Postglacial vegetation dynamics and environmental conditions of southwest Patagonia Argentina (49º S; 72º W). Pollen and plant macrofossils analysis

ECHEVERRÍA, M.E.; BAMONTE, F. P.; MARCOS, M.A.; SOTTILE, G.D.

Bariloche

Congreso; IAL IPA 2022; 2023

Towards the end of the Last Glacial Maximum, southern Patagonia glaciers began their retreat, allowing the lakes and bogs formation and plant colonization in Andean Patagonia. The main purpose of this work was to reconstruct the dynamics of the Nothofagus subantarctic forest community during the deglaciation and their relation with the climatic variations from a sequence of southwest Patagonia Argentina (Mallín del Ciprés). This area is currently dominated by Pilgerodendron uviferum (Ciprés de las Guaitecas), Cyperaceae and Sphagnum. The pollen and plant macrofossils content was analyzed for the period between ca. 18,500 and ca. 11,000 cal years BP using standard techniques. Between 18,000 and 14,500 cal years BP, the pollen data suggest a sub-shrub steppe dominated by Ephedra, Empetrum, Azorella and shrubs such as Asteraceae subf. Asteroideae. At a local scale, a lacustrine-type deposit with moisture-indicating vegetation such as Caryophyllaceae, Gentianaceae, Urticaceae and Myriophyllum was inferred. Then, up to 10,000 cal years BP a shift towards a Poaceae steppe and the beginning of an open Nothofagus forest was suggested. Nothofagus remains such as leaves and buds indicated the local presence and expansion of the forest in the area. Identification of leaf fragments indicates the dominance of Nothofagus pumilio in the forest. At a local scale, a development of a mire deposit dominated by Cyperaceae and Bryophytes is inferred. The results obtained in this work coincide with global temperature models, the gradual increase in temperature recorded regionally is evidenced by the change from a sub-shrub steppe to a grass-Nothofagus forest ecotonal environment. The integration of plant macrofossil analysis with pollen analysis gives a more detailed picture of the composition of the local vegetation and, therefore, a more accurate environmental and climatic reconstruction.