Population demography and seed and seeding ecology of the Great Lakes endemic, Pitcher's thistle (Cirsium pitcheri, Asteraceae) / by Samara I. Hamze.
| Author/creator | Hamze, Samara I. author. |
| Other author | Jolls, Claudia Lee, degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 1998. |
| Description | viii, 114 leaves : illustrations, map ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Cirsium pitched is a monocarpic perennial endemic to the Great Lakes dunes. I examined the population demography, seedling dispersion, and seed and seedling ecology of C. pitched in Michigan. I also measured the effects of removal of an invasive thistle population demography. A three-year study in a 1600 m^plot revealed that Pitcher's thistle seedling recruitment and survival are variable among years; seedling and juvenile stages are the most sensitive. Non-destructive morphometric measurements indicated that plants remain in the vegetative stage for several years before flowering. Flowering is size dependent; belowground biomass (taproot) was a better predictor of flowering than aboveground biomass. Seedling dispersion was measured around 106 potential parents. Approximately 50% of parents had seedlings within 5 m and successful parents had at least one seedling within 1.27 m. Despite wind dispersal of seeds, there was no directionality to seedling dispersion around parents. Most seedlings (80%) were found in areas ofat least 60% bare sand. Seed dormancy was broken by time and moist-stratification. Germination was highest in the dark. Burial increased the probability of germination, but burial at 8 cm decreased seedling emergence. In the presence of an exotic, Gypsophilapaniculata, C. pitcheri abundance decreased during a 15 year period. Weed removal with an ax did not appear to alter the demography of the endemic species; thistle recruitment actually increased. The proportions of seedlings and flowering C. pitcheri were low in the weed's presence suggesting competitors may delay flowering. The life history of Pitcher's thistle may buffer populations from extirpation. Plants achieve flowering size over a period of several years resulting in a continuous input of seeds to the populations. Seedling abundance in areas of high sand cover suggests that this species is dependent on the dynamic processes ofthe dunes. The probability of germination increased with burial; this further suggests dependence of Pitcher's thistle on sand movement. Pitcher's thistle populations appear to be in decline where invasives decrease sand movement. Therefore, the long-term protection of this taxon is ultimately dependent on the dynamic processes that maintain open sand dunes around the Great Lakes. |
| General note | Submitted to the faculty of the Department of Biology. |
| General note | Advisor: Claudia L. Jolls |
| Dissertation note | M.S. East Carolina University 1998 |
| Bibliography note | Includes bibliographical references (leaves 110-114). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
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