| The daily variation characteristics of soil N2O and CO2emission fluxes from four land use types, dominantly composed of natural secondary forest, Scots pine(Pinus sylvestris var.mongolica), grassland and farmland respectively in typical black soil region were studied by using the method of static chamber-gas chromatographic techniques, based on the observation of N2O and CO2emission continually for24h in the original location. On this basis, the black soil area of farmland as the research object, Use the indoor simulation method to study the different freeze-thaw cycles and the early stage of the different water content on the influence of CO2and N2O and CH4emission, and under different soil water content before and after freezing and thawing process measured the changes of soil physical and chemical properties as well as the correlation of the change of CO2and N2O and CH4emission analysis, thus provide the reference for scientific evaluation and measurement black soil area the ecological function of vegetation restoration, and provide the basis for further research under the action of freezing and thawing characteristics of black soil in greenhouse gases emission.The result showed that the daily emission fluxes of soil CO2under four plots all showed a single-peaked curve with a variation range of352.7～938.3mg·m-2·h-1from08:00am to06:00am the next day which in natural secondary forest and Scots pine were higher to maintain a high level, following from grassland and farmland was lower significantly than from others (p<0.05). The daily emission fluxes of soil N2O also showed a single-peaked curve, and varied from21.4to159.6μg·m-2·h-1which was significantly higher in farmland than that in other three plots (p<0.05). Compared with soil water content, soil CO2and N2O emission fluxes were correlated more significantly with soil temperature, indicating that soil temperature was the main factor for soil CO2and N2O emission fluxes in typical black soil region. The results could provide reference for studying soil greenhouse gases emission characteristics and evaluating and measuring ecological function of vegetation restoration in typical black soil region.After three times and nine times freeze-thaw simulated cycle treatment, the accumulated soil CO2emission fluxes are respectively higher than no freeze-thaw cycle simulated cycle treatment1.69times and1.49times(p<0.05), and the amplitude of rised soil CO2emission fluxes are decreased with the increase of freeze-thaw cycles. For the soil N2O emission fluxes, two kinds of freezing and thawing simulated cycle cumulatived soil N2O emission fluxes are significantly higher than no freezing and thawing circulation processing soil accumulated N2O emission fluxes (p<0.05), and the amplitude of rised soil N2O emission fluxes are decreased with the increase of freeze-thaw cycles. After three times and nine times freeze-thaw simulated cycle treatment, the accumulated soil N2O emission fluxes are respectively higher than no freeze-thaw cycle simulated cycle treatment1.56times and1.24times (p<0.05). The influence of the freeze-thaw cycle effect on soil CH4emission was also significant. The amplitude of rised soil CO2emission fluxes are increased with the increase of freeze-thaw cycles and the soil CH4emission fluxes of nine times freeze-thaw circulation processing is higher than three times freeze-thaw circulation processing and no freeze and thaw treatment5.18times and14.94times (p<0.05).It can be consider that freeze-thaw event can effect the greenhouse gases emissions from the soil in typical black soil region.In three treatments of soil water content, the content of>5mm dry aggregate are decreased with the increasing freeze-thaw cycles, and the content of2-5mm dry aggregate are opposite to the>5mm dry aggregate. The early stage of the water content can only significantly effect<5mm water stability of aggregate distribution ratio (p<0.05), and dry aggregates are more sensitive by freezing and thawing; With the increasing times of freeze-thaw cycles, the content of soil pH and total nitroge are decreased; NO3content is increased; NH4+and soil organic matter contents are to increase after the fall, but are higher than no freezing and thawing cycle treatment. Soil CO2emissions have high correlations with soil organic matter content, but no significantly; Soil N2O emissions and soil NH4+content are significant negative correlation (p<0.05); Soil CH4emissions and soil pH value are significant negative correlation(p<0.01)and are significantly correlated with the soil NO3-content(p<0.05)... |
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