Carbon and nitrogen isotope composition of natural pastures in the dry Puna of Argentina: a baseline for the study of prehistoric herd management strategies

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This study represents an isotopic survey of modern plants developed to establish baseline isotopic values in order to explore prehistoric herd management strategies employed by the South American camelid herders that occupied the southern Andean highlands during the past 3000 years. We present car- bon (δ 13 C) and nitrogen (δ 15 N) isotopic compositions of natu- ral pastures collected from different plant communities along an altitudinal gradient in the dry Puna of Argentina. Our results show that C3 plants are the most abundant along the whole altitudinal gradient and that C3 and C4 plants exhibit a differential distribution, the latter being less abundant in those sites located above 3900meters above sea level (masl). At the same time, plants growing at low-altitude sites with low water availability exhibit higher δ 15 N values than plants growing at high-altitude sites with higher water availability. These results explain the negative correlation found between altitude and South American camelid bone collagen δ 13 Ca ndδ 15 Nv alues published in previous studies. This work represents a funda- mental steptowards the buildingofanisotopicecology for the dry Puna area with the ultimate goal to explore herd manage- ment strategies employed by human groups in the past. In this sense, modern plant and South American camelid tissue isotopic compositions would provide a frame of reference to interpret isotopic compositions measured on archaeofaunal remains recovered at pastoral sites, with the aim to explore mobility and pastureland use by prehistoric herders.