Intraspecific Competition in Hot Deserts

Intraspecific Competition in Hot Deserts.

Park S. Nobel, Professor, Department of Biology
University of California, Los Angeles (UCLA)

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Funded by United States Department of Energy.

Selected References

Robberecht, R. 1988. Big galleta grass --- a warm-season bunchgrass in the Sonoran and Mojave Deserts. Rangelands 10:58-60.

    Summary The Sonoran and Mojave Deserts of the American southwest present formidable environments for the establishment and survival of plant species. Plants in these hot, arid environments have evolved many adaptations to the high temperatures and limited soil water supply, as exemplified by the numerous species of succulents in these areas. A dominant warm-season grass species in the hot deserts of southeastern California, southern Nevada and Utah, western Arizona, and parts of Baja California is big galleta grass (Hilaria rigida (Thurb.) Benth. ex Scribn). This perennial plant has a bunchgrass growth form and exhibits some interesting physiological adaptations to hot, arid environments. In addition to the stress imposed on plants by these desert habitats, this bunchgrass species may be subject to a high degree of utilization by native bighorn sheep and domestic livestock (Hughes 1982). Despite its potential importance as a forage species in these hot deserts, little is known about its life history, ecology, and response to grazing.
Nobel, P. S., and A. C. Franco. 1986. Annual root growth and intraspecific competition for a desert bunchgrass. Journal of Ecology 74:1119-1126.

Robberecht, R. and P.S. Nobel. 1986. Intraspecific competition in Hilaria rigida, a C4 bunchgrass endemic to southwestern United States desert rangelands. Pages 463-464 in P.J. Joss, P.W. Lynch, and O.B. Williams, editors. Rangelands: A resource under siege. Australian Academy of Sciences, Canberra, Australia.

Robberecht, R., B.E. Mahall, and P.S. Nobel. 1983. Experimental removal of intraspecific competitors - effects on water relations and productivity of a desert bunchgrass, Hilaria rigida. Oecologia 60:21-24.

    Abstract Intraspecific competition in the C4 bunchgrass Hilaria rigida was examined on a Sonoran Desert site in southeastern California. Potential competition within monospecific stands was experimentally altered by removal of the aboveground portions of all plants within a 1.5 m radius of a monitored plant. Compared with unaltered plots, altered plots had less negative soil water potentials during periods of soil drying. Leaf blades on monitored plants of altered plots remained green longer and had greater stomatal conductances than those on monitored plants on unaltered plots. Production of new culms was twice as great on altered plots. Greater root biomass and root length were observed in altered plots, and root extension into soil areas formerly occupied by roots of neighboring plants occurred within one year after treatment. The results indicate that removal of the aboveground biomass of neighboring plants reduces the competition for limited available soil water in this desert environment.

Nobel, P. S. 1981. Spacing and transpiration of various sized clumps of a desert grass, Hilaria rigida. Journal of Ecology 69:735-742.

Nobel, P. S. 1980. Water vapor conductance and CO2 uptake for leaves of a C4 desert grass, Hilaria rigida. Ecology 61:252-258.