The effects of nutrient additions on mixtures of Typha latifolia L. and Typha domingensis pers. along a water-depth gradient

Abstract

Over a 2-year period, nutrients (N, P and K) were added to mixtures of Typha latifolia L. and T. domingensis Pers. growing across a water-depth gradient in order to determine: (1) the relationship between nutrient limitation and water depth; (2) the differential effect of nutrient addition on species performance. In addition, sediment characteristics were determined for untreated mixtures, monocultures and bare sediment. Additions of nutrients resulted in a rapid increase in total shoot density compared to controls. Increases in total shoot biomass, however, occurred gradually over time in response to nutrient additions. Nutrients enhanced T. latifolia in shallow to medium depths while T. domingensis was enhanced in medium to deep waters. Compared to bare sediment, pH was not affected by the presence of either species. Redox potential, however, was increased by T. domingensis in medium depths while unaffected by T. latifolia. Coupled with the observation that T. domingensis is capable of growing in deeper water than T. latifolia, the E h data suggest that T. domingensis may have a greater capacity to aerate its roots and rhizosphere. Sediment ammonium concentrations were reduced by c. 90–95% by plant growth while potassium was reduced by c. 35–55%. Phosphate was unchanged compared to bare sediment. These results suggest that sediment nitrogen was the most limiting nutrient.