Stable carbon isotope analysis as a direct means of inferring crop water status and water management practices

Stable carbon isotope analysis of plant remains is a promising tool for researchers studying palaeoclimate and past agricultural systems. The potential of the technique is clear: it offers a direct measure of the water conditions in which plants grew. In this paper, we assess how reliably stable carbon isotope discrimination can be used to infer water conditions, through the analysis of present-day crop plants grown at multiple locations across the Mediterranean and south-west Asia. The key findings are that: (1) C-13, as expected, provides an indication of water conditions, (2) even for plants grown in similar conditions there is variation in C-13 and (3) C-13 may reflect crop water status for a period beginning well before the grain filling period. A new framework is presented which increases the robustness with which C-13 values of plant remains can be interpreted in terms of the water conditions in which ancient crops grew.