Comparison of Seed Germination ofAgriophyllum squarrosum(L.) Moq. andArtemisia halodendronTurcz. Ex Bess, Two Dominant Species of Horqin Desert, China

Both Agriophyllum squarrosum and Artemisia halodendron play essential roles in the vegetation rehabilitation process in Horqin desert. Responses of germination to temperature, water potential, and burial depth in the two species were studied experimentally. The results showed that: (1) seeds of the two species could germinate with high final percentages (> 67%) at prevailing surface soil (0–5 cm) temperatures from April to July. However, Agriophyllum squarrosum had more efficient mechanisms to ensure that seeds germinate quickly at prevailing May temperatures but slowly at the temperatures of April and July, in comparison to Artemisia halodendron; (2) Artemisia halodendron had higher final germination percentages than Agriophyllum squarrosum when water potential was low (p < .0.01); and (3) seedlings of Artemisia halodendron emerged well only at a depth less than 1 cm and did not emerge at all when the burial depth reached 4 cm, while those of Agriophyllum squarrosum emerged with a final percentage of 21.6% even at the depth of 4 cm. These different characteristics of seed germination and seedling emergence could partially explain the phenomenon that Agriophyllum squarrosum always precedes Artemisia halodendron in establishing on moving sand dunes in Horqin desert.