Robberecht, R. and P.S. Nobel. 1986. Intraspecific competition in Hilaria rigida, a C4 bunchgrass endemic to southwestern United States rangelands. Pages 463-464 in Proceedings of the Second International Rangeland Congress.

Highlight. The physiology and productivity of the desert bunchgrass, Hilaria rigida, was significantly influenced by intraspecific competition for soil water. Removal of intraspecific competitors surrounding a particular Hilaria plant significantly increased the soil water available for the remaining plant, and resulted in significantly greater leaf longevity, culm production, and root biomass production.

Introduction. Arid rangelands with low annual precipitation and high growing season temperatures present an environment where competition for water may greatly influence the establishment, growth, and distribution of plant species. Plants of similar growth form, phenology, and resource requirements would be expected to exhibit the most intense competition for soil water in such desert environments. The degree of competition should be accentuated further as the soil water resource becomes depleted.

The present study used an experimental approach to elucidate the effects of intraspecific competition among plants of Hilaria rigida (Thurb.) Benth. ex Scribn., a desert perennial known as big galleta grass. Because of the morphological and physiological similarities among individuals in monospecific stands of H. rigida, and with water as the primary limiting resource, this system is particularly useful for the study of intraspecific competition. Experimentally reduced intraspecific competition in the field, through the selective removal of plants in monospecific stands of H. rigida, was expected to result in enhanced growth, mediated through an ameliorated soil water regime.

This research was supported by United States Department of Energy contract DE-AM03-76-SF00012.