Environmental controls on leaf wax δD ratios in surface peats across the monsoonal region of China.

Leaf wax molecular and isotopic ratios are generally considered robust isotopic pale-ohydrologic proxies. Here we evaluate the proxy value of the molecular distributions and hydrogen isotopic compositions of long chain n-alkanes (δD_alk ) in surface peats collected from peatlands across a range of annual air temperatures from 1 to 15°C and a range of annual mean precipitation from 720 to 2070 mm in the monsoonal region of China. The alkane ratios (ACL and CPI) and δD_alk values show relatively large variations in multiple samples from a single site, highlighting the complexity of these ratios at a small spatial scale. In the montane Zoigê peatland, the apparent fractiona-tion between precipitation and δD_alk is more positive than in the other six sites, which is possibly an effect of the higher conductivity of the water in this high elevation site (3500 m a.s.l.). At a larger spatial scale, the site-averaged CPI ratios and the δD_alk values of n-C₂₉ and n-C₃₁ alkanes show significant correlation with the air temperature and precipitation. These results support the application of the CPI ratio and the δD_alk ratios of n-C₂₉ and n-C₃₁ alkanes as sensitive paleohydrologic proxies on millennial and larger timescales. [ABSTRACT FROM AUTHOR]