冻融作用对松嫩平原草甸土物理性质的影响

The effect of freeze-thaw action on soil physical property of Songnen Grassland

冻融作用可改变土壤容重、孔隙度、团聚体稳定性,及饱和导水率等物理性质。本文设置冻融强度-15～25℃和-5～25℃,冻融循环次数0、1、3、5次和初始低含水率Lw 6.5%,高含水率Hw 17%三个变量,旨在从机理上分析草甸土物理性质对冻融作用的响应机制。结果表明:除土壤容重和孔隙度外,土壤团聚体稳定性和土壤饱和导水率均发生显著变化(P<0.05)。冻融作用使土壤容重和孔隙度分别呈现出减小和增大的趋势,随着冻融循环次数的增加,容重和孔隙度变化幅度逐渐减小,最后基本趋于稳定;冻融作用降低土壤团聚体稳定性,-15～25℃和-5～25℃条件下,分别在5次和3次达到稳定;冻融作用增加土壤饱和导水率,随着冻融循环次数的增加,土壤饱和导水率逐渐增加;相同条件下,冻融强度和含水率的增加均能使上述土壤物理性质指标变化更明显。

The physical properties of soil such as bulk density,porosity,aggregate stability and saturated hydraulic conductivity were affected by freee-thaw process.The freeze-thaw intensity(-15~25℃and-5~25℃),freeze-thaw cycles(0、1、3、5℃)and initial moisture content(6.5%,Lw;17%,Hw)were set in this paper to analyze the response mechanism of the physical properties of Grassland soil to freeze-thaw action.The results showed that the soil stability aggregates and the saturated hydraulic conductivity changed significantly(P<0.05)except for bulk density and porosity of soil.The soil bulk density was decreased and the soil porosity was increased by freeze-thaw process.With the increase of freeze-thaw cycles,the variation of soil bulk density and soil porosity decreased gradually,and tended to be stable status finally.The stability of soil aggregates was decreased by freee-thaw process,and reached stable status for 5 times at-15~25℃and 3 times at-5~25℃,respectively.The soil saturated hydraulic conductivity was increased by the freee-thaw process,and the soil saturated hydraulic conductivity increased gradually with the increase of freeze-thaw cycles.Under the same conditions,the changes of soil physical properties mentioned above became more obvious by the increasing of freeze-thaw intensity and soil moisture content.