M2 internship position

Soil fauna and microbial contributions to MAOM formation in tropical cropping systems under contrasting hydrological conditions

Context

Soil organic carbon stabilization is a key process for maintaining soil fertility and mitigating climate change. A major fraction of this carbon is stored as mineral-associated organic matter (MAOM), whose formation is largely driven by soil microorganisms and fauna. However, their respective roles remain poorly understood in tropical agricultural systems, especially under contrasting water regimes such as flooded rice and upland crops.

Objective

The objective of this internship is to assess how hydrological conditions (flooded vs non-flooded) and fertilization practices (organic vs mineral) influence the activity of soil microorganisms and fauna, and how these biological processes control the incorporation of litter-derived carbon into MAOM in tropical cropping systems.

Tasks

•  Install and retrieve ¹³C-labelled litterbags with different mesh sizes (microbes only vs microbes + fauna)

•  Collect soil samples and perform laboratory fractionation (POM and MAOM)

•  Measure indicators of microbial activity (respiration, enzymatic activity) and in soil fauna assessments

•  Process and analyze data in R (descriptive statistics, models)

Skills

•  Background or strong interest in soil science

•  Willingness to conduct field and laboratory work

•  Basic experience with data analysis in R (or motivation to learn)

•  Good organizational skills, autonomy and scientific rigor

•  Ability to work in an international research environment and communicate in English

Location

Soils and Fertilizers Institute, Hanoï, Vietnam

Supervisors

Nicolas Bottinelli (iEES-Paris based in Hanoï); Cornelia Rumpel (iEES-Paris); Quang Van Pham (VNU) and Duc Anh Nguyen (IEBR, VAST)

Duration

Starting date flexible (ideally January–February 2025) (~500 € /month).

Prospects

This internship will provide strong training in soil ecology, stable isotope approaches and carbon cycling, and may lead to PhD opportunities in soil biogeochemistry research. A high-achieving student (excellent academic record) may be eligible to apply for a PhD fellowship funded by the French Embassy.

Contacts

nicolas.bottinelli@ird.fr

References of the team

Song, C., Bottinelli, N., Tran, T.-M., Ruiz, F., Colombini, G., Zi, Y., Jouquet, P. & Rumpel, C. (2023). Land use determines the composition and stability of organic carbon in earthworm casts under tropical conditions. Soil Biology and Biochemistry, 190, 109291.

Chenu, C., Rumpel, C., Védère, C., & Barré, P. (2024). Methods for studying soil organic matter: nature, dynamics, spatial accessibility, and interactions with minerals. In Soil microbiology, ecology and biochemistry (pp. 369-406). Elsevier.