十年来在意大利卡斯戴耳彼亚诺(Bastelpiano)种植杨树的试验都失败了,而只有几株树龄较大的杨树能正常生长。后来发现这几株老树原来是围在林地外的木柱深插在土中以期固定沙丘的。于是仔细地把这些杨树掘起来研究其根系,观察后发现其根部一直伸入到地下水面。在继续该项试验时使用三年生杨树干,树干下端 Tests of poplar cultivation in Bastelpiano, Italy, for ten years have failed, with only a few older poplars growing normally. Later found that several old trees turned out to be surrounded by wood in the wood outside the deep in order to fix the sand dunes. So carefully dig these poplar to study its root system, after observation found that its root has been extended to the groundwater. Three-year-old poplar trunk was used for the continuation of the experiment, with the lower end of the trunk