Artemisia sphaerocephala and A. ordosica are two dominant shrub species in Mu Us sandy land (Inner Mongolia, China) and are widely used for vegetation restoration. However, there are two different conclusions about the effect of light on their germination: light promotes germination versus light inhibits germination. The aim of this study was to evaluate these two conclusions and relate the results to instances of failure of these two species to germinate well when air-dispersed in revegetation projects. The effects of fluctuating temperature, light/dark, source (population), position on mother plant, storage condition, and storage time were tested on germination of achenes of these two species. At low temperature, final percent germination (FPG) of achenes in dark and nearly dark conditions was significantly higher than those in light. At 10:20 degrees C, achenes of both A. sphaerocephala and A. ordosica had higher FPG in dark than in light regardless of source, position on mother plants or storage condition. At suboptimum (5:15 degrees C) and supraoptimal (25:35 degrees C) temperatures, germination of A. sphaerocephala and A. ordosica achenes was inhibited in both light and darkness. It was concluded that light inhibits germination of A. sphaerocephala and A. ordosica achenes at low (10:20 degrees C) temperature but not at high (15:25 degrees C) temperature. Since the temperature in Mu Us sandy land is around 10:20 degrees C in early June, when air sowing is done, achenes should germinate best when they are covered by a thin layer of sand.

Keywords Artemisia ordosica, Artemisia sphaerocephala, Desertification, Germination, Light intensity, Mu Us sandy land, Vegetation rehabilitation