Aquatic macrophytes in natural and managed wetlands of Rio Grande do Sul State, Southern Brazil

Ana Silvia Rolon,Leonardo Maltchik,Henrique Flores Homem

doi:10.1590/s2179-975x2010000200003

Abstract

AIM: This study gathers the main results obtained from studies regarding dynamic of aquatic macrophyte community in natural and managed wetlands of Southern Brazil. We analyzed the aquatic macrophytes diversity in wetlands of Southern Brazil, the environmental factors that determine the structure of the aquatic macrophyte community in fragmented wetlands, the effects of floods on the dynamics of macrophytes, and the contributions to the rice field for the conservation of aquatic macrophytes; METHODS: The information was obtained from several researches carried in several spatial scales and different wetlands types over the last 10 years in Southern Brazil; RESULTS: The studies have reported the occurrence of approximately 250 species of aquatic macrophytes. Wetland area, habitat diversity, altitude and hydroperiod were determinant for macrophyte richness and composition in wetlands of Southern Brazil. Furthermore, flood events, long or short-term ones, are strongly associated to the structure of the aquatic macrophyte community. The rice field systems of Southern Brazil (crops and irrigation channel) shelter a representative number of species of macrophyte found at natural wetlands in this region. The agricultural practices adopted over rice cultivation cycle in the rice fields have influenced the macrophyte richness and biomass. The different hydrological management practices adopted after the harvesting period (presence or lack of water surface) did not influence the macrophyte richness and biomass, however it influenced the species composition; CONCLUSIONS: The increasing process of wetland degradation (e.g. fragmentation, flood control and rice field expansion) presents a threat to the conservation aquatic macrophyte species.

Highlights

Wetlands are important sites for biological conservation because they support a rich biodiversity and present high productivity (Mitsch and Gosselink, 2000)
The diversity and the dynamics of aquatic macrophytes in rice fields in Southern Brazil were assessed in six rice fields (Rolon and Maltchik, 2010) and in four irrigation channels of the Coastal Plain of Rio Grande do Sul between 2006 and 2007
Our studies carried recently in wetlands in Southern Brazil, which focused on different spatial scales, have reported the occurrence of approximately 250 species of aquatic macrophytes (Maltchik et al, 2002; Bertoluci et al, 2004; Rolon et al, 2004; Rolon et al, 2008) (Table 1)

Summary

Introduction

Wetlands are important sites for biological conservation because they support a rich biodiversity and present high productivity (Mitsch and Gosselink, 2000). Biodiversity in wetlands has been reduced worldwide (Shine and Klemm, 1999) – a loss of more than 50% of these ecosystems in the last century due to human activities (Shine and Klemm, 1999). The impact of wetland loss on biodiversity was verified by the decline of populations of several wetland-dependent species (Millennium Ecosystem Assessment, 2005). The principle that a large area supports more species (Arrhenius, 1921; Rosenzweig, 1995) has been put into practice in conservational planning. By assuming wetlands to be ecological islands surrounded by terrestrial habitats, the relationships among species richness and wetland size were extensively used for wetland management (Hall et al, 2004)

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Results