| The global saline-alkali soil accounts for about 7%of the total land area,saline-alkali soils are widely present in China,accounting for about 10% of the total land area.The study of CO2 and CH4 ffluxes in saline-alkali soils plays an important role in the global carbon cycle.However,the study of CO2 and CH4 ffluxes between saline-alkali soil and atmosphere is still relatively scarce,the source and sink of CO2 and CH4 in saline-alkali soils is not clear yet.Therefore,three kinds of soils with different salinity were selected in this study:non saline-alkali soil(NS),moderately saline-alkali soil(MS)and saline soil(SS).Through the undisturbed soil cores culture experiment,the CO2 and CH4 ffluxes of soils with different salinity degrees were measured by static opaque chamber-gas chromatography through undisturbed soil cores incubation experiment.The effects of soil temperature,soil moisture,soil salt content,p H value,ammonium nitrogen,nitrate nitrogen and dissolved organic carbon(DOC)on CO2 and CH4 ffluxes were investigated.The research results are helpful to determine the sources and sinks status of CO2 and CH4 ffluxes in saline-alkali soils and their influencing factors,provide data support for the estimation of regional saline-alkaline soil CO2 and CH4 ffluxes models,and help understand the soil carbon cycle of saline-alkali ecosystems.The important role in the global carbon cycle provides a theoretical basis for reducing the uncertainty of climate change predictions.The main research results are as follows:(1)In the temperature and moisture controlled incubation stage,the increase of salinity-alkalinity would inhibit the emission of CO2.the mean value of CO2 emission fflux of soils with different saline-alkali degrees were as follows:non saline-alkali soil(18.7±0.5mg Cm-2h-1)>moderately saline-alkali soil(15.5±0.6mg Cm-2h-1)>saline soil(5.2±0.3mg Cm-2h-1).Under the condition of freeze-thaw cycle incubation,the mean value CO2 emission ffluxes of soils with different salinities were as follows:non saline-alkali soil(12.5±0.6mg Cm-2h-1)>moderately saline-alkali soil(11.8±0.5mg Cm-2h-1)>saline soil(9.6±0.6mg Cm-2 h-1).(2)The increase of salinity will inhibit the absorption of CH4 y soil.In the incubation process of controlling temperature and moisture,the CH4 ptake fflux of soils with different saline alkali degrees were as follows:non saline-alkali soil(5.6±0.3?g Cm-2h-1)>moderately saline-alkali soil(2.3±0.6?g Cm-2h-1)>saline soil(0.9±0.3?g Cm-2h-1).In the process of freeze-thaw cycle incubation,the mean value of CH4 fflux in three different saline-alkali soils were non saline-alkali soil(-1.2±0.2?g Cm-2h-1),moderately saline-alkali soil(-0.4±0.2?g Cm-2h-1)and saline soil(0.7±0.2?g Cm-2h-1).(3)The increase of soil temperature will promote CO2 mission,but the increase of soil moisture will inhibit CO2 mission.The increase of temperature is conducive to the absorption of CH4 y soil,while soil moisture only affects the CH4 flux of non saline-alkali soil.There was a significant or extremely significant positive linear correlation between CO2 flux and soil moisture(p<0.05 or p<0.01).There was a significant or extremely significant linear negative correlation between CO2 flux and soil moisture(p<0.05 or p<0.01).In most treatments,CH4 flux decreases with the increase of soil temperature,which means that the increase of soil temperature is beneficial to the absorption of CH4 n soil.There was a significant positive correlation between CH4 flux and soil moisture only in non-saline alkali soil(p<0.05),and the increase of soil moisture inhibited the absorption of CH4 n non-saline-alkali soil.(4)The increase of soil DOC significantly promoted soil CO2 mission(p<0.05).Soil CO2 flux first increased and then decreased with the increase of soil ammonium nitrogen content,showing a univariate quadratic nonlinear correlation(p<0.05).With the increase of soil DOC,the absorption of CH4 ncreased,and the CH4 flux and DOC showed a very significant linear negative correlation(p<0.01).(5)The increase of soil conductivity and p H value will inhibit the emission of soil CO2(p<0.01).With the increase of soil conductivity,soil absorption of CH4 ecreased,and soil conductivity could explain 54% f CH4 flux(p<0.01).Among the combined effects of soil physical and chemical properties on CO2 and CH4 flux,soil conductivity(EC)and p H value are the main controlling factors affecting CO2 flux,and soil conductivity is the main controlling factor affecting CH4 flux. |
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