Interspecific competition of Hygrophila genus at different flow rates in artificial channels

Vegetation has been shown to be a dominant factor that affects flow capacity and flow conditions. Most empirical studies of the effects of plants on flow have been conducted in artificial channels, using plastic leaves or rigid cylindrical materials, and they have focused on hydraulic effects. Relatively few studies have examined plant-induced flow resistance in open channels, the morphological adaptation of plants to flow conditions, or differences in plant responses to competitive environments. In this study, the native species Hygrophila genus were chosen as planting materials to investigate the effects of inter-specific competition and compare responses to flow resistance between two aquatic macrophytes at different flow rates. It was found that the average number of green leaves, leaf area, ratio of vascular bundle area to cross-section area, plant height and root length of Hygrophila pogonocalyx were higher than those of the Hygrophila salicifolia. However, the survival rate of Hygrophila salicifolia was higher than that of Hygrophila pogonocalyx in both the control and experimental groups. When facing a competitive environment, the response mechanism of Hygrophila salicifolia is to reduce plant height, root length and stem section area more significantly than Hygrophila pogonocalyx. Experimental results suggest that the average root length of Hygrophila is reduced for the purpose of adapting to changes in the flow rate when the plants are mixed. Overall, flow-resistance adaptation of Hygrophila was different for both species when mixed species were planted than when species were planted alone, which demonstrates the presence of inter-specific competition.