PARENT SESSION
Oral Session #88: Wetland Ecology.
Presiding: K. Ewel
Thursday, August 8. 1:00 PM to 3:45 PM. Gila Meeting Room, TCC.

Low-dose phosphorus enrichment in a phosphorus-limited wetland: effects on plant nutrient stoichiometry and biomass.

EDWARDS, ADRIENNE^*,1, NOE, GREGORY², LEE, DAVID², CHILDERS, DANIEL², TREXLER, JOEL², JONES, RONALD², ¹ Illinois Natural History Survey, Champaign, IL² Florida International University, Miami, FL

ABSTRACT- Phosphorus enrichment of naturally P-limited wetlands can result in ecosystem state change, partly due to changes in plant nutrient assimilation, productivity, and species interactions. These responses can cascade through the ecosystem affecting, for example, decomposition rates and nutritional quality for herbivores. We tested the response of pristine wet prairie vegetation to low-level P additions (0, 5, 15, and 30 g L-1 above ambient) flowing through three replicate, 100 m flumes in Everglades National Park. The dominant emergent macrophyte, Eleocharis cellulosa, shifted aboveground nutrient concentrations and stoichiometry only in the 30 g P/L treatment. Concentrations of P in live shoots increased in the second and third years of dosing. Tissue N concentration increased in the third year, while C content was unchanged. P additions also decreased N:P, C:P, and C:N ratios. Aboveground biomass changed irratically over the same time period. Responses to P dosing were heterogeneous, depending on the distance downstream from the source of added P, duration of P additions, and a combined site/loading rate factor. Eleocharis cellulosa responded after most other ecosystem components (periphyton, floc, consumers), but prior to detection of excess soil P. Aquatic macrophytes may respond slowly to low-levels of added P, and likely obtain nutrients from the layer of flocculent, detrital organic matter above the soil surface.

KEY WORDS: CNP ratios, aquatic macrophytes, Everglades, Eleocharis cellulosa