Comment on "Oxygen isotope ratios (¹⁸O/¹⁶O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy I: Insight from a climate chamber experiment" by Zech et al. (2014)

Zech et al. (2014) reported oxygen isotope ratios of stem hemicellulose for three species of plants grown at different temperatures and humidity. The authors did not consider temperature effects on biochemical fractionation during hemicellulose synthesis as an important determinant of the oxygen isotope ratio of hemicellulose. However, a closer examination of their data shows that, indeed, temperature has a significant effect on the oxygen isotope biochemical fractionation. Lower temperature has no effect on the proportion of oxygen isotope exchange with cell water, but it increases the biochemical fractionation of the exchange reaction. These results are consistent with previous observations.