Sithea Sath: SPECTRO-KHMER: Predicting soil carbon stocks in Cambodia.

Project summary

SPECTRO-KHMER: Prediction of soil carbon stocks in Cambodia. Training and calibration transfer between spectral databases acquired in various laboratories in Cambodia and France. 

Project Summary and Added Value of the Exchange. 
Through an exchange between IEES-Paris and the UMR Eco&Sols-Montpellier, during Sithea Sath’s forthcoming stay in France in 2026, the project aims to strengthen this PhD student’s skills in the spectral prediction of soil carbon stocks, to contribute to spectral databases, and to study calibration transfers between spectrometers within the ALAMOD project. Indeed, on the one hand, this visit to the UMR Eco&Sols (Montpellier) will enable Sithea to acquire the spectra of 300 soil samples (150 points × 2 depths), collected at the Chrey Bak observatory in Cambodia, using the two PIR and MIR spectrometers available at this UMR and following two different preparation methods (sieving to 2 mm vs. grinding to 0.2 mm). Furthermore, his visit will provide an opportunity to meet Aurélie Cambou (IR IRD Eco&Sols), who will be on assignment in Montpellier in June 2026, and to discuss the analysis of spectral data, with a particular focus on calibration transfers. The aim of the mobility programme will be to standardise the spectral databases obtained using the various spectrometers involved in the project (in Cambodia and France). The effect of the sample preparation method (grinding to 200 µm versus sieving to 2 mm) during spectral acquisition will also be investigated in the context of predicting COS stocks. This work will therefore contribute directly to Sithea Sath’s PhD thesis, whilst strengthening the ALAMOD project by optimising methods for analysing spectral data to predict carbon stocks and by improving the interoperability of spectral databases acquired using different instruments or following different sample preparation protocols (e.g., sieving vs. grinding) . 

Proposed itinerary
Sithea Sath will be in France in January 2026 for a period of six months. The start of her stay in France will be devoted to measuring the total C and N content of her samples, and analysing their signatures using MIR spectroscopy. Ideally, she could spend one month in Montpellier in May or June 2026.

Integration of the project within the framework of the FairCarboN PEPR and its stated objectives, particularly with regard to the development of the French research community: Publication of the results of the PhD research in one or more articles involving iEES Paris and Eco&Sols, and contribution to the spectral database developed as part of the ALAMOD project. Another important aspect is the strengthening of the partnership with the TC, as Sithea Sath will be recruited as a research lecturer upon completion of her PhD. One of the planned tasks is the use of IR spectroscopy to quantify carbon stocks in forest ecosystems, as part of the country’s participation in the REDD+ programme. 

Benefits of mobility
Training for partners; strengthening collaboration between the iEES Paris and Eco&Sols joint research units (UMRs) in the use of spectral data to quantify soil carbon stocks.