Seasonality of the altitude effect on leaf wax n-alkane distributions, hydrogen and carbon isotopes along an arid transect in the Qinling Mountains

摘要

Reconstructing paleoelevation allows the temporal evolution of biogeochemical processes and hydrodimate regimes to be understood and quantified. A dual-isotope biomarker of clumped hydrogen and carbon isotopes of leaf wax n-alkanes was recently proposed in humid tropical forests, and it was proven to be superior to a single-isotope proxy that was previously reported. However, it remains unknown whether the dual-isotope biomarker is suitable in arid conditions. The present study investigated leaf wax n-alkane distribution, hydrogen (δ~2H_(wax)) and carbon (δ~13C_(wax)) isotopes in terrestrial plants along an arid mountainous transect. We found that the effects of seasonality on n-alkane distribution, δ~2H_(wax) and δ~13C_(wax) were minimal for all species (p ＞ 0.05), and that species-specific δ~2H_(wax) values remained almost unchanged for most species, in contrast to δ~13C_(wax) values. Significant correlations between altitude and δ~2H_(wax) values (R~2 = 0.54,0.58, and 0.75 for spring, summer, and autumn, respectively), instead of δ~13C_(wax) values (R~2 = 0.08,0.43, and 0.12 with p = 0.24,0.01, and 0.19 for spring, summer, and autumn, respectively), were observed, suggesting that δ~2H_(wax) values, but not δ~13C_(wax) values, can be reliably used as a proxy for reconstructing paleoelevation in arid conditions. Therefore, it will be necessary to identify other proxies to supplement δ~2H_(wax) values under a dual-isotope approach in future research.