220
R. DAUBENMIRE
in thc plant, ash. Any H U C ~
hypothesis must account for the promptness
of the responHe, and graw may respond within a few days. Furthermore
the same htimulation should be obtainable merely by clipping and
sweeping a plot, especially if the surface is then darkened with powdered
charcoal.
Most opportunities to study fire ecology derive from unintentional
burning, and although conditions are wholly natural and therefore of
more certain ecologic significance, there are never any records of temperature conditions. Some success has been achieved by using the nature
of the unburned plant residues as indicators of relative heat levels. I n
eastern Idaho, Blaisdell (1953) classed the fire as “light” if foliage of
the Artemiviu shrubs had been killed without the twigs being consumed,
“moderate” if twigs were consumed but thick stems remained standing,
and “heavy” if the entire shoot system had burned away. I n Oregon
Conrad and Poulton (1966) classified burning intensity with respect to
individual plants of the caespitose grasses: Class 1, plants unburned but
may be scorched; Class 2 , plants partly burned but not within 50 mm
of the “root crown”; Class 3, plants severely burned but with some unburned stubble under 50 mm high; Class 4, extremely burned but with
some unburned stubble, this mostly confined to an outer ring; Class 6 ,
all shoot material consumed.
R . O R G A N I C MATTER
1. Litter
Following a fire that consumes both standing and fallen litter in a
dormant stand of grass, all the new shoots stand more stiffly erect when
they dry, in which position they decompose extremely slowly (McCalla,
1943). Also tht: reduced shade ~ 1 1 0 ~ s
the soil surface to dry readily, and
this keeps microhial activity to a minimum (Dix, 1960). Both of these
inflnent-es tend to interrupt the normal turn-over process, but their
influence declines progressively 8s the seasons pass.
Two growing .retisons in eastcrn Illinois allowed the accumulation of
A ndropogon gerardi and Korghastrum nutnns litter to so closely approximate that of an unburned control, that 2-3 years was estimated as the
turn-ovcr rate (Hudlry and Kiekhefer, 1963). This was a site deep
within the “prairie peninsula” where only fire had prevented forest
growth before the arrival of white man. In the adjoining state of Iowa,
in fhP western edge of the “prairie peninsula” where Andropogon scop0riu.s nnd A . yerardi are the characteristic dominants, 5 years have
been estimated as the time to equilibrium for litter restoration (Ehrenreich and Aikman, 1963). To the north in Minnesota, again near the
climatic edge of forest, litter cover was back to normal in 2-3 seasons
(Tester and Marshall, 1961).
R. DAUBENMIRE
in thc plant, ash. Any H U C ~
hypothesis must account for the promptness
of the responHe, and graw may respond within a few days. Furthermore
the same htimulation should be obtainable merely by clipping and
sweeping a plot, especially if the surface is then darkened with powdered
charcoal.
Most opportunities to study fire ecology derive from unintentional
burning, and although conditions are wholly natural and therefore of
more certain ecologic significance, there are never any records of temperature conditions. Some success has been achieved by using the nature
of the unburned plant residues as indicators of relative heat levels. I n
eastern Idaho, Blaisdell (1953) classed the fire as “light” if foliage of
the Artemiviu shrubs had been killed without the twigs being consumed,
“moderate” if twigs were consumed but thick stems remained standing,
and “heavy” if the entire shoot system had burned away. I n Oregon
Conrad and Poulton (1966) classified burning intensity with respect to
individual plants of the caespitose grasses: Class 1, plants unburned but
may be scorched; Class 2 , plants partly burned but not within 50 mm
of the “root crown”; Class 3, plants severely burned but with some unburned stubble under 50 mm high; Class 4, extremely burned but with
some unburned stubble, this mostly confined to an outer ring; Class 6 ,
all shoot material consumed.
R . O R G A N I C MATTER
1. Litter
Following a fire that consumes both standing and fallen litter in a
dormant stand of grass, all the new shoots stand more stiffly erect when
they dry, in which position they decompose extremely slowly (McCalla,
1943). Also tht: reduced shade ~ 1 1 0 ~ s
the soil surface to dry readily, and
this keeps microhial activity to a minimum (Dix, 1960). Both of these
inflnent-es tend to interrupt the normal turn-over process, but their
influence declines progressively 8s the seasons pass.
Two growing .retisons in eastcrn Illinois allowed the accumulation of
A ndropogon gerardi and Korghastrum nutnns litter to so closely approximate that of an unburned control, that 2-3 years was estimated as the
turn-ovcr rate (Hudlry and Kiekhefer, 1963). This was a site deep
within the “prairie peninsula” where only fire had prevented forest
growth before the arrival of white man. In the adjoining state of Iowa,
in fhP western edge of the “prairie peninsula” where Andropogon scop0riu.s nnd A . yerardi are the characteristic dominants, 5 years have
been estimated as the time to equilibrium for litter restoration (Ehrenreich and Aikman, 1963). To the north in Minnesota, again near the
climatic edge of forest, litter cover was back to normal in 2-3 seasons
(Tester and Marshall, 1961).