226
R. DAUBENMIRE
the ash is so scanty in comparison as to seem of negligible importance.
Nye (1959), for example, showed that in Ghana the quantity of nutrients
released in burning the herb layer of savanna is only a fraction of that
released by the burning of forest:
P - 8.4 kglhectare, forest 16 times a~ much,
K - 49.2 kglhectare, forest 18 times as much,
Ca - 37.2 kglhectare, forest 73 times as much,
Mg - 27.6 kglhectare, forest 13 times as much.
Nevertheless, through biometric analysis of experimental data, Curtis
and Partsch (1950) obtained slightly significant relations between the
ash increment and the number of inflorescences produced by Andropogm gerurdi following fire in Wisconsin. No other work supports this
(e.g. Mark, 1965c), although the suspicion that ash fertilization may be
a Significant factor in post-burn stimulation has often been expressed
in publication, and in fact even the Romans believed that burning a
cover of dry grass increased soil fertility (Russell, 1950).
I n the Bouteloua steppe of southeastern Arizona determinations of
the soluble salt content of the upper 25 mm of soil following fire revealed no consistent evidence of increase (Reynolds and Bohning, 1956).
Sampson (1944) grew Bromus mollis, a species prospering in the frequently burned annual grassland of California, in soil to which plant
ash (from woody plants) was added. An ash increment 3 mm thick
(considerably more than a grass fire would yield, especially in California) stimulated Bromus in its early stages, but later the stimulation
disappeared and flowering was reduced in the ash-treated cultures.
2. pH Value
Annual burning of Themeda grassland in southern Africa has been
reported 88 raising the pH of the upper 38 mm of the soil from 5.8 to
6.7 (Cook, 1939). Also the pH of Nigerian savanna soil is raised by
annual burning from 6.0 to 6.2, if the burns are late in the dry season
and very hot, or to 6.3 if the burning is early in the dry season when
temperatures are not so high (Moore, 1960).
A grassland fire in Iowa increased the pH of the upper 18 mm of the
soil from 8.8 to 6.1, with the increase tending to be proportional to the
amount of litter oxidized (Ehrenreich and Aikman, 1963). But within
a year the pH was back to normal, presumably in consequence of
dissipation of bases by leaching. In the next state to the east, the burning of a Poa-forb community raised pH about equally, from 5.8 to 6-3
(Rice, 1932). On the coastal plain of southeastern North America grass
burning likewise has been shown to raise soil pH (Heyward and Barnette, 1934; Greene, 1935a; Heyward, 1936; Garren, 1943).
In all the above localities grass burning consistently raises the pH of
R. DAUBENMIRE
the ash is so scanty in comparison as to seem of negligible importance.
Nye (1959), for example, showed that in Ghana the quantity of nutrients
released in burning the herb layer of savanna is only a fraction of that
released by the burning of forest:
P - 8.4 kglhectare, forest 16 times a~ much,
K - 49.2 kglhectare, forest 18 times as much,
Ca - 37.2 kglhectare, forest 73 times as much,
Mg - 27.6 kglhectare, forest 13 times as much.
Nevertheless, through biometric analysis of experimental data, Curtis
and Partsch (1950) obtained slightly significant relations between the
ash increment and the number of inflorescences produced by Andropogm gerurdi following fire in Wisconsin. No other work supports this
(e.g. Mark, 1965c), although the suspicion that ash fertilization may be
a Significant factor in post-burn stimulation has often been expressed
in publication, and in fact even the Romans believed that burning a
cover of dry grass increased soil fertility (Russell, 1950).
I n the Bouteloua steppe of southeastern Arizona determinations of
the soluble salt content of the upper 25 mm of soil following fire revealed no consistent evidence of increase (Reynolds and Bohning, 1956).
Sampson (1944) grew Bromus mollis, a species prospering in the frequently burned annual grassland of California, in soil to which plant
ash (from woody plants) was added. An ash increment 3 mm thick
(considerably more than a grass fire would yield, especially in California) stimulated Bromus in its early stages, but later the stimulation
disappeared and flowering was reduced in the ash-treated cultures.
2. pH Value
Annual burning of Themeda grassland in southern Africa has been
reported 88 raising the pH of the upper 38 mm of the soil from 5.8 to
6.7 (Cook, 1939). Also the pH of Nigerian savanna soil is raised by
annual burning from 6.0 to 6.2, if the burns are late in the dry season
and very hot, or to 6.3 if the burning is early in the dry season when
temperatures are not so high (Moore, 1960).
A grassland fire in Iowa increased the pH of the upper 18 mm of the
soil from 8.8 to 6.1, with the increase tending to be proportional to the
amount of litter oxidized (Ehrenreich and Aikman, 1963). But within
a year the pH was back to normal, presumably in consequence of
dissipation of bases by leaching. In the next state to the east, the burning of a Poa-forb community raised pH about equally, from 5.8 to 6-3
(Rice, 1932). On the coastal plain of southeastern North America grass
burning likewise has been shown to raise soil pH (Heyward and Barnette, 1934; Greene, 1935a; Heyward, 1936; Garren, 1943).
In all the above localities grass burning consistently raises the pH of