[Soil N2O flux and its affecting factors under different vegetations in central Guizhou Province]

By using close chamber-GC method, the N2O fluxes in de-farming grassland, bush land, Pinus massoniana forestland, and broadleaved forestland in central Guizhou were measured in situ in 2006 and 2007 to investigate the seasonal change patterns of soil N2 O flux under different vegetations in karst region of southwest China. The results indicated that in a whole year round, the soils in all test sites played the source of atmospheric N2O, only acting as a N2O sink in exceptional months. The soil type and the vegetation had obvious effets on the N2O flux from soil. Yellow soil had a smaller N2O flux than calcareous soil, except for broadleaved forestland. The N2O fluxes from de-farming grassland and bush land were higher in spring and lower in autumn and winter, and varied within the range of -20.7 - 103.09 microg N x m(-2) x h(-1) and -33.0-67.3 microg N x m(-2) x h(-1), respectively; while those from P. massoniana forestland and broadleaved forestland were the highest in spring but had no definite change patterns in other seasons, and varied within the range of -5.3 - 35.0 microg N x m(-2) x h(-1) and -14.4 - 152.8 microg N x m(-2) x h(-1), respectively. The correlation analysis showed that there existed a negative correlation between soil moisture content and N2O flux, suggesting that soil moisture was the main factor driving the seasonal change of N2O flux. Temperature indirectly affected the soil N2O flux through affecting soil moisture.