Abstract: Erodium oxyrrhynchum is a dominant ephemeral plant in the Gurbantunggut Desert. Its diaspore can successively establish on soil bio-crust. In this paper, a laboratory experiment was conducted under controlled conditions, and scanning electron microscopy was used to observe the morphological changes of the diaspore following hygroscopic absorption. The appending hairs located on the epidermis of the diaspore had four types, playing important roles in the moisture retention and diaspore fixation, and being considered as an adaptation strategy to the dispersion and establishment of E. oxyrrhynchum. There existed transition areas and gaps in the conjunction of fruit and awn. During the process of hygroscopic absorption, the angle between awn and major axis decreased gradually, and the epidermal cells changed in shape, which were the basis of the hygroscopic movement. These morphological changes could promote the mobility of the diaspore on soil surface, and benefit the seed establishment when the habitat was suitable. Our results provided morphological evidences for the further study on the establishment mechanisms of E. oxyrrhynchum.

Key words: Soil particle size fractionation, Loess Plateau, Canadian Prairie