尾叶桉遗传资源引进及其生物学入侵风险评估

Introduction of Eucalyptus urophylla and the Evaluation of Its Biological Invasion Risk

尾叶桉为高大乔木,其生长快、干形通直、材性好,原始分布于印度尼西亚.我国自1976年开始引种尾叶桉,分别在广东、广西、海南等地建立了种源/家系试验林,保存了大量的遗传资源并营造了大面积的人工林,现已成为我国推广栽培面积最大的桉树树种之一.桉属树种全部为外来引进树种,我国没有自然分布,不能与我国本土树种发生杂交,不存在与我国本地树种发生基因交流或杂种化的风险.桉树在我国能正常开花结实,但种子特别小,很难自然发芽成活,不能自然更新和扩张,不会出现自发入侵本地生态系统、占据其它树种栖息地、造成生物入侵危害的现象.桉树与其它植物的水肥竞争或化感作用导致其林下植被贫乏还存在争论,但我国华南地区年降雨量多,林下植被一般都很丰富,也有多种动物栖息.大量引种栽培试验也证明,桉树在我国华南一带种植对其它植物的化感作用不明显,桉树人工林的发展完全可以人为控制.

Eucalyptus urophylla is originally distributed in a few islands of Indonesia.It is a big woody tree species.It was first introduced into China in 1976.Now,Eucalyptus urophylla and its clones are widely planted in Guangdong,Guangxi and Hainan.Almost all provenances and families of Eucalyptus urophylla are collected in the trials located in Guangdong,Guangxi and Hainan.All these trials are now kept as gene banks.Eucalyptus is a kind of exotic plants,with no natural distribution in China and it is impossible for Eucalyptus to hybrid with the native trees.Thus there is no risk of gene exchange or hybridization between Eucalyptus and native trees.Eucalyptus urophylla trees flower and seed well in China but its seeds are very small and cannot germinate or grow up on wild land.Eucalyptus species cannot regenerate or re-inhabit wild land by themselves.So there is no risk of Eucalyptus invasion into native ecosystems or land with indigenous plants.There are debates on Eucalyptus allelopathy and on the relationship between allelopathic effect of Eucalyptus and environmental condition.Eucalyptus allelopathy occurs while the weather is drought.In south China,allelopathy rarely happens because the climate is wet（annual rainfall usually more than 1 500 mm）.