Effects of hydrological regimes on soil seed banks in the Carex hummock in wetlands: Implications for restoration.

Changes in the hydrological regime can significantly alter the structure, function, and biodiversity of wetlands. Soil seed banks (SSB) are crucial for maintaining the species diversity and plant regeneration in wetlands. Although the relationships between plant communities and hydrological conditions have been widely studied, the intrinsic mechanisms driving SSB dynamics are poorly understood because a tendency to neglect the influence of hydrological regimes on SSB. Field survey and germination experiments were conducted to determine the structure and composition of the aboveground plant community and SSB of Carex hummock wetlands under different hydrological regimes in the Western Songnen Plain of China and investigated the driving process of the hydrologic regime on SSB dynamics. The results showed that, compared with those under flooded (surface water depth was maintained at 5–10 cm for long-term) and drought (no still water on the soil surface, soil moisture content <65% for about 9–11 months annually) conditions, the values of characteristics of aboveground vegetation (Carex hummock, C. schmidtii population, and plant community) were generally higher under moist (no still water on the soil surface, soil moisture content >65% for about 8–9 months annually) conditions. C. schmidtii is the dominant species of plant community under different hydrological regimes. In response to hydrological regime changes, SSB differed in their density, richness, and diversity, and the soil bulk density and soil water content explained 41.8% and 6.8% of SSB structural variation, respectively. A non-metric multidimensional scaling analysis indicated the significant differences between the species composition of SSB and aboveground vegetation under different hydrological regimes in Carex hummock wetlands. Based on the structural equation model, it was found that the variation in the hydrological regime directly affected the hummock morphology, plant community density, and SSB density. Additionally, it indirectly influenced the density of aboveground vegetation by directly associating with the density of SSB. This study demonstrates that the hydrological regime exerts an influence on the species composition of SSB, thereby governing the role of SSB in the process of plant community regeneration within Carex hummock wetlands. These findings enhance our understanding of the effects of hydrological regimes on SSB and provide crucial information for the restoring of degraded Carex hummock wetlands. • Density and richness of soil seed bank(SSB) were regulated by hydrologic regime; • Hydrologic regime affects the similarity between aboveground plants and SSB; • Hydrologic regime directly and indirectly affects the soil seed bank in wetlands. • SSB is an important resource for implementing soil bioengineering. [ABSTRACT FROM AUTHOR]