Usage des terres, ruissellement de surface, érosion des sols : analyse multi-échelle de l’impact des plantations de teck dans un agro-écosystème montagneux tropical humide

Soutenance de thèse de Layheang Song

Le jury sera composé de :

Mme Olga VIGIAK (Senior Scientist – European Commission, Joint Research Centre, Rapporteur)
M. Luc DESCROIX (Directeur de recherche – IRD, PALOC, Rapporteur)
Mme Pinnara KET (Maîtresse de conférences – Institute of Technology of Cambodia, Examinateur)
M. Guillaume NORD (Physicien-Adjoint – UGA, IGE, Examinateur)
M. Christian VALENTIN (Directeur de recherche émérite – IRD, iEES Paris, Examinateur)
Mme Laurie BOITHIAS (Physicienne-Adjointe – Université Toulouse III, GET, Directrice de thèse)
M. Chantha OEURNG (Professeur – Institut de Technologie du Cambodge, Co-directeur de thèse)
M. Olivier RIBOLZI (Directeur de recherche – IRD, GET, Co-directeur de thèse)

Abstract: Soil erosion is one of the most concerning environmental problems on the global scale. Soil erosion is increasingly driven by anthropogenic activities, in a changing climate context. The mountainous area of northern Lao PDR is prone to soil erosion, particularly after the conversion of the traditional shifting cultivation agricultural system to teak tree plantations over the last 20 years. Although tree plantations are often thought to provide ecosystem services similar to the ones supplied by natural forests, in this thesis we will show that teak tree plantations managed without understory on sloping land are a significant source of soil loss and sediment transfer, leading to onsite effects such as the decline of both soil quality and agricultural production, and to offsite effects such as the contamination of stream water and dam siltation. The thesis relies on a multiple-scale approach, with in situ observation and modelling scales ranging from the point-source (1 m²) to the small catchment (0.6 km²). Mitigation measures such as understory and riparian vegetation conservation will be suggested for alleviating soil erosion and enhance the erosion control ecosystem service. This information may help farmers and policymakers to adopt and promote sustainable land management practices.

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