Effects Of Rainfall Erosion On Stability Of Soil Aggregate And Mineralizatin Of Organic Catbon Nad Nitrogen

Soil erosion is one of the main driving forces of the surface process,and it is also one of the most severe environmental problems faced by human society.It has important influence on the major processes and service functions of the ecosystem.The formation of soil aggregates can not only improve soil erosion resistance,but also have important physical protection effects on soil carbon and nitrogen and play an important role in erosion.Rainfall erosion often results in the dispersion of soil aggregates and the loss of fine particles in the soil,which affects the soil ecological function of aggregates.However,the current response to agglomerate stability and its carbon and nitrogen mineralization characteristics in response to rainfall erosion is unclear.In this paper,the loess plateau and soils in different locations in Heilongjiang,Jiangxi,and Sichuan are taken as the research object,and the distribution characteristics of soil aggregates,the carbon and nitrogen content of aggregates and their mineralization characteristics before and after rainfall erosion are analyzed,and the soil is analyzed.The relationship between texture and land use and these responses was used to establish the impact of rainfall erosion on the aggregate carbon and nitrogen processes.The main conclusions obtained are as follows:(1)Rainfall erosion reduces the relative content of smaller aggregates and increases the relative content of larger aggregates,which is related to soil texture and land use types.As the soil texture becomes coarser,the loss of small aggregates and the increase of large aggregates gradually increase.Rainfall erosion reduces the aggregate stability.However,the decrease gradually decreases with the soil texture changed from coarse to fine.(2)Rainfall erosion significantly reduced the content of organic carbon and total nitrogen in soil and water-stable aggregates,which was related to the loss of soluble carbon and nitrogen and loss of carbon and nitrogen mineralization during rainfall erosion.The degree of carbon and nitrogen loss in soils and aggregates after erosion is affected by land use types and has nothing to do with the soil texture.In general,the absolute amount of soil and aggregate carbon and nitrogen losses is higher in woodland,and grassland and farmland are close.Soil and aggregates in different textures have similar carbon and nitrogen losses.In all soils,<0.25 mm aggregates contributed most to soil carbon and nitrogen,but different grades of aggregates contributed similarly to soil carbon and nitrogen losses after rainfall erosion.(3)Soil carbon and nitrogen mineralization are reduced significantly after rainfall erosion,which is related to loss of mineralizable carbon and nitrogen during soil erosion.Rainfall erosion reduced organic carbon mineralization and nitrogen net mineralization decreased by 80-95% and 3-72% under different soil textures.The reduction of soil N mineralization was mainly caused by the reducing in nitrification.In addition,the amount of soil organic carbon and nitrogen mineralization in the eroded farmland and woodland decreased more,but the grassland decreased more.The impact of this land use type was also related to the study site.(4)Rainfall erosion significantly reduced the mineralization of organic nitrogen in most aggregates,with a decrease in 1-0.25 mm and <0.25 mm grade aggregates and less decrease in >2 mm and 2-1 mm grade aggregates.The reduction of aggregate organic carbon mineralization and nitrogen net mineralization after rainfall erosion has nothing to do with soil texture,but is related to land use types.After the rainfall erosion,the organic carbon mineralization of 1-0.25 mm aggregates was reduced,and the reduction of organic carbon mineralization in all grades of aggregates was dominated by grassland and agricultural land.All the 0.25 mm aggregates had the least decrease in the grassland soil,while the <0.25 mm aggregates had the least decrease in the farmland soil;all the grades of the aggregate nitrogen mineralization decreased more in forestland soils.