very characteristic plants, these trees have very big size and from the botanic point of view they can’t be considered as trees. Some of these trees are native and can grow in different environment and ecosystem in Spain but the majority of this species are from different continents. 1.1. JUSTIFICATION OF THE SUBJECT In Barcelona there 14 kind of green spaces which the classification of these urban green spaces requires specific maintenance plan, management according to each type of spaces. Among these 14 type of spaces the two specific parts which are the tree in urban parks and street trees will be study, which the impact of trees in these two selected spaces will be discussed. The first area of studies are urban parks, in Barcelona there are 37 urban parks these areas contain significant size of landscaped spaces and are facilitated with both sport and entertainment activities. These areas included most adaptable trees(plants) to Mediterranean climate and the vegetation grow with their natural treetop. The second area of studies are the street trees which consist of over 150.000 trees in the streets, boulevards, avenues, Ramblas and mediants of Las Rondas which is one of the signs of identity of Barcelona and are currently increasing the species most resistant to the weather conditions of the city. Parcs i Jardins is an entity municipal formed with the basic objective of creating and maintaining of green spaces of Barcelona, by promising that each year they will enforce to increase and improve green spaces and trees in the city according to the sustainability criteria of Agenda 21. The big cities almost all have in common, that the density of people living in it is very high and large amount of human being living in few m2,so the aim is to find out how the politic of green spaces in Barcelona can provide nice environment condition for the people to live in it by choosing specific and suitable specimens that balances their environmental conditions of the cities which is the problem of the most populated cities in the world and they suffer from lack of quality of public space. 1.2. OBJECTIVES General Objectives 1. The evolution of public spaces of the city and the strategies that were taken to develop the city structure. 2. Studying the general green structure of the city during the history of Barcelona and how they were developed according to the city context and the important people who influence this green patrimony. 3. Understanding the role of green in public spaces of the city. Specific Objectives 1. Identifying the principles species which are used in Barcelona and the strategies that were taken for the selection of these species and their distribution in the city. 2. Studying the strategies of the institute of the Parcs i Jardins to protect and enrich the trees in the city of Barcelona. 3. Determine the function of trees, different usage of the trees according to their type and conditions. 4. Analyzing the environmental impact of the trees in different type of spaces by the analysis of the case studies of Moll de la Barceloneta and Parc de la Diagonal Mar.
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