Kidae Kim

Woody plant roots enhance slope stability by increasing soil shear strength, although reinforcement by roots varies with forest type, growth form, root diameter, and disturbance history. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we reviewed 253 publications and extracted data relevant to the Wu and Waldron model, including mean root tensile strength, root diameter–tensile strength parameters, root area ratio (RAR), and post-disturbance declines in root strength or cohesion. Broadleaf species had higher mean tensile strength and RAR than conifers. Shrubs showed higher mean tensile strength than trees; however, when adjusted for root diameter using α and β₁ parameters, trees exhibited greater strength. This highlights the importance of accounting for root diameter when comparing root tensile strength. The vertical distribution of RAR decreased with soil depth, with most roots concentrated in the upper 30 cm of soil. After disturbances, 71.4% of reported half-lives of root strength or cohesion were five years or less, although variation depended on disturbance type and intensity. These findings emphasize that assessments of root reinforcement must consider forest type, growth form, root diameter, RAR, and strength decline after disturbances.

Identifying potential sources of suspended sediment (SS) in headwater catchments is crucial for water quality management. To differentiate these potential SS sources, we investigated the distribution of two fallout radionuclides (FRNs), ¹³⁷Cs and ²¹⁰Pb_ex, using gamma spectrometry along with soil organic matter (SOM) analysis in a headwater catchment with five potential SS sources: cultivated land, non-harvested forest floor, eroded hillslope, harvested forest floor, and stream bank. The ¹³⁷Cs and ²¹⁰Pb_ex concentrations and the SOM content were considerably higher in the harvested forest floor materials than in the other four potential SS source materials. FRN concentrations revealed distinct properties according to the type of potential SS sources. Specifically, the combination of FRNs (with the effect of SOM content removed) associated with the mineral fraction and SOM showed distinguishable differences among the potential SS sources, except for no difference between cultivated land and eroded hillslope. Therefore, SOM and FRNs, or their combination, can be effective indices to differentiate or trace potential SS sources on various land use/land cover types within a catchment. Further field tests will allow the tracing techniques that bind FRNs with SOM to contribute to understanding SS transport from non-point sources within a catchment.

In order to determine the suitability of reusing the sediment deposited in the upper part of the dam as soil for growing forest products, a total of eight treatment plots were formed by mixing cultivated soil, compost, and biochar with the sediment in a volume ratio. Generally, the soil fertility of SS100 was relatively lower than that of CS, with Av. P₂O₅ being only 22%. SS70 and SS50 increased soil physicochemical properties including OM, exchangeable cations, CEC, and BS by 1.1–2.9 times more than SS100, thus, A. scaber Thunb. treated in SS70 and SS50 showed increased photosynthetic parameters including A, V_cmax, J_max, and the growth characteristics, especially in the aboveground part, were 20% and 31% higher than the SS100, respectively. Furthermore, A. scaber in CS, SS50, Bc10, and Comp had higher PI_abs, DFI_abs, and SFI_abs while maintaining lower V_K/V_J after 10 days of drought stress, Comp and Bc10, in particular, had a high Y(NPQ) and a low Y(NO). Bc5 and Bc10, revealed no discernible differences in soil physicochemical properties, nonetheless, A. scaber in Bc10 demonstrated relatively high drought tolerance. Overall, CS, SS50, and Comp had relatively well-balanced plant growth, and drought tolerance was found to be higher in CS, Comp, SS50, and Bc10, which is thought to have higher water-holding capacity and soil fertility. As a result, if appropriate treatment methods are established, such as mixing sediment soil with cultivated soil at a one-to-one ratio or adding compost, increase the public value of forests by promoting activities such as watershed conservation, soil runoff prevention, and reducing the financial burden associated with sustainable forestry management and SS50 is recommended as the most cost-effective method.