| Methane and nitrous oxide were two of the most important green-house gases after carbon dioxide. Papers about methane and nitrous oxide were concerning in bare land soil and the effect factors up today. Almost no information was on the nitrous oxide and methane fluxes from greenhouse soil and its microbiological mechanisms. Therefore, it was valuable to observe the fluxes of methane and nitrous oxide from green-house soil and demonstrate its microbiological mechanisms.This paper deals with the fluxes of nitrous oxide from green-house soil, the methane oxidation by the soil, and microbiological mechanisms. The results obtained were reported as the followings:1) It showed that the flux of N2O from the greenhouse was much higher than that from the bare land. The fluctuation of the flux related to the seasonal change. Irrigation could stimulate the N2O flux and the population of denitrifiers, however, inhibited the population of nitrifiers in the soil at 0-15cm of depth. The N2O flux was much higher (about 2 fold) in urea-applied soil than in the CK (without urea). The decrease of populations of the nitrifiers and denitrifiers was observed in urea-applied soil plots at same time. The controlled-releasing urea could not significantly stimulate the flux of N2O. The flux of N2O was up to the maximum at pH 7.3 of soil. Glucose could obviously increase the flux of N2O among the carbon sources detected. That the methane-oxidizing bacteria probably were also one of microbiological populations producing N2O was proposed, based on research work.2) Methane oxidation ability of green-house soil was detected. The results showed that methane oxidation ability was different in various soil and possibly it was related to the basic properties of the soil. Microorganisms were responsible tomethane oxidation. The water content of soil could influence methane oxidation dramatically. N sources (including organic and inorganic N tested) and C sources tested could restrain methane oxidation. Cellulose inhibited methane oxidation most weakly while the high concentration of methanol and glucose did dramatically, but the proper concentration of methanol could stimulate soil methane oxidation sharply. In the middle process of methane oxidation, addition of glucose could restrain methane oxidation shortly but the inhibition could be relieved about 5 days later when supplied again with enough oxygen. The utilization of C sources by a methanotrophic isolate from the soil was also detected. It was supposed that the facultative methanotrophs might be dominant for methane oxidation as methane released weakly in the greenhouse soil. 3) A heterotrophic nitrifier, named strain HN, was isolated from the greenhouse soil. The cells of isolates were Gram positive, rod or coccus. The clones of the strain were orange-red. Strain HN could ammonize organic nitrogen compounds and nitrify ammonia itself when it grew on acetamide companying the formation of ammonia and nitrite. It also could denitrify nitrate companying the formation of nitrite. The phylogentic analysis based on 16S rRAN suggested strain HN was the closest relative of Rhococcus n/berwith 99% sequence identity. The phylogenetic analysis of strain HN was performed by PHYLIPS and the phylogenetic tree of strain HN and the neighbouring nitrifiers was given.
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