High water levels and low light co-inhibit colonization of fragments from the clonal invader Alternanthera philoxeroides

Natural disturbances and human activities frequently fragment aquatic plants. Vegetative fragments of invasive clonal plants have a high capacity for colonization and regrowth, which results in rapid spreading of these plants. A case study was conducted to explore the effects of the water level and light on the colonization and regrowth of a clonal invasive plant – Alternanthera philoxeroides. In the study, the growth of 10-cm-long fragments of A. philoxeroides was followed in three water levels (0, 2, and 10 cm) and two light conditions (10% and 80% of natural light). Results showed that total biomass of A. philoxeroides under all treatments except 10% of natural light and 10 cm of water level was higher than the initial biomass, which suggested that fragments of A. philoxeroides can regrow under most conditions. However, treatments of high water levels and low light inhibited regrowth, clonal expansion, and vegetative propagation of clonal fragments by reducing their total biomass, number of nodes and storage root biomass. Creating habitats of high water levels and low light, for example, by planting native emergent aquatic plants, can hamper the spread of this clonal invader. Our study contributes a new perspective to controlling the spread of invasive clonal plants by creating habitats that inhibit the colonization of invasive plant propagules.