Ráðunautafundur - 15.02.1989, Side 14

-6-
1988).
Habitat use by livestock affects both livestock production and range condition.
Livestock production is affected because the carrying capacity of the range is
directly dependent on the degree to which livestock dispense across the landscape
(Stoddart et al„ 1975). Range condition is positively affected when livestock
disperse widely and negatively affected when they overutilize certain locations such
as riparian zones. To the extent that we can understand habitat use by livestock,
we can better enhance dispersion of livestock on rangelands including riparian zones
(Provenza and Balph, 1987).
Little research has been conducted on habitat use. This research focused on
describing such factors as where certain species of livestock spend their time on
rangelands and the steepness of slopes they are willing to negotiate (Stoddart et al.,
1975). Future research should focus on genetic and environmental determinants of
habitat use (Provenza and Balph, 1987). There is evidence that different subgroups
within livestock populations use different areas of the same range (Hunter and
Milner, 1963; Key and Maclver, 1980; Roath and Krueger, 1982), and that such
habitat preferences are learned (Hunter and Milner, 1963; Key and Maclver, 1980).
This suggests that we could manipulate habitat use by selectively culling individual
animals (Provenza and Balph, 1987). However, there has been no concerted effort to
explain or critically experiment with habitat use. Thus we do not understand why
livestock use areas of the range differentially. Of the four processes of importance
to grazing management, this is perhaps the most important and the least understood.
CONCLUSION
My contention is that contemporary range scientists should develop fundamental
understanding of the basic processes involved in grazing management: plant
antecology, plant synecology, diet selection and habitat use by herbivores. To date
range scientists have neglected their role in developing fundamental understanding
of these processes. I believe the next major advances in grazing management will
occur when researchers turn their attention from describing what occurs in
plant/herbivore interactions to understanding the hows and whys of plant-herbivore
interactions as they relate to grazing management.
REFERENCES
Archer, S.R. & L.L. Tieszen, 1986. Plant response to defoliation: hierarchical
considerations. In Crazing Research at Northern Latitudes (ed. O. Gudmundsson).
Plenum Press, New York: 45-59.
Bryant, J.P., F.D. Provenza & A. Gobena, 1987. Environmental controls over woody
plant chemical defenses: implications for goat management. In Proc IV Intnl Conf
on Goats (eds. O.P. Santana, A.G. da Silva & W.C. Foote). Departmento de Difusao