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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (9): 150-156.doi: 10.11707/j.1001-7488.20150919

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Characteristics of Photosynthesis and Transpiration of Five Evergreen Tree Species in Summer

Xue Xue1,2, Li Juanjuan3, Zheng Yunfeng4, Zhang Jinchi1,2, Zhuang Jiayao1,2, Wang Yingxiang1,2   

  1. 1. Soil and water conservation and ecological restoration laboratory of Nanjing Forestry University Nanjing 210037;
    2. Collaborative Innovation Center of Sustainable China of Jiangsu Province of Nanjing Forestry University Nanjing 210037;
    3. Disney Research CHINA Shanghai 200021;
    4. East China forestry planning and designing institute Hangzhou 310039
  • Received:2014-10-28 Revised:2015-07-24 Online:2015-09-25 Published:2015-10-16

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Abstract:

[Objective] In this study, the diurnal variation characteristics of photosynthesis and transpiration of five evergreen tree species in Shanghai were measured in summer to understand the physiological and ecological characteristics of urban main greening trees. This study investigated the tree species' adaptability to urban environment and rationality of spatial configuration, and evaluated the ecological function, in order to provide scientific-based reference for selection and maintenance of urban greening tree species for mitigating urban heat island effect. [Method] During July 21-23, 2013 the typical hot and sunny summer days in Shanghai, five main urban evergreen tree species, including Photinia serrulata, Magndia grandiflora, Distylium racemosum, Cinnamomum campora, Osmanthus fragrans, were selected to measure the photosynthesis and transpiration variation and the surrounding environmental factors by using LI-6400XT photosynthesis system. The measured parameters included net photosynthesis rate (Pn), net transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci), leaf temperature (Tl), vapor pressure deficit (VPD), atmospheric CO2 concentration (Ca), photosynthetic active radiation (PAR), air temperature (Ta), relative humidity (RH). The correlation analysis between measured parameters and environmental factors was conducted accordingly.[Result] The diurnal variation of Pn of the five tree species showed doubled-peaks curve and indicated "midday depression" at midday, which was mainly due to non-stomatal limitation. The diurnal variation of Tr of the measured trees showed doubled-peak curve besides C. campora that was with single-peak curve. The daily mean value of Pn and Tr of P. serrulata was significantly higher than the other four species, with D. racemosum the lowest. A significant positive correlation was found between Pn and Gs, Ci, Tl, PAR, Ta, while a significant negative correlation was found between Tr and Gs, Ci, PAR, RH, VPD, WUE. [Conclusion] The daily mean value of Tr and Pn was relatively lower for M. grandiflora and D. racemosum. The WUE was relatively higher for D. racemosum, and lower for M. grandiflora. It is suggested that appropriate shading measures should be taken for M. grandiflora and D. racemosum in order to reduce their photoinhibition effect. The daily mean value of Tr was highest and WUE was lowest for C. campora, indicating that more irrigation and shading measure should be taken to reduce moisture loss resulting from transpiration. In summer, P. serrulata, C. campora and O. fragrans performed better than M. grandiflora and D. racemosum in terms of the abilities of resisting strong sunlight and high air temperature, while P. serrulata and D. racemosum were more efficient regarding using soil moisture and adapting to dry climate and environment.

Key words: evergreen tree species, diurnal variation, photosynthesis and transpiration characteristics, transpiration rate, photosynthetic and physiological parameters

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