Study on the herbaceous plant communities in the Lower Delta islands of the Paraná River (Argentina)

Abstract

The Lower Delta of Paraná river in Buenos Aires is a wide costal freshwater wetland of 2,071 km2. In this study, native, herbaceous plant communities of the Lower Delta islands were identified and described in order to propose a conceptual model for the interpretation of  the spatial distribution of plant communities. The main hypothesis was that the hydrological regime and the landscape pattern are key factors determining the regional heterogeneity and conditioning the presence and abundance of species and plant communities. Values of  cover-abundance for each species were estimated in 177 plots placed in 21 sites in the region. Soil samples were also taken. A total of 62 species and 19 plant communities were identified. Plant communities form a heterogeneous mosaic and they are characterized by a low
species richness and the dominance of few graminoid type plants and even less representation of broadleaf plants. The presence and distribution of plant communities in the area are determined by two main factors: (1) the water permanence related to the position along the topographic gradient, and (2) the origin and dynamical action of the water supply, both affected  mainly by the connection with the main water channels and the location of plots in relation to the regional gradient of the fluvial estuary.