Original Research Article Methane emissions from five wetland plant communities with different hydroperiods in the Big Cypress Swamp region of Florida Everglades Jorge A. Villa a,b,c, *, William J. Mitsch a,b a Environmental Science Graduate Program, The Ohio State University, Columbus, OH, USA b Everglades Wetland Research Park, Florida Gulf Coast University, Naples, FL, USA c Facultad de Ingenierı´a, Grupo de Investigacio ´n GAMA, Corporacio ´n Universitaria Lasallista, Carrera 51 no. 118 sur—57, Caldas, Antioquia, Colombia 1. Introduction Around 25% (i.e. 190  39 Tg CH 4 yr 1 ) of global methane (CH 4 ) emissions to the atmosphere come from wetlands, the largest single natural source (Melton et al., 2012), with the majority of this CH 4 (i.e. 52–58%) produced in tropical wetlands (Bloom et al., 2010). CH 4 is produced in wetlands when organic matter undergoes anaerobic decomposition in the anaerobic conditions characteristic of these ecosystems. Once in the atmosphere, CH 4 has an adverse effect on the radiation budget of earth with a warming potential 28 times greater than the potential of the same mass of carbon dioxide over 100 years (Myhre et al., 2013). This warming potential can be up to 40% greater when indirect interactions are included (Myhre et al., 2013). However, models based on the Ecohydrology & Hydrobiology 14 (2014) 253–266 A R T I C L E I N F O Article history: Received 31 January 2014 Accepted 29 July 2014 Available online 11 August 2014 Keywords: Methane emissions Subtropical wetlands Hydroperiod Cypress swamp Southwest Florida Climate change A B S T R A C T The majority of the methane (CH 4 ) emitted from wetlands comes from tropical and subtropical zones. On a global scale, the variability of these emissions had been attributed to water table variations; however, at landscape scales this variability is poorly understood. We measured CH 4 fluxes from five characteristic wetland plant communities of southwest Florida representing a gradient in inundation periods. From wettest to driest conditions, communities were designated as deep slough, bald cypress, wet prairie, pond cypress and hydric pine flatwood. Non-steady-state rigid chambers were deployed at each community sequentially at three different times of the day during a 24-month period. CH 4 fluxes did not show a discernible daily pattern, in contrast to a marked seasonal increase in emissions during inundation. All wetland communities acted as temporary sinks of CH 4 , but overall were net sources. Median and mean  standard error fluxes in CH 4 -C m 2 d 1 were higher in deep slough (11 and 55.3  21.5), followed by the wet prairie (9.01 and 53.3  26.6), bald cypress (3.31 and 5.54  2.51) and pond cypress (1.49, 4.55  3.35). The pine flatwood community acted as a net sink during the study period (0.0 and 1.22  0.81). Seasonality in CH 4 emissions was positively correlated with water levels, but not with soil temperature. However, longer inundation periods did not necessarily result in higher CH 4 emissions. These findings add to our current knowledge of CH 4 fluxes from subtropical wetland ecosystems and have implications for modeling at ecosystem scales in heterogeneous wetland landscapes. ß 2014 European Regional Centre for Ecohydrology of Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved. * Corresponding author. Current address: Facultad de Ingenierı ´a, Grupo GAMA, Corporacio ´n Universitaria Lasallista, Carrera 51 # 118 sur – 57, Caldas, Antioquia, Colombia. Tel.: +57 4 320 1999x205. E-mail address: jorvilla@lasallistadocentes.edu.co (J.A. Villa). Contents lists available at ScienceDirect Ecohydrology & Hydrobiology jo u rn al h om ep age: w ww.els evier.c o m/lo c ate/ec oh yd http://dx.doi.org/10.1016/j.ecohyd.2014.07.005 1642-3593/ß 2014 European Regional Centre for Ecohydrology of Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.