Hydrological changes of the past 1400 years recorded in δD of sedimentary n-alkanes from Poyang Lake, southeastern China

Abstract

Hydrogen isotopic compositions (δD) of plant leaf wax have been increasingly used for paleohydrological reconstructions over various geological timescales. Here, we analyzed downcore variations of δD values of long-chain C31 and C33 n-alkanes from Poyang Lake in southeastern China to infer hydrological changes recorded in terrestrial higher plants during the past 1400 years. Variations in δD values of long-chain n-alkanes were generally consistent with fluctuations of published rainfall proxy (Dry–Wet Index) in southern regions of the middle and lower reaches of the Yangtze River Valley. We suggest that the δD record from Poyang Lake is likely influenced by the regional rainfall variations, which is interpreted as a result of the combined effect of ‘amount effect’ and evapotranspiration. More negative δD values during ca. AD 1200–1500 with a higher amount of rainfall suggested a wetter ‘Medieval Warm Period’ (MWP), and more positive δD values at ca. AD 1500–1900 with a lower amount of rainfall indicated a relatively dry ‘Little Ice Age’ (LIA). This pattern of hydrological changes generally corresponded to the intensity of the Asian summer monsoon (ASM) as recorded in oxygen isotopic compositions (δ18O) of stalagmite from the Wanxiang Cave in central China, providing further support that ASM has played an important role in controlling hydrological changes during the MWP and LIA in monsoon-dominated southeastern China.