We investigate Lake Estanya's diatom and pollen records from the Late Glacial (LG) to the Early Holocene (EH), in order to compare limnological and vegetation responses to common climate forcing. The biotic changes recognized in this study largely agree with the hydrological evolution of the lake described previously for the same period. The diatom record shows high sensitivity to fluctuations in both lake level and salinity concentration as a consequence of climate shifts. In addition vegetation results indicate that the area could have played an important role as regional vegetation refuge. Shallow lake conditions during the Last Glacial Maximum (LGM) were punctuated by relatively deeper freshwaters between 19.3 and 18.6. cal. kyr BP and at 18.0. cal. kyr BP, as recorded by diatom shifts. A subsequent increasing aridity trend, coinciding with the Mystery Interval (MI), affected the diatom accumulation rates, which dropped to its minimum values between 17.2 and 14.7. cal. kyr BP. Particularly dry and cold conditions during the LGM and MI are supported by the largest values of steppic pollen taxa of the whole sequence, which account for up to 40%. However, relatively high values of Betula during the Heinrich Event 1 suggest a plausible regional vegetation refuge. Abrupt cooling and warming episodes within the LG triggered remarkable ecological threshold crossings in the diatom communities, especially during the stadial/interstadial episodes. At this point, the vegetation reflects the onset of warm conditions during the Bølling/Allerød with the partial substitution of Betula by Marcescent and Evergreen Quercus, which probably indicates the arrival of temperate taxa to the area and the likely migration of birch to higher altitudes. The Younger Dryas Stadial shows a complex ecological response. Diatoms are very poorly preserved, but aquatic taxa reach their highest values. An increase in Marcescent Quercus during this cold stage lends further support to the hypothesis that this is a regional vegetation refuge. Low lake levels recorded during the EH affected the development and preservation of diatom communities. A delay in the onset of humid conditions for the EH is also supported by the vegetation composition, characterized by the maximum expansion of Juniperus.
Bibliographical noteFunding Information:
This research has been funded through the projects LIMNOCLIBER ( REN2003-09130-C02-02 ), IBERLIMNO ( CGL2005-20236-E/ CLI ), LIMNOCAL ( CGL2006-13327-C04-01 ), PALEODIVERSITAS ( CGL2006-02956/BOS ), GLOBALKARST ( CGL2009-08415 ), GRACCIE-CONSOLIDER ( CSD2007-00067 ), DINAMO ( CGL2009-07992 ), DINAMO2 ( CGL2012-33063 ); provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT) ; and PIRINEOSABRUPT ( PM073/2007 ), provided by the Diputación General de Aragón . Mario Morellón Marteles and Graciela Gil-Romera hold post-doctoral contacts funded by the “ JAE-Doc/CSIC ” ref.- and “ Juan de la Cierva ” (grant ref. JCI2009) programs respectively. Ana Pérez-Sanz has been supported by a PhD Fellowship provided by the Aragon Government . We also thank Beatriz Bueno and Aída Adsuar for lab assistance. Finally, we are grateful to Antonia Andrade Olalla for helping in initial pollen analyses and to Joan Gomà for assistance in diatom taxonomic determinations. Two referee's constructive criticism and suggestions helped improved a former version of this paper.
Copyright 2013 Elsevier B.V., All rights reserved.
- Biological responses
- Ecological threshold
- Mediterranean basin
- Multiproxy approach