Soil CH₄ Uptake In Winter Wheat Field In The North China Plain

Methane is an important greenhouse gas in the atmosphere , and the only known biological CH4 sink is the soil where methane trophic bacterium consume CH4 by oxidization . Experimental studies were conducted at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences during the period from March to June in 2003 . Respiration of a pulverous sandstone soil was studied under cultivation of winter wheat over a growth season . Soil CH4 was measured by the Static-Chamber method combined with Gas Chromatography (GC) technique .The results indicated that the soil of winter wheat field in rapid growth season is a weak sink of CH4. Uptake of CH4 by the soil showed an obvious seasonal and diurnal variation in this period of time . The mean value of CH4 fluxes was -18.3 μg.m-2.h-1 , the range of variation is from -4.3 to -24.4 μg.m-2.h-1; There were two peaks at the day time and the night time respectively , and the time of peaks varied with the change of wheat growth .The relationship between seasonal soil CH4 fluxes and soil temperature was not remarkable , but a closely negative correlation was found between soil CH4 fluxes and soil moisture (0~20mm) (r=0.7171, α=0.01?n= 15) ; The diurnal soil CH4 fiux was aiso closely related to temperature not of the soil surface but of 5cm depth .Soil CH4 fluxes would reduce with increase of NH4+ concentration , Straw's returning to fields , went against soil oxidation of CH4 . Wheat may increase soil CH4 uptake , which is the reason why more CH4 methanotrophs have been found around the roots of the plant.