Abstract: This paper studied the effects of different concentrations (0,5,20,and 100 mg·kg^-1) metolachlor and its enantiomer S-metolachlor (Dual Gold) on soil catalase activity.The results showed that 20 mg·kg^-1 metolachlor had the most successive stimulating effect,5 mg·kg^-1 metolachlor had an inhibitory effect in the early period,while 100 mg·kg^-1 metolachlor had a stimulating effect in the late period.Different concentrations Dual Gold displayed a tendency stimulation-inhibition-stimulation.5 and 100 mg·kg^-1 metolachlor might have more damage on soil ecosystem than different concentrations Dual Gold.

Key words: Minqin oasis, Landscape change, Landscape index, Driving force