High resolution multiproxy data (pollen, sedimentology, geochemistry, chironomids and charcoal) from the Basa de la Mora (BSM) lake sequence (42°32' N, 0°19' E, 1914m a.s.l.) show marked climate variability in the central southern Pyrenees throughout the Holocene. A robust age model based on 15 AMS radiocarbon dates underpins the first precise reconstruction of rapid climate changes during the Holocene from this area. During the Early Holocene, increased winter snowpack and high snowmelt during summer, as a consequence of high seasonality, led to higher lake levels, a chironomid community dominated by non-lacustrine taxa (Orthocladiinae) related to higher inlet streams, and a forested landscape with intense run-off processes in the watershed. From 9.8 to 8.1calkaBP, climate instability is inferred from rapid and intense forest shifts and high fluctuation in surface run-off. Shifts among conifers and mesophytes reveal at least four short-lived dry events at 9.7, 9.3, 8.8 and 8.3calkaBP. Between 8.1 and 5.7calkaBP a stable climate with higher precipitation favoured highest lake levels and forest expansion, with spread of mesophytes, withdrawal of conifers and intensification of fires, coinciding with the Holocene Climate Optimum. At 5.7calkaBP a major change leading to drier conditions contributed to a regional decline in mesophytes, expansion of pines and junipers, and a significant lake level drop. Despite drier conditions, fire activity dropped as consequence of biomass reduction. Two arid intervals occurred between 2.9 and 2.4calkaBP and at 1.2-0.7calkaBP (800-1300 AD). The latter coincides with the Medieval Climate Anomaly and is one of the most arid phases of the Holocene in BSM sequence. Anthropogenic disturbances were small until 700 AD, when human pressure over landscape intensified, with Olea cultivation in the lowlands and significant deforestation in highlands. Colder and unfavourable weather conditions during the second part of the Little Ice Age caused a temporary cease of high-land management. The most intense anthropogenic disturbances occurred during the second half of 19th century. Last decades are characterized by recovery of the vegetation cover as a result of land abandonment, and lowered lake levels, probably due to higher temperatures.
Bibliographical noteFunding Information:
Financial support for research was provided by the former Spanish Inter-Ministry Commission of Science and Technology (CICIYT) through the projects DINAMO ( CGL2009-07992 ), DINAMO2 ( CGL2012-33063 ), GRACCIE-CONSOLIDER ( CSD2007-00067 ) and HORDA ( 83/2008 ), from Parques Nacionales . Additional funding support has been provided by the Aragon Government through the project PM073/2007 and by Geoparque del Sobrarbe through the project “ High resolution chronological control of Basa de la Mora” .
Ana Pérez-Sanz has been supported by a PhD Fellowship provided by the Aragon Government. Ana Moreno, Graciela Gil-Romera and Mario Morellón hold post-doctoral contracts funded by the “Ramón y Cajal”, “Juan de la Cierva” and “JAE-DOC CSIC” programs, respectively. We thank to Santiago Giralt, Alberto Sáez, Armand Hernández, Carlos Martí, Mayte Rico, Juan Pablo Corella and Antonio Vallejo for coring assistance in 2008. We also thank Beatriz Bueno and Aída Adsuar for their help in lab procedures. We are indebted to Prof. Sandy Harrison for her assistance with the English review that has led to a noticeable improvement of the manuscript.
Copyright 2013 Elsevier B.V., All rights reserved.
- Abrupt changes
- Central Pyrenees
- Climate evolution
- Vegetation history
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