Leaf wax n-alkane distributions across plant types in the central Chinese Loess Plateau

摘要

Terrestrial ecosystems generally contain various plant types (e.g. dicots, monocots, gymnosperms), and an evaluation of the dominant plant type in an ecosystem is the key to understanding geological records in paleoenvironmental research. In this study, we examined n-alkane chain length distributions in terrestrial higher plants in the central Chinese Loess Plateau, and found that average chain length (ACL) could be utilized as an indicator for differentiating gymnosperms from angiosperms. ACL(21-33) was less than 27 for gymnosperms, but more than 27 for angiosperms. Moreover, a derived P-nu index from a selected n-alkane ratio, (i.e. (C-31 + C-33)/Sigma Cn(n=27-33)), provided a relative criterion for distinguishing between dicots and monocots within the angiosperms. When P-nu -0.1, the ecosystem was predominated by dicots, but those with P nu 0.1, were dominated by monocots. Discrimination of the dominant plant type in an ecosystem is important when leaf wax n-alkanes are used as a proxy for paleoenvironmental reconstructions. (C) 2018 Elsevier Ltd. All rights reserved.