Allelopathic effects of Eucalyptus urophylla on ten tree species in south China

Aqueous leaf leachate and leaf volatile of Eucalyptus urophylla were used to investigate their effects on seed germination and seedling growth of seven native tree species (Cinnamomum burmanni, Cryptocarya concinna, Machilus chinensis, Photinia benthamiana, Pygeum topengii, Diospyros morrisiana and Pterospermum lanceaefolium) and three exotic tree species (Acacia confusa, Albizia lebbeck and Albizia falcataria). It was revealed that aqueous leaf leachate suppressed the seed germination and seedling growth of Photinia benthamiana, Pygeum topengii, Diospyros morrisiana and Pterospermum lanceaefolium. In case of Cryptocarya concinna, leaf leachate decreased only the seed germination. Leaf volatile concentration beyond 250 g per desiccator had a significant suppression effect on germination of Cinnamomum burmanni, Cryptocarya concinna, Machilus chinensis, Diospyros morrisiana and Pterospermum lanceaefolium. The seedlings growth for most species was affected at concentration of 50 g and above, with the exception of Cryptocarya concinna, Pygeum topengii and Albizia falcataria which were not obviously suppressed at 50 or 150 g leaf weight. However, the growth of Pterospermum lanceaefolium remained uninhibitory till when volatile at the concentration of 350 g leaf weight was applied. From the result it can be concluded that the allelochemical effects of the donor varies with the dose applied, and species respond differently to allelochemical released by the Eucalyptus.