ECOLOGY OF FIRE IN GRASSLANDS
211
a repetition of burning at such short intervala aa to perpetuate firemodified vegetation types, the “fire-climaxes” of Tansley (1935), and
in recent years botanists have come to realize that a surprisingly large
portion of natural vegetation owes much of ita character to the frequence of man-induced fires. In some areas, e.g., east central Afrioa,
devastation by man-made fires continues to extend grassland at the
expense of forest (West, 1966), whereas in the upper Mississippi Valley
of the U S A . the arrival of white settlers who built roads that served
as unintentional fire-breaks, combined with active control of fire out of
fear of losing crops, livestock and buildings, led to rapid forest invasion
of grasslands which the aborigines had long maintained aa fire climaxes.
Likewise in southeastern U.S.A. there is evidence that the proportion
of grass in the vegetation mosaics when white man arrived was greater
than could be maintained without frequent fires (Garren, 1943).
The problems presented by fire in forests and in grasslands are basically different, and this is reflected even in their historical aspects. In
North America the conspicuous consequences of forest fires, the obvious
length of time required for the development of a new forest, and the
formerly more direct dependence of modern man on foreate for fuel and
building timbers, all helped direct attention to the economic loas incurred by forest burning early in this century. Grwland firm~, important chiefly through a temporary loss of pasturage, did not share
the spotlight of attention fhen, the attitude being one of indifference
or of deliberate burning in a belief that grazing was thus improved. In
fact, in 1731 a law in North Carolina required the annual burning of
pastures in March (Garren, 1943)!
Somewhat later, as conservation consciousness developed, khere arose
a strong current of opinion condemning firs in graaelands, this attitude
being simply an extension of judgment that had been passed on forest
burning. Thus a canvam of opinion reported by Rosevear in 1948, that
represented all of South America, indicated a practically universal disapproval of grassland burning on that continent. An illustration of the
extent to which this same opinion became; incorporated in reputable
scientific journals in North America is provided by the following comment published in 1926: “Scientific studies show mnclusivelyJ’ that
grassland fires “gradually decreaae the fertility of the soil by burning
up the humus. They also reduce the vitality of the desirable grasses
and thus encourage the spread of undeeirable graesea and wee&.’’ If
one were forced to take an unequivocable stand on these points today,
the mass of verifiable data that has accumulated make the opposite of
these statements more nearly correct. While it is true that most of this
evidence has accumulated subsequently to the quotation, it is equally
true that there ww no factual basis for such a statement at the time of
211
a repetition of burning at such short intervala aa to perpetuate firemodified vegetation types, the “fire-climaxes” of Tansley (1935), and
in recent years botanists have come to realize that a surprisingly large
portion of natural vegetation owes much of ita character to the frequence of man-induced fires. In some areas, e.g., east central Afrioa,
devastation by man-made fires continues to extend grassland at the
expense of forest (West, 1966), whereas in the upper Mississippi Valley
of the U S A . the arrival of white settlers who built roads that served
as unintentional fire-breaks, combined with active control of fire out of
fear of losing crops, livestock and buildings, led to rapid forest invasion
of grasslands which the aborigines had long maintained aa fire climaxes.
Likewise in southeastern U.S.A. there is evidence that the proportion
of grass in the vegetation mosaics when white man arrived was greater
than could be maintained without frequent fires (Garren, 1943).
The problems presented by fire in forests and in grasslands are basically different, and this is reflected even in their historical aspects. In
North America the conspicuous consequences of forest fires, the obvious
length of time required for the development of a new forest, and the
formerly more direct dependence of modern man on foreate for fuel and
building timbers, all helped direct attention to the economic loas incurred by forest burning early in this century. Grwland firm~, important chiefly through a temporary loss of pasturage, did not share
the spotlight of attention fhen, the attitude being one of indifference
or of deliberate burning in a belief that grazing was thus improved. In
fact, in 1731 a law in North Carolina required the annual burning of
pastures in March (Garren, 1943)!
Somewhat later, as conservation consciousness developed, khere arose
a strong current of opinion condemning firs in graaelands, this attitude
being simply an extension of judgment that had been passed on forest
burning. Thus a canvam of opinion reported by Rosevear in 1948, that
represented all of South America, indicated a practically universal disapproval of grassland burning on that continent. An illustration of the
extent to which this same opinion became; incorporated in reputable
scientific journals in North America is provided by the following comment published in 1926: “Scientific studies show mnclusivelyJ’ that
grassland fires “gradually decreaae the fertility of the soil by burning
up the humus. They also reduce the vitality of the desirable grasses
and thus encourage the spread of undeeirable graesea and wee&.’’ If
one were forced to take an unequivocable stand on these points today,
the mass of verifiable data that has accumulated make the opposite of
these statements more nearly correct. While it is true that most of this
evidence has accumulated subsequently to the quotation, it is equally
true that there ww no factual basis for such a statement at the time of