陇东黄土高原土壤干旱特征分析

通过对黄土高原典型残塬"董志塬"麦田不同时期土壤各层次水分含量的分析,揭示了陇东黄土高原塬区土壤干旱特征,逐月分析了干旱的季节分布以及不同季节水分在土壤各层次的分布特征。分析认为2m土层干旱概率明显高于0.5m土层,但0.5m土层重旱出现概率明显偏高,各层次干旱出现频率均未超过45%。干旱的季节分布特征表现为:3月～6月土壤水分持续减少,干旱持续发展,6月上中旬是陇东麦田最干旱的时期。小麦收获后,7月分土壤水分开始回升,7月～9月为土壤水分恢复平衡阶段,10月为土壤水分恢复平衡后相对稳定阶段。收墒期降水可以使2m土层土壤水分基本恢复到适宜状态,土壤储水主要分布在2m土层,即2m为土壤水库下限深度。8月开始,麦田中下层土壤水分运动方向发生逆转,由前期的向上运动转变为向下运动。麦田涝渍现象出现在秋季,主要出现在土壤中下层。早春和晚秋麦田重旱发生概率较低,秋季是陇东麦田土壤水分含量最高的时期,晚秋2m土层平均含水量超过早春,土壤水分于秋季恢复平衡,晚秋-早春,即越冬期降水量小于土壤蒸散量,土壤水分有一定损耗。

Soil Arid Characteristics on Loess Plateau in East of Gansu Province

This results obtained from soil moisture changes in Dongzhi wheat field showed that soil arid probability in 2m depth was higher than that in 0.5m,but serious arid probability appeared often in 0-0.5m soil layer(<45%). Aridity distributing characteristics were that soil moisture continuingly reduced from March to June,the first ten days and the middle ten days of June were the period of wheat field most arid in east of Gansu Province. After wheat harvest,soil moisture began to rise in July,and equipoise from July to September. October was relatively stabile stage. Precipitation made soil moisture in 2m depth store up more water,so the 2m depth was the lower limit depth of soil reservoir. Waterlogging phenomena of wheat field appeared in Autumn. Serious aridity probability of wheat field was lower in early Spring and late Autumn. Wheat field soil moisture content was the highest in Autumn.