Abstract: The alternation of freezing and thawing in desert area significantly changes soil temperature and water conditions, with consequences on seed germination of desert plants. Here, we examined the effects of freezing and thawing process on seed germination of four typical ephemeral plant species, Eremopyrum orientale, Lappula patula, Erodium oxyrrhynchum and Alyssum linifollum, in the Gurbantunggut Desert. We measured the seed germination parameters (germination rate, germination potential, germination index, and seed vigor) of those four species under the treatments of different temperatures, soil moisture, and freezing-thawing cycles. The results showed that temperature did not affect seed germination parameters of the four species, whereas water condition, cycle number of freezing and thawing, and their interaction showed significant effects (except for the effects of soil moisture on A. linifollum). In addition, increased freezing and thawing times promoted seed vigor and seed germination after the freezing and thawing treatments, especially under low moisture condition. High soil moisture in the freezing and thawing period significantly reduced the seed germination rate of E. orientale, but such effects on other species depended on day temperature and numbers of freezing and thawing cycles. Under the same soil moisture condition, high temperature during the freezing and thawing period usually promoted seed germination. In general, freeze-thaw process had a significant species-specific effect on seed germination of desert ephemeral plants, which would lead to speciesspecific variation in seedling growth after the freeze-thaw period and thus affect plant community structure in the desert.

Key words: Gurbantunggut Desert, freeze-thaw cycle, ephemeral plant, seed germination, temperature, soil moisture.