6th Experimental Archaeology Conference Abstract – Pascal Flohr et al
From the 6th Experimental Archaeology Conference, York, 2012.
Reconstructing past water availability with plant stable isotope ratios: re-assessing a method by using experimental archaeology
Pascal Flohr(1), Gundula Müldner(1) and Emma Jenkins(2)
1 Department of Archaeology, University of Reading, UK
2 School of Applied Sciences, Bournemouth University, UK
It has been argued that stable isotope ratios of archaeological plant remains can be used to reconstruct past water availability, both as rainfall and related anthropogenic practices such as irrigation. The use of the method is based on the relationship between plant carbon stable isotopes and water availability as attested in modern crops. Because this method is potentially very valuable but its application to archaeological samples is relatively new, this research seeks to improve its empirical basis and test the suitability of archaeological samples, using experimental archaeology.
The relationship between water availability, other environmental variables, and plant stable isotope ratios was assessed by using experimentally grown cereals. Wheat, barley and sorghum were raised at three sites in Jordan for up to three years, each receiving five different amounts of irrigation. Results indicate a relationship between water availability and carbon stableisotope ratios of wheat and barley grains, but one that is site-specific. No relationship between nitrogen stable isotope ratios and water availability was found, but significant differences in nitrogen stable isotope ratios were present between sites.
Because archaeobotanical remains are often preserved in a charred state, the possible effect of charring on stable isotope ratios was assessed. Isotope ratios of grains experimentally charred in a muffle furnace and in open fires were altered in a few cases, but these can be corrected for.
In addition, samples were buried at sites in the UK and Jordan and retrieved after up to two years to assess possible effects of soil processes on their isotopic composition. Results indicate that burial for this amount of time does not alter isotopic ratios in any systematic way. This paper will thus argue that based on these experiments the method can be applied to archaeological samples for reconstruction of past water availability, but with some limitations.