Abstract: Based on the direct measurements of annual N₂O emission from 207 field experiments reported in literatures between 1982 and 2003,this paper established a database of annual N₂O emission from agricultural fields.Correlation analysis indicated that the N₂O emission from agricultural soils was significantly correlated with climatic factors temperature and precipitation,while no significant correlations were observed between N₂O emission and edaphic parameters pH,organic carbon and nitrogen.According to the definition of N₂O emission factor and its quantification by the Intergovernmental Panel on Climate Change,the N₂O emission factor was modified by annual mean temperature and annual precipitation,respectively. The results suggested that the modification with precipitation might significantly reduce the estimated error of N₂O emission by about 16%,while that with temperature did not reduce the error,in comparison with the default emission factor by the Intergovernmental Panel on Climate Change.

Key words: 16S rRNA, Oligonucleotide probes, Quantitative hybridization, Microbial ecology