Hydrogen isotope ratios of leaf waxes are used to reconstruct past hydroclimate because they are a reflection of meteoric water, but the interpretation of these signatures from ancient sedimentary archives relies on a thorough understanding of the drivers of modern isotope variability and controls on fractionation. These studies are particularly valuable in the high latitudes, regions especially vulnerable to rapid climate change and increasingly used for plant-based proxy reconstructions of past hydroclimate, but also where modern vegetation is understudied compared to the lower latitudes. Here we investigate δ2H values from leaf wax n-alkanes of vascular tundra plants in the Kangerlussuaq area of western Greenland. We collected a variety of common tundra species to study possible interspecies variability in δ2H values including dwarf shrubs (Betula nana, Empetrum hermaphroditum, Salix glauca), forbs and graminoids (Vaccinium uliginosum, Rhododendron tomentosum, and Calamagrostis lapponica), a horsetail species (Equisetum arvense), and a submerged aquatic macrophyte from a local lake (Stuckenia filiformis). Using previously measured leaf and stem waters to help constrain potential drivers of leaf wax n-alkane δ2H values, we find that the overall net fractionation (εapp) from the studied species is −75 ± 20‰. The εapp at Kangerlussuaq is consistent with other studies of Arctic vegetation that find smaller εapp than from the majority of lower latitude sites. The fractionation of leaf water and xylem water (εlw/xw) and the fractionation of xylem water and precipitation (εxw/p) are both relatively constant, suggesting stable leaf and soil related fractionations across species. Estimates of biosynthetic fractionation (εbio), as evidenced from the fractionation of the δ2H values of n-alkanes and leaf water (εwax/lw), are not constant across species as sometimes assumed, and are small (average of εbio is −120 ± 27‰) compared to many published estimates. This supports a significant role in εbio shaping the εapp in this high latitude setting, where lipid biosynthesis may be driving differences in n-alkane δ2H values. This finding suggests that lipids in the Kangerlussuaq plants studied rely on the use of some proportion of different hydrogen sources during lipid synthesis, such as stored NADPH. The cumulative results of this survey of Kangerlussuaq area n-alkane δ2H values and water-wax fractionations suggest that fractionation in the high latitudes during the short summer growing season may play an important role in governing the small εapp compared to many low latitude sites. Better understanding of appropriate εapp and the importance of εbio in controlling plant wax fractionation from the high latitudes is necessary for future reconstructions of hydroclimate using leaf wax δ2H values in these regions.
- Arctic plants
- Hydrogen isotope fractionation
- Leaf wax
ASJC Scopus subject areas
- Geochemistry and Petrology