Aims: We investigated N2O emissions from stems of Fraxinus angustifolia and Fagus sylvatica, hypothesizing that trees emit N2O through the stem via diffusion out of the transpiration stream. Methods: We used static chambers fixed at different heights of the stem to estimate N2O stem effluxes. Chambers were also used for monitoring soil N2O emissions. To stimulate soil N2O production and stem N2O emissions we fertilized the soil. Results: Before soil fertilization, stem N2O emissions were at most 2 μg N2O-N m−2 bark h−1. After fertilization, stem and soil emissions were linearly correlated; stem emissions decreased linearly with increasing height. Stems of Fagus sylvatica emitted up to 80 μg N2O-N m−2 bark h−1 at 20 cm above soil level; at 200 cm, stem N2O emissions were below detection limit. Fraxinus angustifolia stem N2O emissions reached 35 μg N2O-N m−2 bark h−1 after soil fertilization. Conclusions: Stem N2O emissions in upland trees occur even without aerenchyma, associated with xylem water transport. However, stem N2O emissions represented only 1–3 % of total (soil + stem) N2O emissions at the forest level. If this holds for other forest ecosystems, stem N2O emissions would be a minor pathway of N2O loss from terrestrial ecosystems into the atmosphere.
Bibliographical note© Springer International Publishing Switzerland 2015
- Fagus sylvatica L
- Fraxinus angustifolia Vahl
- Soil N2O emissions
- Tree stem N2O emissions