Insight into the reasons of leaf wax δDn-alkane values between grasses and woods

Many studies have observed that leaf wax δDn-alkanes values differed significantly between woods and grasses in modern plants, with grasses D-depleted by 40 ‰-70 ‰. The reasons for the differences in leaf wax δDn-alkane values between woods and grasses, however, remain unclear. In this study, we measured the δD values of soil water (δDsw), leaf water (δDlw), and leaf wax n-alkane (δDn-alkane) for woods and grasses. We found no significant differences in the δD values of soil water (P = 0.82) and leaf water (P = 0.74) between the two life forms of plants. Therefore, the differences in leaf wax δDn-alkane values between woods and grasses may correlate with inherent properties of different plant life forms, such as leaf structures, biosynthetic processes, and leaf morphologies. Moreover, it is also possible that soil water with different δDsw at different depths utilized by woods and grasses may be responsible for some of the differences in leaf wax δDn-alkane values between the two life forms of plants, if woods mainly use soil water from the >100 cm depth, whereas grasses mainly use soil water from the <100 cm depth. The results of this work allow us to better understand the leaf wax δDn-alkane values of different plant life forms in a region.