ECOI,OOY OF MRP: IN QEASSLANDS
21 9
Fire affect8 post-burn soil temperature indirectly through the removal of living plant shoots and litter that had previously intercepted
much of the direct insolation and retarded loss of soil heat by radiation,
these influences radically altering the thermal regime of the soil surface
and the adjacent' layer of air as well.
Where the grass beneath pine had been recently burned in southeastern North America, soil temperature at a depth of 7.0 cm was
found to average 04--3.3"C higher (Garren, 1943; Greene, 1935a;
Wehlenberg, 1955).
In the eastern half of the central grassland of North America where
Andropogon scoparius and A . gerardi are characteristic dominants,
maximum soil surface temperatures in mid-afternoon have been found
2.2-9-8"C higher on burned plots in spring, with the difference declining progressively as plant cover develops during the first post-burn
Beason (Kucera and Ehrenreich, 1962). In comparable habitat types in
the same general region, Steiger (1930) found late March soil temperatures 5.6"C warmer a t 2.5 and 7.6 cm, and 3.9 warmer a t 15 cm. In
Kansas the maximum temperature at a depth of 2.5 om was raised
about 6.7"C, and the minimum likewise raised by 1.1"C (Hensel, 1923a),
but in Iowa minimum soil surface temperatures were not significantly
altered by fire (Kucera and Ehrenreich, 1962). Others have reported the
soil warmer up to 18 rm deep (Aldous, 1934; Ehrenreich and Aikman,
1963). In this same steppe region the maximum air temperature at an
elevation of 2.5 cm was raised 5.6"C, and the minima generally lowered
at night (Ehrenreich and Aikman, 1963).
I n British grazing lands the mean maximum air temperature a t the
base of a burned Motinia mrulea tussock was found 3.3"C higher, with
the minimum reduced by O.S"C, as compared with a corresponding
position beside an unburned plant (Grant et al., 1963). Here, in the
second month after a spring burn, soil temperatures averaged 1.1"C
higher at a depth of 7.6 cm. In a follow-up experiment, the growth of
potted Molinia plants with soil temperatures held fairly constant and
a t somewhat intermediate levels, was compared with growth in another
RerieA in which temperatures fluctuated from warmer to colder than
natuml ronditions. Molinia produced more tillers and more inflorescences under the latter regime. This suggested that the warmer soil
following fire may account for t
Even in thehctic, grassland burning raises soil temperatures in spring,
thk resulting in an earlier melting of ice in the soil (Fridriksson, 1963).
One of the hypotheses accounting for the frequently observed stimulative effects of'krassland fires is that the stimulation is more an indirect
result of altered temperatures than of readily available nutrients freed
21 9
Fire affect8 post-burn soil temperature indirectly through the removal of living plant shoots and litter that had previously intercepted
much of the direct insolation and retarded loss of soil heat by radiation,
these influences radically altering the thermal regime of the soil surface
and the adjacent' layer of air as well.
Where the grass beneath pine had been recently burned in southeastern North America, soil temperature at a depth of 7.0 cm was
found to average 04--3.3"C higher (Garren, 1943; Greene, 1935a;
Wehlenberg, 1955).
In the eastern half of the central grassland of North America where
Andropogon scoparius and A . gerardi are characteristic dominants,
maximum soil surface temperatures in mid-afternoon have been found
2.2-9-8"C higher on burned plots in spring, with the difference declining progressively as plant cover develops during the first post-burn
Beason (Kucera and Ehrenreich, 1962). In comparable habitat types in
the same general region, Steiger (1930) found late March soil temperatures 5.6"C warmer a t 2.5 and 7.6 cm, and 3.9 warmer a t 15 cm. In
Kansas the maximum temperature at a depth of 2.5 om was raised
about 6.7"C, and the minimum likewise raised by 1.1"C (Hensel, 1923a),
but in Iowa minimum soil surface temperatures were not significantly
altered by fire (Kucera and Ehrenreich, 1962). Others have reported the
soil warmer up to 18 rm deep (Aldous, 1934; Ehrenreich and Aikman,
1963). In this same steppe region the maximum air temperature at an
elevation of 2.5 cm was raised 5.6"C, and the minima generally lowered
at night (Ehrenreich and Aikman, 1963).
I n British grazing lands the mean maximum air temperature a t the
base of a burned Motinia mrulea tussock was found 3.3"C higher, with
the minimum reduced by O.S"C, as compared with a corresponding
position beside an unburned plant (Grant et al., 1963). Here, in the
second month after a spring burn, soil temperatures averaged 1.1"C
higher at a depth of 7.6 cm. In a follow-up experiment, the growth of
potted Molinia plants with soil temperatures held fairly constant and
a t somewhat intermediate levels, was compared with growth in another
RerieA in which temperatures fluctuated from warmer to colder than
natuml ronditions. Molinia produced more tillers and more inflorescences under the latter regime. This suggested that the warmer soil
following fire may account for t
Even in thehctic, grassland burning raises soil temperatures in spring,
thk resulting in an earlier melting of ice in the soil (Fridriksson, 1963).
One of the hypotheses accounting for the frequently observed stimulative effects of'krassland fires is that the stimulation is more an indirect
result of altered temperatures than of readily available nutrients freed