Abstract
AbstractLimited information on greenhouse gas emissions from tropical dry forest soils still hinders the assessment of the sources/sinks from this ecosystem and their contribution at global scales. Particularly, rewetting events after the dry season can have a significant effect on soil biogeochemical processes and associated exchange of greenhouse gases. This study evaluated the temporal variation and annual fluxes of CO2, N2O, and CH4 from soils in a tropical dry forest successional gradient. After a prolonged drought of 5 months, large emissions pulses of CO2 and N2O were observed at all sites following first rain events, caused by the “Birch effect,” with a significant effect on the net ecosystem exchange and the annual emissions budget. Annual CO2 emissions were greatest for the young forest (8,556 kg C ha−1 yr−1) followed by the older forest (7,420 kg C ha−1 yr−1) and the abandoned pasture (7,224 kg C ha−1 yr−1). Annual emissions of N2O were greatest for the forest sites (0.39 and 0.43 kg N ha−1 yr−1) and least in the abandoned pasture (0.09 kg N ha−1 yr−1). CH4 uptake was greatest in the older forest (−2.61 kg C ha−1 yr−1) followed by the abandoned pasture (−0.69 kg C ha−1 yr−1) and the young forest (−0.58 kg C ha−1 yr−1). Fluxes were mainly influenced by soil moisture, microbial biomass, and soil nitrate and ammonium concentrations. Annual CO2 and N2O soil fluxes of tropical dry forests in this study and others from the literature were much lower than the annual fluxes in wetter tropical forests. Conversely, tropical dry forests and abandoned pastures are on average stronger sinks for CH4 than wetter tropical forests.
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