Soil Aggregates And Organic Carbon Fractions Under Agroforestry Systems In Yellow River Flood Plain Of China

The Yellow River Flood Plain is the accumulated sandy land formed by the successive flooding,diversion and siltation of the Yellow River and the sediment transported and deposited by the wind along the river.Wind erosion and desertification driven by the strong wind in winter and spring coupled with the bare surface is one of the most important environmental problems in this area.Soil wind erosion not only causes low and unstable land productivity and restricts local economic development,but also affects the carbon storage of soil carbon pool,the largest carbon pool in the region.Soil organic carbon stability,soil aggregate and organic carbon components are closely related.Agroforestry is one of the important systems of agricultural and forestry industry development in the region.The study on soil aggregate stability and organic carbon fractions in different agroforestry systems is of great significance to the study of soil organic carbon stability,carbon cycle and carbon sequestration.In this study,the characteristics of soil aggregates and organic carbon components under different agroforestry systems were investigated by field sampling and indoor quantitative analysis on the ash plantation and understory crops under different agroforestry patterns in Dongming Forest Farm,Shandong Province.In order to further reveal the effects of agroforestry systems(white ash and soybean,white ash and peanut,white ash and chrysanthemum)on soil aggregates and organic carbon components in the Yellow River Flood Plain,and provide a basis for the evaluation of soil quality and soil carbon storage in different agroforestry systems and the selection of models.The main conclusions were as follows:(1)Soil physical and chemical properties were significantly different under different agroforestry patterns.Sand is the main component of soil particles in yellow flood sandy land,accounting for 79.13% on average.The contents of soil organic carbon,total nitrogen and carbon storage in different agroforestry patterns decreased with the increase of soil depth in0-60 cm soil layer.(2)Different agroforestry systems could improve the stability of soil aggregates and improve soil structure.The distribution and stability of soil aggregates differed significantly under different agroforestry systems.The MWD and GMD contents of soil macroaggregates in agroforestry were significantly higher than those in pure ash forest.The MWD and GMD of ash and soybean in different agroforestry systems were significantly higher than those of the other three treatments,showing higher aggregate stability.(3)Soil organic carbon fractions in different agroforestry systems decreased with the increase of soil depth in the Yellow River Flood Plain,reflecting a certain "surface aggregation".Soil organic carbon fractions differed significantly under different agroforestry systems.The active and resistant carbon fractions of soil in different agroforestry systems were as follows: ash and soybean > ash and peanut > ash and chrysanthemum.The CPMI value also indicated that ash and soybean had higher carbon sequestration efficiency.(4)RDA results showed that the soil physicochemical properties had significant effects on soil aggregate and organic carbon,soil aggregate distribution and aggregate stability and C/N,sticky powder,SOC,TN and part of organic carbon was significantly positively related to soil organic carbon composition and p H,C/N negative correlation,sand content,soil organic carbon fractions contribute to the formation of large aggregates,enhance the stability of large aggregates.SEM results showed that soil organic carbon storage in Yellow River Flood Plain was affected by physicochemical properties,aggregates,active carbon fractions and resistant carbon fractions,among which resistant carbon fractions directly affected the organic carbon storage,which was the key factor to determine the soil organic carbon storage in Yellow River Flood Plain.