On the error of respiration flux calculation along the pH gradient (comment to the study of Schroeder and co-authors (2024))

Schroeder and co-authors (2024) recently attempted to accomplish a very challenging task, i.e. to quantify the effect of pH change caused by liming on carbon use efficiency (CUE) of soil microbial biomass. The information provided by the authors in the ‘Material and Methods’ section and the Supplementary data file raise concerns about the precision of authors' main conclusions due to a possible error in the calculation of the respiration flux and thus CUE across the gradient of soil pH. In our letter, we calculate the theoretical relative error of respiration flux measurement across the pH gradient using information provided by Schroeder and co-authors (2024). We show that the relative error increases to almost 84% when soil pH increases to 8.6. This estimate is significantly higher as compared to the relative error calculated by the authors in the Supplementary data file for the same experimental conditions (i.e. 0.7%). We also show how the calculated error can affect the main conclusion. We believe that the authors need to explain their calculations and possibly correct the article, as the current description of methods and results raise concerns about misleading interpretations. •CUE estimation depends on accuracy of respiration flux measurement/calculation.•Relative error of respiration flux measurement increases from 0.5% to 84% along pH gradient 5.5–8.6 due to CO2 dissolution.•Apparent trend of increasing CUE due to increasing pH may reverse when CO2 dissolution is accounted for.