MIXED ALLELOPATHIC EFFECT OF <em>EUCALYPTUS</em> LEAF LITTER AND UNDERSTOREY FERN IN SOUTH CHINA

Abstract

Exotic Eucalyptus, introduced to China, has been widely planted because of its fast growth and versatile uses. In Eucalyptus plantation ecosystems in South China, understory vegetation is often composed of the dense heliophyte fern, Dicranopteris dichotoma. Both Eucalyptus and D. dichotoma have been reported to have strong allelopathic effects. However, traditionally it is believed that native tree seedlings grow poorly in Eucalyptus plantations with understory fern D. dichotoma and cannot be used for rehabilitation. Thus, bioassay and greenhouse experiments were conducted to test the allelopathic effects of Eucalyptus and D. dichotoma and the growth performance of tree seedlings in South China. Both species, individually and in combination, had strong allelopathic potential. The allelopathic effects varied with concentration and donor species used. The results suggested that D. dichotoma had antagonistic effect at higher concentration, while Eucalyptus individually and two species together had synergistic effect at lower concentration. These results contradicted traditional views and suggested that the negative effects of Eucalyptus and D. dichotoma mainly came from their allelopathic properties. Thus, Eucalyptus plantations could be reconstructed by transplanting seedlings of native, evergreen, broad-leaved species, after clearing the understory ferns, to avoid competition and to create multi-species mixed forests which could improve ecosystem services.