Biology Reference
In-Depth Information
Table 12.1.
Characteristics of little bluestem (
Schizachyrium scoparium
)
plants from three areas in Kansas where plants from grazing exclosures
could be compared to those exposed to grazing by domestic animals.
Comparisons were of plants grown under identical controlled condi-
tions for 10 months. (Data from Carman and Briske 1985.)
Total plant
Number of
Biomass per
Leaf blade
Population
biomass (mg)
tillers (>6 cm)
tiller (mg)
length (cm)
K
ANSAS
S
TATE
U
NIVERSITY
Grazed
707
18.9
46
17.6
Ungrazed
734
14.1
66
18.4
F
ORT
R
ILEY
#1
Grazed
460
12.6
40
17.1
Ungrazed
961
12.8
87
20.1
F
ORT
R
ILEY
#2
Grazed
663
15.2
53
18.3
Ungrazed
783
12.8
65
20.3
regrew after being clipped.The weight of leaves per unit area was less for
regrowth leaves of plants from the grazed sites.
Thus, little bluestem plants with a long grazing history showed a mod-
ified growth form in which a greater proportion of their biomass was
close to the ground surface. In addition, in direct response to removal of
tissue by grazing, tillering pattern and carbon investment in leaf regrowth
were modified.
A second recent study examined the responses of side-oats grama
(
Bouteloua curtipendula
), another perennial grass, to livestock grazing
(Smith 1998). Smith compared plants from atop a small mesa, inaccessible
to large animals, near Tucson, Arizona, with plants from a nearby site that
had been grazed regularly since 1900. Plants from both sites were accli-
matized to greenhouse conditions for more than a year, during which
they were clipped at 6-wk intervals. The plants were then divided into
three groups and subjected to clipping at 2-, 4-, or 8-wk intervals for 24
wk. Differences in tillering pattern were apparent. Overall, plants from the
regularly grazed area possessed more tillers than those from the ungrazed
area at the time of final clipping. Plants from the regularly grazed area also
maintained a greater number of tillers relative to the number present at
the beginning of the experimental treatments throughout the 4- and 8-