季节性冻融对典型黑土区土壤团聚体特征的影响

以东北典型黑土区耕地土壤为研究对象,通过对不同水分补充条件下、不同频度和程度的冻融交替处理后土壤干筛团聚体和水稳性团聚体组成、破坏率(PAD0.25、PAD1.0)、平均质量直径(Dmm)、平均质量比表面积(SAmm)和分形维数(D)等特征指标的测定与分析,研究季节性冻融对典型黑土区表层土壤团聚体特征的影响.结果表明:无水无冻融及无水冻融显著增加了5mm干筛团聚体和0.25mm水稳性团聚体的含量,干筛和水稳性团聚体的Dmm分别较冻融前增加了7.98%～29.41%和36.11%～44.44%,SAmm、D的变化规律也表现为促进大团聚体的团聚作用.少水冻融和季节冻融则显著增加了2mm干筛团聚体和0.25～1mm水稳性团聚体的含量,Dmm、SAmm、D均表现出加剧风干团聚体拆分的趋势,水稳性团聚体的SAmm和D分别降低了10.88%～25.52%和1.02%～3.40%(P0.05),团聚作用有所增强.季节性冻融后PAD0.25降低了33.45%(P0.05),PAD1.0无明显变化,典型黑土区季节性冻融增强了土壤团聚体的水稳定性.

Effects of seasonal freeze-thaw cycle on soil aggregate characters in typical phaeozem region of Northeast China

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 (PAD_0.25, PAD_1.0), mean mass diameter (D_mm), mean mass soil surface area (SA_mm), 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 D_mm of the aggregates by 7.98%-29.41% and 36.11%-44.44%, respectively. The measurement of SA_mm 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 SA_mm 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 PAD_0.25 decreased by 33.45% (P<0.05) but PAD_1.0 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.