Effects of seasonal freeze-thaw cycle on soil aggregate characters in typical phaeozem region of Northeast China.
季节性冻融对典型黑土区土壤团聚体特征的影响

Taking the cropland soil in typical phaeozem region of Northeast China as test object, this paper analyzed its dry-sieved and water-stable aggregates composition, disruption rate (PAD0.25, PAD1.0), mean mass diameter (Dmm), mean mass soil surface area (SAmm), and fractal dimension (D) under different water supplement and different frequency and rate of freeze-thaw cycle, aimed to study the effects of seasonal freeze-thaw cycle on the top soil aggregate characters in the region. No water supplement plus no freeze-thaw cycle and no water supplement plus freeze-thaw cycle increased the amounts of >5 mm dry-sieved and >0.25 mm water-stable aggregates significantly, and the Dmm of the aggregates by 7.98%-29.41% and 36.11%-44.44%, respectively. The measurement of SAmm and D also indicated the promotion of the aggregation of macroaggregates. However, smaller water supplement plus freeze-thaw cycle and seasonal freeze-thaw cycle increased the amounts of <2 mm dry-sieved aggregates and 0.25-1 mm water-stable aggregates significantly, accelerated the disruption of air-dried aggregates, and decreased the SAmm and D of water-stable aggregates by 10.88%-25.52% and 1.02%-3.40%, respectively, indicating that aggregation was somewhat promoted. After seasonal freeze-thaw cycle, the PAD0.25 decreased by 33.45% (P<0.05) but PAD1.0 had less change, suggesting that the seasonal freeze-thaw cycle in typical phaeozem region did not weaken soil splash-resistibility, while strengthened the water-stability of soil aggregates.