Risk Possibility of Plane trees in Chahār Bāgh Abbasi Street of Isfahan

As one of the most important development indicators of urban communities, green space has various functions indifferent dimensions of urban life, including air softening, shading, and reducing heat (Akbari & Dorsano, 1992), reducing noise pollution (Nowak, 1992; 48), decreasing water and soil erosion (Colding, 2007), creating physical privacy fences (Tang et al., 2007), developing tourism industry and creating beautiful landscapes (Fung & Wong, 2003). First and foremost, urban space is a geographical space that is determined by distances, areas, and densities. Urban green spaces have social, economic, and ecological roles; they have benefits such as treating diseases, and at the same time, they are considered as an indicator for promoting the quality of living space and improving community (Nahibi & Hasandokht, 2014). Among important debates on urban streets are green space and green space aesthetics. Due to its environmental values, urban green space is one of the most important characteristics of each city such that the first step in planning and managing urban green space is to know information about street trees (Pourmajidian et al., 2014, Nafian et al. 2019). Urban green spaces playa main role in the function of cities, and their shortage can cause disturbances in urban life (Mohammadi et al., 2007). Today, hazard trees are of particular importance in the management of urban forests. Hazardous trees are often neglected unless damage occurs due to their hazard (Mortimer & Kane, 2004). Additionally, we cannot separate the hazardous and non-hazardous trees regularly since most trees are potentially hazardous (Harris, et al, 1999). Always large numbers of people and vehicles pass by hazardous trees, and if these trees are damaged and broken for any reason, they will directly damage people, vehicles, and facilities adjacent to them (Pourhashemi et al., 2012; Pourmajidian et al., 2014, Nafian et al. 2020).

Oriental Plane (Platanus orientalis Linn.) is one of the most ancient and oldest trees that have received attention from all ethnic groups and different nations, especially Iranians (Sharifinia, 1992). Having unique characteristics such as great stature, well-shaped branches, wide crown, and broad shadow, the Plane tree has created beautiful landscapes and is considered one of the important and effective factors in green space (Khoshgoftarmanesh, 2007). The large size, beauty, and rapid growth rate of the Plane tree have made it the first choice for streets margin in many parts of Iran (Mortimer & Kane, 2004; Roohani, 2005; Shiravand & Rostami, 2009). Additionally, the presence of plane trees of great antiquity inmost streets of Isfahan city indicates the history of using these trees in creating urban green space (Khoshgoftarmanesh et al., 2013). Pourhashemi et al. (2012) assessed the hazardous oriental plane (Platanus orientalis Linn.) trees on Valiasr Street in Tehran. Results showed that dead branches and twigs and structural weakness have the greatest contribution to hazard trees while unsuitable branching and decay are the least important criteria. Assessing hazardous Plane trees in Babol city, Pourmajidian et al. (2014) found that dead branches and twigs and root problems criteria had the greatest contribution to hazard. In a case study conducted in Shahrekord city, Moradian et al. (2016) investigated the hazard of Elm (Ulmus carpinifolia var. umbelifera) trees planted on the verge of the streets. Results showed that dead branches and twigs and structural weakness in 49% and 39% of the whole trees had the greatest contribution to hazard potential in trees, respectively, while the existence of cracks in the trunks was the least important criterion. Finally, it was recommended to take corrective and care measures such as crown and dead branches pruning. Banj Shafiei et al. (2015) also sought to determine the quantitative and qualitative characteristics and the level of risk posed by Plane trees in Urmia city. In their study, which was conducted based on risk factors rating, 18 trees with moderate risk ratings were identified. Today, indifferent developed countries, criteria for diagnosis and identifying hazardous trees have received a lot of attention from environmental and urban green space researchers (Golkar, 2001; Pourhashemi et al., 2012: Albers et al, 1992: Kane, 2008; Kong, 2000; Laflamme, 2005; Maruthaveeran & Yaman, 2010; Murad, 2000; Roloff et al., 2009; Yang, 2009). Investigating the level of risk posed by urban trees in Chahār Bāgh Abbasi Street and part of Chahār Bāgh Paeen Street, Isfahan, is of paramount importance. Given the necessity of awareness of hazards posed bystreet trees as one of the prerequisites for their proper management and the importance of Plane tree as one of the largest and oldest trees from past to present, attempts were made to identify the hazardous Plane trees in Isfahan city and investigate the level of risk posed by them in the above-mentioned region for the first time so that in addition to identifying and investigating these trees, urban forestry of Palm trees can be managed in abetter way.