Relationship between the hydrosedimentological regime and tree distribution patterns in the floodplain of the Upper Paraná River (Argentina)

NEIFF, J.J.; CASCO, S.L.; NEIFF, M.; ARENAS IBARRA, JOSÉ ANTONIO

Iquitos

Simposio; XI Symposium River Coastal and Estuarine Morphodynamics; 2015

Universidad de la Amazonía Peruana-Center for Research and Education of the Amazonian Rainforest (CREAR

Riparian vegetation have evolved within the context of flowing water habitats for which the flooding and droughts are the forcing factors that shape the community features, either through a positive or negative effect on the ecosystem?s function, according to the timing, frequency and magnitude of such events. In the Paraná floodplain landscape, topographic position is an indicator along the complex gradient, but it also includes information about flood/drought periods and trees? resilience to extreme hydrological phases. Our contribution explain the relationship between the hydrosedimentological regime and the trees distribution patterns in the floodplain of the Upper Paraná River, in Argentina, downstream of Yacyretá dam, along 245 Km since Ituzaingó to Corrientes city. We compare the current composition of woody species, with our data at the same places before the construction of the dam using the data of occurrence of each species. Our results suggest that each tree species have a preferred position in the topographic gradient where the observed counts were more frequent. At same time, comparing the hydrological behavior of the river in the previous period and in the post-Yacyretá dam period, significant differences on the pulse regime were found. Comparing the hydrological behavior of the river in the previous period and the period after Yacyretá reservoir significant differences on the pulse regime, which were stronger near of the reservoir. Considering the total number of tree species in this section of river, no significant differences were found among sites before the construction of the dam. In the sampling done 20 years after, were observed significant changes in the occurrence of species at each site and among sites at both ends of the studied area. Alterations in pulse regime lead to a new balance in the landscape, in which some tree species are favored and others are excluded. We explore the use of genetic algorithms to predict this new balance. We think that engineering works that alter the hydrological dynamics of the large rivers should pay more attention on the distribution of riparian forests because they are indicators that summarize the changes in hydrological dynamics, geomorphology and landscape functioning and because they are the support for the wildlife of the river