Urbanization and development of cities are rapidly increasing across the world and urban forests constitute important tools that maintain the basic environmental and ecological functions of cities on which plant, animal and human existence depend. This paper presents a literature review on importance, utilization and health of urban forests that are important in providing ecosystem services for the sustainability of cities. Analysis of the literature from the main academic resources databases indicates that urban forest is a dynamic system which includes trees, shrubs, green space, soil and water that supports them. Urban forests provide many functions, services and benefits which are needed for the sustainable development of urban areas. In addition, health and appearance of trees’ composition are the most important factors in determining a city’s visual image and quality of life. Thus, urban forests are an important component of an ecosystem in any community development. Furthermore, management of urban forests can increase their potentials and therefore their functions, services and benefits. Green infrastructure and ecosystem services are the most efficient tools that cities can utilise to remain healthy, robust and liveable. Hence, the planners, architects, engineers, foresters, agriculturists and all those involved in decision making should be utilized the present literature review and incorporate the concept of urban forest in their  plans and programs so as to achieve the sustainability of cities.

Chestnut blight caused by Cryphonectria parasitica has been one of the major reasons for the decline of chestnut cultivation in Greece over the last 50 years. A previous detailed study of the vc types of the fungus has revealed only four vc types in the entire country, those of EU-1, EU-2 and EU-10 with the dominant being EU-12 counting for 88% of the isolates. As the loss in orchard trees reached in some chestnut producing prefectures over 35% of the trees, the decision was taken to apply biological control on a nationwide scale. The project was implemented in 17 prefectures during the period 2007-2009. Hypovirulent (hv) strains of C. parasitica which were infected by the CHV-1 subtype I (Italian subtype) viruses which occur naturally in Greece were used. The necessary hypovirulent inoculum was prepared at the Forest Research Institute during the period 2007-2009 on a large scale, however, with laboratory care. Three million inoculations were made around accessible developing cankers over three consecutive years by trained personnel. An extensive evaluation conducted in 2011 in the 12 of the 17 treated prefectures, where no natural hypovirulence had been found before, demonstrated not only the successful establishment of hypovirulence but also profound dissemination and healing of non-inoculated cankers. The extent of dissemination varied significantly among sampling plots and among prefectures. The conclusion is drawn that CHV-1 subtype I has successfully established and spread into chestnut orchards and coppice forests resulting in a gradual decline of chestnut blight.

Oak (Quercus robur) powdery mildew is a common and damaging fungal disease. In a local survey at Reading, UK, oak powdery mildew was common on trees of all height classes but was most common on trees of 3-9 m. A variety of other fungal species were commonly found growing in association with oak powdery mildew colonies. The abundance of such fungi was estimated through stratified sample surveys for 2.5 years. The taxa most commonly associated with oak powdery mildew were Acremonium sp., Trichoderma sp., Ampelomyces/Phoma sp. and Leptosphaerulina australis. Nearly 90% of mildew colonies were associated with L. australis, which is not generally considered as a mycoparasite or antagonist, in contrast with the other three fungi. Abundance varied between June and October surveys. Acremonium sp. abundance was greater in summer samplings, whereas L. australis and Trichoderma sp. abundances were greater in autumn samplings. Ampelomyces/Phoma sp. was never observed in the absence of powdery mildew. Relationships between the mildew-associated fungi and oak powdery mildew appeared curved and differed significantly between sampling years. L. australis was positively correlated with the other three associated fungi studied when powdery mildew was also present. The variety and high population densities of the mildew-associated fungi suggest that they may be important in determining the final density of oak mildew and the damage caused by it.

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