[Responses of soil structure to seasonal freezing-thawing in a typical black soil cultivated region].

Taking the soil in a typical black soil cultivated region as test object, this paper analyzed its aggregate size distribution, wedge resistance, bulk density, porosity, saturation degree, and generalized structure index after a seasonal freezing-thawing cycle, and evaluated the effects of the freezing-thawing cycle on the soil structural characters. The seasonal freezing-thawing cycle aggravated the disruption of air-dried aggregates, but strengthened the aggregation of water-stable aggregates and lowered their destruction rate. After the freezing-thawing cycle, soil wedge resistance decreased by 15.45%, and soil bulk density remained relatively constant from 1.10 to 1.11 g x cm(-3). The volume percent of soil solid phase increased, and soil total porosity and capillary porosity decreased to different degree. Soil saturation degree was improved by 13.06%, which in turn decreased the soil potential storage capacity. Seasonal freezing-thawing cycle improved the soil structure and soil arability and increased the erosion resistance of soil aggregates, but decreased the soil erosion resistance and increased the risk of the water erosion of black soil.