The Characteristics Of Study On Soil Greenhouse Gas Emission In Different Recovery Stages Of Changting Soil Erosion Area

There are serious water and soil erosion problems in red soil area of southern China,and vegetation recovering has been carried out widely for a long time.Due to the global climate change,the increase of extreme rainfall events has resulted in more and more common soil dry and wet alternation.Drought-wetting-redrying-repeated cycles affect the process of carbon and nitrogen of forest ecosystems,which then have a certain impact on greenhouse gas emission.However,the response of soil greenhouse gas emission to dry and wet alternation at different vegetation recovery stages has not been fully understood.Therefore,the soil at different vegetation recovery stages of Changting soil erosion areas was taken as the main research object in this paper,and indoor experiments were carried out,which set up different moisture gradient?20%,60%and100%?,dry and wet alternation and constant humidity?40%?to study on the dynamic change of greenhouse gas rate in soil.The soil greenhouse gases?CO₂,CH₄ and N₂O?at different recovery stages were indoor observed regularly,which further discovered the characteristics of greenhouse gas emissions and the law of its dynamic change.On this basis,the characteristics of soil greenhouse gas emission and its impact factors which the dry and wet alternation was imposed on at different vegetation recovery stages were analyzed and studied.The main results were as follows:1.At different vegetation recovery stages,the CO₂ emission rate of the soil and dry and wet alternate soil were both positive.The average emission rate of soil CO₂ and dry and wet alternate soil CO₂ at different vegetation recovery stages was 30 years recovery forest>natural forest>20 years recovery forest>10 years recovery forest>bare land,but at the initial stage,the order of dry and wet alternate soil CO₂ emissions rate was natural forest>30 years recovery forest>20 years recovery forest>10 years recovery forest>bare land,and there was significant difference?P<0.05?.2.It was found that there were both emission and absorption concerning CH₄ of the soil and dry and wet alternate soil at different vegetation recovery stages through the study.The average rate of soil CH₄ emission of the soil and dry and wet alternate soil at different vegetation recovery stages is the same as that of CO₂.On the one hand,the soil CH₄ of bare land,10 years recovery forest,20 years recovery forest was in a net absorption state,that is,the soil was the "converge" of CH₄.On the other hand,the soil CH₄ of 30 years recovery forest and natural forest was in a net emission state,that is,the soil was the "source" of CH₄.3.The study showed that both emission and absorption were discovered referring to N₂O of the soil and dry and wet alternate soil at different vegetation recovery stages,and in the dry and wet alternate treatment,the order of N₂O accumulative emission was bare land>20 years recovery forest>natural forest>30 years recovery forest>10 years recovery forest,which had already taken place great changes,compared with the temperature and humidity treatment.Among them,there was a significant increase in the accumulative emission of forest N₂O in the bare land,10 years recovery forest and 20 years recovery forest,and the emission of humidification treatment was 2-7 times that of the dry-wet alternating treatment.30 years recovery forest was basically unchanged,and the emission of natural forests decreased by more than 40%.4.It was found that the characteristics of soil greenhouse gas?CO₂,CH₄ and N₂O?emission and their impact factors were not consistent between the soil and dry and wet alternate soil at different vegetation recovery stages,which might relate emission to soil moisture.By fitting analysis,it was discovered that there was significant difference?P<0.05?between CO₂,CH₄ and N₂O emission and moisture of the soil and dry and wet alternate soil at different vegetation recovery stages.All the forests except bare land and 10 years recovery forest were demonstrated that there were significant differences in CO₂ and N₂O emission and the soil moisture,and there was no significant difference in CH₄ emission except for the 20-year restoration forest?P<0.05?.