Abstract: In spring and autumn of 2005, the alien weeds in various habitats of Kaifeng suburb, including farmland, orchard, vegetable garden, and wasteland, were investigated, and the niche breath and overlap of the alien weeds and main native weeds were measured. A total of 11 alien weed species were recorded, 7 species occurring in spring, 7 species in autumn, and 3 species in both seasons. In spring, the relative abundance of Veronica didyma and Conyza canadensis was higher, being 0.239 and 0.111, respectively; in autumn, Cyperus rotundus had a higher relative abundance, being 0.409. In spring, C. Canadensishad a wider niche breath (0.854); in autumn, the niche breath of Eleusine indica, Amaranthus retroflexus, and C. rotundus was 0.986, 0.822, and 0.807, respectively. The niche overlap values of alien and native weeds were mainly under 0.5, and there existed polarizations in utilizing resources between them. The alien weeds had advantages in population expansion.

Key words: Macrophytes, Constructed wetland, COD, Total Nitrogen, Purification