Water level fluctuation and inorganic nitrogen enrichment are two serious problems caused by anthropogenic disturbances in aquatic ecosystems. They cause resource fluctuation and thus might influence the invasiveness of alien plants. Alternanthera philoxeroides is an amphibious and widespread clonal plant which exhibits significant invasiveness. This experimental study examined the plant's morphological traits under different nitrogen concentrations and water levels. The responses of A. philoxeroides to water levels and nitrogen concentrations were similar for both land-like and riverbank-like initial conditions. A. philoxeroides showed an escape strategy of shoot elongation when its growth was suppressed by shallow submergence. No toxic symptoms but increased clonal spread was observed at high nitrogen concentrations, suggesting that A. philoxeroides not only tolerated but benefitted from nitrogen-polluted water. High nitrogen level mitigated the negative effects of submergence on its leaf survival, thereby enhancing its adaptation to water level fluctuation. Such strong adaptability and clonal spread helps A. philoxeroides to grow and invade successfully in shallow eutrophic water.K Ke ey y w wo or rd ds s: : Alternanthera philoxeroides, eutrophication, nitrogen enrichment, plant invasion, submergence, water level.
a b s t r ac tStudies on phosphorus (P) distributions comparing planted and unplanted systems often lead to controversial results regarding the importance and growth seasons of plants. In the present study, the distribution and mobility of phosphorus fractionations (PFs) in eutrophic water and sediments were investigated in the absence or presence of two macrophytes, that is, reed and cattail, in a constructed wetland in autumn and spring. The removal efficiencies of total P in water, soluble reactive phosphorus and total dissolved phosphorous were 51.85%-63.75%, 74.52%-95.96% and 72.23%-83.02%, respectively. PFs mainly presented in permanent forms in sediments. In the absence of macrophytes in autumn, P in the overlying water was related to the mobile iron-bound phosphorus (Fe-P) in the sediment. In the presence of macrophytes, P in the overlying water was related to stable occluded phosphorus (O-P) in sediments which reduced the possibility of P release. In summary, macrophytes contributed to the stability of P in sediments and limited the release of P from sediment to overlying water, especially in spring.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.