|Richardson, Curtis - DUKE UNIVERSITY|
Submitted to: Springer Verlag
Publication Type: Book / Chapter
Publication Acceptance Date: January 5, 2007
Publication Date: May 1, 2008
Citation: Goslee, S.C., Richardson, C.J. 2008. Establishment of seedling growth of sawgrass and cattail from the everglades. In: Richardson, C. editor. The Everglades Experiments: Lesson for Restoration. Springer Verlag. p. 547-564. Interpretive Summary: Not applicable.
Technical Abstract: In many areas of the Everglades, the formerly dominant sawgrass (Cladium jamaicense) is being replaced by a profusion of cattail (Typha domingensis). Although cattail is native to the Everglades, it has historically existed at a very low abundance. The cause for the expansion has been variously linked to nutrient influxes into the oligotrophic system from agriculture, and to changes in the hydroperiod due to water management. We investigated the effects of nutrient enrichment on the reproductive output of sawgrass and cattail from enriched and unenriched locations in Water Control Area 2A, and further investigated the effects of nutrient availability and water level on germination and seedling performance of sawgrass and cattail from the two sites. Supplemental experiments examined the potential role of chilling as a dormancy breaker for these species, and of light as a requirement for germination. Cattail reproductive output was heavily impacted by a low-nutrient environment, with little seed production in the unenriched area, while sawgrass produced more seeds at that site. Sawgrass seeds were much larger than cattail seeds; cattail seeds were somewhat larger at the enriched site, while sawgrass was unaffected. Cattail seed germinated faster and more thoroughly, but cattail seedlings were considerably smaller and slower-growing than sawgrass seedlings. Cattail germination was lower in dark environments, but sawgrass germination was unaffected by light. Cattail presents an opportunistic pattern: producing many small, wind-dispersed seeds that require favorable conditions for success. Cattail seeds sink, so the need for light will prevent them from germinating under deep water, or buried deeply in sediments. Sawgrass is a stress-tolerator, with fewer, larger seeds that produce robust seedlings that can survive in less-hospitable and lower-nutrient conditions. The high nutrient levels now seen in the Everglades favor seed production and establishment of cattail over sawgrass. Even if nutrient levels could be instantaneously returned to their former low state, the now enormous seed bank of cattail will allow the continued increase of cattail any time a favorable site becomes available.