Browsing by Author "Vidal-Elgueta, Ale"

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    Challenging the Atacama desert: Agronomic and water conditions for pre-Hispanic maize agriculture in hyper arid environments inferred by 518O isotopes
    (2024) Vidal-Elgueta, Ale; Luecke, Andreas; Perez, M. Fernanda; Wissel, Holger; Maldonado, Antonio; Uribe, Mauricio
    During the Formative Period (ca.2400-950 years BP), pre-Hispanic farmers in Pampa del Tamarugal developed a complex agricultural system in the hyper-arid Atacama Desert in Tarapaca, northern Chile. This system involved numerous agricultural fields congregated near the Tarapaca Valley's perennial stream and the Guatacondo ravine's ephemeral stream. Well-established villages such as Caserones, Pircas, Ramaditas, and Guatacondo accompanied these developments. However, the importance of understanding the water sources has been neglected despite the efforts to understand the relationships between pre-Hispanic agriculture and their living environment. Thus, we presumed the use of local water sources without a clear understanding of their exploitation methods or the associated technological implications. Furthermore, there is limited research on groundwater use in Tarapaca. This research aims to understand water sources used in the cultivation of maize (Zea mays) using 518O isotope values obtained from pre-Hispanic maize kernels in Tarapaca. We compared these values with published 518O values of water sources and applied a generalized linear model (GLM) with a Gaussian distribution, performing a Tukey's post hoc test for multiple comparisons of means with heteroscedasticity-consistent covariance estimation. The best-fit model was identified using a stepwise model selection procedure based on the Bayesian information criterion (BIC). Our results indicate that mean 518O values of organic matter from maize kernels range from 24.73 %o to 31.65 %o. The best performing model on 518O only included Group (BIC=298.2) as the explanatory variable as Period, Site, and Weight had no effects. These findings point towards a significant statistical relationship between the 518O values of organic matter derived from maize kernels and the specific geographic regions they originate from. These values also show an enrichment of 518O isotope in Tarapaca samples, except for Pica 8. These results indicate diverse agricultural strategies that utilized different water sources including perennial flow in the Tarapaca River, ephemeral runoff at Guatacondo, and groundwater in the Pampa del Tamarugal. Also, due to the enrichment of 518O, we suggest that the circular structures found among the fields were used as water reservoirs leading to the observed enrichment of 518O isotope values. We discuss the role of ancient agriculture technology in water management, the role of maize, cultural strategies, and the relationships with their environment. In conclusion, pre-Hispanic farmers managed limited water sources successfully despite intermittent drought for hundreds of years until the 1970 s, when agriculture was abandoned due to multiple factors.
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    'White gold' guano fertilizer drove agricultural intensification in the Atacama Desert from ad 1000
    (2021) Santana-Sagredo, Francisca; Schulting, Rick J.; Mendez-Quiros, Pablo; Vidal-Elgueta, Ale; Uribe, Mauricio; Loyola, Rodrigo; Maturana-Fernandez, Anahi; Diaz, Francisca P.; Latorre, Claudio; McRostie, Virginia B.; Santoro, Calogero M.; Mandakovic, Valentina; Harrod, Chris; Lee-Thorp, Julia
    The archaeological record shows that large pre-Inca agricultural systems supported settlements for centuries around the ravines and oases of northern Chile's hyperarid Atacama Desert. This raises questions about how such productivity was achieved and sustained, and its social implications. Using isotopic data of well-preserved ancient plant remains from Atacama sites, we show a dramatic increase in crop nitrogen isotope values (delta N-15) from around ad 1000. Maize was most affected, with delta N-15 values as high as +30 parts per thousand, and human bone collagen following a similar trend; moreover, their carbon isotope values (delta C-13) indicate a considerable increase in the consumption of maize at the same time. We attribute the shift to extremely high delta N-15 values-the highest in the world for archaeological plants-to the use of seabird guano to fertilize crops. Guano-'white gold' as it came to be called-thus sustained agricultural intensification, supporting a substantial population in an otherwise extreme environment.