234
R. DAUBENMIRE
the heat required to convert the ice back t o liquid (Byram, 1948).
Where deliberats burning is dcsirablc to eliminate littcr, selection of a
date when the soil iu wet and the litter hltR barely dried minimizes the
rate of h a t release arid so involvm least risk of damaging plants
(Aldous, 1935).
Hcadfires generally cause less damage than backfires because the
maximum temperature along the vertical fire profile is well elevated
above the ground where seeds and perennating buds are located. Backfires are more damaging (other factors being equal) because the maxima
are nearer the ground and higher than in headfires.
The greater the amount of fuel (Conrad and Poulton, 1966; Hopkins
et al., 1948; Iwanami and Iizumi, 1966b), the more the habitat has been
degraded by erosion (Robocker and Miller, 1955), or the drier the climate the greater the damage has been observed, other conditions being
equal. In southern Africa according to Bosman (1932) fire is detrimental to grassland only in areas with less than 30 in. annum, precipitation. Burbidge ( 1943) in Australia, oberved that Triodia pungens
is usually killed by fire in inland areas but not along tho coast. This
difference may be related to climate.
Plant characteristics are also important determingnts of fire damage,
especially the phenologic condition at the time. Generally as the new
foliage of perennials reaches its full size, the major part of the food
reserves have been withdrawn from the underground organs, so that
fire destroying leaves at this time injures the plant most severely
(Aldous, 1934). Thus when a fire ran through a mixed planting of grass
species in Wisconsin, species which had started growth early were
damaged, whereas others escaped injury (Robocker and Miller, 1955).
This relationship between damage and phenology probably accounts
for the widely observed phenomenon of fire damaging PIX pratensi8
in the midcontinental grasslands of North America, whereas associated
species are stimulated (Curtis and Partsch, 1948; Graber, 1926). Poa
is a genus of northern derivation that starts growth early, whereas the
native dominants such as Adropogm, Sorphaetrum, Panicurn, are of
southern extraction and remain dormant; until the warm season is
more advanced. In the Transvaal (Cook, 1965; Phillips, 1919, see West,
1965) and Natal (West, 1943, 1951, see West, 1966) too, the later the
date of burning after the start of the rainy setwon which causes resumption of growth, the greater the damage to grasses. When individual perennial grass plants were burned at different seaaom by igniting sufficient shredded paper to raise temperature at the bases of the
plants to approximately 90 or 200°C, the month of treatment had a
significant effect on the degree of damage (Wright and Klemmedrson,
1 965).
R. DAUBENMIRE
the heat required to convert the ice back t o liquid (Byram, 1948).
Where deliberats burning is dcsirablc to eliminate littcr, selection of a
date when the soil iu wet and the litter hltR barely dried minimizes the
rate of h a t release arid so involvm least risk of damaging plants
(Aldous, 1935).
Hcadfires generally cause less damage than backfires because the
maximum temperature along the vertical fire profile is well elevated
above the ground where seeds and perennating buds are located. Backfires are more damaging (other factors being equal) because the maxima
are nearer the ground and higher than in headfires.
The greater the amount of fuel (Conrad and Poulton, 1966; Hopkins
et al., 1948; Iwanami and Iizumi, 1966b), the more the habitat has been
degraded by erosion (Robocker and Miller, 1955), or the drier the climate the greater the damage has been observed, other conditions being
equal. In southern Africa according to Bosman (1932) fire is detrimental to grassland only in areas with less than 30 in. annum, precipitation. Burbidge ( 1943) in Australia, oberved that Triodia pungens
is usually killed by fire in inland areas but not along tho coast. This
difference may be related to climate.
Plant characteristics are also important determingnts of fire damage,
especially the phenologic condition at the time. Generally as the new
foliage of perennials reaches its full size, the major part of the food
reserves have been withdrawn from the underground organs, so that
fire destroying leaves at this time injures the plant most severely
(Aldous, 1934). Thus when a fire ran through a mixed planting of grass
species in Wisconsin, species which had started growth early were
damaged, whereas others escaped injury (Robocker and Miller, 1955).
This relationship between damage and phenology probably accounts
for the widely observed phenomenon of fire damaging PIX pratensi8
in the midcontinental grasslands of North America, whereas associated
species are stimulated (Curtis and Partsch, 1948; Graber, 1926). Poa
is a genus of northern derivation that starts growth early, whereas the
native dominants such as Adropogm, Sorphaetrum, Panicurn, are of
southern extraction and remain dormant; until the warm season is
more advanced. In the Transvaal (Cook, 1965; Phillips, 1919, see West,
1965) and Natal (West, 1943, 1951, see West, 1966) too, the later the
date of burning after the start of the rainy setwon which causes resumption of growth, the greater the damage to grasses. When individual perennial grass plants were burned at different seaaom by igniting sufficient shredded paper to raise temperature at the bases of the
plants to approximately 90 or 200°C, the month of treatment had a
significant effect on the degree of damage (Wright and Klemmedrson,
1 965).