Taxonomic, anatomical, and spatio-temporal variations in the stable carbon and nitrogen isotopic compositions of plants from an African savanna

Stable carbon (δ13C) and nitrogen (δ15N) isotope ratios are commonly used to reconstruct palaeodiets and palaeoenvironments. The method is based on our knowledge of isotopic patterns in plants, which are subject to taxonomic and environmental variability. While previous researchers have addressed isotopic variability amongst plants, no studies have looked extensively at a broad suite of taxa over multiple temporal scales from within the savanna biome so as to provide baseline data for palaeodietary and palaeoenvironmental studies. Here we document variations in the isotopic compositions of plants collected over two years from the Kruger National Park, South Africa, with respect to species and anatomical differences, and the influences of geological substrate and spatio-temporal shifts in climate. Results show that environmentally-induced carbon isotopic variations in plants within this region are generally smaller than 2‰, which is lower than what has been previously reported for plants compared across multiple habitat-types. These data suggest that δ13C differences of ∼2‰ or more (or ∼1‰ if the diet is predominantly C4) between animals from a given area reliably indicate real dietary differences. Plant δ15N values vary greatly between different microhabitats (by up to 4‰), responding to a range of environmental influences that may, in turn, significantly influence variation in animal δ15N values.