Seasonal variations in photosynthetic functions of the urban landscape tree species Gingko biloba : photoperiod is a key
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ORIGINAL ARTICLE
Seasonal variations in photosynthetic functions of the urban landscape tree species Gingko biloba: photoperiod is a key trait Tomomitsu Kinoshita1 · Atsushi Kume2 · Yuko T. Hanba1 Received: 30 April 2020 / Accepted: 9 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Key message Seasonal variations in the leaf photosynthetic traits of an urban tree, Ginkgo biloba, were almost synchronized with the photoperiod. Non-stomatal limitations were a cue for photosynthesis in Ginkgo biloba. Photosynthetic functions, which are key traits in determining the carbon uptake of urban trees, exhibit significant seasonal variations in temperate zones. It is essential to clarify the seasonal dynamics of photosynthesis to evaluate the C O2 uptake in urban areas. We investigated seasonal variations in the photosynthetic traits of Ginkgo biloba, which is a major urban deciduous tall tree often planted in Japan. Seasonal variations in the leaf photosynthetic traits, including the maximum photosynthesis rate, maximum carboxylation rate, and mesophyll and stomatal conductance, were well fitted to quadratic models, in which they peaked around the summer solstice and then declined with time. Seasonal variations in the environmental variables, such as photoperiod, temperature, and solar radiation, were compared to those of the leaf photosynthetic traits, in which the photoperiod explained well variations in the leaf photosynthetic traits. Seasonal variations in photosynthesis were largely governed by non-stomatal limitations, i.e., mesophyll and biochemical limitations. The high synchrony of the photoperiod and photosynthetic traits during leaf maturation may cause an enhancement in the daily carbon uptake of G. biloba leaves around the summer solstice, which has the longest photoperiod, and thus, will lead to an increase in the annual carbon uptake. Keywords Maximum temperature · Photosynthetic limitation · Carboxylation efficiency · Summer drought
Introduction Urban landscape trees have significant roles in carbon flows in urban areas, and thus, have key roles in atmospheric CO2 cycling in urban ecosystems (Kordowski and Kuttler 2010; Kuittinen et al. 2016). The annual CO2 uptake by urban trees and carbon storage in trees and soils accounts for 58% of the annual carbon emissions from fossil fuel use in urban areas in Korea (Jo 2002). In the USA, the national average urban forest carbon storage density is estimated to be 25.1 tC/ha, which is 47% of 53.5 tC/ha in forest stands (Nowak and Crane 2002). CO2 uptake by urban subtropical trees offsets CO2 emissions from cities by 1.8–3.4% in Florida, USA * Yuko T. Hanba [email protected] 1
Kyoto Institute of Technology, Matsugasaki, Sakyo‑ku, Kyoto 606‑8585, Japan
Faculty of Agriculture, Kyushu University, 744 Motooka, Nishi‑ku, Fukuoka 819‑0395, Japan
2
(Escobedo et al. 2010). Photosynthetic functions are key traits for determining the carbon uptake of trees, in which many environmental factors including temperature, solar ra
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