Modern n-alkane abundances and isotopic composition of vegetation in a gymnosperm-dominated ecosystem of the southeastern US coastal plain

Prior analyses of n-alkyl lipids in vegetation indicate low concentrations of n-alkanes in gymnosperm leaves and significant offsets in lipid carbon isotope values of angiosperms and gymnosperms. This finding has implications for paleoenvironmental studies utilizing n-alkyl lipid proxies in gymnosperm-dominated ecosystems, such as the pine ecosystems of the U.S. southeastern coastal plain. I provide here the n-alkane abundances and distributions for 19 of the most dominant taxa in the longleaf pine ecosystem along with n-C-29 alkane delta C-13 values (delta C-13(n-c29)). Additionally, I assess modern relationships between stable hydrogen isotope values of n-C-29 alkanes (delta H-2(n-c29)) and mean annual precipitation to constrain apparent fractionations (epsilon H-2(n-C29/MAP)) necessary to conduct regional paleoclimate reconstructions. Gymnosperms of the coastal plain have extremely low n-alkane abundances relative to angiosperms and are unlikely to contribute significantly to sedimentary archives. Lake surface sediment n-alkane distributions, delta H-2(n-c29), and delta C-13(n-c29) values indicate that they are primarily sourced from less-dominant angiosperms. The epsilon H-2(n-C29/MAP) values are similar to 10.0 parts per thousand VSMOW more positive for gymnosperms relative to angiosperms and epsilon C-13(alkane/leaf) values are similar to 1.5 parts per thousand VPDB more positive for gymnosperms relative to angiosperms, but with overlap. (C) 2016 Elsevier Ltd. All rights reserved.