CONICET | Buscador de Institutos y Recursos Humanos

High-Andean cushion peatlands are among the most unique and characteristic ecosystems of the Andes. They are situated on steep slopes below wells or in wet brooks and valley bottoms at 4000 to 4800 masl. The primary cushion-forming and peat-producing plant species of thesesoligenous peatlands in NW Argentina are among the Juncaceae and Cyperaceae. As they have the quality to be very sensitive towards environmental changes, they are wellsuited for palaeoecological studies. These high-altitude peatlands can develop astonishing accumulation rates, depending on topography and a permanent and balanced water input.Correct site selection and the investigation of the drainage areas are fundamental for the understanding and interpretation of the peat cores. Once having dried out, caused by dry climate phases and/or erosion, the plant cover dies rapidly and the peat oxidizes. Results of multi-proxy studies of several peat cores from high-altitude cushion peatlands ofthe Eastern Cordillera of the NW Argentine Andes (Jujuy and Salta provinces) are presented. AMS 14C dates provide continous chronologies for the last 2000 years with one site covering 10000 years. During the mid-Holocene dry phase (8,5 to 2 ka BP) peat accumulation wassignificantly reduced or not existent. Biological (plant macrofossils and fossil charcoal particles) and geochemical (TC, TN, humification) analysis, so far, were used to detect palaeoenvironmental changes. Theinvestigation of plant macrofossils represents one of the first advances concerning Andean peatlands. The abundant presence of charred gramineae particles (only before 900 BP) is surprising and gives evidence of a vegetation change, possibly supported by a change towards a more shrub-dominated highland steppe as a result of intensified pasturing activities by the growing Andean human population. The dominating control on fire before 900 BP appears to be climate.

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