Interspecific competition for seed production between two naturalized dandelions under different levels of fertilizer supply

Two naturalized dandelions, Taraxacum officinale and Taraxacum laevigatum , were grown in mixed stands at various plant densities and mixing ratios with various levels of fertilizer supply until seeds were produced. The effect of fertilizer supply on the competitive relationship for seed production between the species was analyzed. In pure stands, the simultaneous effects of plant density and fertilizer supply on mean plant weight were formulated for each species. By introducing the density conversion factor, the results of plant weight growth in mixed stands were formulated successfully. T. laevigatum produced more seeds than T. officinale at the same plant weight. The relationship between mean plant weight and mean number of mature seeds produced per plant was also formulated for each species. Ratio diagrams were predicted with these formulas. The density conversion factors showed that T. officinale was always dominant over T. laevigatum for plant weight growth within a generation. The ratio diagrams showed that T. officinale became dominant over T. laevigatum for seed production with repeating generations at higher levels of fertilizer supply, but that the species with a larger ratio of plant density became dominant over the other species at lower levels of fertilizer supply.