Open AccessHydrologic effects on methane dynamics in riparian wetlands in a temperate forest catchment
Author(s) -
Itoh Masayuki,
Ohte Nobuhito,
Koba Keisuke,
Katsuyama Masanori,
Hayamizu Kana,
Tani Makoto
Publication year - 2007
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jg000240
Subject(s) - biogeochemical cycle , environmental science , wetland , riparian zone , water table , hydrology (agriculture) , groundwater , temperate climate , soil water , subsurface flow , dissolved organic carbon , drainage basin , temperate forest , environmental chemistry , ecology , soil science , geology , chemistry , geotechnical engineering , cartography , habitat , geography , biology
To understand how hydrological processes affect biogeochemical and methane (CH 4 ) cycles in temperate riparian wetlands, we measured CH 4 fluxes and dissolved chemical constituents and CH 4 concentrations in groundwater, and monitored several environmental factors in wetlands located within a forested headwater catchment in a warm, humid climate in Japan. Variation in redox components dissolved in groundwater, including nitrate (NO 3 − ), Mn, Fe, and sulfate (SO 4 2− ), depended on temperature and soil‐water conditions. Strongly reducing conditions usually occurred in the high‐temperature months of July, August, and September. Dissolved CH 4 in groundwater changed with redox conditions and was highest in summer and lowest in winter. CH 4 emissions from riparian wetlands were observed almost throughout the year and displayed clear seasonality. Occasionally in summer, emission rates were more than 4 orders of magnitude greater than hillslope uptake rates. Although CH 4 emissions increased markedly during most of the summer, they were constrained by (1) fluctuation of the water table, which when lowered can shift the subsurface zone to a more oxidized condition, and (2) the oxygen‐rich water such as precipitation and lateral subsurface flow from the hillslope. These results suggest that hydrological processes in forest headwater catchments play an important role in supplying oxygen to soils and consequently affect biogeochemical cycles, including CH 4 formation, and that small wetlands in forest watersheds function as large sources of CH 4 , especially in regions with warm humid summers.