A comprehensive census of adult trees complemented by a density survey of seedlings and juvenile individuals was conducted within the Podocarpus macrophyllus forest on a sand spit in the western Izu Peninsula. In total, 225 adult P. macrophyllus trees were identified, which demonstrated no significant change in population since their designation as natural monuments in 1980. However, majority of the trees were in subtree layer (58.5%). Only 31.6% were tall trees that reached the upper layers of the forest canopy. Cinnamomum camphora, a co-occurring species, were mostly large-diameter tall trees, indicating a shift in dominant species. While P. macrophyllus trees which have shade tolerance currently exhibit no significant health decline despite the presence of C. camphora. Pinus thunbergii was characterized by the presence of numerous large-diameter tall trees, which preferentially occupied the sea-facing regions. In contrast, P. macrophyllus displayed a preference for interior habitats. The seedling density of P. macrophyllus exhibited high variability across sites with 7–431 seedlings per 100 m². It is worth noting that the majority of seedlings were typically <20 cm tall. Relative light intensity in the forest was low, averaging 2.6% at 100 cm above ground level, and the scarcity of young P. macrophyllus exceeding 100 cm in height suggests a low rate of regeneration within the forest. The Polysticho-Machilus thunbergii community was established on a nearby sandbar, and many species commonly occur on the forest floor with this P. macrophyllus forest.

Stormwater management and cooling in summer are among important goals of green roof technology for enhancing the urban sustainability, while few studies focused on the effects of the water storage layer, which could potentially enhance stormwater retention and evaporative cooling. In this study, pots with the water storage layers (0, 5, and 10 cm deep at the bottom) were filled with green roof substrates (organic vs. mineral base materials), heated by LED lights (60℃), for comparing 28-day hydrologic and thermal measurements between scattered vs. heavy precipitation patterns. We found that water storage layers did not affect hydrologic and thermal measurements in the scattered precipitation pattern. In the heavy precipitation pattern, pots having 10 cm deep water storage layer had 8.2～11.3℃ lower soil surface temperature, 23.4～24.6% more stormwater retention, and 26.5～30.9 mm more cumulative evaporation than the control (pots without water storage layer). Our findings suggest that the water storage layer at the bottom of the green roof substrate layer could enhance stormwater retention and evaporative cooling if heavy precipitation increases in the course of climate change, while full-scale field research is needed to test if the effects of the water storage layer can be maintained for a long term.

This study aimed to explore the factors associated with the loyalty to a rooftop green space on a commercial complex by applying know-how from the marketing field and a data-driven approach using machine learning. Cross-sectional study was conducted through a face-to-face questionnaire survey with Microsoft Forms and tablet devices during weekdays and holidays from October to December 2023. The site was Parks Garden on Namba Parks in Osaka City. In this study, we first segmented four items related to the loyalty (frequency of use of the commercial complex and the rooftop green space, willingness to repeat and recommendation of the rooftop green space) using k-means cluster analysis. Subsequently, we generated classification trees with these segments as the objective variables. The results showed that the loyalty to the rooftop green space was segmented into four segments: near drop-outers, potential loyal customers, loyal customers, and silent repeaters. The factors most associated with the loyalty to the rooftop green space were the process of visiting the rooftop green space such as onward route, possession of a membership, and the category of weekday or holiday. Next to those factors, the factors associated with the loyalty to the rooftop green space were the attractiveness of the rooftop green space and activities in the rooftop green space.

Rain gardens are globally recognized as a solution for urban flooding. However, their prevalence in Japan is very low since their effects to control runoffs have not been sufficiently evaluated for actual facilities. In this study, the runoff control effect of a demonstration rain garden was quantitatively evaluated based on the model for two types of rainwater infiltration facilities, “permeable pavement model” and “rectangular box model”. The former model allows rainwater to permeate from the surface and infiltrate from the bottom of the facility, while the latter considers bottom and side infiltration. We found that the calculation formula for specific infiltration of the “rectangular box model” better matched the observed results than that of the “permeable pavement model”; the design infiltration capacity of the “permeable pavement model” was a conservative evaluation but underestimated the actual infiltration capacity. Additionally, we found that the runoff control effect against planned rainfall can be easily demonstrated by appropriately quantifying the storage height and infiltration intensity of the rain garden.

To acquire the fundamental data for UAV-revegetation, germination, emergence, and survival experiments were carried out with extruded pellets and capsules containing seeds at a collapsed hillslope and fields with thin containers. With the precipitation in the rainy season, Bermuda grass germinated or emerged from all conditions and sites, there were no significant differences. At the slope, volumetric soil water content was decreased by 8% and some germinated individuals were alive. On the other hand, in thin containers, all germinated individuals died with 3% soil water content. Revegetation execution in early summer with Bermuda grass seeds, it is suggested target slope should be restricted where soil water content did not drop under 9% or the necessity of amelioration with irrigation.