FIRE EFFECTS
SPECIES: Vaccinium angustifolium | Low Sweet Blueberry 



IMMEDIATE FIRE EFFECT ON PLANT : 
Low sweet blueberry is tolerant of heat [56].  Underground portions of
the plant generally survive wildfires or prescribed fires [157], even
even when all aboveground vegetation is consumed [28,41].  In jack pine
barrens, rhizomes have survived brief exposure to fires producing soil
surface temperatures up to 1,013 degrees Fahrenheit (545 deg C) [140].
However, exposure to temperatures of 1,295 to 1,513 degrees Fahrenheit
(702-823 deg C) for 80 sec apparently resulted in some rhizome mortality
[111].

Fire effects vary with fire severity and intensity, and season of burn
[136].  Rhizome mortality increases as heat penetration into the soil
increases [136].  In a northern Wisconsin muskeg, survival was poor
after hot fires burned out layers of sphagnum [161].  Plants are
generally most severely harmed by hot summer fires which occur when food
reserves are low [55].  Seedlings that lack a well-developed rhizome
system are often killed by recurring fires [96].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Low sweet blueberry generally sprouts from rhizomes and the root crown
after aboveground vegetation is consumed by fire [65,83].  Plants may
also sprout from buds located on the stem base [83,157], but stems that
arise from underground rhizomes are generally more vigorous than those
that develop from partially burned aboveground stems [107].  Rhizome
sprouting is much slower than crown sprouting [148].  Some
reestablishment via seed germination may occur under favorable
conditions [117].

Fire intensity and severity, season of burn, community type, and soil
are important factors influencing postfire response [138,148,161].
Cover and stem density commonly increase rapidly [55], and recovery may
be well underway within 4 to 5 postfire months [55,57].  Low sweet
blueberry was well represented within 4 months after an intense fire
destroyed all aboveground vegetation in a spruce stand in Manitoba [84].
In many areas, including parts of Nova Scotia and Ontario, low sweet
blueberry regains prominence 2 to 3 years after fire [6,106,144].
Although initially reduced after fire in jack pine and black spruce
communities, low sweet blueberry increased beyond prefire levels after 5
years [10,42,109].  Recovery may be delayed after hot fires.  Low sweet
blueberry was present within 13 years after a severe wildfire in a red
pine-white pine forest [11]. Hall and others [72] reported that V. a.
forma nigrum tends to increase more rapidly than does V. a. forma
angustifolium in fields that are burned regularly.

Fruit is not produced the year of the burn but is produced in abundance
during the next 3 postfire years [25,28,161].  In general, young
healthy plants regenerate more successfully than older, decadent ones
[93].  Where clones are extremely decadent, it may take three seasons of
postfire growth before fruit production and vigor reach "satisfactory
levels" [131].  Some researchers report that burning too frequently can
cause fruit yields to decline [25].

Increases in low sweet blueberry after fire may be due in part to the
stimulatory effect of nutrients added by ash deposition or changes in pH
[70].  Blackened ground absorbs heat and may promote earlier fruit
ripening [28].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Season of burn:  In general, low sweet blueberry is most reduced by
summer fires [50].  Flinn and Wein [58] reported higher stem densities
after burning in fall, when plants had completed photosynthate storage
and had reserves available for new growth.  Smith [138] reported no
increases in density or productivity after plants were burned in summer
in northern Ontario.  Eaton and White [50] observed that the number of
sprouts and flowers was greatest after spring fires.  Plants burned
after July 1 did not sprout until the following year [110].  Plants
burned in August, September, October, or November, do not sprout until
the following spring [50].  Spring fires typically promote fewer
competitors than do fall fires [139].  In commercial blueberry fields,
increases in dry matter and percent cover have been noted after both
spring and fall fires [139]. 


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire:  Prescribed fire can be used to improve fruit yields
[77,132].  In order to remove decadent aboveground foliage without
damaging rhizomes, hot fires should be avoided [124].  

Fuels and flammability:  Fuel loads are low and discontinuous in xeric
jack pine-red pine forests dominated by low sweet blueberry, common
juniper (Juniperus communis), lichens, and mosses [24].  Fires in these
communities tend to be of irregular intensity.  The probability of crown
fires increases in later successional stages in more mesic stands [24].
In northeastern New York, Stergas and Adams [145] reported that
"fire-line intensities greater than 1500 kW/m can easily develop into
crown fires."  Low rates of spread may be necessary to keep a prescribed
fire under control given the potential fuel loading and heat content of
the aboveground understory vegetation, which is dominated by low sweet
blueberry, black huckleberry, and lichen [143].  Ash content of low
sweet blueberry ranges from 4.20 to 4.54 percent, high heat content from
20,134 to 20,298 KgJ/kg, and ash-free high heat content from 21,040 to
21,084 kJ/kg [143]:

Wildlife considerations:  In central Wisconsin, prescribed fires are
recommended at 4-year intervals where management aims include limiting
shrub growth and providing habitat for white-tailed deer, sharp-tailed
grouse, and prairie chickens [27].  Fire can be used to aid the
restoration of sand barren vegetation [27].  Vogl [163] reported that
burning at 10-year intervals would allow low sweet blueberry to reach
maximum fruit yields and allow time for maximum fuel accumulations to
reduce competing oaks, aspen, and birch.  Prescribed fire can be used to
increase grouse numbers in Pennsylvania hardwood forests with a low
sweet blueberry understory [131].

Disease:  Regular burn pruning can limit the spread of red leaf disease
[113] and blueberry leaf spot [12].  However, some diseases such as
powdery mildew and rust (Pucciniastrum myrtilli) tend to increase with
the proliferation of the host plant [12].

Nutrients:  Nutrient content of low sweet blueberry foliage is altered
by burning [29,78,116].  Leaf tissue from burned plants is typically
higher in nitrogen and phosphorus [78].  Comparative values are
available [29,116].

Related categories for Species: Vaccinium angustifolium | Low Sweet Blueberry