永瀬 彩子

Urban densification has led to the adoption of vegetated façades as a nature-based strategy to increase urban green spaces and enhance urban living conditions. However, limited knowledge regarding suitable plants for vegetated façades can impede the process. In this field experiment conducted in Southern Finland, we investigated the performance of 12 potential plant taxa for a vegetated façade by assessing their visual appearance and sizes in relation to façade orientation, floor height, substrate pH, and mycorrhizal inoculation. The 12 plant taxa were categorized into 4 growth forms according to their morphologies: spreading conifers, dwarf conifers, creeping conifers, and climbers. We aimed to evaluate plant performance during the initial two growing seasons, which is critical for the successful establishment of these plants in vegetated façades. Eight of the twelve plant taxa exhibited relatively high performance in terms of visual appearance and size. Notably, creeping conifers outperformed other growth forms in visual appearance, which was most likely due to their close-to-ground morphology. Façade orientation and substrate pH were the most influential predictor variables. Façade orientation affected both plant visual appearance and size, while substrate pH primarily affected plant visual appearance. The east-facing façade (less exposure to sun and wind) and mildly acid substrate (pH 6–6.5) were more conducive to most of the plant taxa. Certain species and cultivars, such as Juniperus communis ‘Lalli’, maintained constant plant visual appearance and size regardless of façade orientation and substrate pH, suggesting their adaptability and stability across various conditions. Floor height and mycorrhizal inoculation only displayed marginal and taxon-specific impacts. Given that some plants in our vegetated façade exhibited optimal performance different from those in their reported natural habitats, we encourage conducting long-term, on-site experiments to identify suitable plants for vegetated façades to ensure successful vegetated façade implementation.

The availability of pollen in urban-rural landscapes is an essential factor that influences the population dynamics of insect pollinators. The amount and diversity of pollen play a pivotal role in the foraging ecology of pollinators for their growth and health, but investigations on the spatio-temporal patterns of foraged plants remain rare, especially in cities as neo - ecosystems. Here, we explored the temporal foraging habits of a highly pollinator (Apis mellifera L.) in Tokyo, including different landscape classes from rural to urban areas. Mixed-pollen samples in each month and each location (N = 17) were analysed using DNA meta-barcoding to identify plants visited by honeybees. The results showed that the landscape class (rural, suburban and urban areas) explains spatial variations in pollen source-plant composition foraged by honeybees, but not in taxa richness. Furthermore, pollen diversity and pollen source-plant composition showed a strong seasonal dependence. A higher plant richness and foraged woody taxa was found to occur in spring, which was mainly dominated by the genera Prunus and Acer. In summer and autumn, the genera Trifolium and Plantago of the herbaceous stratum were the most visited plants. The Fabaceae, Rosaceae, Brassicaceae, Plantaginaceae, and Onagraceae plant families were the most frequently observed in all combined samples. The present study contributes to a deeper understanding of the foraging ecology of A. mellifera colonies across urban-rural gradient surrounding mega-cities such as Tokyo.