Objective  This paper aims to study the distribution and its influencing factors of coarse roots of typical tree species, and provide scientific basis and data support for the good growth of trees in Lesser Xing’an Range of northeastern China.

Method  Taking Pinus koraiensis, Larix gmelinii, Picea koraiensis and Pinus sylvestris as the research objects, 8 sample plots were selected for testing in the Liangshui Experimental Forest Farm. Taking the sample tree as the center, using the tree radar unit to scan the coarse root on the circumference of 0.5, 1, 1.5, 2 m radius. The soil physical and chemical properties were determined by cutting ring method and soil sample method. The tree height, DBH and crown width were measured. The distribution of coarse root in Lesser Xing’an Range was analyzed. The correlation between the density of coarse root and tree and soil factors was analyzed.

Result  (1) In the horizontal direction, the coarse root density of four typical tree species decreased with the increase of distance from the trunk. In the vertical direction, with the increase of soil depth, the coarse root density of Pinus koraiensis and Larix gmelini decreased gradually, while that of Picea koraiensis and Pinus sylvestris increased first and then decreased. There were 82.1%, 82.0%, 89.6% and 67.6% coarse roots for Pinus koraiensis, Larix gmelini, Picea koraiensis and Pinus sylvestris distributing in the 0−40 cm depth of soil, respectively. (2) There was a significant positive correlation (P < 0.05) between the coarse root density and tree height, DBH and crown width, and no significant correlation with tree average resistance value (P > 0.05). (3) The coarse root density of trees was significantly positively correlated (P < 0.05) with soil moisture content, saturated water-retaining capacity, and capillary water capacity. The coarse root density was significantly negatively correlated with soil bulk density (P < 0.05) and had the highest correlation with capillary water capacity (r = 0.538, P = 0.012). The coarse root density was significantly positively correlated with the content of soil organic matter, total nitrogen, total phosphorus and hydrolyzed nitrogen (P < 0.05), and had the highest correlation with total nitrogen content (r = 0.646, P = 0.002).

Conclusion  The results show that both tree and soil factors have different effects on the coarse root distribution of four typical tree species in the Lesser Xing’an Range of northeastern China. The distribution of coarse roots is not only related to their own characteristics, but also related to their living environment, and not related to the material quality of trees.