Assessing the uncertainty of estimated annual totals of net ecosystem productivity: A practical approach applied to a mid latitude temperate pine forest

► A robust method is presented to quantify uncertainty of annual totals of net ecosystem productivity (NEP). ► The method contains uncertainty estimates for the most important known components of the total uncertainty: measurement error and flux calculation uncertainty, self-heating correction uncertainty, u* threshold uncertainty, statistical selection uncertainty and gap-filling uncertainty. ► The uncertainties associated with the friction velocity threshold criterion and measurement error and flux calculation are substantial and much higher than the other uncertainties. ► Total uncertainty of NEP for the Loobos site was on average ±32 g C m−2 a−1 (±8% of NEP).