Objective  This paper aims to study the DBH class structure and arbor biomass of Juglans mandshurica secondary forests in different mountains in northeastern China, then provide scientific basis for follow-up related research on secondary forests and reasonable forest management in this area.

  Method  A total of 202 sample plots were set up in 21 typical areas of Zhangguangcai Mountain, Changbai Mountain, Laoyeling Mountain and Longgang Mountain of northeastern China in this study, and the three-parameter Weibull distribution, Johnson’s SB distribution and negative exponential distribution were used to fit the tree DBH in the survey sample plots. The relative deviation and root-mean-square error were tested for accuracy, and the biomass per hectare of each sample plot was calculated based on the survey data and the reference arbor allometric biomass equation.

  Result  DBH class structure of forest stands in the four mountain ranges was basically similar, showing a trend of decreasing gradually and an inverted “J”-shaped distribution. There were more trees in the middle and small DBH classes, mainly in the 6−14 cm DBH class. The number of trees per hectare in Zhangguangcai Mountain was more than that in Changbai Mountain, Laoyeling Mountain and Longgang Mountain. According to the parameters and model fitting, as well as the comparison of the relative deviation and the root mean square error between the measured plant number and the simulated plant number, the simulation effects of three models were relatively close to the actual values, among which, the three-parameter Weibull distribution simulation effect was better than the other two curves in the four mountains, and the three-parameter Weibull function fitting effect of Zhangguangcai Mountain was better than other mountains. The order of the aboveground part biomass and total biomass per hectare of all species in each mountain range was Changbai Mountain > Longgang Mountain > Zhangguangcai Mountain > Laoyeling Mountain. The biomasses of Changbai Mountain and Longgang Mountain were similar, significantly higher than those of Zhangguangcai Mountain and Laoyeling Mountain (P < 0.05 ). The order of aboveground part biomass and total biomass of Juglans mandshurica was Changbai Mountain > Longgang Mountain > Zhangguangcai Mountain > Laoyeling Mountain, and the biomass of Juglans mandshurica in the forests of Changbai Mountain was significantly higher than those in other mountains (P < 0.05).

  Conclusion  The renewal status of the forest stands in the four mountains is good, the simulation of the stand DBH class structure is the best with the three-parameter Weibull function, and the biomass of all tree species in the stand and a single tree species of Juglans mandshurica have the best performance in Changbai Mountain of northeastern China.