Best practice for upscaling soil organic carbon stocks in salt marshes

Calculating the amount of soil organic carbon (SOC) stored in coastal environments, including salt marshes, is needed to determine their role mitigating Climate Crisis. Several techniques exist calculate SOC content a unit land from upscaling cores. However, no comprehensive assessment has been made on performance commonly used until now. We measured cores gathered two Scottish marshes. Two values were for upscaling; 1 m standardised depth (as recommended by IPCC), and modern marsh deposit (identified stratigraphy as transition organic-rich (marsh) mineral-rich (intertidal flat) soil. Twenty-two (SOC × area, interpolative, regression-based extrapolative calculations). Leave-one-out cross-validation procedures prediction interval widths assess accuracy each technique. Digital Terrain Models Normalized Difference Vegetation Indices covariate surfaces regression models. found that marsh-scale stocks varied much fifty-two times depending which sampling technique was used. The largest differences emerged when comparing upscaled deep deposits. Using IPCC inflated intertidal flat environments included calculation. Ensemble models weighted average seven machine learning algorithm outputs produced highest accuracies across marshes depths. Simple area calculations comparable stock more advanced ensemble detailed maps distribution marsh, associated uncertainty values. Our findings are broadly applicable other where large-scale assessments needed.