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A new in-field indicator to assess the impact of land management on soil carbon dynamics

Thoumazeau A., Chevallier T., Baron V., Rakotondrazafy N., Panklang P., Marichal R., Kibblewhite M., Sebag D., Tivet F., Bessou C., Gay F., Brauman A.. 2020. Geoderma, 375 : 10 p..

DOI: 10.1016/j.geoderma.2020.114496

The assessment of the impacts of land-use and management on soil organic carbon (SOC) dynamics is a major environmental concern, as the soil carbon cycle underpins key ecosystem services. However, assessments based on short-term SOC dynamics face methodological and experimental difficulties. Hurisso et al. (2016) proposed a method to assess SOC dynamics by coupling two methods: Permanganate Oxidizable Carbon (POXC) and Basal Soil Respiration (BSR). This method has been used in laboratory on dried and re-wetted soil samples from temperate regions mainly. In our study, we adapted this method to the field and proposed a cost-effective in-field indicator combining the POXC and in situ Basal Soil Respiration (SituResp® method). We tested the indicator at four study sites (n = 169 points) within various tropical land-use and management contexts based on rubber, soybean and oil palm cropping systems respectively in Thailand, Cambodia and Indonesia. The results demonstrated the relevance, sensitivity and robustness of the POXC-SituResp® indicator to characterize the impact of a gradient of disturbance on SOC dynamics. The results also highlighted the potential of conservation agriculture (no-tillage and crops residues) and compost amendments to accumulate SOC. Rock-Eval® analysis showed that POXC-SituResp® indicator is negatively linked to excess of potentially mineralizable labile carbon. Carbon pools targeted by the POXC were specified by Rock-Eval® pyrolysis measurements to be a rather thermal resistant pool of SOC. Our study confirms that the integrated indicator based on POXC and BSR assess a relative carbon stabilization of SOC pools. This indicator can be measured in the field by a rapid and cost-effective method.

Mots-clés : gestion foncière; Évaluation de l'impact; impact sur l'environnement; dynamique des sols; carbone organique du sol

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