248
R. DAUBENMIRE
gerardi sucdlings ttppcared abundantly after (t fire, and the germination of Am6rosiu arternissifolia (annual forb) was stimulated at the
same time (Curtis and Partsch, 1!)48). The aame has been reported for
Ckionochloa rigida in New Zealand (Mark, 196513) and for Heteropogon
contortua in Australia (Shaw, 1967). Shaw (1957), who found seedlings
of Heteropogon contortus appearing in great numbers only on burned
surfaces, obtained soil samples both before and after burning and found
that they produced equal numbers of seedlings in a glasshouse environment. Thus the stimulation in that case at least, seems a consequence of
altered environment, rather than a change in the condition of the
caryopses themselves.
Seeds harvested from recently burned grassland in Iowa (Ehrenreich
and Aikman, 1957) and in Britain (Grant et al., 1963) were found to have
a higher percentage germination than those on nearby unburned gramland, thus reflecting the greater vigor and vitality of burned plants.
VI. EFFECTS O N PLANT COMMUNITIES
A. CHANGES I N FLORA
Species growing together may respond very differently to the same
fire. Some may be in an active state of growth and especially sueceptible
at the time, whereas others are dormant and less susceptible. Thw in
the Mississippi Valley the early resumption of growth in spring by the
boreal Poa pratensis renders it very susceptible to injury by spring
burning, whereas the still dormant austral species of Andropogon,
Sorghtrum and Yanicum are not the least damaged (McMurphy and
Anderson, 1965). Some species may have perennating buds held above
the ground surface where they are easily killed, while associates have
their buds b u r i d in the soil. Sometimes differences in post-burn composition reflects not so much differences in damage aa in promptness of
recovery, for possession of latent buds or an ability to produce adventitious buds promptly when stimulated, gives competitive advantage
to survivors. Then, too, differing responses to post-burn environment
must exert their own measure of influence on post-burn population
balances.
Woody species that do not sprout from their roots can be either
eliminated (Scott, 1961; West, 1965), or reduced to a thin stand of small
individuals (Humphrey, 1958) by repeatcd burning. Fire is therefore
widely used RS a means of maintaining grass domiriance in environments where in its absence woody vegetation would overwhelm gram
This is true of much of the tropical savanna (Cook, 1939; Scott, 19Sl)
and of the open pine forest and savanna on the Atlantic Coastal Plain
of southeaatern North America (Garren, 1943).
R. DAUBENMIRE
gerardi sucdlings ttppcared abundantly after (t fire, and the germination of Am6rosiu arternissifolia (annual forb) was stimulated at the
same time (Curtis and Partsch, 1!)48). The aame has been reported for
Ckionochloa rigida in New Zealand (Mark, 196513) and for Heteropogon
contortua in Australia (Shaw, 1967). Shaw (1957), who found seedlings
of Heteropogon contortus appearing in great numbers only on burned
surfaces, obtained soil samples both before and after burning and found
that they produced equal numbers of seedlings in a glasshouse environment. Thus the stimulation in that case at least, seems a consequence of
altered environment, rather than a change in the condition of the
caryopses themselves.
Seeds harvested from recently burned grassland in Iowa (Ehrenreich
and Aikman, 1957) and in Britain (Grant et al., 1963) were found to have
a higher percentage germination than those on nearby unburned gramland, thus reflecting the greater vigor and vitality of burned plants.
VI. EFFECTS O N PLANT COMMUNITIES
A. CHANGES I N FLORA
Species growing together may respond very differently to the same
fire. Some may be in an active state of growth and especially sueceptible
at the time, whereas others are dormant and less susceptible. Thw in
the Mississippi Valley the early resumption of growth in spring by the
boreal Poa pratensis renders it very susceptible to injury by spring
burning, whereas the still dormant austral species of Andropogon,
Sorghtrum and Yanicum are not the least damaged (McMurphy and
Anderson, 1965). Some species may have perennating buds held above
the ground surface where they are easily killed, while associates have
their buds b u r i d in the soil. Sometimes differences in post-burn composition reflects not so much differences in damage aa in promptness of
recovery, for possession of latent buds or an ability to produce adventitious buds promptly when stimulated, gives competitive advantage
to survivors. Then, too, differing responses to post-burn environment
must exert their own measure of influence on post-burn population
balances.
Woody species that do not sprout from their roots can be either
eliminated (Scott, 1961; West, 1965), or reduced to a thin stand of small
individuals (Humphrey, 1958) by repeatcd burning. Fire is therefore
widely used RS a means of maintaining grass domiriance in environments where in its absence woody vegetation would overwhelm gram
This is true of much of the tropical savanna (Cook, 1939; Scott, 19Sl)
and of the open pine forest and savanna on the Atlantic Coastal Plain
of southeaatern North America (Garren, 1943).