Date of Award:

5-1-1982

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Ivan G. Palmblad

Committee

Ivan G. Palmblad

Committee

Martyn Caldwell

Committee

Arthur H. Holmgren

Committee

James MacMahon

Abstract

The germination and dispersal ecology of Phacelia cookei, an annual plant under review for Federal Endangered plant status, was studied in relation to its occurrence in disturbed habitats. Within the range of disturbed habitats presently available in the study area Phacelia cookei is restricted to sites of visible human disturbance (especially roadbanks and areas of recently cleared vegetation) in field surveys. The natural habitat is an enigma. Animal trails and burned areas represented the only sites of non-human disturbance with which P. cookei may be associated. Seven to eight plants were found at two sites in animal trails. Several plants occurred in the site of an April fire, but may also have responded to soil disturbance caused by heavy equipment used in combating the fire. In seed introduction experiments, seedlings emerged from seed introduced to undisturbed natural openings (0.2 and 0.3 percent) as well as in a fuelbreak (1.2 percent), pine plantation (0.4, 2.1 and 2.4 percent) and roadbank habitats. High emergence from natural seed reserves confounded the calculation of percent emergence in roadbank habitats. Comparison of an index of relative reproductive potential (IRR) based on numbers of plants present in plots after June 8 appears to show trends paralleling disturbance history of the plots. The maximum IRR occurred in the fuelbreak plots (first season after disturbance) followed by pine plantations (four to seven years after disturbance) and undisturbed natural openings. Temperature regimes significantly affect germination (p< 0.001) in laboratory germination experiments using seeds on moist filter paper. Evidence for germination promotion by light treatments differed between experiments. Light flash treatments significantly affected germination after 9 and 15 weeks stratification in moist sand (p< 0.01) but not after 4.5 weeks stratification on moist filter paper or in analysis of variance of the three combined experiments. Possible light leaks and high mortality due to fungal attack may have obscured the interaction of light flash treatment and stratification in the combined analysis. Both local dispersal of seed at the parental site and chamaechoric (tumbleweed) dispersal occurred in individual P. cookei plants. Chamaechoric dispersal, tested using "mark-recapture" techniques on plant fragments, was highly effective in areas free of vegetation or with low, sparse vegetation (up to 22 m movement in 24 h) and ineffective in small natural openings (0 to 56 cm movement in 24 h, no movement between openings). Approximately 57 percent (s.d. = 18.2 percent) of the seeds produced by vigorous plants in 1979 and 1980 were potentially available for chamaechoric dispersal. Suggestions for further research are given

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .