在人工林中,混交豆科或非豆科的固氮树种,可增加林地土壤的氮素含量,提高林分的生产力。苏、美曾分别进行过加拿大杨、灰杨、黑杨、花旗松等和固氮树种赤杨的混交试验,都取得了肯定的结果。其中9年生的加拿大杨和灰杨平均木的材积可提高9倍之多(Pe-(?) 1960)。证明混交固氮树种是提高人工林产量的一个经济而有效的途径。 In planted forests, the addition of leguminous or non-legume nitrogen-fixing species can increase the nitrogen content of forest soil and improve the productivity of the stands. Su, the United States had conducted Canada Yang, aspen, black poplar, Douglas fir and other nitrogen fixation and algae hybrid experiment, have achieved positive results. Among them, the average annual volume of 9-year-old Canadian poplar and aspen can be increased ninefold (Pe- (1960)). Prove that mixed-nitrogen fixation is an economical and effective way to increase plantation yield.