Reconstructing vapor pressure deficit from leaf wax lipid molecular distributions

Yvette L Eley,Michael T Hren

doi:10.1038/s41598-018-21959-w

Yvette L Eley, Michael T Hren

Open Access

https://doi.org/10.1038/s41598-018-21959-w

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Abstract

Estimates of atmospheric moisture are critical for understanding the links and feedbacks between atmospheric CO2 and global climate. At present, there are few quantitative moisture proxies that are applicable to deep time. We present a new proxy for atmospheric moisture derived from modern climate and leaf biomarker data from North and Central America. Plants have a direct genetic pathway to regulate the production of lipids in response to osmotic stress, which is manifested in a change in the distribution of simple aliphatic lipids such as n-alkanes. The Average Chain Length (ACL) of these lipids is therefore statistically related to mean annual vapor pressure deficit (VPDav), enabling quantitative reconstruction of VPD from sedimentary n-alkanes. We apply this transfer function to the Armantes section of the Calatayud-Daroca Basin in Central Spain, that spans the Middle Miocene Climatic Optimum (MMCO) and the Middle Miocene Climate Transition (MMCT). Reconstructed VPDav rises from 0.13 to 0.92 kPa between 16.5 and 12.4 Ma, indicating a substantial drying through the MMCT. These data are consistent with fossil assemblages and mammalian stable isotope data, highlighting the utility of this new organic molecular tool for quantifying hydrologic variability over geologic timescales.

Highlights

The distribution of ecosystems across the globe is strongly regulated by the availability of water[1]
Conflict between paleosol and fossil bone carbonate δ18O records[4,12] is likely due to the fact that the isotopic composition of ungulate tooth enamel can record the influence of a complex mixture of factors such as temperature, water availability and atmospheric circulation patterns[14], as well as the ability of animals to migrate significant distances to continue residing in their ideal habitat[15]
The molecular distribution of leaf wax n-alkanes, commonly described by indices such as the Average Chain Length (ACL), is shown to vary along a latitudinal gradient, a phenomenon previously interpreted to be driven by changes in temperature[33,34,35]

Summary

Introduction

The distribution of ecosystems across the globe is strongly regulated by the availability of water[1]. The molecular distribution of leaf wax n-alkanes, commonly described by indices such as the Average Chain Length (ACL), is shown to vary along a latitudinal gradient, a phenomenon previously interpreted to be driven by changes in temperature[33,34,35].

Results

Conclusion