Rooting characteristics of forest trees is an important trait both for silviculture and also for genetic improvement,but its progress which was made on its improvement was rather small due to the complexity and heavy work for rooting traits measurement.Fractal theory provided a new idea and also a method to deal with such complicated traits.The rooting characteristics based on cuttings of 46 poplar clones were investigated,poplar cuttings were cultivated in two kinds of medium,perlite and fresh water.Pictures were took for each cutting with a digit camera and then edited with Photoshop 6.0,Fractal dimensions were obtained for each picture by the software(FDC1.0).For the two rooting traits(length,dry mass)investigated,there were significant differences existed among clones.The variation ranges of fractal dimension of cuttings were 1.173～1.533 for 46 clones cultivated in perlite,and 1.513～1.814 for 34 clones cultivated in water.A significant positive correlation was found between fractal dimension and dry mass of roots,thus,fractal dimension might be a substitutive index for rooting characteristics.In general,the more the cutting roots,the bigger the fractal dimension.
