Variation in survival and biomass of two wetland grasses at different nutrient and water levels over a six week period1

was greatest in moist and emergent water levels. Both species produced greater biomass in the high nutrient treatment than in the low nutrient treatment. Root: shoot biomass ratio increased for both species with decreasing nutrient level; however, the root: shoot ratio of Echinochloa was significantly lower than that of Phalaris at both nutrient levels. Interspecific competition did not adversely affect survival or biomass allocation strategy of either species; rather, their greater survival in mixture than in monoculture suggests that intraspecific competition is relatively more important for both. In wetlands, Phalaris may be more successful than Echinochloa in fluctuating and submerged water because of low Echinochloa survival.