ECOLOGY OF FIRE IN URABYLANDS
247
c-hcrvations from Kansas where the progreseive decline in seed production after a fire was of%wt by applications of N (Cornelius, 1960).
In Britain, Grant et al. (1963) could not duplicate the flowering stimulus
that results from f i e by adding nutrients to unburned plots.
G . P L A N T F O R M
Earlier it was pointed out that burning may shorten leaves, but a t
the same time increase the number of tillers sp thgt dry-matter production of the plant is not materially altered (O’Connor and Powell,
1963). Where this observation was made it waa &o noted that the new
foliage was held more erect, thus reducing the protection of the soil
between plants against the beating of rain. On burned grasslands in
Iowa plants remained stiffly erect even in winter after they cured
(Aikman, 1955).
The above observations raise a question as to how much of the change
in coverage often reported as an indirect consequence of burning grasslands is a consequence of altered posture of the tillers, rather than
change in the volume of space occupied. by the shoot system, length of
leaves or basal area.
H. EIEED SURVIVAL A N D GERMINATION
Among herbaceous perennials fire devastates a population only where
lethal temperatures descend t o the level of the perennating buds which
are at or below the soil surface, but among annuals fire-sensitivity is a
matter of the survival of &s
which are located usually on or above
the wil surface. It was pointed out earlier that fire, occurring when an
annual plant is desiccating but before its seeds have dropped, kills
most of the seeds. In stands of annual graa containing the undesirable
Elymue caput-medwa, the vegetation can be burned at a time when
this plant is most susceptible and thus reduce its relative dominance in
the community (Furbush, 1963; Major ed al., 1960). The timing of this
operation should be early enough to scorch the stems and prevent seed
maturation.
Temperature tolerances of seeds of mme annual grasses that are
abundant in the frequently burned grmslands of California are given
in Table I. The heat generated by fires where these grasses are dominant
is sufficient to kill any seeds in the upper part of the litter, or still in
the inflorescences (Bentley and Fenner, 1958), but seeds lying on the
ground usutllly survive.
Seeds not killed by fire may be altered to germinate earlier. Thus the
germination of fresh seed of Them& triandru, an African grass that is
generally favored by fire, was “significantly increaeed” by treatment with
dry heat (West, 1943, 1961, see West, 1966). I n Wisconsin Andropoqon
247
c-hcrvations from Kansas where the progreseive decline in seed production after a fire was of%wt by applications of N (Cornelius, 1960).
In Britain, Grant et al. (1963) could not duplicate the flowering stimulus
that results from f i e by adding nutrients to unburned plots.
G . P L A N T F O R M
Earlier it was pointed out that burning may shorten leaves, but a t
the same time increase the number of tillers sp thgt dry-matter production of the plant is not materially altered (O’Connor and Powell,
1963). Where this observation was made it waa &o noted that the new
foliage was held more erect, thus reducing the protection of the soil
between plants against the beating of rain. On burned grasslands in
Iowa plants remained stiffly erect even in winter after they cured
(Aikman, 1955).
The above observations raise a question as to how much of the change
in coverage often reported as an indirect consequence of burning grasslands is a consequence of altered posture of the tillers, rather than
change in the volume of space occupied. by the shoot system, length of
leaves or basal area.
H. EIEED SURVIVAL A N D GERMINATION
Among herbaceous perennials fire devastates a population only where
lethal temperatures descend t o the level of the perennating buds which
are at or below the soil surface, but among annuals fire-sensitivity is a
matter of the survival of &s
which are located usually on or above
the wil surface. It was pointed out earlier that fire, occurring when an
annual plant is desiccating but before its seeds have dropped, kills
most of the seeds. In stands of annual graa containing the undesirable
Elymue caput-medwa, the vegetation can be burned at a time when
this plant is most susceptible and thus reduce its relative dominance in
the community (Furbush, 1963; Major ed al., 1960). The timing of this
operation should be early enough to scorch the stems and prevent seed
maturation.
Temperature tolerances of seeds of mme annual grasses that are
abundant in the frequently burned grmslands of California are given
in Table I. The heat generated by fires where these grasses are dominant
is sufficient to kill any seeds in the upper part of the litter, or still in
the inflorescences (Bentley and Fenner, 1958), but seeds lying on the
ground usutllly survive.
Seeds not killed by fire may be altered to germinate earlier. Thus the
germination of fresh seed of Them& triandru, an African grass that is
generally favored by fire, was “significantly increaeed” by treatment with
dry heat (West, 1943, 1961, see West, 1966). I n Wisconsin Andropoqon