Abstract: The knowledge of symbiotic associations with tree legumes is less well understood, yet that microorganisms appear on land with higher plant is of major importance in maintaining soil nitrogen in shrub and forest communities, therefore a generally historical background, current advances and research trend of the study of tree legumes nitrogen fixation have been discussed in this treatise, with appropriated introduction of some authors' research results and experiences.The major emphasis in the present review is laid on the nodulation of tree legumes. Within the legumes, however, the Caesalpinioideae are largely unnodulated, while the Papilionoideae and Mimosoideae are mostly nodulated. There are also several reviews concerning more detailed information on classification of nodule bacteria of tree legumes, possible factors involved in the inability to nodulate of tree legumes and so on.

Key words: Tree legumes, Rhizobium, Bradyrhizobium, Symbiotic nitroxen fixation