An Experimental And Simulated Study On The Effects Of Erosion On Soil Organic Carbon And Its Stability In Red-yellow Soil

Since the global food crisis in the middle and late of the last century,people have attached great importance to the loss of productivity caused by soil erosion.The content and stability of soil organic carbon is not only an important evaluation index of soil productivity,but also the key to evaluate soil carbon pool.However,there are few studies on the effect of erosion on the content and stability of organic carbon in red-yellow soil.In this study,a simulated plot with different erosion thickness was constructed based on the method of soil cutting and soil mixing.The effects of erosion on the content and stability of soil organic carbon in red-yellow soil were monitored and analyzed.The main results are as follows:（1）The soil organic carbon content of red-yellow soil decreased significantly with the increase of erosion thickness.In the early stage of simulation plot construction（2012）and years after planting（2018）,the soil organic carbon content showed a very significant decrease trend with the increase of erosion thickness,and the intensity of organic carbon loss was-0.24 g C kg^-1 cm^-1 and-0.11 g C kg^-1 cm^-1,respectively.The regression coefficient（R²=0.56,P<0.01 in 2012）between the erosion thickness at the initial stage of construction and the loss of soil organic carbon erosion is smaller than that after years of planting（R²=0.66,P<0.01 in 2018）.In 2018,the correlation between organic carbon and physical and chemical properties of erosion simulation plot was stronger than that in the early stage of plot construction（2012）.It shows that the initial stage of simulated erosion plot construction is greatly disturbed by human,and it needs a certain time to monitor the dynamic changes of organic carbon to ensure the reliability of artificial erosion plot construction.（2）Soil erosion reduced the physical stability of soil organic carbon in red yellow soil.The content of 0.25～0.053 mm microaggregate in yellow red soil was the smallest,only 5.78～10.67%,and decreased significantly with the increase of erosion thickness.>The organic carbon content of 2 mm（large aggregate）,2～0.25 mm（middle aggregate）,and<0.053 mm powder+clay aggregate decreased with the increase of erosion thickness,while the protection ability of small aggregate to organic carbon was low,while the erosion thickness was negatively related to the organic carbon content of aggregate,indicating that soil erosion could reduce the physical stability of organic carbon in red-yellow soil.（3）Soil erosion affects the content of soil organic carbon functional groups and reduces the chemical stability of organic carbon.Among the organic carbon functional groups in each erosion plot,the easily decomposed and unstable methoxy carbon and dioxo alkyl carbon increase with the increase of erosion thickness,indicating that organic carbon decomposes rapidly;the non easily decomposed and stable phenolic carbon decreases gradually with the increase of erosion thickness,indicating that the content of organic carbon functional groups decreases;the ratio of hydrophobic carbon to hydrophilic carbon is larger,and the ratio of alkylcarbon to oxoalkyl carbon is smaller The results showed that the chemical stability of soil organic carbon decreased with the increase of erosion thickness.In summary,erosion can reduce the organic carbon content of red-yellow soils.It takes many years of experiment to construct erosion plots using artificial simulation methods to eliminate the effects of artificial disturbances and obtain reliable results of the impact of erosion on soil performance.This paper reveals the influence of erosion on the physical and chemical stability of soil organic carbon in the yellow-red soil area by monitoring the changes of soil aggregates and organic carbon functional groups in the red-yellow soil under different erosion thicknesses.Provide references for degradation prevention and protection of organic carbon in cultivated land.