Project

land-use change; compound-specific radiocarbon; soil biomarkers; paleolimnology; organic geochemistry; soil erosion

Lead
Au cours des derniers millénaires, l’homme est devenu le premier agent géologique, transformant entre un tiers et la moitié de la surface terrestre. Le défrichage, l’établissement de l’agriculture et la domestication du bétail ont provoqué une augmentation dramatique du taux d’érosion des sols. Dans le cadre du projet PALEOFARM, nous allons analyser des sédiments lacustres afin de lier les variations de déstabilisation des sols avec l’évolution de l’usage des sols.
Lay summary
Contenu et objectifs du travail de recherche Notre principal objectif est de contribuer à une meilleure compréhension de l’érosion historique et préhistorique des sols causée par l’établissement de l’agriculture et son évolution. Afin de distinguer les impacts de différents types d’agriculture, nous allons analyser des carottes sédimentaires de plusieurs lacs ayant des histoires distinctes de l’occupation et des activités humaines dans leur bassin versant. Nous allons déterminer la vulnérabilité des sols aux usages anciens principalement au moyen de biomarqueurs moléculaires. Contexte scientifique et social du projet de recherche Les pertes par érosion de sol arable seraient désormais d’un ordre de grandeur plus élevé que leur taux de formation, représentant une sérieuse menace pour notre avenir. L’approche inédite que nous allons prendre permet une évaluation complète des usages passés et de l’état de dégradation des sols. Les analyses isotopiques sur composés organiques individuels ouvrent de nouvelles perspectives dans la compréhension de la dynamique de la matière organique des sols. De récents développements techniques, à l’instar des datations radiocarbone sur composés spécifiques, permettent désormais l’investigation du temps de résidence de la matière organique et des effets des activités humaines sur le stockage de celle-ci dans les sols.

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Last update: 06.05.2015

Natural persons

Roman-driven cultural eutrophication of Lake Murten, Switzerland

Author	Haas, Mischa; Baumann, Franziska; Castella, Daniel; Haghipour, Negar; Reusch, Anna; Strasser, Michael; Eglinton, Timothy Ian; Dubois, Nathalie
Publication date	01.01.2019
Persistent Identifier (PID)	https://doi.pangaea.de/10.1594/PANGAEA.895676
Repository	PANGAEA

Data for: Land-use evolution in the catchment of Lake Murten, Switzerland

Author	Haas, Mischa
Publication date	08.03.2020
Persistent Identifier (PID)	doi: 10.17632/fp3y3mryx4.1
Repository	Mendeley Data
Abstract

Data tables for Haas et al. "Land-use evolution in the catchment of Lake Murten, Switzerland"

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Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

The largest human alteration of the natural environment occurred centuries to millennia ago, with the clearing of forests to establish cropland and pasture, and the exploitation of forests for firewood and construction materials. As a result of these human activities, soil erosion experienced a sharp increase. Although the sustainable use of soil is a pressing societal issue, little is known about the history of human impact on soil and pre-anthropogenic conditions. In this project, we propose to analyze lake sediments to reconstruct changes in soil erosion and soil carbon dynamics with the evolution of land-use.In order to distinguish how different types of farming impact soil and lake ecosystems, we will recover and analyze sediment cores from four lakes with contrasting histories of human occupation and land-use in their catchment. The first site, in Greenland, experienced human occupation for only a limited time (985-1450 AD), with almost exclusively pastoral activities in its watershed. Land abandonment during the following 500 yr - until the recent re-establishment of modern farming - led to a progressive re-naturalization of the environment. The second site, in the Republic of Karelia (NW Russia), experienced an unconventional shift from cropland to pasture in 1940 AD, as the former Finnish territory was ceded back to the Soviet Union. The third site, Lake Murten in Switzerland, was chosen as representative of the traditional long-term evolution into intensive farming, i.e. from forest to pasture to agriculture. The last site, Lake Joux in the Swiss Jura Mountain, is currently under investigation as part of a pilot study and experienced a more tardive human occupation.Key to this research, we will use an innovative approach to quantify soil degradation and link it to farming practices: We will analyze lacustrine sediments to reconstruct the soil residence time of organic molecules originating from terrestrial plants and soil bacteria. We will use radiocarbon dating to assess the age differences between rapidly deposited plant debris and these fossil molecules (biomarkers) that are retained in the soil system for some time. This information will increase our understanding of the extent of human disturbance on soil carbon dynamics, and provide tools to assess measures taken for the sustainable use of soils. Our hypothesis is that the development of modern practices such as tillage affected deeper soils than ever before. The flushing of these old soils into lake repositories should be reflected by a significant ageing of the terrestrial biomarkers relative to the “fresh” plant debris deposited in the same sediment layers. However, it may be possible that early deforestation or grazing played the most significant role in the soil destabilization process. This study will allow discriminating the relative impact of these different land-use activities.The horizons of interest will be detected by changes in sedimentological and geochemical characteristics in the sediment cores. The vegetation changes that accompany the evolution of agricultural practices will be determined from pollen assemblage. In conclusion, this study will emphasize the relevance of paleolimnological approaches to assess not only the reference ecological conditions for modern lakes but also the reference state for soil.