| Nitrous oxide (N2O) is a one of the major greenhouse gases and has a296-fold higher greenhouse effect than carbon dioxide (CO2), the emission of N2O from agricultural soil has become one of the most concerns to global scientific researchers. Different soil use types have effect on N2O through different soil organic carbon and nitrogen content. The other influence factors of soil N2O emissions are maily environment factors, such as soil temperature, soil moisture, and etc. It is very important to research on different soil use types N2O emission, mechanism, impact facter and reducing measure.This study was carried out in Xianning red soil Area. We examined soil N2O and CO2fluxes and the relationship obtained by environmental factors in different land use types of woodland, tea garden and upland. We also set up an incubation experiment to explore the affect of upland soil N2O and CO2emission with the addition of glucose, sucrose, citric acid and mannitol in52%WFPS and81%WFPS. The results of this study are presented as follows:1) Significant seasonal differences of N2O and CO2fluxes were observed from all across the years in three land use types. Except for tea garden, in the other two types, soil N2O emission showed maximum in Summer and lowest in Winter. Soil N2O and CO2fluxes were significantly higher in hot-humid season as compared to cool-dry season, as was approximately consistent with the changes of air and soil temperature.2)The range of viaration of N2O emission was-6.31～391.29μg/(m2·h) in woodland,-22.71～470.53μg/(m2·h) in tea garden and-15.47～953.86μg/(m2·h) in upland, the average flux indicated upland>tea garden>woodland. The range of viaration of CO2emission was18.82～257.83mg/(m2·h) in woodland,14.55～127.84mg/(m2·h) in tea garden and13.05～349.95mg/(m2·h) in upland, the average flux showed upland> woodland> tea garden.3) Soil N2O emissions were positively correlated with CO2emissions in upland soil, R2was0.588, no obviously relationship was found in woodland and tea garden. But the relationship was found in woodland when soil NH4+-N content was more than20mg/kg, R2was0.29, in tea garden the positively relationship was found between soil N2O and CO2emissions when soil NH4+-N content was less than20mg/kg, R2was0.312. When the DOC content was more than70mg/kg, N2O flux and DOC content had significant or highly significant correlationship, R2were0.274,0.138and0.313for woodland, tea garden and upland.4) The results demonstrated that the N2O fluxes in upland have significant differences with the addition of four kind of carbon sources, and the water content had significant influence on N2O. For the low and high WFPS rates, the ranges of N2O emissions of glucose, sucrose, citric acid and mannitol respectively are0～42.03and0～407.59μg/(kg·h),0.02～42.71and-0.04～326.86μg/(kg·h),0.02～2.28and0.03～124.92μg/(kg·h),-0.02～5.99and0.03～282.7μg/(kg·h). Cumulative emissions of N2O from soil after application of the four carbon sources are0.59,0.66,0.07,0.16mg/kg at52%WFPS and13.2,7.35,6.73,13mg/kg at81%WFPS during incubation time.5) After the addition of different soluble carbon in upland soil, water content had significant effect in the relationship between soil N2O and CO2emissions. Soi N2O and CO2emissions had significant or highly significant correlation relationships in four soluble carbon addition soil in52%WFPS during the incubation time. R2were0.989,0.906,0.943and0.788. Howerver, in81%WFPS soils, we only found the relationship between soil N2O and CO2emissions in control treatment which was not added carbon source, R2was0.565. |
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