Using the urban environment for conservation of rare understory shrub species Daphne jejudoensis and Maesa japonica

Abstract

To investigate the potential for urban environments on Jeju Island, South Korea, to support the conservation of rare understory shrub species, specifically Daphne jejudoensis and Maesa japonica with limited habitat availability, several study sites were selected to assess the performance of these plants after transplanting. A study site similar to the original habitat (Fo), sites between building gaps (GapJ and GapC), a flowerbed in front of a building (FbJ), the rooftop of a building (Roof), and indoor terraces at higher latitude areas (TeSD and TeSM) were selected. Building gap sites and terrace sites displayed similar but a little lower canopy coverage to the forest site (80−90 %). The flowerbed site showed ∼ 50 % coverage, and the Roof site showed ∼ 30 % canopy coverage. Therefore, urban environmental sites (GapJ, GapC, TeSD, and TeSM) displayed similar canopy coverage to original habitats of D. jejudoensis and M. japonica, with stronger light intensity than the Fo site. Shortwave radiation energy from the sky hemisphere at urban environmental sites was only 15−50 % that of the Roof site and only 3 % that of the Fo site. Therefore, urban environmental sites displayed intermediate radiation between canopy open areas and forest sites. This increased light intensity and radiation led to significantly better performance for both shrub species in terms of photosynthetic rate, water use efficiency, and chlorophyll content at urban environmental sites compared with canopy-opened Roof sites. Furthermore, these sites supported similar plant growth for D. jejudoensis and better growth for M. japonica compared with the Fo site. Therefore, urban environments possess huge potential for successful conservation of rare tree species with limited habitat range. Additionally, results for terrace sites suggest that D. jejudoensis and M. japonica have great potential as indoor gardening plants, which could support species conservation through public engagement. As a pioneering study, our findings highlight the great potential for species conservation using stable and accessible urban environments around buildings.