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

GONZALO R. TORRES; NORA INES MAIDANA; LILIANA C. LUPO; PAULA VIGNONI; CORDOBA, FRANCISCO E.; ACHIM BRAUER

Bariloche

Congreso; Congreso; International Association of Limnogeology and International Paleolimnology Association Joint Meeting; 2022; 2022

IPA Asociación Internacional de Paleolimnología

In order tocontribute evidence about the paleoecological development of the biospherereserve of the Yungas in the Eastern Cordillera of NW Argentina, we haveconducted a bioproxy analysis from a 5 m long sediment core retrieved in LagunaComedero (24°06´54.7" S - 65°29´7.2" W, 2,035 m asl). We present thefirst results from the pollen, spores and diatom dataset spanning the last ca. 1300 yrs. The preliminarychronological framework (14C) and the zonation of fossil sequences allow us to distinguish, different seral stages. Before 670 cal AD, a very low concentrationof palynomorphs and the absence of diatom remains suggest low humidityconditions with sparse vegetation and reduced water level. Between ca. 810 and 1350 cal AD, an ecesisprocess probably occurred with the establishment of xerosere communities (e.g. montanegrassland) in more humid conditions These changes are based on a noticeableincrease of the pollen richness. Poaceae pollen dominated in association withsaxicolous plants and fern spores of semiarid environments. Also, pollen ofmacrophytes appears and a group of small epiphytic araphid diatoms dominate thediatom assemblages. From ca. 1470 to 1760cal AD human activity might have caused structural changes in the landscape.Poaceae pollen decreased whereas pollen from shrub and grazing indicator plantsincreased. In the lake, benthic diatoms from well-developed littoralenvironments suggest that the water level remained high. From ca. 1850 cal AD to the present, the grasslandwas replaced by a woodland habitat accompanied by the progressiveeutrophication of the lake. Pollen concentration of the current tree speciesincreased. This reconstruction provides valuable information on natural andanthropogenic changes at centennial scales and can be useful to the managementof this protected area.