Postglacial environments in the southern coast of Lago Fagnano, central Tierra del Fuego, Argentina, based on pollen and fungal microfossils analyses

Abstract

We analyzed a peat-bog sequence from the central region of Tierra del Fuego, southernmost Patagonia, to reconstruct the environmental changes over the past 15,000years. Postglacial vegetation was mainly composed by grasslands and shrubby communities with sparsely distributed Nothofagus trees under dry conditions. The predominance of Glomus sp. and Gelasinospora sp. may also indicate less humid conditions related to the steppe communities. The presence of herbivorous grazers is suggested by the record of ascospores of coprophilous Sordaria-type and Sporormiella-type throughout the profile. Between 11,200 and 6500calyr BP, the Nothofagus woodland established under warmer and wetter climate than before. However, precipitation must have remained below present-day levels. Most fungal remains (Gaeumannomyces sp., Glomus sp., Gelasinospora sp., Microthyriaceae, Spegazzinia tessarthra, Alternaria sp.) are likely associated with the development of forest-steppe ecotone communities. Following 6500calyr BP, when climate conditions were more humid and colder than before, the closed-canopy forest dominated the landscape, and Microthyriaceae remains prevailed among fungi. During the last 1000years, the record showed open forest communities accompanied by the presence of Glomus sp. These palaeoenvironmental changes observed along the sequence suggested variations in the amount of precipitation of westerly origin related to shifts in the position and/or strength of the southern margin of the westerlies. This study revealed that fungal remains complement pollen/spores analysis by providing important independent information on the palaeoenvironmental and palaeoclimate conditions that prevailed during the late Pleistocene-Holocene in the Lago Fagnano area.