Soil conditions had obvious influences on the root-node formation and nitrogen fixation in the saplings of several species of trees. Amorpha fruticosa, Alnus cremastogyne can get higher N2-fixing ability only on the neutral medium loam and on the calcium light loam. Coriaria sinica, Robinia pseudo acacia can get high N2-fixing ability on the neutral medium loam, but lower on the acid soil Acacia mearnsii can obtain higher N2-fixing ability on the acid soil, but low on the neutral soil, and it can not show a...