FIRE EFFECTS
SPECIES: Vaccinium myrtilloides | Velvetleaf Blueberry 



IMMEDIATE FIRE EFFECT ON PLANT : 
Aboveground portions of velvetleaf blueberry are commonly killed by
fire, but underground rhizomes generally survive wildfires or controlled
burns [24,88,90].  Mortality typically increases with higher fire
intensity and severity [56,78], although in the West, some rhizomes
commonly survive even hot wildfires, as long as soil is sufficiently
deep to offer some protection [90].  Some plants may survive even after
lethal heat penetration to depths of 3.5 to 4.7 inches (9-12 cm) [23].
Rhizomes are typically most susceptible to heat damage during the period
of active growth [78].

Seed:  Seeds of most Vacciniums are of short viability and are readily
killed by heat [55].



DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Vegetative response:  Velvetleaf blueberry typically sprouts from
underground rhizomes after aboveground portions of the plant are
consumed by fire [29,90].  Sprouting from latent buds located on the
stump or bole can occur where damage to the aboveground portions of the
plant is only partial [11,28,90].  Response depends on a number of
factors including season of burn, fire intensity and severity
[24,78,90], and subsequent weather conditions.

Seedling establishment:  Seed banking does not appear to represent an
important regenerative strategy in the velvetleaf blueberry.  However,
birds and mammals may transport some seed to burned sites.

Season of burn:  Response of velvetleaf blueberry is generally best
after spring or fall burns [23,90].  Rapid regeneration or regrowth has
been noted after spring fires in northeastern Minnesota and in red
spruce-black spruce forests of eastern Canada [61,85].  Generally,
poorest response occurs after plants are burned in summer during periods
of most active growth [79].  Fires during dormant periods remove old
shoot growth and provide additional nutrients which result in greater
cover and enhanced productivity [78].  Good regrowth was noted after
fall burns in eastern Canada which occurred after storage of
photosynthate.  Stored nutrients were presumably available for new
growth in spring after the burn [25].  In eastern Canada, plants burned
in mid-August exhibited reduced berry production by the end of the
second growing season.  Plants burned in late August showed no increase
in berry production but did increase in cover [78].  Late October burns
produced increases in both fruit production and cover whereas, burns
conducted in late May reduced cover and did not increase berry
production [78].

Fire intensity and severity:  Light to moderate fires presumably remove
decadent material and stimulate the growth of velvetleaf blueberry while
increasing nutrient availability [79].  Plants are commonly observed on
lightly burned plots in white spruce-paper birch-aspen communities [4]
and elsewhere [78].  However, cover and fruit production may be greatly
reduced after hot fires which result in greater heat penetration into
the soil [55,78,79].  In a northern Ontario study, largest increases in
cover and fruit production were noted after fires of 684 degrees F (362
degrees C) and 751 degrees F (417 degrees C) lasting 40 seconds per
meter square [78].  Fruit production was much reduced after hot fires of
1,296 to 1,513 degrees F (702-823 degrees C) with a duration of 80
seconds per meter square [78].  Recovery may be slow after hot fires
[61].  Ohmann and others [61] report that velvetleaf blueberry was more
common in mature forests than in areas burned by a severe wildfire 33
years earlier.

Soil:  Soil characteristics may also influence the postfire response of
velvetleaf blueberry.  Reductions in cover and production may be more
pronounced when the soil is dry [78].  The extent of lateral rhizome
development may be greatest where organic soil layers are relatively
thick [77].  Thus, the capacity to regenerate through rhizomes could be
reduced where a thin mantle of organic soil prevents the development of
an extensive rhizome network.

Postfire recovery:  Recovery of velvetleaf blueberry is generally rapid
wherever portions of underground rhizomes survive [55,78].  This shrub
regained prominence within 2 to 3 years after fire in jack pine
communities of the East [83].  Relatively rapid increases in both cover
and biomass have also been documented [62,63].  Rapid increases in
biomass are often particularly dramatic during the first 2 years after
fire [63].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Season of burn:  Response of velvetleaf blueberry is generally better
after early spring or fall burns than after late spring or summer burns.
Response by season of burn was documented as follows in forests of
eastern Canada [25]:

season of burn            relative abundance (stem density for velvetleaf
                          blueberry in plot/stem dens. for all species
                          in plot) x 100

                         preburn     1 month    3 months    5 months 

late spring (early July)  ---         ---        ---         17 %
summer (July 20-22)       ---         ---        ---         25 %
fall (September 15-17)    ---         ---        37%         30 %

Postfire recovery:  Reestablishment of velvetleaf blueberry is often
fairly rapid where surviving portions of the plant resprout.  Postfire
increases in cover and biomass were as follows in northeastern Minnesota
[62,63]:

      year postfire          percent cover (avg. of 7 sites)

            1                        0.6
            2                        0.2
            3                        1.1
            4                        0.7
            5                        1.1

         postfire growing         individual dry      number of
         season                   weight (gms)        individuals

            1971                       .16                140
            1972                       .75                 29
            1973                       .70                 64
            1974                      1.43                 84
            1975                      1.60                151

In northern Minnesota, comparative values from burned and unburned three
year old stands were as follows [76]:

                      unburned      burned
 stems/0.1 m sq.        2.3           2
 flower buds/plant      6             8
 stem length (cm)      22            24


FIRE MANAGEMENT CONSIDERATIONS : 
Wildlife:  Evidence suggests that fire suppression may be having an
adverse impact on bear habitat in some areas [55,96].  Once-productive
berry fields are being invaded by conifers.  Since plants beneath a
forest canopy generally produce few berries, fruit production has been
steadily declining in many areas [57].  Berry fields can be treated with
fire if maintenance or enhancement of berry crops is a prime management
objective.  Logging treatments which include severe soil scarification
or slash burns may also reduce berry production.  Even where timber
harvest favors berry production, lack of cover in early years can limit
bear use.  Wildfires often create diverse habitat mosaics which
incorporate elements of hiding cover and favor bear use [96].

Prescribed fire:  Prescribed fire has long been used to increase yields
in commercial low sweet blueberry fields of the East by naturally
pruning decadent shoots [23,42,57].  Flower buds generally tend to be
more numerous on new shoots and periodic removal of old shoots can
increase fruit yield as well as enhance overall vigor [57,75].
Prescribed fire has also proven effective in increasing fruit yield for
wildlife and recreationists in noncommercial forest stands of the Upper
Midwest [7].  In northern Minnesota, fruit production of blueberries
(Vaccinium spp.) was enhanced by the second growing season after fire
[7].  In addition to increased numbers of berries, fruit size was
noticeably larger than on adjacent unburned plots [7].

Spring burns, conducted when the soil is still moist, tend to be
effective in promoting fruit production.  In the Great Lakes Region,
Kautz [42] recommends burning blueberry (Vaccinium spp.) stands with 4
to 5 years fuel accumulation during the early afternoon on warm, clear,
sunny days with average wind speeds of 5 to 10 miles per hour (6-8
km/hour).  Fast-moving fire fronts, which burn aboveground parts but
leave underground regenerative structures intact, generally produce best
results.  Therefore, when increased blueberry fruit production is a
primary management objective, head fires are preferable to backing
fires.  It may be necessary to add fuels when burning blueberry stands
in the East.  In the Great Lakes Region, areas to be burned should be
rotated over a 4- to 5- year interval to maintain adequate berry
production for recreationists and wildlife [42].  In the Great Lakes
region, blueberry stands are typically burned at 4 to 5 year intervals
rather than at the 1 to 2 year intervals common in the Northeast [76].

Many commercial stands made up of both low sweet blueberry and
velvetleaf blueberry, have been burned at two year intervals [88].
While burning at this interval is beneficial to low sweet blueberry,
velvetleaf blueberry generally decreases [30,88,90].  However, burning
at three year intervals appears to benefit woodlots made up of both
species [28].  Commercial berry fields are commonly burned in spring or
fall [5,76,78].  Moderate burns conducted during dormant periods are
generally most effective [78].  Flame throwers may be used [56] and hay
or straw spread at the rate of 1 ton per acre.  Damage to underground
portions of the plant can be minimized by burning when the ground is
still frozen [5].

Timber harvest:  Thinning by pulpwood cutting commonly produces vigorous
velvetleaf blueberry plants.  However, clearcutting when followed by
burning within one year often causes shrubs to decline.  Clearcutting
exposes small plants, often of poor vigor, to direct sunlight.
Presumably, when already weakened shrubs are burned, mortality can
occur.  If plants are allowed to grow for several years after
clearcutting and attain good vigor, most generally survive subsequent
fires.  Velvetleaf blueberry typically responds better if the tree
canopy is opened gradually, or if narrow strips are cut allowing
vigorous rhizome expansion from adjacent undisturbed areas.  After
timber harvest in the fall of 1949 and an April 1951 burn in New
Brunswick, velvetleaf blueberry responded as follows [28]:

                     1949       1950       1951       1952
                        (plots sampled in June)

# of stems            45         44         71         77
frequency              8          9          7          2
percent cover          1.6        0.2        0.5        0.1

Biomass production of velvetleaf blueberry one year after timber harvest
and fire was as follows in northeastern Minnesota [63]:

                          dry g/m sq.         

  unlogged-unburned       0.12
  logged-unburned         1.53
  head fire-logged-burned  --
  back fire-logged-burned 0.09

Application of fertilizer and mulch:  The effects of mulch and
fertilizer application on burned velvetleaf blueberry stands has been
examined in detail.  Study results indicate that plants on burned sites
respond more favorably if fertilizer applications are delayed for one
year to allow plants additional time for regrowth [76].

Related categories for Species: Vaccinium myrtilloides | Velvetleaf Blueberry