Effect of Sampling Frequency on Estimates of Annual Nitrous Oxide Fluxes.

Nitrous oxide fluxes are renown for their high temporal variability. Frequency of sampling is therefore critical when determining annual N₂O fluxes and associated emission factors. We investigated the effect of sample frequency on estimates of annual N₂O fluxes using published data collected on a subdaily-basis using automated chamber systems. Study sites varied geographically (Australia, China and Germany), and included agricultural and forest soils in temperate, semiarid and subtropical climates. Annual fluxes based on subdaily N₂O fluxes ranged from <0.1 to 7.6 kg N ha^-1 yr^-1 depending on the study site, and were calculated using at least three replicate chambers per experimental treatment. Sampling frequency effects on annual N₂O fluxes were assessed using a jack knife technique. We avoided interferences resulting from the effect of time-of-day sampling by using the average daily flux for each replicate chamber. Findings will be used to guide those designing sampling regimes for manual chambers.