Potential N 2 O Emissions from the Tanks of Bromeliads Suggest an Additional Source of N 2 O in the Neotropics.

We studied the propensity of the tank bromeliad Werauhia gladioliflora to emit the greenhouse gas nitrous oxide (N2 O) at current and at increased N deposition levels in the range of predicted future scenarios. Potential production rates and net accumulation of N2 O from tank substrate corresponded to N availability. N2 O was produced in excess at all N levels due to a low level of N2 O reductase activity which agreed well with a low abundance of N2 O reducers compared to nitrite reducers. Transcriptional activation, however, indicated that expression of denitrification genes may be enhanced with increasing N supply eventually leading to more efficient N2 O turnover with potential for adaptation of denitrifier communities to higher N levels. Our findings indicate that tank bromeliads may constitute a novel source of N2 O in Neotropical forest canopies but further studies are required to understand the size and significance of in situ N2 O fluxes from tank bromeliads to the environment.