Discussion on C3 and C4 plant contribution calculation

The research reported by Jaesoo Lim et al. (2010) (Jaesoo Lim, Wook-Hyun Nahm, Jin-Kwan Kim, Dong-Yoon Yang, 2010. Regional climate-driven C3 and C4 plant variation in the Cheollipo area, Korea, during the late Pleistocene. Palaeogeography, Palaeoclimatology, Palaeoecology 298, 370–377) provides an interesting northeast Asian case for palaeoecological response to palaeoclimatic change. However the method used in the paper to determine the contribution of C3 and C4 plant in bulk organic carbon isotope values deserves discussion when the proportion of C3 and C4 plant is used as an important indicator for palaeoecological analysis.