Nitrous oxide emissions from a beech forest floor measured by eddy covariance and soil enclosure techniques

M. Pihlatie (1) , J. Rinne (1) , P. Ambus (2) , K. Pilegaard (2) , J. R. Dorsey (3) , Ü. Rannik (1) , T. Markkanen (1) , S. Launiainen (1) , T. Vesala (1)

1 Department of Physical Sciences [Helsinki]
2 Biosystems Division [Roskilde]
3 ESPM - Department of Environmental Science, Policy, and Management [Berkeley]

Spring time soil nitrous oxide (N₂O) fluxes were measured in an old beech (Fagus sylvatica L.) forest with eddy covariance (EC) and chamber techniques. The aim was to compare the two techniques and to test whether EC can be used in the trunk-space of the forest to measure N₂O. Mean N₂O fluxes over the five week measurement period were 5, 10 and 16 ?g N m^-2h^-1 from EC, automatic chamber and manual chambers, respectively. When data from one hot spot chamber was excluded the mean N₂O flux of 8 ?g N m^-2h^-1 from the soil chambers nearly equaled to the mean flux of 7 ?g N m^-2h^-1 measured with EC from the direction were soil chambers located. Spatial variability in the N₂O emissions was high in soil chamber measurements, while the EC integrated over this spatial variability and suggested that N₂O emissions were uniform within the footprint area. The highest emissions measured with the EC occurred during the first week of May when the trees were leafing and when soil moisture content was at its highest. To our knowledge, this is the first study to demonstrate that the EC technique can be used to measure N₂O fluxes in the trunk-space of a forest. If chamber techniques are used to estimate ecosystem level N₂O emissions from forest soils, placing of the chambers should be considered carefully to cover the heterogeneity in the soil N₂O emissions.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

M. Pihlatie, J. Rinne, P. Ambus, K. Pilegaard, J. R. Dorsey, et al.. Nitrous oxide emissions from a beech forest floor measured by eddy covariance and soil enclosure techniques. Biogeosciences Discussions, 2005, 2 (3), pp.581-607. ⟨hal-00297751⟩