黄土高原西部兰州市郊人工林地水分亏缺与调控研究

Soil Water Deficit and Control in Planted Forest in Lanzhou Suburb on Western Loess Plateau

通过定位监测与对比分析，对兰州市南北两山不同水分管理人工林地植物水分亏缺度及植物水分亏缺补偿度的时空分布进行了研究。结果表明：灌溉林地的植物水分亏缺度最小，亏缺度大部分时间都在20％以下，有自然坡面集雨的林地植物水分亏缺状况好于不灌溉的林地，侧柏林地喷灌、自然坡面集雨和不灌三种处理方式下的植物水分亏缺度虽然稍有差异，但都处于水分极度亏缺的状况。补充灌溉除满足林地正常生长所需要的水分外，对土壤水分也有一定的补偿，补偿度在70％左右。其他不灌溉地块补偿度都为负值，说明这些地块整个雨季没有对水分进行补偿，还将土壤以前贮藏的部分土壤水分利用。植物水分亏缺度在空间上的变化与植物根系的分布相一致。既在水平方向上，随着离树干距离的加大，植物水分亏缺度依次降低。在垂直方向上，表层植物水分的亏缺度最低，随着深度的增加，亏缺度逐渐增大，100～120cm深达到最大，以后又缓慢降低。植物水分补偿度是降雨与植物水分亏缺程度的反映，植物水分亏缺度越高，补偿度越大。

By position-monitoring and comparatively analyzing, we studied the soil water deficit degree and the spatio-temporal distributions of compensation degree of plant water storage deficit in a plantation site under different water administration measures in the southern and northern mountains of Lanzhou city. The results showed that the deficit degree of plant water storage in irrigative plantation was the smallest, it was less than 20 % in most times, the deficit situation in plantation with natural slope water-harvesting was better than that in non-irrigative plantation. Although the deficit degree of soil water of plantations under the three different disposal methods （sprinkling irrigation, natural slope water-harvesting, non-irrigation） was some different, all of them were on the condition of plant water＇s severe deficit. Besides satisfying with plant＇s growing, compensatory irrigation could compensate some soil water, the compensation degree was about 70 %. The compensation degree of non-irrigative plots was negative, which showed that there was no compensation for soil water in whole rainy season in these plots. The spatial change of plant water deficit degree had relation with the distribution of plant root. In level direction, the deficit degree of plant water decreased along with the increase of distance from the root crown. In vertical direction, the deficit degree of plant water in surface layer was the minimum, along with the increase of depth, the deficit degree increased, in 100～200 cm layer it was the maximal, then it decreased gradually. The compensation degree of plant water was the reflection of rainfall and plant water deficit degree, the higher the deficit degree of plant water was, the bigger the compensation degree was.