Tree Diversity and Identity Effects on Aboveground Biomass Are Stronger than Those of Abiotic Drivers in Coniferous and Broadleaved Forest Restoration Sites of South Korea

Abstract

Forest restoration sites have a critical role in the maintenance and improvement of forest ecosystem health and resilience, as well as increasing carbon storage capacity. However, previous studies on forest restoration sites have primarily focused on monitoring vegetation changes and investigating changes in carbon storage (e.g., aboveground biomass). Research on identifying the controlling drivers of aboveground biomass (AGB) between/among forest types according to stand age within restoration sites remains limited. Our study analyzed data from a total of 149 plots in forest restoration sites in South Korea, comprising 57 coniferous forest plots (38.3%) and 92 broadleaved forest plots (61.7%). This study employed a piecewise structural equation model to determine the main biotic (i.e., stand structural diversity, species diversity, functional diversity, and tree identity) and abiotic drivers (i.e., topographic, climate factors driver, stand age, and soil properties) influencing AGB in each forest type. The results revealed that stand structural diversity was the most critical driver of AGB across all forest types, highlighting the importance of structural complexity in early stage restoration. Specifically, in coniferous forests, stand structural diversity (DBH STD) and tree identity (CWM WD) were more influential, whereas in broadleaved forests, SR and climatic conditions played a greater role. Therefore, our findings provide empirical evidence for understanding AGB dynamics in early stage forest restoration sites and may help inform the development of management strategies for each forest type and early restoration planning in similar ecosystems.