Contrasting Spatio-temporal Variation of Fine Root Dynamics in Nearby Evergreen Korean Pine and Deciduous Oak Forests and Their Potential Impact on Soil Properties

Background and Aims Soil organic carbon (SOC) is the biggest uncertainty when estimating the global C budget. Fine root turnover is the main source of SOC, but it exhibits significant spatio-temporal variation. Therefore, understanding the complex interactions of fine roots is essential for assessing soil carbon dynamics in forest ecosystems. Methods Fine root dynamics were investigated in adjacent evergreen pine (TCK) and deciduous oak (TBK) forests. Minirhizotron images were taken over two years to analyze root production, mortality, turnover, and longevity. Sequential coring was used to assess root biomass and morphological characteristics, as well as soil chemical properties at different depths. Results Although TCK roots had larger diameters compared to TBK, TCK unexpectedly showed higher turnover rates. Additionally, TCK exhibited a bimodal phenological pattern while TBK exhibited a unimodal pattern. Across different soil depths, TBK had a higher length (SRL) compared to TCK, while root tissue density was similar. Regarding soil depth, TBK had concentrated biomass in shallow soils with significantly higher SRL and faster turnover rates compared to deeper soils, whereas TCK displayed similar values across soil depths. These differences in root characteristics were evident in higher soil carbon in TCK compared to TBK. In TCK, carbon was evenly distributed throughout the soil depth, whereas TBK had more carbon in shallow soils. Conclusion These findings emphasize the importance of adopting spatio-temporally comprehensive approaches to evaluate fine root dynamics, providing better insights into the belowground portion of terrestrial biosphere models and forest ecosystem carbon cycling.