EXPERIMENTAL-EVIDENCE THAT INTERSPECIFIC COMPETITIVE ASYMMETRY INCREASES WITH SOIL PRODUCTIVITY

This study tests the assertion that the degree of competitive asymmetr y between pairs of plant species increases with increasing soil produc tivity. We measured the average degree of competitive asymmetry in an outdoor experiment involving 18 species of herbaceous wetland plants i n each of three levels of soil productivity (1/10 NPK fertilizer + dra ined soil, full NPK fertilizer + drained soil and full NPK fertilizer + saturated soil). Plants, two per pot, were grown from seed over one growing season. The degree of competitive asymmetry increased 1.31 tim es in level 2 and 1.45 times in level three of the soil productivity t reatment, relative to the least productive treatment.