Modern n-alkane abundances and isotopic composition of vegetation in a gymnosperm-dominated ecosystem of the southeastern U.S. 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-C29 alkane δ13C values (δ13Cn-c29). Additionally, I assess modern relationships between stable hydrogen isotope values of n-C29 alkanes (δ2Hn-c29) and mean annual precipitation to constrain apparent fractionations (ε2Hn-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, δ2Hn-c29, and δ13Cn-c29 values indicate that they are primarily sourced from less-dominant angiosperms. The ε2Hn-C29/MAP values are ∼10.0‰ VSMOW more positive for gymnosperms relative to angiosperms and ε13Calkane/leaf values are ∼1.5‰ VPDB more positive for gymnosperms relative to angiosperms, but with overlap.