Seed bank of seasonally flooded grassland: experimental simulation of flood and post-flood

Abstract

Wetland seed banks comprise the propagules of plant species that have species-specific germination requirements for germination in either flooded or dry conditions. At the community level, wetland structure and succession during and after a seasonal flooding event depends upon the early lifehistory requirements of species, including germination under flooded and dry conditions. We examined the effects of simulated flood and post-flood scenarios on seedling emergence from a seed bank of seasonally flooded grassland in the Pantanal, Brazil. Field samplings were conducted in both wet and dry seasons, both of which were subject to flood and post-flood conditions. A total of 70 species emerged from the seed bank, dominated by Poaceae and Cyperaceae. Sixteen species were exclusive to the wet and one exclusive to the dry season. The richness of perennial species was higher under flood conditions, while the richness of annuals was greater postflood. In general, the aquatic and amphibious species exhibited a significant germination response to flooding. Terrestrial species only germinated in post-flood conditions, with higher richness in the dry season. Four species had high seedling abundance in both treatments. The capacity of regeneration by seeds is high in these grasslands and can be increased by

Seasonal flooding, topography, and organic debris interact to influence the emergence and distribution of seedlings in a tropical grassland

“…Flooding in the Pantanal is considered to act as an ‘environmental filter’ that regulates the richness and abundance of the seed bank (Bao et al . , , ). In our study, communities were dominated by rapidly colonizing emergent species ( e.g ., D. kuntzei , L. octovalvis , R. grandiflora , and R. ramosior ) during both seasons.…”

“…However, the presence of amphibious plants in both in the post‐flood and post‐dry seasons is a consequence of their life form (Capon & Brock ), which can germinate in dry or wet soil (Bao et al . ). There is little research on the ecophysiology of drought resistance or flooding tolerance of the species of the Pantanal, but there are many reports on plant distributions according to soil moisture gradients ( e.g ., Pott et al .…”

“…The species that occurred both in the post‐flood season and in the post‐dry season are likely part of a persistent seed bank (Brock ) rich in annual species whose seeds tend to germinate regardless of season (Bao et al . ).…”

“…) and the persistence of seeds in the soil (Bao et al . ). Drought‐resistant species can appear in dry pond beds in dry years, and flood‐tolerant plants can grow on higher ground in wetter years (Pott & Silva ).…”

“…The growth form and life history characteristics of species influence their prevalence in both the seed bank and the aboveground community (van der Valk 1981). For example, during flood periods, the density of submerged and floating macrophytes such as Hydrocleys parviflora, Sagittaria guayanensis, Nymphaea amazonum, and Nymphaea gardneriana is high (Bao et al 2017). At the end of the dry period, an increase in soil moisture increases the germination of amphibious species and the establishment of aquatic vegetation (Brock 2011).…”