TheImprovement ofTropical and Subtropical Rangelands

REHABILITATION TEOHNIQUES 143
habitat type and rejecting others, but is true only in an undisturbed
situation.
Plant species or plant associations are released from their habitat
range restrictions by reducing the adjoining better adapted species or
plant U80ciations. This reduction or elimination of competition can
be brought about by "continued disturbance." The more common
types ofdisturbance are frequent burning, drought, and continual and
excessive harvesting. The greatest and fastest change can be caused
by two or more factors acting in conjunction. Drought in conjunction
with excessive harvesting, for example, has been a leading cause of
disturbance in many areas of the world.
Control of unwanted plants will make more water available for
the reproduction and production of desirable vegetation. This may
be accomplished by chemical, biological, or mechanical means; by
judicious use of fire; or by the use of certain animal species.
Control by PlaDned lire
The use of fire is best known in relation to "slash-and-burn"
agriculture in many tropical countries. This approach, if misused, is
generally not beneficial in terms of stabilizing the long-term nutrient
base. However, for subsistence agriculturalists, it is the easiest and
cheapest way to clear land of unwanted vegetation, drive out game
or predators and snakes, and provide the first crop with a flush of
nutrients from the ash.
Rangeland burning may be designed to fit one or more objectives:
• Increase or improve livestock forage by eliminating lOme competing
plants.
• Reduce litter and stimulate growth ofdesirable forage plants.
• hnprove wildlife habitat by opening up dense plant cover
while retaining diversity and adequate escape cover or nesting sites.
• Reduce high volumes of fuel, which lowers the chance of
catastrophic wildfire in forests and scrublands.
• hnprove visibility oflivestock and wildlife after planned burning
of certain ranges, especially in denae tree and shrub areas.
• Reduce the labor costs of handling livestock.
• Reduce predation losses in general.
Follow-up management after a prescribed burn differs in several
ways from an emergency treatment that is usually applied following
wildfires. The frequency of repeated burning is critical and, in general,
frequent burning is undesirable as a management tool. Because