UNDERSTANDING THE RELATIONSHIP BETWEEN ENVIRONMENTAL FACTORS AND THE DEUTERIUM/HYDROGEN RATIOS FOUND IN N-ALKANES BETWEEN VARYING PLANT SPECIES

Reconstruction of paleoclimate is important, particularly within the context of understanding and modeling future climate change. Recently, use of deuterium/hydrogen ratios (δD) in normal alkanes (n-alkanes) derived from terrestrial plant leaf waxes have been used as a proxy for meteroic δD. However, it is well known that the δD_waxes is impacted by evaporation of soil water prior to uptake into the plant, variations in evapotranspiration rates and stomatal regulation between different plant types, and variations in the timing of wax synthesis, among other factors. Here we examine the variation in plant wax δD for four different plant classes along a large sampling transect in western United States (grasses, angiosperm trees, gymnosperm trees, forbs). Sampling sites cross a large gradient in temperature, precipitation, relative humidit, elevation, and latitude. The data also show consistent differences for δD_waxes between different plant groups at the same site throughout the sampling gradient. These variations reflect differences in timing of wax synthesis and or stomatal regulation. However, variations between plant species are averaged in soils. These data indicates that within an ecosystem, variations of individual plant species can impact the apparent ε_wax, complicating biomarker reconstruction of δD_{precipitation}. Thus, paleoenvironmental interpretations using plant wax isotopes are best when utilized in a multiproxy approach.