Date of Award:

1985

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Natural Resources

Department name when degree awarded

Range Science

Advisor/Chair:

Neil E. West

Abstract

Northern Utah rangelands have become infested with dyers woad (Isatis tinctoria L.) and control is needed. Mechanical and chemical control on rangelands produce undesirable effects. A possible alternative is biological control, but information is not available on plant response to this control method. This autecological study and simulation of control methods examined dyers woad phenology, seed endurance and response to simulated grazing, hand rogueing and plowing. The phenology study documented dyers woad growth patterns from May 1982 to November 1983. During the first year, 65 percent of the seedlings died while the remaining 35 percent grew rosette leaves. During the following growing season, 50 percent of the remaining population flowered and died. The other 50 percent continued to grow rosette leaves. The seed endurance study showed seed viability remaining high and relatively stable, but germination decreased during the ten month study period. Methods used indicate future germination and viability studies should more closely simulate field conditions. The simulation of control methods involved clipping dyers woad once at three different heights to simulate grazing, hand rogueing and plowing on three different dates that correspond with the phenological stages of initial rosette growth, pre-bolting, and post-bolting. Simulated grazing stimulated plant survival and growth. Simulated plowing and hand rogueing reduced plant survival. Treatment at all three levels after initial rosette growth depressed flowering for one year. Treatment to simulate plowing and hand rogueing during initial rosette growth depressed flowering compared to the untreated controls. Treatment early in the growing season did not significantly affect plants receiving simulated grazing. Seed production was depressed by simulated plowing but was promoted by simulated hand rogueing when compared to untreated controls. The ability of plants to survive and/or flower after treatment could not be predicted from this study because a one time clipping of dyers woad did not produce significant population decreases. A more severe treatment in the form of more clippings per season is suggested for future study.

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