Stadtbäume: Wachstum, Funktionen und Leistungen-Risiken und Forschungsperspektiven

Urban trees and green infrastructures are a main element of the cityscape; they are important for aesthetic and recreational purposes. However, not only their aesthetics influence the urban environment but rather their structure and appearance as well as their services for the urban climate. While science focuses mainly on the positive effects of urban trees like carbon storage, cooling, shading, biodiversity and runoff mitigation; negative aspects of urban green such as costs for planting and maintenance, allergenic potential and damages through falling branches further debris need to be mentioned altogether. Moreover, the typical growing site of trees in the city is characterized by numerous factors detrimental for tree growth, vitality and services leading to increased costs for maintenance and replacement. Those are e.g. high temperatures, limited rooting space, water availability and nutrients as well as pollutants, shading by high buildings and injuries. In addition, the urban heat island effect and climate change can further amplify the negative effects of the urban environment on the growth of urban trees. Therefore these interactions are gaining increased attention of urban planners. City councils and science try to develop sustainable planting concepts and management plans to preserve a vital, diverse, attractive urban tree forests. This review discusses the current state of knowledge and highlights the positive and negative aspects of urban trees. The impacts of urban trees on city dwellers and the urban climate as well as the effects of the growing site on tree vitality are presented. The effects of climate change on tree growth are analyzed and modern concepts and research prospects discussed.