PARENT SESSION
Poster Session #50: Climate Change.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
21
Soil moisture control on nitrous oxide fluxes in a large enclosed rainforest ecosystem .
van Haren, Joost*,1, Lin, Guanghui1, Colodner, Debra2, 1 Columbia University, Biosphere 2 Center, Oracle, AZ 856232 Flandrau Science Center, University of Arizona, Tucson, AZ 85719
ABSTRACT- Tropical evergreen forests account for almost a quarter of the annual global nitrous oxide (N2O) production. N2O production rates in forests are linked to soil moisture and thus dependent on climate changes, such as El Niño induced drought in the Amazon rainforest basin. High nitrogen content (0.2 to 0.4%), low carbon/nitrogen ratio (~ 11), and a large biosphere/atmosphere ratio make the Biosphere 2 rainforest uniquely suited for investigations of N2O flux changes in relation to soil physical properties, such as soil moisture. At Biosphere 2 Center, we have been conducting month-long experiments controlling rain in a ~ 26,700 m3 enclosure of rainforest vegetation. During these experiments we measured N2O fluxes and soil moisture content on a daily basis and soil N2O concentrations and fluxes, soil nitrate concentration and SF6 concentration in soil and atmosphere on a weekly basis. Our results show that a 10-15% decrease in soil moisture leads to ~ 60% decrease in N2O flux in the Biosphere 2 rainforest soils. Soil gas analyses show that gas transport rates increase with decreasing soil moisture and thus N2O production rates should decrease more dramatically. Furthermore, nitrate and mineralization rates generally increase with decreasing soil moisture content, indicating that nitrification dominates denitrification in drier conditions.
KEY WORDS: nitrous oxide, soil moisture, drought