The Fluvial Forests as Indicators of the Flow and Permanence of Water

Abstract

We evaluated the influence of the horizontal flows of the Paraná River on the composition and distribution of the floodplain landscape and we defined the ecohydrologicalsignature of some species-index in the low Paraná River section, (27° 38? 04? S and 58° 50? 46? W). During the drought phase, the structure of the vegetation were characterizad using a Cottam & Curtis method. The trees were positioned in the topographic gradients during the flood phase, taking as reference the river water sheet in the nearest hydrometric gauge. To obtain the pulse attributes in different positions of the geomorphological gradient, PULSO software was used considering the daily water levels at Corrientes city between 1985 and 2015. Two main types of flooded forests were identified: pionner forest, dominated by one or two species (Salix humboldtiana, Tessaria integrifolia) in recent bars and islands, and pluri-specific flooded forests (Albizia inundata, Cecropia pachystachya, Croton urucurana, Inga uruguensis, Ocotea diospyrifolia, Nectandra angustifolia and Peltophorum dubium) occupying bars of the highest islands, with shorter flood phases, with trees are distributed in 2-3 strata in a closed canopy. Pulses were more frequent in pioneer forests than in multispecific forests. The ecohydrological signature allows the optimum condition and distribution limits of each species to be established. It is a tool to know the adjustment of biotic elements (populations) to the river variability regime. The procedure usedcan be used to anticipate the possible reorganization of the river plain landscape as a result of flow variations predicted by climate change models.