| At present, it has been the focus problem concerned by the whole society thatglobal change with global warming as the main indicator of the environment.Investigating its reason, it is mainly due to the increasing human activities thatresulting in atmospheric concentrations of greenhouse gases increased dramatically,atmospheric counter radiation enhancement, the greenhouse effect tend to seriousand global temperatures tend to rise. According to the assessment report ofIntergovernmental Panel on climate change, the carbon that land use change releasedinto the atmosphere is only less than the burning of fossil fuels released. Land usechange is one of the main human driving force in current biosphere carbon cycle,and has become the second adults carbon source which released to the atmosphere.The reserves of soil carbon is about2~3times than the carbon of atmospheric,while the soil carbon emissions (mainly soil respiration) is the main form of soilcarbon into the atmosphere. Because of the current research which domestic andinternational made is mostly focused on researching the ecological system of theland use change which has occurred and has tends to be stable, and is stillinsufficient in researching the type of short term effect of land use change. Therefore,our study is focused on the types of land use change conducted recently byconverting the long-term rice field into the orchard to explore the effect of land usechange on soil CO2and CH4flux in the typical soil and climatic conditions, so as tostudy the changing rules and its transformation mechanism of greenhouse gases andthe key carbon cycle in the process of the transformation.The research analyzed the experimental data from the small watershed ofAcademy of Sciences of the Chinese Qianyanzhou experimental station, and theresults show that the emission flux of soil CH4significantly reduced in the process ofthe land use patterns from paddy field to the orchard. The emission flux of CH4frompaddy field on fertilizing and unfertilizing treatment conditions were respectively7.40±1.61and5.86±1.30mg C m-2H-1, and after it became the orchard the CH4fluxeson the fertilization and unfertilization treatment were respectively0.03±0.01and0.02±0.01mg C m-2H-1.The result showing that fertilization can significantlypromoted the soil CH4emission of paddy while to the orchard, it is not that obvious.The soil CO2fluxes from paddy field on fertilizing and unfertilizing treatmentconditions were respectively153.8±13.2and115.1±8.6mg C m-2H-1, and after itbecame the orchard the CO2fluxes on the fertilization and unfertilization treatmentwere respectively130.1±9.9and116.9±6.4mg C m-2H-1. The soil CO2flux declineafter the land use patterns changed, but it is not obvious. For rice field and orchardplots, fertilization significantly promoted soil CO2emission.In the process of the transformation, two kinds of greenhouse gas emissions are both reduced, which canbe considered orchard have carbon sink function relative to the paddy fields,andmake the amount of greenhouse gases into the atmosphere decreased through soilrespiration. Therefore, the process of land use patterns from paddy field to the orchardhas slowed down the greenhouse effect, and is significant to the ecologicalenvironment. |
