Abstract: To explore the spatiotemporal pattern of soil seed bank and its influencing factors after farmland abandonment in the tropics, we used seed germination experiments to examine the composition and distribution of soil seed banks in different soil layers (0-5, 5-10, 10-20 cm) in different abandonment years (2nd, 5th, and 10th year of abandonment) in the western and eastern regions of Hainan Island. The results showed that the maximum soil seed bank density of abandoned land in the western and eastern regions of Hainan Island in the second year after farmland abandonment was 49906 and 55417 seeds·m^-2 respectively. There was no significant difference between the two regions (P> 0.05). After five years of abandonment, soil seed bank density in the eastern region was significantly higher than that in the western region. After 10 years of abandonment, soil seed bank density in the western region was significantly higher than that in the eastern region. As the years of abandonment increase, soil seed bank density in the western part of Hainan Island decreased first and then increased, and soil seed bank density in the eastern part of Hainan Island showed a gradual decreasing trend. The richness and diversity of soil seed banks in both regions increased over years. Aboveground vegetation and soil seed banks showed non-consistency during succession, resulting in a low similarity between the two, ranging from 3% to 21%, with a downward trend over time. Years of abandonment and its interaction with region had significant effects on soil seed bank density and diversity (P<0.05). The results provide an important reference for understanding the spatiotemporal pattern of soil seed bank and its influencing factors after farmland abandonment in tropical areas, with theoretical and practical significance for guiding farmland restoration and utilization and ecological environment protection.

Key words: tropical area, soil seed bank density, abandoned time, diversity, similarity, richness