Vegetation and geochemical responses to Holocene rapid climate change in the Sierra Nevada (southeastern Iberia): the Laguna Hondera record

Marta Rodrigo-Gámiz,Gonzalo Jiménez-Moreno,Jose M. Mesa-Fernández,R. Scott Anderson,Jon Camuera,María J. Ramos-Román,Francisca Martínez-Ruiz,Antonio García-Alix,Francisco J. Jiménez-Espejo

doi:10.5194/cp-14-1687-2018

Abstract

Abstract. High-altitude peat bogs and lacustrine records are very sensitive to climate changes and atmospheric dust input. Recent studies have shown a close relationship between regional climate aridity and enhanced eolian input to lake sediments. However, changes in regional-scale dust fluxes due to climate variability at short scales and how alpine environments were impacted by climatic- and human-induced environmental changes are not completely understood. Here we present a multi-proxy (palynological, geochemical and magnetic susceptibility) lake sediment record of climate variability in the Sierra Nevada (southeastern Iberian Peninsula) over the Holocene. Magnetic susceptibility and geochemical proxies obtained from the high mountain lake record of Laguna Hondera evidence humid conditions during the early Holocene, while a trend towards more arid conditions is recognized since ∼7000 cal yr BP, with enhanced Saharan eolian dust deposition until the present. This trend towards enhanced arid conditions was modulated by millennial-scale climate variability. Relative humid conditions occurred during the Iberian Roman Humid Period (2600–1450 cal yr BP) and predominantly arid conditions occurred during the Dark Ages and the Medieval Climate Anomaly (1450–650 cal yr BP). The Little Ice Age (650–150 cal yr BP) is characterized in the Laguna Hondera record by an increase in runoff and a minimum in eolian input. In addition, we further suggest that human impact in the area is noticed through the record of Olea cultivation, Pinus reforestation and Pb pollution during the Industrial Period (150 cal yr BP–present). Furthermore, we estimated that the correlation between Zr and Ca concentrations stands for Saharan dust input to the Sierra Nevada lake records. These assumptions support that present-day biochemical observations, pointing to eolian input as the main inorganic nutrient source for oligotrophic mountain lakes, are comparable to the past record of eolian supply to these high-altitude lakes.

Highlights

This study investigates a multi-proxy sediment core record from Laguna Hondera (LH), located in the Sierra Nevada range with two main goals: (1) identifying and characterizing climatic variability during the Holocene, with a focus on vegetation changes, eolian input and runoff sediments variations, and (2) understanding the Saharan dust influence on past lake sedimentation and geochemistry
The multi-proxy paleoclimate analysis from LH has allowed the reconstruction of the vegetation and climate evolution in the Sierra Nevada and southern Iberia during the Holocene, and the possible factors that have triggered paleoenvironmental changes
An arid interval is recorded between 4000 and 2500 cal yr BP, with a vegetation assemblage dominated by xerophytes

Summary

Introduction

The southern Iberian Peninsula has been the location for a number of recent studies detailing past vegetation and former climate of the region (Carrión et al, 2001, 2003, 2007, 2010; Carrión, 2002; Jiménez-Espejo et al, 2008; Martín-Puertas et al, 2008, 2010; Combourieu Nebout et al, 2009; Fletcher et al, 2010; Nieto-Moreno et al, 2011, 2015; RodrigoGámiz et al, 2011; Moreno et al, 2012; Jiménez-Moreno et al, 2015). A subset of recent studies have attempted to determine how Mediterranean alpine environments have been affected by Holocene climate change through the study of sedimentary records from high-elevation wetlands in the Sierra Nevada (Anderson et al, 2011; García-Alix et al, 2012, 2013; Jiménez-Moreno and Anderson, 2012; JiménezMoreno et al, 2013; Jiménez-Espejo et al, 2014; RamosRomán et al, 2016; García-Alix et al, 2017) These alpine lake and bog records show minimal anthropic influence because they are usually at a higher elevation than major regional late Holocene human landscape modification. Even though human impact is less important at high elevations, the impacts of human activities has been reconstructed from these late Holocene sedimentary records (Anderson et al, 2011; García-Alix et al, 2012, 2013, 2017, 2018)

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Conclusion