240
R. DAIJBENMTRE
this Heywarcl (1!)38) states t'hat, if a fire does Iiot, raise soil temperature
above about 100"( ', soluble salts and ammonia. are increased in the soil,
and Hart et uZ. (1 93%) observed that wliero the soil was high in fertility,
burning had less effect on plant! chr?niistry. Laboratory experiments
have sliown that within the range of 3-1 lo(', a t letmt, the higher the
temperature the more rapidly ammoninni is oxidized to nitrate (Anderson, 1 gfiO), and raised soil temperatures almost invariably result from
burning. However, different conclusio~is can be drawn from other evidence. Hart. et al. (1!)32) for example, compared the quantity of P
liberated in the burning; of annuals with the amount of subsequent
increase of I' in plantj tissue ;md noncluded t.hat the ash could not
account for the increiLse in plant tissues. Sampson (1944) added ash
from burned vegetation t.o soil in which nnnuds were grown and found
that, this usiially had no effect, on their ash constituents or their crude
protein a t maturity. It is also pertinent to note that not all of a group
of associated species are necessarily improved in palatability to livestock subsequent, to burning, and that increased palatability is unrelated
to whether the plant has been darnagod or stimulat.ed by the fire (Sewell,
1948). Among woody plants (Shafer, 1'364) as among grasses (Cassady,
1953), rejuvenation following other t.ypes of dama,ge, increases the protein cont.ent of the new growth as regularly a.s it does following fire.
Another possible explanation for the higher nut,rient content of
foliage on burned itreas is that living but senescent parts of previous
year's tillers lnily &>press the growth of new tillers by competing with
the latter for iiutrients. I n support of this Mes (1958) found that shade
from detmhed foliage incrctised N and itsh cwnt;ent, of new grass shoots,
but intact foliage from t)he past sexwii, stdl feebly active, depressed N
and ash content.
Still anotht:r posfiible explaiiat ion is that fire stimulation may incromc the activity of the roots of the hirned plants, this in turn would
increase tlic uptake of nutrients (Mes, 1958).
l'lie mtLnncr in which grazing iirigulates seek out burned spots in
grassland may not reflect, the tastiness of the foliage so much tts its
condition of being available all the wa.v to the ground in consequence
of a lack of standing litter. The relirtive iln1;)ortanc.e of these factors
could easily t)c tested by simplo t:xperiniwts. I t is significant that in
annual grasslands in Chliforriia observed differences in tissue chemistry
had disnppearcd hy t,he t'hird post-burn seiison, yet animals still preferred to grszc: on the old burn (Hart el al., 1932). But this may be an
indication that our lahorrttory analyses i m t relatively crude and ignore
important! constituents, for animals reveal distinct preferences where
there are seemingly slight or no chemical differences between plants
(Albrecht,, 1915).
R. DAIJBENMTRE
this Heywarcl (1!)38) states t'hat, if a fire does Iiot, raise soil temperature
above about 100"( ', soluble salts and ammonia. are increased in the soil,
and Hart et uZ. (1 93%) observed that wliero the soil was high in fertility,
burning had less effect on plant! chr?niistry. Laboratory experiments
have sliown that within the range of 3-1 lo(', a t letmt, the higher the
temperature the more rapidly ammoninni is oxidized to nitrate (Anderson, 1 gfiO), and raised soil temperatures almost invariably result from
burning. However, different conclusio~is can be drawn from other evidence. Hart. et al. (1!)32) for example, compared the quantity of P
liberated in the burning; of annuals with the amount of subsequent
increase of I' in plantj tissue ;md noncluded t.hat the ash could not
account for the increiLse in plant tissues. Sampson (1944) added ash
from burned vegetation t.o soil in which nnnuds were grown and found
that, this usiially had no effect, on their ash constituents or their crude
protein a t maturity. It is also pertinent to note that not all of a group
of associated species are necessarily improved in palatability to livestock subsequent, to burning, and that increased palatability is unrelated
to whether the plant has been darnagod or stimulat.ed by the fire (Sewell,
1948). Among woody plants (Shafer, 1'364) as among grasses (Cassady,
1953), rejuvenation following other t.ypes of dama,ge, increases the protein cont.ent of the new growth as regularly a.s it does following fire.
Another possible explanation for the higher nut,rient content of
foliage on burned itreas is that living but senescent parts of previous
year's tillers lnily &>press the growth of new tillers by competing with
the latter for iiutrients. I n support of this Mes (1958) found that shade
from detmhed foliage incrctised N and itsh cwnt;ent, of new grass shoots,
but intact foliage from t)he past sexwii, stdl feebly active, depressed N
and ash content.
Still anotht:r posfiible explaiiat ion is that fire stimulation may incromc the activity of the roots of the hirned plants, this in turn would
increase tlic uptake of nutrients (Mes, 1958).
l'lie mtLnncr in which grazing iirigulates seek out burned spots in
grassland may not reflect, the tastiness of the foliage so much tts its
condition of being available all the wa.v to the ground in consequence
of a lack of standing litter. The relirtive iln1;)ortanc.e of these factors
could easily t)c tested by simplo t:xperiniwts. I t is significant that in
annual grasslands in Chliforriia observed differences in tissue chemistry
had disnppearcd hy t,he t'hird post-burn seiison, yet animals still preferred to grszc: on the old burn (Hart el al., 1932). But this may be an
indication that our lahorrttory analyses i m t relatively crude and ignore
important! constituents, for animals reveal distinct preferences where
there are seemingly slight or no chemical differences between plants
(Albrecht,, 1915).