Stansell, N. D. , Steinman, B. A. , Abbott, M. B. , Rubinov, M. , Roman-Lacayo, M.

Stansell, N. D., Steinman, B. A., Abbott, M. B., Rubinov, M. and Roman-Lacayo, M.: Lacustrine stable isotope record of precipitation changes in Nicaragua during the Little Ice Age and Medieval Climate Anomaly, Geology, 41(2), 151–154, doi:10.1130/g33736.1, 2013.

Lacustrine stable isotope record of precipitation changes in Nicaragua during the Little Ice Age and Medieval Climate Anomaly

Thermo Trace GC, high-temperature pyrolysis reactor at 1450�C, Thermo Finnigan Delta V isotope ratio mass spectrometer

The effective moisture (ratio of precipitation to evaporation) is considered as the main factor controlling the ?D values of lipid n-alkanes in terrestrial plants (Polissar and Freeman, 2010). In a previous study, the ?D record from a loess profile in the Chinese Loess Plateau displayed a strong correlation to changes in the magnetic susceptibility (MS) over the past 130 ka, and the isoto- pic variation was thought to be strongly affected by aridity (Liu and Huang, 2005). Furthermore, a humidity control experiment in the field verified the correlation between D enrichment and rela- tive humidity (McInerney et al., 2011). A study of lipids from the Santa Barbara Basin from the past 1400 years also revealed the ?D of mid-chain acids to be partially correlated with existing data of drought severity (Li et al., 2011).

Variation in vegetation type (shrubs and grass) is the main factor influencing the [d2H of leaf waxes in] sediments of Lake Sugan, because of the dD values of Chenopodiceae shrubs are higher than those of grasses. We can still discuss the moisture history using the hydrogen-isotope record, because the vegetation type would be consistent with hydrological condition. [i.e., Chenopodiaceae shrubs tend to be more abundant in dry climates, and Chenopodiaceae shrubs have a smaller apparent fractionation, so dry climates would not only cause greater evaporative enrichment of plant source water, but more leaf waxes with relatively enriched d2H would be produced by Chenopodiaceae shrubs.] In the arid area of western China, vegetation type is controlled by moisture changes (Wu, 2011).  The authors conclude that variations in vegetation type (shrub or grass), which are caused by moisture changes, are the main factor controlling the δD records in the study area.