Nitrogen oxides emission from two beech forests subjected to different nitrogen loads

B. Kitzler (1) , S. Zechmeister-Boltenstern (1) , C. Holtermann (2) , U. Skiba (3) , K. Butterbach-Bahl (4)

1 Federal Research and Training Centre for Forests
2 Sellenyg. 2?4/52
3 Institute of Terrestrial Ecology
4 IMK-IFU - Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung

We analysed nitrogen oxides (N₂O, NO and NO₂) and carbon dioxide (CO₂) emissions from two beech forest soils close to Vienna, Austria, which were exposed to different nitrogen input from the atmosphere. The site Schottenwald (SW) received 22.6 kg N y^-1 and Klausenleopoldsdorf (KL) 13.5 kg N y^-1 through wet and dry deposition. Nitrogen oxide emissions from soil were measured hourly with an automatic dynamic chamber system. Daily N₂O measurements were carried out by an automatic gas sampling system. Measurements of nitrous oxide (N₂O) and CO₂ emissions were conducted over larger areas on a biweekly (SW) or monthly (KL) basis by manually operated chambers. We used an autoregression procedure (time-series analysis) for establishing time-lagged relationships between N-oxide emissions and different climate, soil chemistry and N-deposition data. It was found that changes in soil moisture and soil temperature significantly effected CO₂ and N-oxide emissions with a time lag of up to two weeks and could explain up to 95% of the temporal variations of gas emissions. Event emissions after rain or during freezing and thawing cycles contributed significantly (for NO 50%) to overall N-oxides emissions. In the two-year period of analysis the annual gaseous N₂O losses at SW ranged from 0.65 to 0.77 kg N ha^-1 y^-1 and NO losses were 0.18 to 0.67 kg N ha^-1 per vegetation period. In KL significantly lower annual N₂O emissions (0.52 kg N₂O-N kg ha^-1 y^-1) as well as considerably lower NO-losses were observed. During a three-month measurement campaign NO losses at KL were 0.02 kg, whereas in the same time period significantly more NO was emitted in SW (0.32 kg NO-N ha^-1). Higher N-oxide emissions, especially NO emissions from the high N-input site (SW) indicate that atmospheric deposition had a strong impact on losses of gaseous N from our forest soils. At KL there was a strong correlation between N-deposition and N-emission over time, which shows that low N-input sites are especially responsive to increasing N-inputs.

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

B. Kitzler, S. Zechmeister-Boltenstern, C. Holtermann, U. Skiba, K. Butterbach-Bahl. Nitrogen oxides emission from two beech forests subjected to different nitrogen loads. Biogeosciences Discussions, 2005, 2 (5), pp.1381-1422. ⟨hal-00297808⟩