock-northern hardwood forests experienced fire
infrequently [2].  In Wisconsin, mesic hemlock-northern hardwood forests
north and east of the transition zone between the fire-dependent
prairie-savanna mosaic and nonfire-dependent forest probably experienced
fire periodically prior to the fire-suppression era.  The presence of
large, late-successional species indicates that the average interval
between stand-replacing fires was longer than the average lifespan of
major tree species in the region [20].  In the Great Lakes States and
Acadian Forest region, presettlement northern hardwoods-pine-spruce-fir
forests probably had a semieven-aged structure where less shade-tolerant
components were maintained by long-return interval disturbances such as
fire or windstorms.  Most fires in these forests were severe surface
fires, occurring only after prolonged drought, and usually affecting
forests that were breaking up due to other factors (and thus had heavy
fuels).  Estimates for Maine presettlement fire return intervals range
from 806 to 1,923 years [77].

In the twentieth century, forest types containing yellow birch in New
Brunswick have either experienced no fires or have had very long
fire-free intervals.  For sugar maple-yellow birch-fir in New Brunswick,
the mean annual area burned between 1931 and 1970 was about 0.16 percent
of the total area of that type [119].  A similar study for Nova Scotia
reported that 0.03 percent of the total area (of sugar maple-yellow
birch-fir) burned annually between 1915 and 1975 [120].  In northern
Maine, hardwood forests were estimated to have a fire return interval of
approximately 800 years [2].  Northern hardwood forests had estimated
fire return intervals (from data spanning 1903-1956) of 910 years for
Maine and 770 years for New Hampshire [35].

Fire Season and Conditions:  At low elevations in the southern
Appalachians, lightning-caused fires occur less often in the hardwood
forests than in pine-hardwood forests.  Fire frequency by forest type is
related to the month of occurrence.  Fires that occur before May usually
start at higher elevations; after May, more fires start at lower
elevations and are concentrated in the pine-hardwood type, possibly
because after hardwoods have leafed out fuel moistures are too high to
support fire [8].  In Maine, northern hardwoods are less likely to burn
than other forest types, and are more susceptible to fire damage.
Ignition and spread of fire are unlikely except during the most severe
droughts [89].


POSTFIRE REGENERATION STRATEGY : 
   Tree without adventitious-bud root crown
   Initial-offsite colonizer (off-site, initial community)

Related categories for Species: Betula alleghaniensis | Yellow Birch