Abstract:
Tank bromeliads are common epiphytic plants throughout neotropical forests that store
signi?cant amounts of water in phytotelmata (tanks) formed by highly modi?ed leafs.
Methanogenic archaea in these tanks have recently been identi?ed as a signi?cant source of
atmospheric methane. We address the effects of environmental drivers (temperature, tank
water content, sodium phosphate [P], and urea [N] addition) on methane production in
anaerobically incubated bromeliad slurry and emissions from intact bromeliad tanks in
montane Ecuador. N addition ? 1 mg g 1 had a signi?cantly positive effect on headspace
methane concentrations in incubation jars while P addition did not affect methane
production at any dosage (? 1 mg g 1 ). Tank bromeliads (Tillandsia complanata) cultivated
in situ showed signi?cantly increased ef?uxes of methane in response to the addition of
26 mg N addition per tank but not to lower dosage of N or any dosage of P (? 5.2 mg plant 1 ).
There was no signi?cant interaction between N and P addition. The brevity of the
stimulatory effect of N addition on plant methane ef?uxes (1–2 days) points at N
competition by other microorganisms or bromeliads. Methane ef?ux from plants closely
followed within-day temperature ?uctuations over 24 h cycles, yet the dependency of
temperature was not exponential as typical for terrestrial wetlands but instead linear. In
simulated drought, methane emission from bromeliad tanks was maintained with minimum
amounts of water and regained after a short lag phase of approximately 24 h. Our results
suggest that methanogens in bromeliads are primarily limited by N and that direct effects of
global change (increasing temperature and seasonality, remote fertilization) on bromeliad
methane emissions are of moderate scale.
