Paleoecological development at centennial-scale inferred from bio-proxy records in the biosphere reserve of Yungas (NW, Argentina).

TORRES, G.; MAIDANA, N.; LUPO, L.; VIGNONI, P.A.; CÓRDOBA, F.; BRAUER, A.

San Carlos de Bariloche

Congreso; IAL IPA Joint Meeting 2022: Lakes as Memories of the Landscape.; 2022

International Association of Limnogeology (IAL) and International Paleolimnology Association (IPA).

In order to contribute evidence about the paleoecological development of the biosphere reserve of the Yungas in the Eastern Cordillera of NW Argentina, we have conducted a bioproxy analysis from a 5 m long sediment core retrieved in Laguna Comedero (24°06'54.7" S - 65°29'7.2" W, 2,035 m asl). We present the first results from the pollen, spores and diatom dataset spanning the last ca. 1300 yrs. The preliminary chronological framework (14C) and the zonation of fossil sequences allow us to distinguish, different seral stages. Before 670 cal AD, a very low concentration of palynomorphs and the absence of diatom remains suggest low humidity conditions with sparse vegetation and reduced water level. Between ca. 810 and 1350 cal AD, an ecesis process probably occurred with the establishment of xerosere communities (e.g. montane grassland) in more humid conditions These changes are based on a noticeable increase of the pollen richness. Poaceae pollen dominated in association with saxicolous plants and fern spores of semiarid environments. Also, pollen of macrophytes appears and a group of small epiphytic araphid diatoms dominate the diatom assemblages. From ca. 1470 to 1760 cal AD human activity might have caused structural changes in the landscape. Poaceae pollen decreased whereas pollen from shrub and grazing indicator plants increased. In the lake, benthic diatoms from well-developed littoral environments suggest that the water level remained high. From ca. 1850 cal AD to the present, the grassland was replaced by a woodland habitat accompanied by the progressive eutrophication of the lake. Pollen concentration of the current tree species increased. This reconstruction provides valuable information on natural and anthropogenic changes at centennial scales and can be useful to the management of this protected area.