260
It. 1) A U I3 EX M IRE
Ail studies of fire irifliionccH stiould t x relatcrl to specific habitat types
defined on the banis of ttwir I)otn.ntittl naturd vegetation, arid described
in terms of tho current condition of the vegetation. In eastern ldaho,
for example, it has been found that the effects of burning shrub steppe
are less pronounced in habitats where Artfmisia tripartita is the dominant shrub, rather than in habitats where Artemisin tridentnta is dominant (Pechanec et nl., 1954). In Oregon, fire was morc destructive where
Festucu idahoensis was tlie dominant grass than in contiguous stands
where Agropyron spicutum dominated (Conrad and Poulton, 1966).
B. C H A N G E S I N DENSITY A N D PRODUCTIVITY
The previous section was concerned with qualitative changes in
grasslands in consequence of burning. Attention will now be turned to
quantitative changes.
In perennial grassland, burning may increase plant density (Cook,
1965; Cushwa and Kedd, 1966) or reduce it. In annual grassland the
effect is usually to reduce density in consequence of destroying a portion
of the current seed crop. The widely spaced survivors may then grow
to abnormally large sizc during the first post-burn season (Pechanec
and Hull, 1945), producing large quantities of seed so that pre-burn
densities are re-establishcd (luring the second season.
The grazier has an obvious intcrc st in the effects of fire on the amount
of forage subsequently produced, whereas a scientist is more likely to
be interested in production for the contribution such information can
make to an understanding of the manner in which fire affects the functions of an ecosystem. Since the effect of fire on production shows a
remarkable consistency within it geographic region, with wide differences between regions, a geographic arrangement of the available data
is in order.
In southern Florida Aristida stricta grassland must be burned regularly to maintain forage quality at a useful level, despite the fact that
fire reduces productivity, with normal yield not being restored until the
third post-burn season (Hilmon and Lewis, 1962). This reduction is
minimized if burning is done in spring (March-May) rather than fall
and winter (Octoberdanuary) (Lewis, 1964).
Annual burning of the grass beneath open stands of Pinus palwtris
in Georgia and Mississippi was found to increase production of herbage
119% (Greene, 1935a). In Virginia Cushwa and Redd (1966) recorded
6 times as many grass plants on a burned area as on the unburned
control, and 24 times as many herbaceous legume plants. In South
Carolina where the small bamboo Arundinaria tecta constitutes the
understory beneath pine, the productivity of this plant increased progressively after burning, becoming 32% greater by the third post-burn
It. 1) A U I3 EX M IRE
Ail studies of fire irifliionccH stiould t x relatcrl to specific habitat types
defined on the banis of ttwir I)otn.ntittl naturd vegetation, arid described
in terms of tho current condition of the vegetation. In eastern ldaho,
for example, it has been found that the effects of burning shrub steppe
are less pronounced in habitats where Artfmisia tripartita is the dominant shrub, rather than in habitats where Artemisin tridentnta is dominant (Pechanec et nl., 1954). In Oregon, fire was morc destructive where
Festucu idahoensis was tlie dominant grass than in contiguous stands
where Agropyron spicutum dominated (Conrad and Poulton, 1966).
B. C H A N G E S I N DENSITY A N D PRODUCTIVITY
The previous section was concerned with qualitative changes in
grasslands in consequence of burning. Attention will now be turned to
quantitative changes.
In perennial grassland, burning may increase plant density (Cook,
1965; Cushwa and Kedd, 1966) or reduce it. In annual grassland the
effect is usually to reduce density in consequence of destroying a portion
of the current seed crop. The widely spaced survivors may then grow
to abnormally large sizc during the first post-burn season (Pechanec
and Hull, 1945), producing large quantities of seed so that pre-burn
densities are re-establishcd (luring the second season.
The grazier has an obvious intcrc st in the effects of fire on the amount
of forage subsequently produced, whereas a scientist is more likely to
be interested in production for the contribution such information can
make to an understanding of the manner in which fire affects the functions of an ecosystem. Since the effect of fire on production shows a
remarkable consistency within it geographic region, with wide differences between regions, a geographic arrangement of the available data
is in order.
In southern Florida Aristida stricta grassland must be burned regularly to maintain forage quality at a useful level, despite the fact that
fire reduces productivity, with normal yield not being restored until the
third post-burn season (Hilmon and Lewis, 1962). This reduction is
minimized if burning is done in spring (March-May) rather than fall
and winter (Octoberdanuary) (Lewis, 1964).
Annual burning of the grass beneath open stands of Pinus palwtris
in Georgia and Mississippi was found to increase production of herbage
119% (Greene, 1935a). In Virginia Cushwa and Redd (1966) recorded
6 times as many grass plants on a burned area as on the unburned
control, and 24 times as many herbaceous legume plants. In South
Carolina where the small bamboo Arundinaria tecta constitutes the
understory beneath pine, the productivity of this plant increased progressively after burning, becoming 32% greater by the third post-burn