Biogeomorphic succession in a fluvial-lacustrine delta of the Middle Paraná River (Argentina): Feedbacks between vegetation and morphodynamics

MARCHETTI, ZULEICA Y.; VILLALBA, ANDREA B.; RAMONELL, CARLOS; BRUMNICH, FEDERICO; PEREIRA, MARÍA S.

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2020

0048-9697

The Leyes´ Delta lies at the Middle Paraná River, the second-largest fluvial system in South America, and it isbeing quickly formed into the Setúbal fluvial lake, Argentina. In the context of the Fluvial Biogeomorphic Successiontheory, our aim was to better understand interactions between physical and biotic processes contributingto the formation of the Leyes´ Delta. We studied the genesis, morphologic development, and vegetation in threegroups of its deltaic islands with contrasting formation ages. Different methodologies were applied. Genesis andmorphologic development were interpreted from time-series of satellite images and aerial photography obtainedfrom 1974 to 2014. Then landforms and vegetation communities were mapped on the most current images, andthey were corroborated and characterized during fieldwork. Our results evidence that the three island groups(Channel crevasse splay islands, Delta bar-plain islands, and Delta front islands) were formed via two differentgeomorphic processes, determining differences in the initial vegetation colonization. Eight fluvial-lacustrine landformsand eight vegetation communities, both differently represented among the island groups, currently characterizethese islands. The species richness accumulation curves and beta diversity showed that the morphodynamicactivity can be as important in the floristic composition of the deltaic islands as formation ages. The floristiccomposition differed statistically among island groups. After identifying three of the four phases of the FBS,we concluded that even though the morphodynamic activity under which islands were formed determined differencesin the initial vegetation colonization, under similar subsequent levels of morphodynamics the resultingvegetation heterogeneity tends to be similar even under contrasting genesis. Among the vegetation types, Loticprairies would play a key role in the morphologic evolution of the deltaic islands, therefore, their distributionand interactions with flow and sediments should be considered during the studies of social ecological systems asthe Leyes´ Delta, in Santa Fe, Argentina.