FIRE CASE STUDIES
SPECIES: Calluna vulgaris | Heather 



CASE NAME : 
Studies on Fire in Scottish Heathland Communities



REFERENCES : 
Hobbs, R. J.; Gimingham, C. H. 1984 [18,19]


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.

Related categories for Species: Calluna vulgaris | Heather