Abstract: Soil nutrient heterogeneity is ubiquitous in natural ecosystems, which affects the growth and reproduction of clonal plants. Relatively little is known about the interactive effect of soil nutrient heterogeneity and competition on the growth and reproduction of invasive and native plants. In a greenhouse experiment, we grew an invasive clonal species Spartina alterniflora and a native one Phragmites australis in either monoculture or mixture in both homogeneous and heterogeneous soil nutrient conditions. In the monoculture, each pot was grown with six ramets of each species, and in mixture each pot was planted with three ramets of both species. The amount of soil nutrients in each pot was exactly the same in the homogeneous and heterogeneous treatments. Soil nutrient heterogeneity significantly decreased the number of leaves of S. alterniflora, but increasedinternode length and rhizome length of P. australis. Competition increased leaf number, ramet number, internode length, rhizome number, and rhizome length of S. alterniflora, but decreased aboveground biomass, leaf mass and stem mass of P. australis.There were interactive effects of soil nutrient heterogeneity and competition on number of leaves, stem mass and internode length of S. alterniflora, but not on any of the growth characters of P. australis. These findings suggest that soil nutrient heterogeneity can alter the competition between S. alternifloraand P. australis.

Key words: phototaxis, infochemicals, green control, visual mechanism, colored sticky board