Abstract: A 2 × 2 factorial field experiment was conducted to study the effects of sediment nutrition level on the interspecific relationship between two submerged macrophytes, exotic Elodea nuttallii and native Vallisneria spiralis. On the sediments with either high or low nutrition level, E. nuttallii had an obvious superiority in competition. Under the mixed planting with E. nuttallii, the growth of low density V. spiralis was less affected, but that of high density V.spiralis  was inhibited significantly. The same picture was observed in the E. nuttallii growth under the mixed planting with V. spiralis. Sediment nutrition level affected the growth of  E. nuttallii  at both low and high densities significantly, but only had significant effects on the growth of low density V. spiralis. It was suggested that exotic submerged macrophyte E. nuttallii  would affect the species distribution and structure of aquatic plant communities in lake ecosystems.

Key words: Nature reserve, Ecological security, Nature reserve network, Design