Effects of flooding on the spatial distribution of soil seed and spore banks of native grasslands of the Pantanal wetland

Patricia Carla de Oliveira,Catia Nunes da Cunha,José Marcelo Domingues Torezan

doi:10.1590/0102-33062015abb0027

Patricia Carla de Oliveira, Catia Nunes da Cunha + Show 1 more

Open Access

https://doi.org/10.1590/0102-33062015abb0027

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Abstract

To better understand the role that flooding plays in shaping plant communities of native floodable grasslands of the Pantanal and to characterize the spatial distribution of plants, we present the results of a survey of soil seed and spore banks using the seedling emergence method. We hypothesized that terrain subjected to the deepest and longest flooding should have higher propagule abundance and richness. The species composition and distribution of seeds and spores in the soil were assessed at five sites using three sampling positions at each according to inundation intensity. In each sample position 2cm-thick soil samples were collected in quadrats to a depth of 10cm. Litter was also collected as an independent layer. Sample monitoring in the greenhouse resulted in the emergence of 5489 seedlings, or 6353 propagules.m-2. Both the litter layer and the deepest soil layer had low abundances. A total of forty-four morphospecies (16 families) were recorded. Both seedling abundance and species richness were concentrated in the more floodable center sections. Isoetes pedersenii, Eleocharis minima, Sagittaria guayanensis, Rotala mexicana, Eleocharis plicarhachis, and Panicum laxum were the most abundant species. The species composition and spatial distribution of the propagule bank suggests that flooding plays a crucial role in seasonal vegetation dynamics in Pantanal wetlands, mediated by the ability of the soil to host seeds and spores during dry season.

Highlights

Soil seed banks are important to plant communities because they ensure the persistence of vegetation over time (Baskin & Baskin 2001), they facilitate the ability to respond to disturbance (Thompson 1992; Valk 2013), and they provide the main source of new recruits (Cheke et al 1979; Jalili et al 2003)
The overall propagule density (6.3 thousand seeds and spores.m-2) could be considered high but if the spores are excluded from the data the density drops to 2.6 thousand seeds.m-2, a value lower than those reported for other wetlands such as the Everglades (3.7 thousand seeds.m-2) (Valk & Rosburg 1997), and pothole lakes in United States (3.6 thousand seeds-2) (Baskin & Baskin 2001)
It is clear that these center microsites must be considered in management plans, since they are locations of the greatest species richness and abundance

Summary

Introduction

Soil seed banks are important to plant communities because they ensure the persistence of vegetation over time (Baskin & Baskin 2001), they facilitate the ability to respond to disturbance (Thompson 1992; Valk 2013), and they provide the main source of new recruits (Cheke et al 1979; Jalili et al 2003). Water flux serves as a dispersal agent (Middleton 2000) bringing new propagules to the bank and soil hydrology determines both seed recruitment (Peterson & Baldwin 2004; Bao et al 2014) and seedling establishment (Prado et al 1994; Rebellato & Nunes da Cunha 2005). These factors affect the composition of species that will produce seeds and spores that will be incorporated into the soil bank. Analysis of soil seed bank composition of sites with different flooding regimes can provide a way to investigate the influence that flooding has in soil seed bank formation (Hölzel & Otte 2001)

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