The carbon isotopes of leaf wax n-alkanes (δ¹³C) have well recorded the climate and environmental conditions during plant growth. They are an alternative indicator for studying the past hydroclimatic environment changes of the land. 

According to previous studies, leaf wax n-alkane δ¹³C values vary significantly within photosynthetic pathways (C₃ vs. C₄), or among plant types (dicots, monocots, gymnosperms, magnoliids). The "plant type effect" of this leaf wax carbon isotope will cause deviations in the reconstruction of the ancient environment. 

A research team led by associated professor LIU Jinzhao from the Institute of Earth Environment (IEE) of the Chinese Academy of Sciences investigated the variations in n-alkane δ¹³C values with major plant groups, and analyzed the responses of n-alkane δ¹³C values among plant groups to precipitation amount and temperature, by compiling available leaf wax n-alkane δ¹³C data at the global scale. 

They found that the "plant type effect" of plant leaf wax carbon isotopes was clearly present on a global scale: leaf wax carbon isotopes were significantly different between C₃ plants and C₄ plants, as well as monocots and dicots. 

Moreover, leaf wax carbon isotopes of this different plant species respond differently to rainfall and temperature changes: leaf wax carbon isotopes in C₃ plants mainly record rainfall signals, and leaf wax carbon isotopes in C₄ plants mainly record temperature signals. 

This differential response of C₃ plants and C₄ plants to rainfall and temperature signals echoes the difference in ecological taxonomy between the two plant types (dicots vs. monocots). This is because different enzymes in the leaves of C₃ plants and C₄ plants cause differences in the pathways of carbon dioxide utilization. 

The study entitled "Leaf wax n-alkane carbon isotope values vary among major terrestrial plant groups: Different responses to precipitation amount and temperature and implication for paleoenvironmental reconstruction" was published in Earth Science Reviews.