A Method for Estimating Tree Age Based on the Tree Trunk Diameter and the Average Radial Growth Rate in Recent Years

To improve the accuracy of tree age estimation by accounting for variations in radial growth, this study developed a diameter/age model that incorporates the radial growth rate for seven typical tree species across subtropical to cold temperate regions. For each tree species, six trees—representing dominant, intermediate, and suppressed trees—were selected. A total of 646 disks were collected at 1 m intervals along the stems, starting at 0.3 m height. Disk diameters and tree rings were measured, and the radial growth rate of each disk over the past two years was calculated. For each tree species, two-thirds of the data were randomly selected as the modeling dataset, while the remaining one-third served as the testing dataset. Based on scatter plots, we selected linear models, logarithmic models, and exponential models as candidate models. A logarithmic function best described the diameter/age relationship, while an exponential model best fit the radial growth rate/age relationship. A dual-factor nonlinear model combining both variables achieved the highest estimation accuracy (80.29%), significantly outperforming single-factor models based solely on diameter (50.76%) or growth rate (73.01%). These results demonstrate that integrating radial growth rate substantially enhances the precision of tree age estimation.