Response of emergent macrophytes to experimental nutrient and salinity additions

Abstract

Summary1. Nutrient additions often result in species dominance/compositional changes in wetland ecosystems, but the impact of nutrients may be constrained by different salinity levels. Wetlands of northern Belize, distributed along a salinity gradient, are strongly phosphorus-limited and dominated largely by three species of emergent macrophytes: Eleocharis cellulosa Torr., Cladium jamaicense Crantz and Typha domingensis Pers. 2. We conducted a mesocosm experiment to assess changes in growth characteristics [biomass allocation, plant height, relative growth rate (RGR), rhizome length] and nutrient uptake of these three species in response to simultaneous changes in levels of nutrients (nitrogen and phosphorus) and salinity. 3. The growth characteristics of Typha and Eleocharis responded positively to N and especially P addition, whereas the growth response of Cladium was largely insignificant. The RGR of Typha increased under P addition, while RGR of Eleocharis increased with N and decreased with salinity addition. Nutrient addition increased the rhizome number of both Typha and Eleocharis . However, plasticity in rhizome length was observed only in Typha , which showed increased rhizome length at medium and high P. 4. Salinity decreased plant height and shoot and root biomass of Cladium and Eleocharis , while in Typha it reduced only height. Rhizome number and length were decreased only in Eleocharis . 5. Both medium and high P additions increased tissue P content in all three species, but Eleocharis accumulated significantly more P than Cladium and Typha . Nitrogen additions increased tissue N content in Cladium and Eleocharis , but not in Typha . 6. Cladium exhibited strong morphological constraint and behaved as a stress-tolerator that was well adapted to low nutrients. Typha -characterized by its plastic, opportunistic guerrilla growth strategy, fast and efficient space occupancy, and rather wasteful nutrient management -behaved as a typical competitor. Eleocharis responded rapidly to nutrients but displayed limited rhizome plasticity, and its growth was affected at higher salinity. 7. According to recorded traits, we hypothesize that P input into wetlands will result in expansion of Typha , leading to competitive exclusion of both co-occurring species. The only conditions allowing coexistence of all three species are those limiting vertical and horizontal growth of Typha : low P and higher salinity. To ensure the stability of Belizean wetlands, the maintenance of oligotrophic status is therefore crucial.

The Effect of Nutrient Enrichment of Either the Bank or the Surface Water on Shoreline Vegetation and Decomposition

“…Eutrophic species put more biomass into shoot production compared to mesotrophic species, eventually resulting in the exclusion of mesotrophic species due their better competitive ability (Grime 1977). Nutrient enrichment commonly induces a shift from nutrient competition towards light competition (Grime 1977;Portielje and Roijackers 1995;Smith and Smith 1998;Macek and Rejmá nková 2007), in terrestrial as well in aquatic systems (Grimm and others 2003). This trend already became visible within our 3-year study, suggesting even stronger effects in the longer term.…”

Heterotrophic microbial activities and nutritional status of microbial communities in tropical marsh sediments of different salinities: the effects of phosphorus addition and plant species

“…Both Eleocharis and Typha are rhizomatous perennials, but while Eleocharis is a good example of a stress tolerator adapted to P limitation stress, Typha behaves as a competitor (sensu Grime 2001) and is able to outcompete Eleocharis once the P-limitation has been removed (Macek and Rejmánková 2007). We expected that due to their different biomass production, nutrient uptake, and resorption (Rejmánková 2005), these two macrophytes will provide organic material of contrasting amounts and quality to the sediments and, consequently, they will differentially impact the microbial activities in the respective sediments.…”

Effects of salinity on the physiology of Salvinia auriculata Aubl. (Salviniales, Pteridophyta)

“…Salvinia auriculata was subjected to a eutrophicated system before the experiment because the Capibaribe River receives frequent nutrient discharge due to industrial pollution (FLORES MONTES et al, 2011). When subjected to nutrient addition, macrophytes can exhibit an increase in biomass, while at the highest salinity the opposite would be true (MACEK;REJMÁNKOVÁ, 2007).…”

“…Therefore, when the water extraction potential of the roots is affected, high concentrations of Na + and CI -in the plant cells have negative effects on various enzymatic processes (JAMPEETONG; BRIX, 2009b). High salinity levels limit leaf or shoot growth of plants (MACEK;REJMÁNKOVÁ, 2007). It was observed that the leaves of S. auriculata tended to lose their original color, becoming brownish at the end of seawater treatment.…”