Cryptomeria japonica is the most representative tree species in Japan. Although the logging residues generated after non-commercial thinning of Cryptomeria japonica are piled up and left in the watershed, there have been few studies regarding interception losses associated with the logging residues. We estimated interception losses associated with foliage as logging residues in two sub-watersheds (sub-watershed 1: 6.55 ha, and sub-watershed 3: 6.50 ha) in Nagasaka Experimental Watershed, Japan. We conducted an inventory of all thinned trees (diameter at breast height (DBH) ≥ 3 cm) in both sub-watersheds, and measured gross rainfall and throughfall. The mean ( ± standard deviation) DBHs of thinned trees in sub-watersheds 1 and 3 were 13.6 ± 6.0 cm (n = 3,767) and 9.7 ± 3.2 cm (n = 5,848), respectively. Based on a forest inventory of both sub-watersheds, residual foliage was estimated to be 4.28–4.54 t ha⁻¹ after thinning (50% reduction in stem density). During the snow-free period (April to November), gross rainfall was 1,397.5 mm, and throughfall amounts were estimated to be 1,151.8 and 1,179.2 mm in sub-watersheds 1 and 3, respectively. The evaporation from the forest floor was estimated to be 156.9 mm. Assuming a uniform spatial distribution of residual foliage (i.e., 4.28–4.54 t ha⁻¹), interception losses were estimated to be 24.9–26.3 mm, corresponding to 2.1–2.3% of throughfall and 15.9–16.8% of evaporation from the forest floor. However, we assumed that the foliage was locally concentrated in the watersheds at 20.0 t ha^–1; as such, interception losses were estimated to be 116.0–116.1 mm, or 9.8–10.1% of throughfall, corresponding to 74.0% of evaporation from forest floor. Overall, residual C. japonica foliage generated by thinning has local effects on soil moisture conditions.

A prototype “Geochemical Towing Observation System” was developed to detect the presence of volcanic fluids discharging from the coastal seafloor in shallow waters from the sea. We confirmed the stable operation of the observation system and evaluated its ability to detect volcanic fluid discharge in one of the coastal waters of Himeshima Island (Oita Prefecture, Japan), where volcanic CO₂ gas has been discharged from the seafloor. In the observed sea area, as the concentration of dissolved inorganic carbon (DIC) in seawater increases, its δ¹³C value changes toward the estimated δ¹³C of volcanic CO₂, so we believe that the observation system has successfully captured the seafloor discharge of volcanic fluids. In addition to DIC, a significant change in redox potential (ORP/Eh) also appeared, which can be explained by the detection of H₂S dissolved in seawater contained in seafloor gases. Combined measurements of ²²²Rn, salinity corresponding to electric conductivity, and water temperature, which have been effective in detecting submarine groundwater and hot spring water discharges from the seafloor in the Beppu Hot Springs coastal area in the back of Beppu Bay, showed no expected changes. This may indicate that submarine groundwater discharge from the seafloor along the coast of Himeshima Island is not significant and that gas discharge is the main cause.