Local effects on soil leaf wax hydrogen isotopes along a west to east transect through the Pamirs, Tajikistan. (October 2021)

• Record Type: Journal Article
• Authors: Aichner, Bernhard; Rajabov, Nasimjon; Shodmonov, Muzaffar; Mętrak, Monika; Suska-Malawska, Małgorzata; Strecker, Manfred; Sachse, Dirk
• Is Part Of: Organic geochemistry. Volume 160(2021)
• Publication Date: 2021-10
• Subjects: Biomarkers -- Precipitation -- Hydrology -- δ2H -- n-Alkanes; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2021.104272
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: Different patterns of soil leaf wax isotopes in eastern vs western Pamirs. Western/central Pamirs: soil isotopes correlated with altitude and longitude. Isotopic lapse rate vs altitude is lower than the global average. Eastern Pamirs: multiple local effects lead to higher δ 2 H values. Local control on soil isotopes important for interpretation of paleorecords. Abstract: Understanding the control mechanisms that affect soil leaf wax hydrogen isotopes is crucial when interpreting these data in the context of paleoclimatic reconstructions. Within a pilot study we aimed to evaluate the regional controls on leaf wax δ 2 H in the Central Asian Pamir Mountains (Tajikistan), a region characterized by pronounced hydroclimatic gradients. Soil and tap water samples were collected along a ca. 1000 km west-east-gradient, spanning ca. 3100 m of altitude difference. The results give evidence of variable environmental control on soil leaf wax δ 2 H values in different sub-regions of the study area. In the western and central Pamirs, the plant lipids mirror the signal of a mostly riverine water source, with an isotopic signature mainly controlled by winter and spring precipitation. With ca. –1.3‰ change per 100 m altitude, soil leaf wax derived isotopic lapse rates in these samples are lower than in other Asian high-altitude settings and the global average, which confirms earlier findings from surface water analysis from the Pamirs. In contrast, soil samples from the shielded Karakul basin showed significantly higher δ 2 H values. Those most likely reflect the more positive isotope signal of a predominant summer precipitation in the arid eastern Pamirs, with potential additional enrichment due to local vapor recycling and soil- and leaf water evapotranspiration. While the predominant water source (precipitation vs river water) plays an important role on a local scale, the results further highlight the significance of regional climate effects on isotopic signals incorporated into leaf waxes.