The Influence of Intermittent Rainfall Conditions on the Pore Structure and Aggregate Turnover of Black Soil Topsoil

Abstract: [Objective]To investigate the effects of intermittent rainfall conditions on pore structure and aggregate turnover in the black soil topsoil. [Methods]Black soil topsoil was selected as research object, using a combination of rare earth element tracer method + artificial rainfall simulation + CT scanning research method. To elucidate the response of topsoil aggregate characteristics, turnover characteristics of topsoil aggregates, and topsoil pore characteristics to rainfall intensity and number of rainfall events. [Results]Under intermittent rainfall conditions, isolated pores are concentrated in the topsoil layer. With the increase in the number of rainfall events, the connected porosity was always greater than the isolated porosity at a rainfall intensity of 40 mm/h, and the maximum values of connected porosity and isolated porosity alternated at a rainfall intensity of 70 mm/h. For large aggregates, as the number of rainfall events increases，when the connecting porosity decreases，the ability of 5-2 mm aggregates to break up into 0.25-0.053 mm aggregates becomes smaller, and the ability of 5-2 mm aggregates to break up into <0.053 mm aggregates increases . The opposite was true when the connectivity porosity increased. For small aggregates, as the number of rainfall events increases，the ability of 0.25-0.053 mm aggregates to break into <0.053 mm aggregates is stronger, while the ability of <0.053 mm aggregates to aggregate to form 0.25-0.053 mm aggregates decreases gradually. [Conclusion]With the increase in the number of intermittent rainfall, isolated pores were concentrated in the soil top layer, while the ability of large aggregates to gradually break up into small particle sizes gradually increased, but the ability of small aggregates to form large aggregates gradually decreased.

Keywords：intermittent rainfall；pore structure；aggregate turnover；rare earth element；CT scanning