Dissertation
Earth, wind, and fire: resource allocation and dispersal strategies of Rhynchospora knieskernii (Cyperaceae) in a disturbance-dependent ecosystem
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2015
DOI:
https://doi.org/10.17918/etd-7715
Abstract
Rhynchospora knieskernii J. Carey (Cyperaceae) is a federally-threatened sedge that is endemic to the New Jersey Pine Barrens, a fire-dependent and nutrient-poor ecosystem. Although global rare, little is known about its nutrient requirements, dispersal mechanisms, and population dynamics. Autecological studies that elucidate environmental requirements are essential for effective rare plant conservation. Depending on availability, R. knieksernii preferentially allocated nitrogen to either reproduction or storage. When plant N concentration was elevated more N was allocated to storage than to reproduction. Achene mass and volume were less when plant N concentration was higher. Plants in habitat that had been prescribed burned had the greatest N concentrations. In contrast, there was no difference in phosphorus allocation to either reproduction or storage regardless of the level of soil P. Plants in habitat where the canopy was opened following a prescribed burned were taller and produced more achenes. Although there was no difference in the nutrient allocation strategy between R. knieskernii and associate plants, R. knieskernii was the dominant species in habitat that was prescribed burned either the current or previous year. Plant dispersal is often facilitated by specific plant structures. Although the bristles on R. knieskernii achenes suggest adhesive dispersal, I found that achenes were also dispersed by wind and water. Simulated dispersal kernels, using known or estimated dispersal distances, suggested that deer were the vector for the longest -distance dispersal with water being a more effective dispersal vector than wind. Fire suppression and hydrological alteration pose the greatest threat to the stability of R. knieskernii populations. Potential changes to nutrient cycling as a result of climate change may also lead to population declines, particularly if increased precipitation leads to changes in phosphorus availability through increased immobilization. In the absence of wildfire, frequent prescribed burns that mimic natural fire return intervals are recommended for the maintenance of R. knieskernii populations.
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Details
- Title
- Earth, wind, and fire
- Creators
- Marilyn Carolyn Sobel - DU
- Contributors
- Walter F. Bien (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xx, 227 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biodiversity, Earth, and Environmental Science (BEES); College of Arts and Sciences; Drexel University
- Other Identifier
- 7715; 991014632211904721