Variations in carbon isotope ratios of plants across a temperature gradient along the 400 mm isoline of mean annual precipitation in north China and their relevance to paleovegetation reconstruction

Carbon isotope values (δ13C) of plants reflect the balance between photosynthesis and stomatal conductance and vary with environmental conditions. Temperature is an important influential factor for plant δ13C; however, variations of plant δ13C across temperature gradients have yet to be quantified. This impedes interpretation of variability of δ13C in ancient terrestrial organic matter and reconstructions of paleoclimate and paleoecology. In this study, the effect of temperature on δ13C of C3 and C4 plants was assessed by comprehensive investigation of a large number of species (118 C3 plants and 17 C4 plants) from 29 sites across a temperature gradient along the 400 mm mean annual precipitation isoline in north China. After deducting the effects of precipitation on plant δ13C, a strong positive relationship is found between δ13C values of C3 plants averaged for each site and mean annual temperature, with a coefficient of 0.104‰/°C; however, no significant correlation is found for C4 plants. Based on our results, we conduct a sample reconstruction of paleovegetation of the central Chinese Loess Plateau and demonstrate that, to a certain extent, our paleovegetation reconstruction is affected by temperature corrections.

► The effect of temperature on δ13C of C3 and C4 plants was assessed.
► A positive relationship is between δ13C of C3 plants and annual temperature.
► C4 plants show no correlation between δ13C and annual temperature.
► A sample reconstruction of paleovegetation was conducted using the new data.