Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest

Measuring in situ soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO2 flux chamber system (LI-8100A) with a CH4 and N2O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO2 and CH4 fluxes (100% and 98.5% of fluxes were above minimum detectable flux - MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N2O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N2O fluxes (85.6% of measured fluxes are above MDF +/- 0.002 nmol m(-2) s(-1)). Our study highlights the importance of adjusted closure time for each gas