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

摘要

Carbon isotope values (δ~(13)C) of plants reflect the balance between photosynthesis and stomatal conductance and vary with environmental conditions. Temperature is an important influential factor for plant δ~(13)C; however, variations of plant δ~(13)C across temperature gradients have yet to be quantified. This impedes interpretation of variability of δ~(13)C in ancient terrestrial organic matter and reconstructions of paleoclimate and paleoecology. In this study, the effect of temperature on δ~(13)C of C_3 and C_4 plants was assessed by comprehensive investigation of a large number of species (118 C_3 plants and 17 C_4 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 δ~(13)C, a strong positive relationship is found between δ~(13)C values of C_3 plants averaged for each site and mean annual temperature, with a coefficient of 0.104‰/°C; however, no significant correlation is found for C_4 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.