黄土高原人工林根区土壤水分亏缺状况与空间分布

通过定位监测与对比分析，对黄土高原半湿润落叶阔叶林区、半干旱森林草原区和半干旱典型草原区，持续干旱期末人工林根区土壤干旱状况、雨季后土壤水分恢复情况进行了测定分析；同时，通过引入土壤贮水亏缺度这一新的指标，对人工林地土壤水分亏缺度的空间分布进行了研究。结果表明，黄土高原人工林地土壤水分亏缺严重。根区0～320cm土层贮水亏缺量达384．06～466．68mm，相当于该地多年平均降水量的63．95％～77．70％。其中以0～40cm主要根系分布层亏缺量最大。人工林根区土壤贮水亏缺度，在水平方向上具有较为明显的空间分布规律。其中，侧柏、油松土壤贮水亏缺度与距主干距离成正相关，但刺槐则相反；在垂直方向因林分类型不同而异。半湿润落叶阔叶林区传统的一维土壤水分动态监测，难以准确反映半湿润落叶阔叶林区人工林地的水分状况。

Spatial Distribution of Soil Water Deficit in Rhizosphere of Plantations of the Loess Plateau

By means of field measurement of soil water content at the grassland and plantation situated in deciduous broad-leaved forest zone, prairie-timber zone and prairie zone on the Loess Plateau, the deficit degree of soil water and its spatial distributions in rhizosphere were studied. The results showed that the soil water deficit in the rihizos-phere was extremely serious. The water deficit was 384.06 -466. 68 mm at the root zone of 0 - 320 cm, which was equal to 63. 95% -77. 70% of the local annual precipitation, of which, the deficit degree in the topsoil of 0 -40 cm was more serious. The spatial distribution of deficit degree of soil water at root zone was different from that of no-root zone, it was affected by the root distribution of tree species, so it is not accurate for calculatia water balance by measuring vertical soil water content of one dimension traditionally in plantations in the sub-humid vegetation zone of the Loess Plateau.