Influence of stand age class on biomass expansion factor and allometric equations forPinus rigidaplantations in South Korea

The objective of this study was to examine the influence of stand age class (I:<20 years old; II: 21–40 years old; III: 41–60 years old) on BEF and stem density and to develop allometric equations for the three stand age classes in order to estimate the biomass of pitch pine (Pinus rigida Mill.) plantations in South Korea. BEFs (g g−1) were observed to decrease in the three stand age classes with 1.983 for stand I, 1.201 for stand II and 1.131 for stand III. Results showed that there was a significant statistical difference in BEFs (p < 0.05) among the stand age classes. The stem densities (g cm−3) of the three stands were 0.430, 0.451 and 0.481, respectively, and there was no significant statistical difference (p > 0.05) among stand age classes. Both model 1 (DBH as predictor variable) and model 2 (DBH and total height as predictor variables) showed good results based on the model evaluation criteria (R 2 , RMSE and FI). The stem wood had the highest biomass distribution percentage of the three age classes with 52%, 67% and 69% determined for classes I, II and III, respectively. Stand age-dependent BEFs and allometric equations will help forest managers to accurately estimate the biomass and carbon stocks of the different pitch pine plantations in South Korea, which is essential in climate change mitigation.