Continuous growth of the giant grass Zizaniopsis bonariensis in subtropical wetlands

Abstract

1. Zizaniopsis bonariensis (giant grass) is an emergent macrophyte species endemic to subtropical wetlands in Brazil, Argentina, Paraguay and Uruguay. In this study, we show the effects of its continuous clonal reproduction and its 'phalanx' growth strategy in the Taim Wetland (southern Brazil). 2. The continuous clonal growth of this 3-m high grass gave rise to the emergence of 11.7 new shoots m )2 per month and a high total above ground production (2870 g dry weight m )2 year )1 ). The biomass of the new shoots emerging every month formed a wave of growth, moderated by only weak seasonal variation. 3. We show its phalanx growth strategy by analysing the variations in population density and shoot height within a transect through the stand canopy. The inverse relation between density and height from the border to the interior indicates self-regulation of biomass. 4. The plants modified their environment, enhancing resistance to drought within the stand and thus facilitating their dominance. This positive feedback suggests that the dominance of the plant might constitute an alternative state in subtropical wetlands.

Effects of vegetation state on biodiversity and nitrogen retention in created wetlands: a test of the biodiversity–ecosystem functioning hypothesis

“…However, during the course of the study, species diversity of plants became lower in emergent vegetation wetlands than in the other wetlands. It seems likely that the dense cover of tall emergent macrophytes competitively excluded other plant species (Weiher & Keddy, 1995; Zedler & Kercher, 2004; Minchinton, Simpson & Bertness, 2006; Ferreira et al. , 2009).…”

“…However, during the course of the study, species diversity of plants became lower in emergent vegetation wetlands than in the other wetlands. It seems likely that the dense cover of tall emergent macrophytes competitively excluded other plant species (Weiher & Keddy, 1995;Zedler & Kercher, 2004;Minchinton, Simpson & Bertness, 2006;Ferreira et al, 2009). A more diverse plant community developed in free development wetlands than in submerged vegetation wetlands until 2006, perhaps indicating a pre-emption effect in the submerged vegetation wetlands preventing some plant species from establishing (Grace, 1987;Groth, Lovett-Doust & Lovett-Doust, 1996;Chadwell & Engelhardt, 2008).…”

“…Wetlands and shallow lakes tend to exhibit alternative vegetation states, dominated by primary producers belonging to one of several different functional groups: attached or planktonic microalgae or filamentous algae or emergent, floating-leaved, submerged or non-rooted floating macrophytes (Bayley & Prather, 2003;Irfanullah & Moss, 2005;Ferreira, van Nes & Marques, 2009;O'Farrell et al, 2009). Wetland management practices, such as biomanipulation, grazing, mowing or water level fluctuations, therefore often strive to control vegetation state (e.g.…”

Identificação Do Padrão De Distribuição De Macrófitas Aquáticas Emergentes No Banhado Do Taim-Rs-Brasil, Frente a Diferentes Condições Hidrológicas

“…Estudos relatam a relação inversa entre a sua densidade e a altura de seus estandes, a partir de sua borda para o interior indicando uma autorregulação da biomassa, o que possibilita sua expansão e reduz a competição por luz e nutrientes em seu interior. Aliado a essas adaptações, seu sucesso competitivo é elevado devido as suas diferentes formas de reprodução (tanto vegetativa, quanto sexuada e através da propagação de sementes) (Ferreira, 2005;Ferreira et al, 2009). No Banhado do Taim não foram encontrados indícios de perdas das MAE avaliadas durante a condição de seca.…”

Trophic structure of frog assemblages in coastal habitats in southern Brazil

“…Here, we compare the trophic structure of frog assemblages between contrasting coastal habitats: a productive, mesic habitat (wetland) and an adjacent semiarid habitat that is comparatively less-productive (sand dunes). The subtropical coast of southern Brazil contains wetlands and sand dunes that differ markedly in physiography, productivity and biodiversity (Ferreira et al 2009;Portz et al 2016). The wetlands are dominated by diverse aquatic macrophytes (at least 176 species; Rolon et al 2011) and characterised by high primary production.…”