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Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration
Author(s) -
YU KEWEI,
FAULKNER STEPHEN P.,
BALDWIN MICHAEL J.
Publication year - 2008
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2008.01545.x
Subject(s) - swamp , environmental science , carbon dioxide , methane , water table , hydrology (agriculture) , nitrous oxide , sink (geography) , greenhouse gas , soil water , wetland , atmospheric sciences , environmental chemistry , soil science , chemistry , ecology , geology , groundwater , biology , geography , geotechnical engineering , cartography
This study was conducted at three locations in a bottomland hardwood forest with a distinct elevation and hydrological gradient: ridge (high, dry), transition, and swamp (low, wet). At each location, concentrations of soil greenhouse gases (N 2 O, CH 4 , and CO 2 ), their fluxes to the atmosphere, and soil redox potential (Eh) were measured bimonthly, while the water table was monitored every day. Results show that soil Eh was significantly ( P < 0.001) correlated with water table: a negative correlation at the ridge and transition locations, but a positive correlation at the permanently flooded swamp location. Both soil gas profile analysis and surface gas flux measurements indicated that the ridge and transition locations could be a sink of atmospheric CH 4 , especially in warm seasons, but generally functioned as a minor source of CH 4 in cool seasons. The swamp location was a major source of CH 4 , and the emission rate was higher in the warm seasons (mean 28 and median 23 mg m −2 h −1 ) than in the cool seasons (both mean and median 13 mg m −2 h −1 ). Average CO 2 emission rate was 251, 380 and 52 mg m −2 h −1 for the ridge, transition and swamp location, respectively. At each location, higher CO 2 emission rates were also found in the warm seasons. The lowest CO 2 emission rate was found at the swamp location, where soil C content was the highest, due to less microbial biomass, less CO 2 production in such an anaerobic environment, and greater difficulty of CO 2 diffusion to the atmosphere. Cumulative global warming potential emission from these three greenhouse gases was in an order of swamp > transition > ridge location. The ratio CO 2 /CH 4 production in soil is a critical factor for evaluating the overall benefit of soil C sequestration, which can be greatly offset by CH 4 production and emission.