Seasonal variation in rates of methane production from peat of various botanical origins: effects of temperature and substrate quality

The methane produced in pear soils can vary over the growing season due to variations in the supply of available substrate, the activity of the microb ial community or changes in temperature. Our aim was to study how these fac tors regulate the methane production over the season from five different pe at types of different botanical origin. Feat samples were collected on seve n occasions between June and September. After each sampling, the peat soils were incubated at five different temperatures (7, 10, 15, 20 and 25 degree s C) without added substrate, or at 20 degrees C with added substrate (gluc ose, or H-2/CO2, or starch). Rates of methane production averaged over the season differed significantly (P < 0.05, R-2 = 0.76) among the five peat ty pes, the minerotrophic lawn producing the highest rates, and the hummock pe at producing the lowest. The seasonal average Q(10) values for each plant c ommunity varied between 4.6 and 9.2, the highest value being associated wit h the ombrotrophic lawn and the lowest value with the mud-bottom plant comm unity. For the unamended pear samples, the rates of methane production from each plant community varied significantly (P < 0.05) over the season. This implies that the quality of organic matter, in combination with changes in temperature, explains the seasonal variation in methane production. Howeve r, addition of saturating amounts of glucose, H-2/CO2 or starch at 20 degre es C significantly reduced the seasonal variation (P < 0.05) in methane pro duction in peat from the minerotrophic lawn, wet carpet and mud-bottom plan t communities. This suggests that substrate supply (e.g. root exudates) for the micro-organisms also varied over the season at these sites. Seasonal v ariation in methane production rates was apparent in pear from the hummock and ombrotrophic lawn plant communities even after addition of substrates, suggesting that the active biomass of the anaerobic microbial populations a t these sites was regulated by other factors than the ones studied. (C) 200 0 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.