Selection of medium-sized, shade-tolerant trees for urban tropical landscapes, Bangkok, Thailand

Abstract

Urban green spaces are crucial for its residents, particularly in improving their health and providing recreational benefits. Typically, a simple vertical structure of urban trees limits their urban biodiversity and reduces ecosystem services. This study examined the significance of nine medium-sized shade-tolerant tree species in enhancing the urban canopy structure through light response curve modeling. Cluster analysis was used to differentiate the photosynthetic behavior of tree species in relation to variations in light intensity. Clustering was performed based on parameters derived by fitting a non-rectangular hyperbolic model with a linear perturbation term beyond light saturation point. Three distinct groups of light response curves were identified and labeled under saturating, falling, or increasing trends. The results indicated that two native species: Ficus benjamina and Sphaerocoryne lefevrei were light demanding and exhibited an increasing photosynthetic response to light. Meanwhile, Diospyros decandra, Bauhinia purpurea, Guaiacum officinale and Murraya paniculata were categorized as shade-tolerant and could be used for enhancing urban green canopy cover in low-light environments. Calophyllum inophyllum and Gustavia gracillima sequestered the most CO₂, as indicated by their highest maximum photosynthetic rates. The findings can be beneficial for urban planners in selecting suitable species to mitigate climate change, while also increasing the biodiversity and ecosystem services for urban residents.