田间含碎石土壤水分入渗及再分布试验研究

Field Experiment on Water Infiltration and Water Redistribution of Soil Containing Rock Fragments under Simulated Rainfall

为探明碎石存在于田间土壤中如何改变土壤水分运移通道、影响土壤水分运动,揭示田间含碎石土壤水分运动的复杂过程,采用便携式针头降雨器在铜川崾岘梁修建的临时小区进行模拟降雨实验,测定含碎石浅层土体的入渗和水分再分布过程,采用土壤水分运动通量法计算浅层土体不同深度各截面面积的水量在雨后不同时间段的变化,分析含碎石土壤再分布特征及碎石含量对浅层土体入渗和水分再分布的影响。结果表明:碎石有利于田间浅层土壤入渗和蓄存;室内较田间测定的含碎石土壤入渗率小一个数量级以上;降雨后较短时段,碎石含量相对高的林地小区的浅层土体水分在降雨停止后呈增加趋势,表现了蓄水过程,碎石含量较低的撂荒地则表现了释水过程;降雨后较长时段,多数小区浅层土体(0-30 cm)水量变化呈现了"排水-存储交换-排水"过程,少数小区仅呈现了"排水"过程;雨后16 h左右的土体各截面面积的水量与碎石含量呈现了以直线y=0.4873为轴对称的递增和递减的指数为1/2的幂函数关系,说明碎石对黄土区典型土石区土体水分运动具有促进和阻滞双面影响。本文的研究结果可为含碎石土壤的水分利用及水分循环提供参考。

Water flow path in the soil was changed by rock fragments then soil water movement was influenced,and that became more complex especially for the field soil containing rock fragments.In order to reveal the effects of rock fragments in shallow layer on soil water infiltration and redistribution,the simulated rainfall was conducted on the soil containing different rock fragment content in Yaoxian Mountain,Shaanxi,and the one dimensional vertical soil column infiltration was performed in the laboratory.After the rainfall,the dynamic of soil water content was measured by TDR and the variation of water quantity was calculated by surface-flux method.The results show that： rock fragments may facilitate the water infiltration of the shallow soil in the field.The data about infiltration of soil containing rock fragments investigated in the laboratory and field have a great difference;the infiltration rate measured in the field is larger one order of magnitude than that measured in the laboratory for the soil containing similar rock fragment content.The shallow soil water content of artificial forestland with higher proportion of rock fragments presents an increasing trend in the 30 minutes after raining,while that of abandoned land is opposite.For most plots,the change of water quantity in the shallow soil（0-30 cm） reflect a general rule of water redistribution which is from draining to storage-exchange to draining,while other plots present draining process only.The data of curve-regression analysis indicate that the relationship between the percentage of rock fragments and water quantity about 16 hours after raining can be described by power functions of exponent 1/2 with axial symmetry on y=0.4873.It can be concluded that there were both positive and negative effects of rock fragments on soil water movement.These results may provide some references for water cycling and high efficiency of water utilization in mountain area containing rock fragments which is popular on loess plateau of China.