Influence of soil nutrient heterogeneity and competition on sprouting and ramets growth of Alternanthera philoxeroides.
Environmental heterogeneity and plant competition influence plant vegetative sprouting and ramets growth. Many major invasive plants reproduce largely or exclusively by vegetative propagation. The terrestrial invasive Alternanthera philoxeroides mainly regenerates from fleshy roots. Here, it is tested whether resource heterogeneity and intraspecific competition influence the fleshy root sprouting and ramet growth of this species. Four or twelve similar-sized fleshy roots of A. philoxeroides are grown in two soil substrates that are either homogeneous or heterogeneous but have the same total amount of nutrients. After 6 months, the sprouting and ramet growth traits (i.e., ramet number, leaf traits, biomass and biomass allocation) are analyzed. The fleshy root density significantly affects the sprouting and ramet growth traits, but the soil nutrient heterogeneity does not. The sprouting and ramet growth traits decrease in the treatments with high densities of fleshy roots. These results suggest that intraspecific competition has a greater influence on the root sprouting and ramet growth of the invasive terrestrial A. philoxeroides than soil nutrient heterogeneity. Thus, intraspecific competition can limit the establishment of terrestrial A. philoxeroides.