Effects of flooding and its temporal variation on seedling recruitment from the soil seed bank of a Neotropical floodplain

Abstract

Evaluation of the eff ects of fl ooding on seedling recruitment from seed banks helps in understanding vegetation regeneration in fl oodplains. We studied the eff ects of simulated fl ooding on richness and abundance of, and temporal variation in, seedling recruitment from the soil seed bank of a fl oodable savanna of the Pantanal wetland, under two conditions: 1) Post-fl ood = inundated for 30 days followed by irrigation; 2) Non-fl ooded = only irrigated. We recorded emerged seedlings biweekly for 120 days and found a total of 124 species for the two treatments, the most abundant species were annual herbs (e.g., Richardia grandifl ora and Euploca procumbens) and annual graminoids (e.g., Digitaria ciliaris and Cyperus haspan). Flooding positively infl uenced seedling richness and abundance, while seedling emergence from the non-fl ooded soil was slower, but continued during all periods. Th e diff erent temporal patterns between treatments showed that fl ooding increases the abundance of emerged seedlings and acts as a trigger for explosive recruitment shortly after water depletion.

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

“…The species with the highest seedling abundance in both periods included H. brevipes, L. octovalvis, R. grandiflora, and R. ramosior. These pioneer species are found in dried out ponds and seasonal streams (Pott & Pott 1994) and are abundant in the soil seed bank in the region (Bao et al 2014, Souza et al 2016.…”

“…Seasonal ponds can form during flooded periods (Pott & Silva 2015), which promote areal and elevational zonation patterns of vegetation (Damasceno Junior et al 2005). Communities within seasonal ponds may be subjected to greater transport of diaspores by water (Oliveira et al 2015, Souza et al 2016 and high retention of seeds in natural depressions (Bao et al 2014). Seasonal ponds nested within seasonally flooded grasslands create spatial habitat heterogeneity (Hopfensperger et al 2009).…”

Secondary seed dispersal in hydro‐fluctuation belts and its influence on the soil seed bank

“…During the germination period, the plant species, and the life form and seed number of each species germinating in each soil sample were recorded. The secondary seed dispersal experiment was conducted from March to June 2016, whereas the soil seed bank experiment was conducted from April to July 2016 because all seeds available for germination over the summer would be present during this time (Souza, Ferreira, & Pott, ). Seedling emergence was observed for 16 weeks (Lee, Alday, Cho, Lee, & Marrs, ; Souza et al, ).…”

Effect of Fire on the Soil Seed Bank of Neotropical Grasslands in the Pantanal Wetland

“…In flood-free vegetation, for example, such negative effect can last for at least three years (Lipoma et al 2018). Yet regarding the temporal reach of the studies, even the seasonal variations only recently started to be investigated (Bao et al 2014, Souza et al 2016. Among the dominant species in the vegetation established at sampling time, only the grass P. lenticulare was recorded, however, its abundance corresponds to less than 0.25%.…”

“…Here we tested the hypothesis that the soil seed bank of the macrohabitat flood-prone savanna grasslands in the Pantanal is fire sensitive, expecting a negative effect of burning on the soil seed stock, what would have implications on the traditional pasture management still practised in the Pantanal -considering reproductive strategy by seeds as an important one for many savanna plant species (Sarmiento & Monasterio 1983). The following considerations support the negative expectation, in spite of the savanna context of the Pantanal: a) flooding, and not fire, has been massively pointed as main ecological driver in wetlands as Pantanal (Junk et al 2006, Nunesda-Cunha & Junk 2015, Miranda et al 2018; b) regarding seeds and seedlings, the traits reported to flood tolerance and fire tolerance are constrasting: as seed buoyancy and fast seedling growing towards surface, to avoid anoxia or hypoxia, have been reported to plant species in wetlands (Parolin et al 2003, Jackson & Colmer 2005, Junk et al 2006, Parolin & Wittmann 2010; hard coated seeds and fast root seedling growing have been related to fire-prone environments (Saboya & Borghetti 2012, Keeley et al 2011, Ribeiro & Borghetti 2014, Fichino et al 2016; c) fire significantly reduced the soil seed stock of one of the predominant species in a wetland investigated by Miao et al (2010) while flood had positive effects on the soil seed bank of the Pantanal, incresing its abundance and richness (Oliveira et al 2015, Souza et al 2016, and d) there is an expressive number of aquatic macrophytes seeds stored in the Pantanal seed banks (Oliveira 2009, Bao et al 2014, Oliveira et al 2015, Souza et al 2016.…”