Pasture usage by ancient pastoralists in the northern Kazakh steppe informed by carbon and nitrogen isoscapes of contemporary floral biomes

Identification of variation in pasture use by domesticated livestock has important implications for understanding the scale of animal husbandry and landscape use in modern and ancient societies alike. Here, we explore the influence of pasture floral composition, salinity, and water availability on the carbon (δ13C) and nitrogen (δ15N) isotopic composition of plants from the steppes of Kazakhstan. Our findings demonstrate geospatially defined differences in the isotopic composition of sedge marshes, saline marshes, and meadow steppes, information which we then use to inform animal management strategies used in the past. We then examine pasture usage by ancient livestock through carbon and nitrogen isotope analyses of bone collagen from animals that grazed in the northern Kazakh steppe. Pasturing strategies varied according to livestock taxa, with horses exhibiting lower δ13C and δ15N values relative to cattle, sheep, and goat. We argue that horses, which are highly mobile and freely graze over pastures extending over wide areas, were grazed under an extensive pasturing system. These data suggest that the isotopic composition of contemporary vegetation communities can help inform animal management strategies used in the past.