Vegetation response to fire and volcanic disturbances since the Late Pleistocene in the Southern Patagonian Andes (49°S)

MERINO CAMPOS, VICTOR H.; SOTTILE, G. D.; DE PORRAS, M. E.; TONELLO, M. S

Bariloche

Congreso; International Association of Limnogeology (IAL) and International Paleolimnology Association (IPA) Congress 2022; 2022

IAL-IPA

High-Andean fossil records from the southeast Patagonian Andes (49°S) bring a unique perspective for analyzing past vegetation disturbances such as fires or tephra deposition after volcanic eruptions occurred since the Last Glacial Termination (T1) at the eastern margin of the South Patagonian Icefield. Pollen, charcoal and tephra records from two sedimentary sequences from high-Andean lakes were analyzed in order of evaluating potential changes in the vegetation as response to fire activity and tephra deposition from NAVZ (North Austral Volcanic Zone). Pollen data reveal Late Pleistocene to Holocene vegetation dynamics at Laguna Gemelas Este (LGE, 883 m.a.s.l., 49°23’06” S, 72°53’50” W), with high Andean taxa dominating the area before 15,200 cal yrs BP. Then, between 15,200 and 4,600 cal yrs BP, the record shows the onset of Nothofagus forest establishment followed by the development of subantarctic forest as we know today. Laguna Chiquita (LCH, 987 m.a.s.l.; 49°22’22” S, 72°58’28” W) pollen suggest a closed Nothofagus forest with no major changes of vegetation during the last 500 cal yrs BP. Charcoal data reveal high fire activity peaks before 15,200, 4500 and around 500 cal yrs BP at LGE and before 500 cal yrs BP and in modern times at LCH. LGE oldest and higher fire episodes are likely to be related to non-arboreal burned material due to scarcity of local Nothofagus forest presence in the area, while LCH fire peaks are probably linked to forest wood burning. Tephra deposition produced slightly lower concentrations of pollen in the sedimentary sequences, but no major changes in vegetation occurred during/after these events, showing a high resilience of subantarctic forests to such disturbances.