More info for the terms:
bog,
codominant,
cover,
fern,
fire interval,
fire management,
forest,
frequency,
fuel,
heath,
interference,
litter,
phase,
prescribed fire,
seed,
treeMost heaths dominated by heather are a product of interference by humans
and were historically preceded by forest [
30]. In western Europe,
burning at regular intervals has been the principle land management
practice for heaths for over 200 years and has resulted in the
development of pure heather stands over vast tracts of land [
17,
29,
31].
Heaths have been maintained for sheep and red grouse, both of which are
economically important. When managing red grouse habitat, heather is
burned to provide a mosaic of stands with diverse ages, heights, and
densities [
31,
35]. Heaths are not burned after March due to breeding
and nesting [
47].
In dry heaths of western Europe, fire is used to prevent tree invasion
[
36], maintain a balance between young and old heather shoots, and
maintain heather in the building phase at the expense of other species
[
17]. Dominance of heather on these heaths is important because it is
often the most productive and nutritious species found on dry, infertile
heath soils [
10]. Heather production greatly exceeds heather
consumption by herbivores, resulting in a large accumulation of wood and
litter. Decomposition is slow in the cool, wet climate and acid soils
of dry heaths, so a deep layer of plant litter and humus forms. Fire
removes the dead wood and litter. If burning takes place when the
vegetation is too dry or in old stands with large accumulations of dead
woody material, stem bases may be killed. Temperatures above 1,112
degrees Fahrenheit (600 deg C) increase the loss of nutrients,
especially nitrogen and phosphorous, which are often already deficient
in the nutrient-poor soils that heather grows in [
17].
A fire interval of approximately 15 years has been suggested for the
management of heather in heathlands at low to middle altitudes. This
interval maintains heather in its competitive building phase, allowing
it to outcompete other species [
10,
35]. If intervals are longer than 15
years, the heather may be too old to sprout from stem bases or fires may
be too severe. This may lead to an extended period where the
competitive vigor of heather is low, allowing the invasion of bracken
fern or other undesirable species [
10]. Since height is an indicator of
stand phase, it can also be used as a factor in determining appropriate
fire intervals. It has been suggested that heather be burned before it
reaches 12 inches (30 cm) [
19]; heather more than 16 inches (40 cm) tall
often burns very severely and is thus seldom targeted for prescribed
fire [
30]. A well-managed fire removes most of the aerial vegetation
while still permitting vigorous vegetative regeneration [
10,
30].
Temperatures of about 752 degrees Fahrenheit (400 deg C) in the canopy
and less than 392 degrees Fahrenheit (200 deg C) at the soil surface are
optimal [
10]. Moderate heat may stimulate germination of seeds [
31].
Fire management of heather in wet bogs produces inconsistent results
[
10,
16]. Frequent burning of wet bogs in Ireland has in some cases led
to the replacement of heather by deciduous species. This in turn has
resulted in an increased amount of litter produced yearly and a lower
stocking capacity for sheep in winter. To maintain heather, areas can
be burned in long rotations [
24]. Longer intervals between fires (about
20 years) are also suggested for the management of wet bogs in Great
Britain. Frequent burning of heather there temporarily increases the
availability of young shoots, but the resulting community is dominated
by sheathed cottonsedge or moor-grass rather than heather. Burning may
not be required at all since heather remains in a "steady state" in wet
bog habitats [
16].
FIRE CASE STUDY
SPECIES: Calluna vulgaris
FIRE CASE STUDY CITATION : Matthews, Robin F., compiler. 1993. Heather response after moderate to severe fires
on Scottish heathland. In: Calluna vulgaris. In: Fire Effects Information
System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky
Mountain Research Station, Fire Sciences Laboratory (Producer). Available:
https://www.fs.fed.us/database/feis/ [
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REFERENCES : Hobbs, R. J.; Gimingham, C. H. 1984. Studies on fire in Scottish
heathland communities. I. Fire characteristics. Journal of Ecology. 72:
223-240. [
18].
Hobbs, R. J.; Gimingham, C. H. 1984. Studies on fire in Scottish
heathland communities. II. Post-fire vegetation development. Journal of
Ecology. 72: 585-610. [
19].
SEASON/SEVERITY CLASSIFICATION : Spring/moderately-severe to severe fires
STUDY LOCATION : The study sites were located on the Hill Farming Research Organization's
farm at Glensaugh, Kincardineshire, Scotland.
PREFIRE VEGETATIVE COMMUNITY : Prior to burning, the vegetation consisted of stands of species-poor
heath classified as Callunetum and Type A Callunetum by various authors.
Four stands were sampled and described in terms of growth phase of the
heather (there were no degenerate stands at the site):
Stand 1--pioneer (average age 5 years old, high productivity, low biomass)
Stand 2--building (average age 12 years old, high productivity)
Stand 3--mature (average age 14 years old, high biomass, production declining)
Stand 4--mature (average age 14 years old, high biomass, production declining)
Preburn frequencies (percent) of heather, hairgrass, dwarf bilberry,
deer fern (Blechnum spicant), rush (Juncus squarrosus), potentilla
(Potentilla erecta), and some mosses at the site were:
Stand 1 Stand 2 Stand 3
________________________________________________________________
heather 100 100 100
hairgrass 50.0 34.4 25.8
dwarf bilberry 94.5 63.3 57.0
deer fern -- 1.6 --
rush -- 2.3 --
potentilla 1.6 4.7 --
Dicranum scoparium 8.6 7.0 --
Hypnum jutlandicum 20.3 35.1 32.0
Polytrichum longisetum 0.8 4.7 0.8
Preburn vegetation was not reported for Stand 4.
This fire study was also conducted at another site classified as a
species-rich heath of the Arctostaphyleto-Callunetum type. Heather was
codominant at that site and some of the stands were in the degenerate
phase.
TARGET SPECIES PHENOLOGICAL STATE : SITE DESCRIPTION : Site characteristics for the stands follow:
Stand 1 Stand 2 Stand 3 Stand 4
_______________________________________________________________________
Slope (deg) 10 10 7 10
Aspect NW NW NW SW
Altitude (m) 400 400 400 420
The substrate consisted of podzolized soils on quartz schist till. Mean
temperatures in the area are 30 degrees Fahrenheit (-0.8 deg C) in
January and 56 degrees Fahrenheit (13.4 deg C) in July. Annual rainfall
ranges from 35 to 48 inches (870-1,190 mm).
FIRE DESCRIPTION : The four stands at the site varied considerably in size but all were at
least 33 by 66 feet (10 X 20 m), and all were burned on April 26, 1978.
The stands were situated close to one another and some were burned by
the same fire. Prefire conditions were as follows (soil and vegetation
moistures expressed as percent dry weight):
Stand 1 Stand 2 Stand 3 Stand 4
___________________________________________________________________________
Soil moisture 258 259 305 275
Vegetation moisture 101 144 129 109
Mean windspeed (m/sec) 6 6 8 8.5
Fuel consumed (g/sq m) 868 1116 2048 1688
Rate of spread (m/min) 0.25 1.33 0.33 1.0
Duration (min) 5 4 5 5
Width of front (m) 5 12 12 25
Maximum temperature (deg C)
Canopy 340 620 440 660
Soil surface 180 590 560 840
Time above 400 deg C (sec) 0 30 5 30
Time above 600 deg C (sec) 0 3 0 24
Intensity (kW/m) 56 593 227 690
Available heat energy (MJ/sq m) 13.4 26.8 41.4 41.4
FIRE EFFECTS ON TARGET SPECIES : Temperatures and intensities increased with stand age until the mature
phase. These values declined in degenerate stands at the species-rich
Arcostaphyleto-Callunetum heath site. The open, discontinuous stands
(pioneer and degenerate phases) burned more slowly than the more
homogenous stands (building and mature phases). The collapse of the
canopy in degenerate stands altered the fuel configuration so that fire
temperatures remained relatively low.
Postfire vegetative growth of heather was very rapid in the pioneer
phase and led to recovery of dominance by heather. It reached a
frequency of almost 100 percent by the end of the first growing season.
Less postfire vegetative growth occurred in the building phase, which
resulted in a mixed heather-dwarf bilberry community at postfire year 3.
Virtually no vegetative growth occurred after fire in the mature-phase
stands.
Heather seedlings were found in all stands from the second growing
season onwards but remained infrequent except in the building stand. In
the mature stands, regeneration was almost entirely from seed. Numerous
seedlings established and subsequently died in stand four (mature
phase), but their numbers increased during the third postfire growing
season. Early seedling mortality allowed dwarf bilberry and hairgrass
to spread rapidly, and created a dwarf bilberry-dominated community by
postfire year 3.
The densities (number/sq m) of aboveground shoots and seedlings of
heather in the year of the fire and in 2 successive years follow:
Stand 1 Stand 2 Stand 3 Stand 4
___________________________________________________________________
Vegetative shoots
1978 157.0 60.5 3.0 1.7
1979 106.2 51.0 2.0 2.0
1980 70.7 43.0 2.0 2.0
Seedlings
1978 0 0 0 0
1979 2.5 4.2 52.0 11.5
1980 0.7 15.7 4.5 17.0
FIRE MANAGEMENT IMPLICATIONS : Vegetation height may be a useful integrating factor for determining the
state of a stand and its fuel availability. It has been suggested that
heather be burned before it reaches 12 inches (30 cm).
Burning old stands of heather may lead to a rapid spread of rhizomatous
species (such as dwarf bilberry) when these species were present before
the fire, even in small quantities. In old heather stands where
rhizomatous species are not present, colonization by heather seedlings
may take a very long time and bare ground may remain for many years. In
both cases, the lack of rapid heather regeneration is of concern since
it is often the major forage species present on these species-poor
heaths. In addition, soil erosion continues until vegetative cover is
established, and the risk of erosion is much greater when heather growth
is delayed. Fire, therefore, may be an unsuitable form of management in
old stands of heather.
