Layheang Song, PhD student within M-TROPICS CZO, defended his thesis today at GET. His thesis work was under the international double degree program between the University Paul Sabatier and the Institute of Technology of Cambodia.
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 Layheang showed that teak tree plantations managed without understory on sloping land were 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 are 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.