δ13C and δ15N of plants in a longitudinal transect from the Andes to the Atlantic coast: Terrestrial baseline for paleodietary and paleocological studies

Abstract

The application of stable isotopes in ecology, archeology or paleocology highlight the need to understand the variability of the isotopic baselines, as a fundamental step to know the spatio-temporal variability of consumers. The aim of this research is to study the δ13C and δ15N variability in modern plants along a longitudinal transect − 400 km - in southern Patagonia in order to establish the terrestrial vegetation baseline of the food chains in relation to the climatic and environmental variability of the region. The study area, between 47° and 49° south latitude Patagonia Argentina, covered different altitudes, temperatures, vegetation types, and precipitation gradients.δ13C and δ15N values were obtained for 211 samples from 13 different sampling loci. Vegetation surveys indicated a sharp change from temperate forests in the most humid west of the transect - trees and lichens were only present in the forests -, to steppe, dominated by shrubs and grasses. Stable isotopes of vegetation follow the climate gradient, with higher δ15N and δ13C values in the more arid steppe than in the forest sites. The lineal best model for each stable isotope, included mean annual precipitation and biological types as explanatory variable, and explained 58.7 % of the variability for δ15N, and 45.5 % for δ13C. On the broad scale, from the Atlantic coast to the Andes, we can assess the degree of agreement between the isotopic variations recorded in plants and herbivores. In this way, the isotopic variability recorded in both, plants and herbivores, provides unique opportunities to investigate the differential use of space and mobility, both among hunter-gatherer societies and among Patagonian herbivores.