Photosynthetic Characteristics, Carbon Fixation and Oxygen Release Functions of Three Landscape Trees

The amount of carbon fixed per plant (CFC per plant) and oxygen released per plant (ORC per plant) for Platanus acerifolia were 1080.72 and 785.98 g/d, respectively. The highest contents in carbon fixation and oxygen release of P. acerifolia may indicate a good photosynthetic capacity compared to S. japonica and Z. serrata. However, the later two species of trees were found efficient related to the net photosynthetic rate (Pn) and leaf area index (LAI). Introduction Human activities are contributing to the global climate change by greenhouse gas emissions (Barcelos et al. 2014, Liu et al. 2015), and carbon dioxide (CO2). They are most important greenhouse gases in the atmosphere (Bazzaz 1990, Tripathi and Agrawal 2012, Kumari and Agrawal 2014). The concentrations of CO2 have continuously increased and reach 400 ppm on an average per day at Mauna Loa (Ward et al. 2015). Urban areas are directly or indirectly responsible for over 70% of atmospheric CO2 emission (Briber et al. 2013, Velasco et al. 2013). Landscape plants are an important part of urban ecosystem, which can reduce concentrations of atmospheric CO2 by fixing it into carbohydrate in plant organs (Berg et al. 2010, Fuchs 2011). Carbon fixation is one of the dominant biochemical processes in the biosphere, which refers to the conversion process of inorganic carbon (CO2) to organic compounds by plants (Geider et al. 2001, Berg 2011). All the major biological components of carbon fixation are derived from the photosynthetic process of plants (Körner et al. 2005). So far, several studies were carried out focusing the photosynthetic capacity of plants to adapt different environments (Calatayud et al. 2002, Reddy and Zhao 2005, Hamilton et al. 2008, Geissler et al. 2009, Danyagri and Dang 2013, Meng et al. 2014, Niu et al. 2014). However, less information is available on the photosynthetic characteristics and the functions of fixing carbon and releasing oxygen in landscape trees. Three landscape trees, namely Chinese scholar tree (Sophora japonica, Fam. Fabaceae), Japanese zelkova (Zelkova serrata, Fam.: Ulmaceae) and London plane tree (Platanus acerifolia, Fam.: Plantanaceae) are dominant species of deciduous forest in northern China. These species have the important ecological and economical status in urban area. In the present study, the photosynthetic characteristics and the functions of fixing carbon and releasing oxygen in the three landscape trees were studied. By estimating the functions of fixing carbon and releasing oxygen by the three plants, we can determine the role of landscape trees in mitigating climate change and offsetting local CO2 emissions. It would provide critical insights on future research of ecological function evaluation of landscape trees. Author for correspondence: .