N2O production pathway change during drought and following wet-up in a controlled rainforest at Biosphere 2 Center
Abstract
N2O is the fourth most important greenhouse gas and it leads to ozone destruction in the stratosphere. Rainforests account for ∼ 20% of global N2O emissions. In soils N2O can be produced though hydroxylamine oxidation by methanotrophs, nitrification, nitrifier denitrification, and denitrification. The former two processes occur under aerobic and the latter two under anaerobic conditions. During a drought, soils are expected to change from more anaerobic to more aerobic conditions, thus leading to a change in N2O production pathway.
To test this we conducted a 37-day drought in a controlled rainforest mesocosm at Biosphere 2 Center. Three times during the drought and immediately after wet-up, we collected air and soil samples to determine the N2O isotope changes. Top 10 cm soil Water Filled Pore Space (WFPS) decreased from ∼ 60 to 20% and WFPS below 50 cm decreased from ∼ 50 to 40% during the drought. Meanwhile the whole system N2O flux decreased from 120+/-4 to 41.5+/-2.6 μ g-N/m2/hr. δ 15N, δ 18O, and site preference of N2O increased by 7, ∼2, and ∼2.5‰ , respectively. Immediately following wet-up a pulse of N2O was released with δ 15N, δ 18O, and Site preference 15, 3 and 15‰ lower than before. We will present evidence to support that the stable isotope increase with soil water loss can be explained by an increase in contribution of hydroxylamine oxidation by methanotrophs. Whereas the isotopic change following wet-up is due to increased contribution from nitrifier-denitrification to the overall N2O flux.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.B31E0357V
- Keywords:
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- 0315 Biosphere/atmosphere interactions;
- 0400 Biogeosciences