Wonkwang University Iksan, Cholla-bukto, Republic of Korea
With increasing recognition of climate change, research on stand productivity has been associated with increases in carbon storage. In South Korea, forest management for increasing carbon absorption is an important issue because forest productivity is declining owing to aging forests. Thus, investigating how to increase the productivity of Korean forests associated with carbon storage is necessary to develop short- and long-term forest management plans. This study examined how stand density (BA), quadratic mean diameter (QMD), site index, stand structural diversity (SD), stand age, pine proportion, and climate variables (MAT, MAP) influence the productivity of aging Korean red pine stands using random forest regression.
Results show that QMD is the most influential factor on pine stand productivity (periodic basal area increment, PBAI). PBAI decreased with increasing QMD up to 18, slightly decrease up to 27, and then leveled off. PBAI decreased with increasing BA up to approximately 51 and then remained constant. PBAI increased when site index increased from 7 to 12, but decreased from 12 to 17. PBAI decreased for stand age up to 30, levelled off in the 31-35 range, and showed a small increase for ages higher than 35. For stand structure, PBAI slightly increased with increasing SD up to 1.45 and then slight decreased. PBAI mostly increased with increasing MAP. These results indicate that changes in QMD, SD, and stand age are associated with changes in stand density. Increases in these factors lead to higher stand density and result in lower stand productivity. The result suggests that proper stand density management can increase the productivity of pine stands in South Korea.