Non-reversible geosystem destabilisation at 4200 cal. BP: Sedimentological, geochemical and botanical markers of soil erosion recorded in a Mediterranean alpine lake

Description

A 144-cm-long core was obtained in Lake Petit (2200 m a.s.l., Mediterranean French Alps) in order to reconstruct past interactions between humans, the environment and the climate over the last five millennia using a multidisciplinary approach involving sedimentological, geochemical and botanical analyses. We show a complex pattern of environmental transformation. From 4800 to 4200 cal. BP, podzol-type soils progressively developed under forest cover. This stable situation was interrupted by a major detrital pulse at 4200 cal. BP that we consider as a tipping point in the environmental history. At this point, pedogenetic processes drastically regressed, leading to the development of moderately weathered soils. More frequent detrital inputs are recorded since 3000 cal. BP (AD 1050) as the human impact significantly increased in the catchment area. We conclude that destabilisation of the environment was triggered by climate and exacerbated by human activities to a stage beyond resilience.

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