Repression of Nitrogen and Phosphorus Release from Lakeshore Sediment by Five Littoral-zone Plants

Abstract

The article researched the effect of Iris pseudacorus L.,Paspalum distichum L.,Leersia hexandra Swartz,Ludwigia peploides and Hydrocotyle vulgaris on the nitrogen and phosphorus repression in sandy soil from lower reaches of Yangtze River and clay from stored littoral zone. The result indicated that plants had a significant inhibitory effect on total phosphorus release from sediment, with concentration in overlaying water below 0.02 mg·L-1 in Paspalum distichum L., Hydrocotyle vulgaris, Iris pseudacorus group, below 0.03 mg·L-1 in Leersia hexandra Swartz, Ludwigia peploides group; with release rate below 0.1 d-1 in Leersia hexandra Swartz and Ludwigia peploides group, below 0.05 d-1 in Paspalum distichum L., Hydrocotyle vulgaris, Iris pseudacorus group. While the plants were proved to aggravate total nitrogen release by accumulating in sediment, with concentration in overlaying water below 0.4 mg·L-1 in Paspalum distichum and Iris pseudacorus L. group; with release rate below 0.02 mg·L-1. Root weight density, root length density, root surface area density were major factors, which increased the proportion of particles in sediment with diameter of below 50 μm, therefore decreased sediment resuspension against hydraulic disturbance; the root system also enriched total nitrogen in sediment and absorbed phosphorus from sediment. These five kinds of plants in terrestrial-aquatic transverse actually repressed nitrogen and phosphorus release from sediment in two ways mentioned above, Paspalum distichum L. and Iris pseudacorus L. possessed the best effect due to their developed root system, followed by Leersia hexandra Swartz and Hydrocotyle vulgaris, and Ludwigia peploides had the least effect.