Abstract: In a simulated rainfall experiment, the microstructure, bulk density, and shear strength of black soil were determined to study the development process of crust during rainfall, and the effects of the crust on soil infiltration. The results showed that with the process of rainfall, surface soil layer became compact, soil shear strength and bulk density increased, and infiltration decreased. In a period of 120 minutes rainfall, a stable crust layer in 3-4 mm thickness formed, whose bulk density increased by 14.13% and porosity decreased by 6.45%. The removal of raindrop beat weakened the development of crust, with soil porosity decreased by 3.27%, bulk density increased by 7.11%, and accumulated infiltration increased by 41.1%. The black soil in Northeast China had a stable soil structure, and raindrop beat was the dominant factor resulting in the development of crust. During the process of rainfall, no obvious eluviation was observed.

Key words: Aphidius gifuensis, Schizaphis graminum, fluctuating thermal regime, cold tolerance, supercooling point (SCP), energy substance.