Responses of germination strategy of Agriophyllum squarrosum to rainfall pattern in the Tengger desert

Agriophyllum squarrosum (L.) Moq. (Chenopodiaceae) is an annual pioneer psammophyte that is strictly distributed along desert margins. However, little is known about how this species adapts to shifting dunes. In this study, seeds bank was selected and germination behaviors of A. squarrosum were tested in laboratory. In addition, the effects of rainfall patterns on population dynamics were observed in field at the southeastern edge of the Tengger Desert. Soil seed bank density was significantly different in different depth of sand dunes. Under adequate water in Petri dishes, seeds began to germinate in less than 3 h and the germination peak was reached in seven days after watering. It showed that there is no innate dormancy of A. squarrosum. The buried experiments showed that the germination percentage decreased with increasing buried depth, and deeply buried seeds (10 cm) remained ungerminated. Population dynamics in different rainfall pattern of three years in field showed that germination, survival and deaths of A. squarrosum were extremely sensitive to rainfall variation. Our results suggest that precipitation is the key factor in determining population of A. squarrosum. The germination strategy of A. squarrosum ensures the efficiency use of unpredicted and scarce precipitation. The high disturbance of moving sand endowed persistence seed bank of A. squarrosum, which is essential for population continuation, avoiding population extinction under unpredicted precipitation.