Progressive and regressive soil evolution phases in the Anthropocene
Manon Bajard  1@  , Jérôme Poulenard  1@  , Pierre Sabatier  1@  , Anne-Lise Develle  1@  , Fernand David  2@  , Charline Giguet-Covex  3@  , Jérémy Jacob  4@  , Rachel Boscardin  4@  , Christian Crouzet  5@  , Fabien Arnaud  1@  
1 : Environnements, Dynamiques et Territoires de la Montagne  (EDYTEM)  -  Website
CNRS : UMR5204, Université de Savoie
Université de Savoie, Campus scientifique, 73376 Le Bourget du Lac cedex -  France
2 : Centre européen de recherche et d'enseignement de géosciences de l'environnement  (CEREGE)
CNRS : UMR7330, Aix Marseille Université, Institut de recherche pour le développement [IRD] : UR161
Technopôle de l'Arbois-Méditerranée, BP80, 13545 Aix en Provence cedex 4 -  France
3 : Département d'Archéologie, Université de York
Environment Building Wentworth Way York YO10 5DD -  United Kingdom
4 : Institut des Sciences de la Terre d'Orléans  (ISTO)  -  Website
Université d'Orléans, CNRS : UMR7327, INSU, Bureau de Recherches Géologiques et Minières (BRGM)
Campus Géosciences 1A, rue de la Férollerie 45071 Orléans cedex 2 -  France
5 : Institut des sciences de la Terre  (ISTerre)  -  Website
Institut de recherche pour le développement [IRD] : UR219, OSUG, INSU, Université Joseph Fourier - Grenoble I, Université de Savoie, IFSTTAR-GERS, IFSTTAR, CNRS : UMR5275, PRES Université de Grenoble
73376 Le Bourget du Lac -  France

Soils have a substantial role in the environment as they give back several ecosystem services as food supply and carbon storage. But agricultural practices can modify soil properties and soil evolution processes, threatening these services. These modifications are poorly studied and resilience/adaptation times of soils to disruptions are unknown. Here we propose to study the evolution of pedogenetic processes and soil evolution phases (progressive or regressive) in response to human-induced erosion from a 4000 years lake sediment sequence (Lake La Thuile, French Alps). Erosion in this little lake catchment in the montane area is quantified from the terrigenous sediments trapped in the lake and compared to soil formation rate. To access this quantification, soil processes evolution are deciphered from soil and sediment geochemistry comparison. Over the last 4000 years, first impacts on soils are recorded at approximately 1600 yr cal. BP with erosion of surface horizons beyond 10 t.km-².yr-1. With erosion accentuation between 1400 and 850 yr cal. BP, up to 1000 t.km-².yr-1, horizons increasingly deep are eroded during the Middle-Age, leading to remobilization of carbonated and poorly weathered material which rejuvenates soil development. Erosion overpassed soil formation rate and constitute a regression in the development of soils. Tolerable erosion limit is thus defined for erosion ranging from 25 and 30 t.km-².yr-1. Beyond this limit, the sustainability of the agroecosystem is limited and ecosystem services decreased. Since then, pedogenesis goes again from progressive (700-300 yr cal. BP) to regressive (300 yr cal. BP-today) phases. Erosion is less important during the last 700 years than during the Middle-age but with the same weathering stages which indicates that soils were deeply affected during the Middle-age and had not time to be recovered. The overall result highlights the importance of the human factor in the pedogenesis over last millenniums and its impact on the stratigraphy of the lake that moves this agro-ecosystem in the Anthropocene since 1400 years.


Online user: 1 RSS Feed