IIMYC   23581
INSTITUTO DE INVESTIGACIONES MARINAS Y COSTERAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Riparian woody vegetation history in the campos region of Uruguay during two time windows: late Pleistocene and late Holocene
Autor/es:
ALDO R. PRIETO; DOMINIQUE MOURELLE; FELIPE GARCÍA-RODRIGUEZ
Lugar:
Salvador
Reunión:
Congreso; XIV International Palynological Congress - X International Organisation of Palaeobotany Conference,; 2016
Institución organizadora:
ALPP
Resumen:
We present a detailed palynological record of a 163-cm-long sediment core from Laguna Formosa (LF) (31°48´S-54°28´W) situated in the northeastern campos region of Uruguay. Based on seven AMS radiocarbon dates and the presence of a sedimentary hiatus, the record represents two periods: late Pleistocene (from 14,570 to 13,500 cal. years BP) and late Holocene (from 3280 cal. years BP to the present). At ca. 14,570 cal. years BP hydrophilous trees and shrubs were recorded, mainly represented by Salix chilensis, Celtis and Cephalanthus glabratus, which reflected the development of riparian hydrophilous shrublands on the littoral of freshwater bodies. After ca. 14,310 cal. years BP the shrubland diversity gradually increased, indicated by the occurrence of new taxa such as Phyllanthus sellowianus, Lithraea, and Schinus. The development of hydrophilous shrublands probably promoted the fixation of the freshwater bodies? margins, maintaining calmer and clearer water conditions and leading to the development of submerged plants. This is the first evidence of woody riparian vegetation development along the rivers for northern campos during the late glacial period, being the vegetation constituted not only by isolated individuals. The climate must have been relatively wet and not so cool to allow such a vegetation development. At ca. 3280 cal. years BP riparian forests consisted of both hydrophilous and mesophilous woody taxa. Since ca. 2270 cal. years BP woody vegetation gradually increased, accompanied by the incorporation of other taxa (e.g. Allophylus edulis, Erythrina crista-galli and Daphnopsis racemosa) by ca. 940 cal. years BP. The riparian forests changed their abundance and diversity during the late Holocene until achieving a composition similar to the current one at ca. 540 cal. years BP. The increased woody vegetation since ca. 2270 cal. years BP and the evidence of more frequent and intense flooding events in the study area between 1200 and 1800 cal. years BP could be related to higher precipitation over La Plata Drainage Basin. Grasslands and bunchgrasses were regionally dominant throughout the recorded late Pleistocene and late Holocene period. It is interesting to point out that the riparian woody vegetation composition is totally different for both time windows treated here, and the modern composition emerged only after ca. 540 cal. years BP. In addition, we recorded Inga, Trema, Alchornea and even Araucaria pollen during the late Holocene, representing trees that currently no longer develop in the study area, thus suggesting plant migrations from southern Brazil and northeastern Uruguay.