| Abstract: |
The d13C value of a C3 plant is influenced by the species response to its environment, which is subject to natural changes with space and time. This paper reviews the magnitude of the resulting variations in plant d13C valuesthe diVerences between species, and the variations at diVerent spatial and temporal scaleswith particular emphasis on studies of tree wood. Because of these variations, any attempt to estimate the absolute d13C values of a plant food resource at a particular place and time in the past, even when based on analysis of archaeological plant remains, will be subject to uncertainties. Uncertainties due to a single factor are commonly 1, and in many cases a combination of factors will lead to uncertainties of at least 2. Many of these factors are also relevant to archaeological studies based on diVerences between the d13C values of diVerent individuals or populations of animal/humans. Where such diVerences are only a few per mil it may be diYcult to unambiguously ascribe them to palaeodietary, rather than to palaeoenvironmental, causes.
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