N$_{2}$O production pathway change during drought and following wet-up in a controlled rainforest at Biosphere 2 Center

HR: 0830h
AN: B31E-0357 [PDF]
TI: N$_{2}$O production pathway change during drought and following wet-up in a controlled rainforest at Biosphere 2 Center
AU: * van Haren, J
EM: jvanhare@mail.research.bio2.edu
AF: Columbia University Biosphere 2Center, PO Box 689, Oracle, AZ 85623 United States
AU: Yamagishi, H
EM: hyamagishi@depe.titech.ac.jp
AF: Dept. of Environmental Science and Technology, Tokyo Institute for Technology G5-210,4259Nagatsuta,Midori-ku, Yokohama, 226-8502 Japan
AU: Yoshida, N
EM: naoyoshi@depe.titech.ac.jp
AF: Dept. of Environmental Science and Technology, Tokyo Institute for Technology G5-210,4259Nagatsuta,Midori-ku, Yokohama, 226-8502 Japan
AB: N$_{2}$O is the fourth most important greenhouse gas and it leads to ozone destruction in the stratosphere. Rainforests account for $\sim$ 20$%$ of global N$_{2}$O emissions. In soils N$_{2}$O 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 N$_{2}$O 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 N$_{2}$O isotope changes. Top 10 cm soil Water Filled Pore Space (WFPS) decreased from $\sim$ 60 to 20$%$ and WFPS below 50 cm decreased from $\sim$ 50 to 40$%$ during the drought. Meanwhile the whole system N$_{2}$O flux decreased from 120$\pm$4 to 41.5$\pm$2.6 $\mu$g-N/m$^{2}$/hr. $\delta$$^{15}$N, $\delta$$^{18}$O, and site preference of N$_{2}$O increased by 7, $\sim$2, and $\sim$2.5$\permil$, respectively. Immediately following wet-up a pulse of N$_{2}$O was released with $\delta$$^{15}$N, $\delta$$^{18}$O, and Site preference 15, 3 and 15$\permil$ 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 N$_{2}$O flux.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting