Recovery of Methanogenesis Following Summer Drought in Soils from Two Cool Temperate Peatlands, New York State, USA

Abstract

Following a summer drought, intact cores of peat soil from two cool temperate peatlands (a rain-fed bog and a groundwater-fed swamp) were exposed experimentally to three different water table levels. The goal was to examine recovery of anaerobic methanogenesis and to evaluate peat soil decomposition to methane (CH4), carbon dioxide (CO2), and dissolved organic carbon (DOC) upon rewetting. Methane emission from soils to the atmosphere was greatest (mean = 80 μmol m−2 s−1) when the entire peat core was rewetted quickly; emission was negligible at low water level and when peat cores were rewetted gradually. Rates of CO2 emission (mean = 1.0 μmol m−2 s−1) were relatively insensitive to water level. Concentrations of CH4 in soil air spaces suggest that onset of methanogenesis induces, but later represses, aerobic oxidation of CH4 above the water table. Concentrations of CO2 suggest production at the soil surface of swamp peat versus at greater depths in bog peat. Portions of peat soil incubated in vitro without oxygen (O2) exhibited a lag before the onset of methanogenesis, and the lag time was less in peat from the cores rewetted quickly. The inhibition of methanogenesis by the selective inhibitor 2-bromoethanesulfonic acid (BES) decreased CO2 production by 20 to 30% but resulted in an increase in concentrations of DOC by 2 to 5 times. The results show that methanogens in peat soils tolerate moderate drought, and recovery varies among different peat types. In peat soils, the inhibition of methanogenesis might enhance DOC availability.