Evaluating the convergence between eddy covariance and biometric methods for assessing carbon budgets of forests

The eddy-covariance(EC) micro-meteorological technique and the ecology-based biometric methods (BM) are the primary methodologies to quantify CO₂ exchange between terrestrial ecosystemsand the atmosphere (net ecosystemproduction, NEP) and its two components, ecosystem respirationand gross primary production. Here we show that EC and BM provide different estimates of NEP, but comparable ecosystem respirationand gross primary productionfor forest ecosystemsglobally. Discrepancies between methods are not related to environmental or stand variables, but are consistently more pronounced for boreal forests where carbon fluxes are smaller. BM estimates are prone to underestimation of net primary productionand overestimation of leaf respiration. EC biases are not apparent across sites, suggesting the effectiveness of standard post-processing procedures. Our results increase confidence in EC, show in which conditions EC and BM estimates can be integrated, and which methodological aspects can improve the convergence between EC and BM.