Competition Between Hydrilla verticillata and Vallisneria americana Under Different Environmental Conditions
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB
Pagination or Media Count:
The report describes results of a greenhouse investigation of short- term 8 weeks duration competition between the beneficial native plant Vallisneria americana and the introduced, problem plant Hydrilla verticillata. Competitive interactions were evaluated in a factorial arrangement of two levels of each of three environmental factors-light, sediment fertility, and inorganic carbon supply. Plants of each species were grown alone and in 5050 mixtures under each of the eight different environmental treatment combinations. When grown alone, the two species generally produced comparable levels of biomass however, allocation of this biomass differed substantially. Hydrilla produced a dense canopy of leafy shoots at the water surface and was more effective at light capture than Vallisneria, which distributed its biomass more uniformly throughout the water column. Vallisneria allocated a greater proportion of biomass to belowground portions of the plant than did Hydrilla. Both species exerted high demands for dissolved inorganic carbon. In keeping with patterns of biomass allocation, the growth of Hydrilla was, overall, limited primarily by while that of Vallisneria was more limited by sediment fertility nitrogen availability.