Tolerance of seed germination in two native species to the allelopathic effect of Chromolaena odorata and the competition between them

To explore the potential of native species Desmodium heterocarpon and Flueggea virosa for replacement control of the invasive plant Chromolaena odorata, we assessed the tolerance of seed germination in the two native species to the allelopathic effect of the invasive species C. odorata and the competition among them via the culture dish method and a common garden pot experiment, respectively. Seed germination of the two native species was not inhibited at different concentrations of C.odorada root, stem, and leaf water leachate, except that 2.5% leaf leachate inhibited seed germination in D.heterocarpon. When the invader was grown with D.heterocarpon, plant height, underground biomass ratio, and the root/shoot ratio of C.odorada were significantly reduced, while those of D.heterocarpon remained unaffected. Furthermore, the total biomass of D.heterocarpon increased significantly compared to the control. Meanwhile, for C.odorada, the competition parameter relative yield(RY) was less than 1, and the competitive aggressivity coefficient was less than 0, indicating that the competitive ability of C.odorada was less than that of the native plant D.heterocarpon. When the invasive species was grown with Flueggea virosa, the root/shoot ratio decreased; however, plant height and total biomass of C.odorada increased significantly, while the plant height and total biomass of F. virosa decreased markedly. Moreover, the competition parameter RY and the competitive aggressivity coefficient of C.odorada were significantly greater than 1 and 0, respectively. These results indicate that the competitive ability of C.odorada was greater than that of native F. virosa. Furthermore, native D.heterocarpon may compete with the growth of the invasive species C.odorada to a certain degree, potentially serving as one of the objective plants for replacement control of the invasive species. Although the other native F. virosais not quite fit for direct control of the invasive species, it may be used to restore vegetation in the region wherein the invader was eliminated. These results provide a scientific basis for selecting objective species for replacement control of invasive C.odorada, guiding the recovery of biodiversity and renewal of invaded regions by C.odorada.