Date of Award:

5-1989

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Natural Resources

Committee Chair(s)

David Pyke

Committee

David Pyke

Abstract

Belowground competition is pronounced in the arid Great Basin sagebrush ecosystem. Plant demographic and root exclusion approaches were used to examine the influence of roots of adult Artemisia tridentata, Agropyron desertorum, and Agropyron spicatum individuals on seedling survival of Ar. tridentata, Ag. desertorum, Ag. spicatum, and Bromus tectorum. Furthermore, growth rates of Ar. tridentata seedlings and seed production of B. tectorum were assessed.

The probability of a seedling being alive versus dead significantly depended on the seedling species, the neighboring adult species, and on the depth to which root competition was excluded. As seedlings, Agropyron species did not differ in their competitive abilities, whereas Ar. tridentata seedlings showed higher survival rates than either perennial grass. Bromus tectorum, on the other hand, maintained much higher survival rates than any perennial seedlings.

Established Ar. tridentata was more competitive in reducing seedling survivorship than either Agropyron species. Seedling survival significantly increased with greater depth of root exclusion for the perennials but had no significant effect on seedling survival of B. tectorum. Height and growth rates of Ar. tridentata seedlings and seed production of B. tectorum significantly increased with depth of root exclusion. Seed production of B. tectorum was highest when competing with Ag. desertorum and lowest with Ar. tridentata.

Life cycle tables for B. tectorum showed that even though root exclusion had no impact on survivorship it did increase seed production and thereby increase the seed population of B. tectorum in the next generation.

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