A lack of shade-tolerant plant species in the species-pool of urban parks results in degradation of ecosystem services under tree canopies

Abstract

Abstract: The herbaceous vegetation layer in urban parks provides ecosystem services that include places for people to sit on the ground, prevention of mud and dust formation, prevention of soil erosion, and flood prevention via increased rain infiltration. Species composition in green spaces in urban areas varies owing to differences in their histories. In newly developed parks on reclaimed land, shade-tolerant native species that grow on the forest floor in ‘satoyama’, or remnant vegetation, may be absent from the species pool, leading to concerns that the ecosystem services of the forest-floor vegetation may be degraded. In this study, we measured the ecological traits of the species pool (shade and trampling tolerance at the species-pool level) in various parks, and analysed their effects on the ground-surface leaf area index. Because trampling also affects vegetation in parks, we used soil penetration-resistance values to account for its effects. A lack of shade-tolerant species in the species pool reduced the leaf area index of forest-floor plant communities. The shade-tolerant species detected in our surveys included native species such as Houttuynia cordata, Ophiopogon japonicus, Oplismenus undulatifolius, Paederia foetida, Pleioblastus chino, and sedges. Species pools in parks with ‘satoyama’ typically included these species. Species pools containing shade-tolerant native species are important for improving ecosystem services beneath tree canopies, and we recommend conserving historical ‘satoyama’ to prevent the loss of native shade-tolerant floras when renovating or creating parks.