Dr Pascal Flohr

© 2019, The Author(s). This study re-assesses and refines the use of crop carbon stable isotope values (Δ13C) to reconstruct past water availability. Triticum turgidum ssp. durum (durum wheat), Hordeum vulgare (six-row barley) and Sorghum bicolor (sorghum) were experimentally grown at three crop research stations in Jordan for up to three years under five different irrigation regimes: 0% (rainfall only), 40%, 80%, 100% and 120% of the crops’ optimum water requirements. The results show a large variation in carbon stable isotope values of crops that received similar amounts of water, either as absolute water input or as percentage of crop requirements. We conclude that C3 crop carbon stable isotope composition should be assessed using a climate zone specific framework. In addition, we argue that interpretation should be done in terms of extremely high values showing an abundance of water versus low values indicating water stress, with values in between these extremes best interpreted in conjunction with other proxy evidence. Carbon stable isotope values of the C4 crop Sorghum were not found to be useful for the reconstruction of water availability.