Nutrient-use efficiency and nutrient sequestration of urban trees in a settlement area

초록

Trees planted in urban areas provide a wide range of ecosystem services. Information to guide species selection is still limited in decision-making. In particular, knowledge remains scarce about the relationships between nutrient demands and growth in urban trees. Our study estimates nutrient-use efficiency and nutrient sequestration for eight representative urban tree species in South Korea. The eight urban tree species were classified into three functional types: deciduous needle-leaved species (Ginkgo biloba and Metasequoia glyptostroboides), evergreen conifers (Pinus densiflora, P. strobus, and Thuja occidentalis), and deciduous broad-leaved species (Prunus yedoensis, Zelkova serrata, and Acer palmatum). Destructively harvesting 73 trees, we determined dry weight, carbon, and nutrient concentrations for each tree compartment. Biomass allocation among sampled tree species was as follows: roots (33%), stem wood (30%), branches (27%), foliage (6%), and stem bark (4%). Carbon concentrations were highest in stem wood and lowest in roots (p < 0.05), whereas nutrient concentrations were generally lowest in stem wood. Variations between plant functional types were greater than those between species. Nitrogen-use efficiency for producing stem wood carbon and root carbon was highest in evergreen conifers, followed by deciduous needle-leaved species and deciduous broad-leaved species. The highest carbon and nutrient sequestrations were observed in deciduous needle-leaved species. In particular, M. glyptostroboides and P. yedoensis showed greater carbon and nitrogen sequestration than P. densiflora, T. occidentalis, and A. palmatum. Calcium and magnesium sequestration were highest in bark and branches and in deciduous needle-leaved species. Observing both higher nutrient-use efficiency and carbon sequestration indicated limited nutrient supply in urban areas, suggesting that nutrient-use efficiency can inform species selection to sustain growth in urban environments.

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