Root Growth and Distribution Pattern of the Intercropped Polygala aureocauda in Pinus massoniana Plantation

A 19-year old Pinus massoniana plantation was selected for thinning, and three treatments including 450 plants·hm^-2 (SM1 treatment), 600 plants·hm^-2 (SM2 treatment) and 750 plants·hm^-2 (SM3 treatment) were used to analyze the root growth and distribution pattern of the intercropped Polygala aureocauda under different retention densities of Pinus massoniana. The results showed that there were significant differences in the annual root growth and root fresh weight of the intercropped Polygala aureocauda treated with different retention densities, and the root growth of Polygala aureocauda intercropped with the stand retention density of Pinus massoniana of 600 plants·hm^-2 (SM2 treatment) for 6 years was the largest, with the root width growth of 94.9 cm, the root depth of 32.8 cm and the root fresh weight per plant of 506.4 g. The roots of Polygala aureocauda were more concentrated in the horizontal distance of 0-40 cm and the vertical depth of 0-20 cm, which were less crossed with the horizontal distribution and vertical distribution of the main roots of Pinus massoniana. Compared with SM1 and SM3 treatments, the output value of root fresh weight with SM2 treatment was increased by 347.7 yuan·hm^-2 and 520.2 yuan·hm^-2, respectively, showing significant management benefits.