The Effects of Tree Species on Soil Organic Carbon Content in South Korea

The effects of tree species on soil organic carbon (SOC) content have been evaluated in many studies, but only with a relatively small number of sample plots, resulting in ambiguous conclusions. Here we used a total of 595 forest plots in South Korea to investigate the role of four grouped tree speciespines, oaks, other conifers, and other deciduous treesin the forest SOC content in both forest floors and mineral soils. Significant differences were observed in SOC content among the groups. Pines contained 7.12MgC/ha of organic carbon in forest floors, whereas oaks and other deciduous trees contained 5.39 and 5.41MgC/ha, respectively. In contrast, oaks and other deciduous trees contained similar to 66MgC/ha of organic carbon each in mineral soils (0- to 30-cm depth), whereas pines contained 49.50MgC/ha. The total SOC content including both forest floors and mineral soils was the largest under oaks and the smallest under other coniferous trees, due to SOC being approximately an order of magnitude higher in mineral soils than in forest floors. The effects of tree species on SOC storage became apparent for the forest stands with >20-year-old trees, which suggests that the observed differences in the SOC content are likely due to the current stands rather than remnants of previous stands. The decomposition rates of organic materials could be a controlling factor affecting SOC storage, rather than inputs of photosynthesized products to soils. Plain Language Summary Globally, soil contains more than three times the organic carbon (OC) than tree biomass. Fresh and decaying tree litter is piled up on the forest floor, whereas debris of roots and organic matter accumulate in the mineral soil. Different tree species can store different amounts of OC in their soils. However, most studies have been conducted on a relatively small number of plots, that is, less than similar to 50. We used a total of 595 forest plots in South Korea to investigate the role of tree species on SOC content and found that pines store more OC than oaks and other deciduous trees in the forest floor. In contrast, oaks and other deciduous trees have more OC than pines in their mineral soil. Since the SOC content in mineral soil is approximately an order of magnitude higher than that in forest floors, the total SOC content was also higher under deciduous trees than pines. Our results suggest that SOC content can be managed by the selection of tree species.