Seasonality and Budgets of Soil Greenhouse Gas Emissions From a Tropical Dry Forest Successional Gradient in Costa Rica
Sofía Calvo-Rodríguez, Ralf Kiese, Arturo Sánchez‐Azofeifa
Abstract
Abstract Limited 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 CO 2 , N 2 O, and CH 4 from soils in a tropical dry forest successional gradient. After a prolonged drought of 5 months, large emissions pulses of CO 2 and N 2 O 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 CO 2 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 N 2 O 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 ). CH 4 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 CO 2 and N 2 O 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 CH 4 than wetter tropical forests.