Abstract: In this paper，the gradient(0，10，20，40，80 mg·kg^-1)of soil Cd concentrations was established by mixing CdCl₂ with soil，and some ecophysiological responses of five willow clones, Salix 1，Salix 2，Salix E，Salix C and Salix matsudana, to soil Cd contamination were studied by growing their cut seedlings in pots under the nature environment. The results revealed that the seedling growth of all test clones was enhanced under lower soil Cd concentrations (≤20 mg·kg^-1)，and Salix 2 had the strongest response under 10 mg·kg^-1 treatment，with 132.0% and 120.0% of the root and plant growth, respectively, in comparing with the contro1. Then，the growth decreased with increasing soil Cd, and the growth of Salix C decreased the least under the highest Cd concentration, comparing with the control, the root, shoot, leaf and plant growth being 86.1%, 85.3%, 82.9% and 84.9%, respectively. With increasing soil Cd concentration, generally, the activity of SOD, POD, CAT and Root increased first and then declined. However, the CAT activity of every willow clone changed not much under different Cd concentration. For Salix E and Salix C, the activity of SOD and Root first declined significantly under the 40 mg·kg^-1 Cd concentration, but other three clones first declined significantly under lower Cd concentration. Subordinate function analysis suggested that the tolerance of test willow clones to soil Cd contamination was in order of Salix C>Salix 2>Salix 1>Salix matsudana>Salix E. Five willow clones all had some tolerance to Cd pollution and different willow clone could be planted in different Cd polluted soil for different purpose.

Key words: energy willow, soil Cd contamination, energy willow tolerance, protective enzymes, root activity