Experimental Evidence That Interspecific Competitive Asymmetry Increases with Soil Productivity

Abstract

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