TheImprovement ofTropical and Subtropical Rangelands

120 IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
tissues. In the dormant season, a forage supply on the range that
consists ofmature gruees and shrubs will more cloeely meet livestock
nutrient requirements than will a pure stand of either forage class.
The seasonal forage quality and palatability can be managed by
grazing programs to some degree. Maturity results from the natural
behavior of range plants with respect to the annual moisture and
temperature cycle. When a plant is grazed in the growing season, the
annual growth cycle will start over ifthere is sufficient eoil moisture to
permit regrowth. IT enough of the annual evaporation, transpiration,
and precipitation cycle has been completed, the regrowth will not
mature and thus will cure before the quality has declined. The
magnitude of this response will depend on the timing of grazing. On
many range sites, it is pouible to condition the forage by grazing in
the growing season to yield a nutritionally adequate and palatable
forage supply for the dormant season with respect to important
macronutrients.
Controlling the time of grazing is as important as defining the
proper stocking rate and, in fact, may control the stocking rate.
Grazing a perennial grass during the early stages of seed development
will invariably stress the plant, and a period to grow without
grazing will be required if the plant is to recover from that stress.
Conversely, grazing a mature perennial grass offers little stress to
the plant. A higher stocking rate can be supported on a perennial
gr888 range grazed largely in the dormant season than if the same
range were grazed largely in the nondormant season, though in the
dormant season a variety of nutrients would need to be considered
for supplementation.
AIJ previously mentioned, grazing can be used to condition forages
for use later in the year. In these situations, the effect of timing
of grazing may reduce yield while improving quality. The stress on
the vegetation caused by the timing of grazing can be acceptable
when incorporated into future plans for utilization of the specific
pasture. When plants or animals are stressed, their productivity will
decline.
In most range ecosystems, the desirable ecologically stable climax
species are long-lived perennial plants. Many of these plants are
poor seed producers and do not reproduce readily from seed. IT
these desirable species are depleted by overgrazing or drought, it
can be difficult or even impouible to encourage their recovery by
manipulating grazing. In a dominantly perennial plant community,
however, grazing use can be adjusted to encourage seed formation if