Tree selection just got easier!

In November 2016 our Keith Sacre paid a fact-finding visit to Dresden to meet Prof Dr Andreas Roloff, chair of Forest Botany at The Technische Universität Dresden (TU Dresden), and Dr Sten Gillner. Andreas Roloff 's main research areas are urban trees and drought stress.

Barcham has long been interested in species selection or 'right tree, right place', This was why Keith wanted to meet Andreas and Sten to discover more about their work. "Selecting the right tree for the right place sounds easy, but when all the constraints and design requirements of any particular planting site are taken into consideration the complexity of making a choice becomes apparent", he comments.

Andreas and Sten introduced Keith to Citree, a woody species for urban spaces database planning tool. This is the result of a research project at the TU Dresden, which supports professionals in the selection processes of trees and shrubs for urban sites.Andreas Roloff and his team developed this software tool for the selection of trees in urban areas. The tool not only incorporates the characteristics particular to each tree species, but also accounts for common planning practices, health issues (particularly in regard to air quality and allergy potential), and subjective assessments of city residents.

Which trees are to be planted where within a city? What are the criteria used to make these decisions? How can tree selection be both economically efficient and ecologically beneficial? How can urban trees help to reduce CO₂ emissions? What makes urban green attractive for city residents, and how can it provide benefits to their health? These are just some of the questions to which Citree provides answers.

Tree plantings on unfavourable sites need extra maintenance, such as by irrigation and fertilisation, and tend to be more vulnerable to pests and pathogens. This causes higher mortality of planted trees as well as higher costs. Furthermore it has to be considered that plants can be toxic or trigger allergies. Once again, Citree gives sound advice on how to avoid these scenarios.

Taking all these aspects of urban forestry into account is a difficult and complex challenge for urban planners. To address these issues, Andreas built a database serving as an information base and decision-making aid for planners - hoping to improve urban greening, thereby enhancing the quality of life for city residents, as well as increasing urban biodiversity. The underlying research was conducted in Dresden, and the database shows characteristics for more than 390 species and varieties ''I was tremendously impressed by Citree'', says Keith. ''It is available free-of-charge in English, and we have nothing in the UK which is as good or as simple to use as this. I really learned a great deal from Andreas and Sten". Citree is an easy tool to use. Selections can be made by botanical or common name, or by using several criteria. For each species, it is simple to find information on the climatic and soil conditions in which it thrives, its appearance, the risks and interference associated with it, the ecosystem services it provides and its required management. Alternatively, these aspects can be used as criteria by which to search, with resulting trees' suitability expressed as percentages. If preferred, selection can be made by site type, with densely built-up areas, industrial and commercial areas, waterways and ports and traffic being just some of the choices.

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