Abstract: [Objective] In Wei County nursery of Hebei province, we applied different irrigation and nitrogen addition treatments to study the long-term water-nitrogen coupling effect on stand volume of Populus tomentosa.[Method] A split plot experiment design was used to study effects of different water-nitrogen coupling treatments in forest land on stand volume of different clones of P. tomentosa.[Result] Results showed that:1) different irrigation and nitrogen application had significantly different effects on stand volume of different clones. Clone S86 had better response mechanism under high water and fertilizer treatment, but it was opposite to clone 1316. 2) during irrigation to poplar plantation, the field capacity of more than 75% should be set as the critical value of irrigation, and the afforestation region of the environmental conditions, such as planting density, forests age and other factors, should be taken into account. 3) It is suggested that the range of nitrogen fertilizer to poplar plantation should be between 100 kg·hm^-2 to 400 kg·hm^-2, and the amount of fertilization should be adjusted to the fertility level in the experiment area.[Conclusion] Through the comparative study, clone S86 is suitable for the experimental design in the area with field capacity of 75% and nitrogen application rate of 160 g per tree as a fast-growing among the 4 clones (BT17, B331, S86,1316). We suggest that the cultivation of fast-growing and high-yielding poplar plantations in the near areas should be given priority. The results provide scientific theoretical basis for directional cultivation of Populus tomentosa plantation, and put forward a scientific and reasonable variety (line) selection criteria with high-quality, fast-growing and high-yield.

Key words: water and nitrogen coupling, Populus tomentosa, stand volume, clones, fast-growing and high-yield