Hydrogen isotope fractionation of leaf wax n-alkanes in southern African soils

Herrmann, Nicole; Boom, Arnoud; Carr, Andrew S.; Chase, Brian M.; West, Adam G.; Zabel, Matthias; Schefuß, Enno

doi:10.1016/j.orggeochem.2017.03.008

Cited by 36 publications

(30 citation statements)

References 101 publications

(196 reference statements)

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“…While some studies suggest that ε 2H n-alkane/p in plants and topsoils remains relatively constant over latitudinal distances (Liu et al, 2016, Liu andAn, 2019;Vogts et al, 2016), many others show correlations of ε 2H n-alkane/p with relative humidity, mean annual precipitation (MAP) and the aridity index (AI) (Hou et al, 2008(Hou et al, , 2018Douglas et al, 2012;Tipple and Pagani, 2013;Berke et al, 2015;Herrmann et al, 2017;Li et al, 2019). This can be related to more evapotranspirative enrichment under more arid conditions, but plant physiological adaptations might also play a role, as well as changes in vegetation, as e.g., monocotyledons have more negative δ 2 H n-alkane values than dicotyledons (Sachse et al, 2012;Kahmen et al, 2013b;Hepp et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Leaf Waxes and Hemicelluloses in Topsoils Reflect the δ2H and δ18O Isotopic Composition of Precipitation in Mongolia

et al. 2020

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Compound-specific hydrogen and oxygen isotope analyzes on leaf wax-derived n-alkanes (δ 2 H n-alkane) and the hemicellulose-derived sugar arabinose (δ 18 O ara) are valuable, innovative tools for paleohydrological reconstructions. Previous calibration studies have revealed that δ 2 H n-alkane and δ 18 O ara reflect the isotopic composition of precipitation, but-depending on the region-may be strongly modulated by evapotranspirative enrichment. Since no calibration studies exist for semi-arid and arid Mongolia so far, we have analyzed δ 2 H n-alkane and δ 18 O ara in topsoils collected along a transect through Mongolia, and we compared these values with the isotopic composition of precipitation (δ 2 H p-WM and δ 18 O p-WM , modeled data) and various climate parameters. δ 2 H n-alkane and δ 18 O ara are more positive in the arid southeastern part of our transect, which reflects the fact that also the precipitation is more enriched in 2 H and 18 O along this part of the transect. The apparent fractionation ε app , i.e., the isotopic difference between precipitation and the investigated compounds, shows no strong correlation with climate along the transect (ε 2H n-C29/p = −129 ± 14 , ε 2H n-C31/p = −146 ± 14 , and ε 18O ara/p = +41 ± 2). Our results suggest that δ 2 H n-alkane and δ 18 O ara in topsoils from Mongolia reflect the isotopic composition of precipitation and are not strongly modulated by climate. Correlation with the isotopic composition of precipitation has root-mean-square errors of 13.4 for δ 2 H n-C29 , 12.6 for δ 2 H n-C31 , and 1.2 for δ 18 O ara , so our findings corroborate the great potential of compound-specific δ 2 H n-alkane and δ 18 O ara analyzes for paleohydrological research in Mongolia.

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Section: Introductionmentioning

confidence: 99%

Leaf Waxes and Hemicelluloses in Topsoils Reflect the δ2H and δ18O Isotopic Composition of Precipitation in Mongolia

et al. 2020

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“…The hydrogen from rainfall is incorporated into terrestrial plant epicuticular waxes, resulting in a demonstrable correlation between terrestrial plant δD wax and precipitation δD values (e.g., Huang et al., 2004; Sachse et al., 2004), despite an offset in δD wax due to isotopic fractionations from biosynthesis and evaporative processes. In the tropics, there is a strong relationship between δD values and precipitation amount (Dansgaard, 1964; Rozanski et al., 1993), and plant waxes from south Africa predominantly record the δD values of their source waters (Griepentrog et al., 2019; Herrmann et al., 2017). As such, we interpret more positive (negative) values to indicate more (less) arid conditions due to tropical rainfall amount.…”

Section: Resultsmentioning

confidence: 99%

Plio‐Pleistocene Continental Hydroclimate and Indian Ocean Sea Surface Temperatures at the Southeast African Margin

Taylor

Berke

Castañeda

et al. 2021

Paleoceanog and Paleoclimatol

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The Plio-Pleistocene encompasses large-scale changes in climate and may provide an analog for the function of Earth's ecosystems in a high carbon dioxide (CO 2) world. Pliocene climate was characterized by atmospheric CO 2 levels similar to today, reduced sea surface temperature (SST) gradients, and events such as the restriction of the Central American and Indonesian Seaways (Cane & Molnar, 2001; Fedorov et al., 2013). Despite its relative warmth and stability, the Pliocene is defined by long-term cooling that is potentially related to tectonic plate movement and consequent changes in ocean currents and pCO 2 drawdown, especially in the Indo-Pacific region (Cane & Molnar, 2001). The Plio-Pleistocene transition around 2.7 Ma is marked by the breakdown of Pliocene climate conditions, as strong SST gradients between the high-and low-latitudes and across the Pacific Ocean basin were established, and Northern Hemisphere glaciation intensified (Fedorov et al., 2013). The development of stronger zonal SST gradients in the Pacific Ocean was likely related to gradual thermocline shoaling in the Pliocene and an increase in tropical upwelling that led to strengthened Walker circulation (Ravelo et al., 2004). The interaction between these ocean-atmosphere feedbacks and changes in insolation potentially magnified the climate's sensitivity to obliquity, leading to the 41 kyr pacing of higher amplitude glacial cycles in the early Pleistocene (Ravelo et al., 2004).

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“…Hydrogen used for biosynthesis of plant lipids originates directly from the water utilized by the plants (Sessions et al, 1999), which is mainly soil water derived from precipitation (e.g., Sachse et al, 2012). Changes in stable hydrogen isotopic ratios measured in plant waxes are therefore mainly related to isotope shifts in precipitation, potentially amplified by isotopic enrichment in soil and leaf water under low humidity conditions (evapotranspiration, e.g., Kahmen et al, 2013;Herrmann et al, 2017). In regimes of highly seasonal rainfall as in monsoonal regions, however, this secondary enrichment was recently inferred to be of minor importance (Niedermeyer et al, 2016) Geochemistry, Geophysics, Geosystems to deduce that evapotranspiration has no major amplifying effect on the δD C29 range in our samples.…”

Section: Plant Waxesmentioning

confidence: 99%

The Provenance of Terrigenous Components in Marine Sediments Along the East Coast of Southern Africa

Hahn

Miller

Andó

et al. 2018

Geochem Geophys Geosyst

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Terrestrial signals in marine sediment archives are often used for paleoclimatic reconstructions. It is therefore important to know the origin of the different terrestrial sedimentary components. The proximity to a river mouth is often the key location to determine the source. Especially in regions with strong ocean currents, such an assumption might, however, lead to considerable misinterpretations. To investigate the source of various terrigenous sediment fractions in southeastern Africa, a region with strong sediment redistribution, we have performed an extensive comparison between terrestrial material (pollen, plant lipids, detrital modes, and heavy minerals as well as bulk inorganic geochemical composition) from potential source regions and the same components in the adjacent coastal and continental shelf sediments. Onshore the proxy‐indicators reflect small‐scale diversity in sampling locations and associated environments (riverbank sediments, flood deposits, suspension loads, and soils). Nevertheless, the overall trends reflect significant environmental gradients along a SW to NE transect. We note a general comparability of the studied parameters between the continental and marine sediments regardless of their specific differences in transport and depositional characteristics. We propose that the influence of the Agulhas Current affects sediment deposition and distribution only seaward of the midshelf and that pockets of sediment remain preserved in the lee of coastal protrusions where they are protected from erosion. This study provides the essential prerequisite to allow the attribution of temporal variations of compositional changes in marine sediment cores to environmental changes in southeastern Africa.

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Hydrogen isotope fractionation of leaf wax n-alkanes in southern African soils

Cited by 36 publications

References 101 publications

Leaf Waxes and Hemicelluloses in Topsoils Reflect the δ2H and δ18O Isotopic Composition of Precipitation in Mongolia

Leaf Waxes and Hemicelluloses in Topsoils Reflect the δ2H and δ18O Isotopic Composition of Precipitation in Mongolia

Plio‐Pleistocene Continental Hydroclimate and Indian Ocean Sea Surface Temperatures at the Southeast African Margin

The Provenance of Terrigenous Components in Marine Sediments Along the East Coast of Southern Africa

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