Abstract:

In order to guide scientifically planting on forest floor in eucalyptus plantations, screen suitable plants, and understand allelopathic effects of eucalyptus trees with different young ages (1 a, 2 a and 3 a) on the understory species and growth germination rate and seedling growth of five species widely planted in the local region were measured after treatments with different concentration of aqueous leaf extract of Eucalyptus urophylla×E.grandis treatments with different concentration. The results showed that the leaf extract reduced seed germination rate and inhibited seedling growth of all five species, and had a stronger inhibiting effect on radical than hypocotyl growth. The species tested in this study had different sensitivity to the leaf extract. The inhibition rate of Lolium perenne, Sorghum sudanense, Phaseolus aureus, Phaseolus vulgaris and Glycine max was 56.85%, 54.58%, 33.48%, 20.81%, 16.01%, respectively, among which Giycine max and Phaseolus vulgaris were the most insensitive to the leaf extract. The allelopathy of the leaf extract was concentration dependent, increasing with increase of the concentration, and low concentration (0.01 g·mL^-1) had no significant influence on the species. Furthermore, the allelopathy aqueous leaf extract of E.urophylla×E.grandis to the five species had no significant difference with increase of their ages.

Key words: young Eucalyptus urophylla×, E.grandis, allelopathy, seed germination, seedling growth, underwood planting