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 (delta C-13) of plants reflect the balance between photosynthesis and stomatal conductance and vary with environmental conditions. Temperature is an important influential factor for plant delta C-13; however, variations of plant delta C-13 across temperature gradients have yet to be quantified. This impedes interpretation of variability of delta C-13 in ancient terrestrial organic matter and reconstructions of paleoclimate and paleoecology. In this study, the effect of temperature on delta C-13 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 delta C-13, a strong positive relationship is found between delta C-13 values of C-3 plants averaged for each site and mean annual temperature, with a coefficient of 0.104 parts per thousand/degrees 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. (c) 2012 Elsevier Ltd. All rights reserved.