Original paper

Growth response and root system development of the invasive Ludwigia grandifl ora and Ludwigia peploides to nutrient availability and water level

Hussner, Andreas

Abstract

Ludwigia grandiflora and Ludwigia peploides, both native to South America, are aquatic plants, which favourably grow in stagnant or slow flowing waters. Due to their rapid growth both species are considered two of the most important aquatic weeds worldwide. The species have invaded several countries in SW Europe and often cause problems, e.g.in France, The Netherlands or Belgium. In the present study, growth and root system development of L. grandifl ora and L. peploides was investigated under three different hydro regimes and three different substrates with different nutrient contents. Both species showed their strong abilities to grow on drained soils by an increase of the relative amount of root biomass and changes in the root system development. Relative growth rates (RGR) of L. grandiflora and L. peploides did not differ between the species, but were significantly different amongst the treatments for each species, i. e., RGR were significantly influenced by nutrients (both p< 0.001) and water level (L. grandiflora n. s., L. peploides p< 0.001). L. grandiflora and L. peploides showed a significant increase in the relative amount of roots with decreasing water level (both p< 0.001) and nutrients (both p< 0.001), when the relative amount of shoots decreased signifi cantly (both: water level p< 0.001 and nutrients p< 0.001). in addition, both species responded to water level and nutrients with signifi cant changes in the depth distribution of their root system. in conclusion, L. grandiflora and L. peploides showed a high tolerance to different water levels, which may be important for potential habitat distribution in the future.

Keywords

invasive aquatic plantbiomassplant invasionrelative growth rateroot system growthrhizotron