Stoichiometric homeostasis of wetland vegetation along a nutrient gradient in a subtropical wetland. Understanding stoichiometric mechanisms of nutrient retention in wetland macrophytes.

Nutrient homeostasis relates ambient stoichiometric conditions in an environment to the stoichiometry of living entities of the ecosystem. In wetland ecosystems, vegetation can be a large, highly variable and dynamic sink of nutrients. This study investigated stoichiometric homeostasis of dominant emergent and submerged aquatic vegetation (EAV and SAV, respectively) within two treatment flow-ways (FW) of Everglades Stormwater Treatment Area 2 (STA-2). These FW encompass a large gradient in plant nutrient availability. The hypotheses of this study is that wetland vegetation is non-homeostatic relative to ambient nutrients and consequently nutrient resorption will not vary along the nutrient gradient. We developed a framework to investigate how vegetation uptake and resorption of nutrients contribute separately to homeostasis. Overall, the wetland vegetation in this study was non-homeostatic with respect to differential uptake of nitrogen (N) vs. phosphorus (P). Resorption evaluated for EAV was high for P and moderate for N, resorption efficiency did not significantly vary along the gradient and therefore did not affect overall homeostatic status. Nutrient addition experiments may help to compensate for some of the limitation of our study, especially with respect to resolving the primary nutrient source (organic vs. inorganic sources, water vs. soil compartment) and nutrient utilization rates.