Alien vs. native plants in a Patagonian wetland: elemental ratios and ecosystem stoichiometric impacts

Wetlands are subject to invasion by exotic plant species, especially during the dry season when they resemble terrestrial systems; therefore, terrestrial plants could exploit this situation to colonize this environment. We analyzed P. anserina invading Patagonian wetlands in terms of elemental ratios that would modify wetland stoichiometry due to organic matter inputs. We studied the elemental relationship (carbon/nitrogen/phosphorus) of P. anserina in comparison with native emergent macrophytes (Eleocharis pachicarpa and Carex aematorrhyncha). These plant species are common and dominant in the wetland. Additionally, we analyzed the presence of mycorrhizal fungi in the roots and their proportion of root infection. Our study reveals that the invasive species presented nutrient (especially phosphorus) allocation in roots and differences in mycorrhizal infection, with a predominance of arbuscular mycorrhiza, compared with native species. During flooded periods with the decay of aerial parts, P. anserina stores phosphorus in the roots and releases dissolved organic matter of high molecular weight molecules, high color, and a high C-to-nutrient ratio in comparison with native macrophytes. These results show the strategy of an invasive terrestrial plant in temporary aquatic systems, and how the elemental relationships of the invasive plant can modify the stoichiometry of the environment.