ECOLOGY OF FIRE IN GRASSLANDS
241
crazing not only complicates the influences of fire through keeping
flammable bhooL residues to a minimum, but where animals have unreRtrictd accese to the new growth on a burn they tend tc, keep it
eaten down to hhe ground surf‘acx, which severely tax- the root reserves and jeopardizes the possibility of recovery. Fire that otherwise
might stimulate increased productivity can in this way be indirectly
devmtating to grass.
It is possible that part of the greater gains made by cattle grazing
on burned grasslands might be derived not from the superior nutritive
quality of the grass, but in part from its completc availability to the
ground surface. This could allow animals to consume a greater bulk in
shorter time without spending too much energy walking about. Furthermore, each mouthful of grass from burned areas is not diluted by
weathered straw which reduces the total intake of highly nutritive
green grass.
In arid climates short species of grasbes (called “sweet veld” in
southern Africa) retain much of their nutritive value as they cure
(Acocks, 1965; Staples, 1945). Here fires not only consume a valuable
standing crop of forage, but the perennial species are usually damaged,
the seeds of annuals depleted, and soil erosion is favored. Under higher
rainfall, in contrast, the taller grasses (called “sour veld” in southern
Africa) lose their nutritive value aa the shoots mature, RO that at least
patches remain ungrazed, with usable forage declining and the firehazard increasing.
The duration of any fire-altered composition is another aspect of the
phenomenon that is not only of major importance in applied ecology
but must be taken into account in any physiologic explanation. In the
main, perennial grasses in the wet tropics have, even when young, a
lower protein content than equivalent temperate zone species, and increases in nutritive quality following a burn fall rapidly as the foliage
matures. At maturity such forage is critically deficient for the nutrition
of livestock (French, 195!3). On the Coastal Plain of southeastern North
America the post-burn improvement of herbage quality lasts only 2+5
months (Campbell and Cassady, 1951 ; Jardine et al., 1945; Hilmon and
Lewis, 1962; Neal and Becker, 1933). In southern Africa it has been a
common practice to burn half of a grazing unit each 6 months to maintain a continuous supply of Ratisfactory forage (Botha, 1945). Thus it
is not, difficult to bee the necessity of at least annual burning in the
mokt tropics, not only to remove unused grass that hm lost its food
valiic and i R tt mechnnicril hindrance to grazing, but to maintain new
herbage in Ratisfactory nutritive condition.
241
crazing not only complicates the influences of fire through keeping
flammable bhooL residues to a minimum, but where animals have unreRtrictd accese to the new growth on a burn they tend tc, keep it
eaten down to hhe ground surf‘acx, which severely tax- the root reserves and jeopardizes the possibility of recovery. Fire that otherwise
might stimulate increased productivity can in this way be indirectly
devmtating to grass.
It is possible that part of the greater gains made by cattle grazing
on burned grasslands might be derived not from the superior nutritive
quality of the grass, but in part from its completc availability to the
ground surface. This could allow animals to consume a greater bulk in
shorter time without spending too much energy walking about. Furthermore, each mouthful of grass from burned areas is not diluted by
weathered straw which reduces the total intake of highly nutritive
green grass.
In arid climates short species of grasbes (called “sweet veld” in
southern Africa) retain much of their nutritive value as they cure
(Acocks, 1965; Staples, 1945). Here fires not only consume a valuable
standing crop of forage, but the perennial species are usually damaged,
the seeds of annuals depleted, and soil erosion is favored. Under higher
rainfall, in contrast, the taller grasses (called “sour veld” in southern
Africa) lose their nutritive value aa the shoots mature, RO that at least
patches remain ungrazed, with usable forage declining and the firehazard increasing.
The duration of any fire-altered composition is another aspect of the
phenomenon that is not only of major importance in applied ecology
but must be taken into account in any physiologic explanation. In the
main, perennial grasses in the wet tropics have, even when young, a
lower protein content than equivalent temperate zone species, and increases in nutritive quality following a burn fall rapidly as the foliage
matures. At maturity such forage is critically deficient for the nutrition
of livestock (French, 195!3). On the Coastal Plain of southeastern North
America the post-burn improvement of herbage quality lasts only 2+5
months (Campbell and Cassady, 1951 ; Jardine et al., 1945; Hilmon and
Lewis, 1962; Neal and Becker, 1933). In southern Africa it has been a
common practice to burn half of a grazing unit each 6 months to maintain a continuous supply of Ratisfactory forage (Botha, 1945). Thus it
is not, difficult to bee the necessity of at least annual burning in the
mokt tropics, not only to remove unused grass that hm lost its food
valiic and i R tt mechnnicril hindrance to grazing, but to maintain new
herbage in Ratisfactory nutritive condition.