SP8: Structure, Functioning and Ecosystem Services of Urban Trees
Head: Prof. Dr. Dr. Hans Pretzsch
Execution: Leila Parhizgar
Urban trees with their manifold ESS and functions offer a means for providing sustainable solutions to climate mitigation and adaptation to environmental, societal and economic challenges. By improving the knowledge about the structure, functioning, and sustainable management of urban trees this project aims at better exploitation of the potential of urban trees for climate-smart urban planning. Our overarching objective is to acquire empirical knowledge about the structure, functioning, and ESS of Urban Trees, and to integrate this knowledge in spatially explicit modeling, and sustainable management of urban tree stocks.
For this purpose, we will:
- (O1) Review and model selected ESS (cooling, shading, C-sequestration, habitat provision, noise reduction) of urban trees depending on site, species and age;
- (O2) Quantify urban tree mortality as essential knowledge gap for modeling and planning;
- (O3) Analyze the interaction between adjacent urban trees (in situ and experiments) as this paves the way to innovative planting and arrangement designs;
- (O4) Create a matrix model for sustainable planning of stocks of urban trees;
- (O5) Put a special emphasis on tall and old urban trees, their growth and ESS, as old trees play an essential role for NBS and are under-represented in research so far.
The overarching hypotheses of this project are that:
- (H1) ESS provision of urban trees is highly dependent on their site-conditions, creating a need for specific urban tree management plans reducing mortality and including interactions;
- (H2) The potential of urban trees for climate-smart sustainable urban planning can be significantly improved by the knowledge-based design of urban tree stocks.
To meet the objectives the set of urban trees ESS will be reviewed (and to some extent measured at experimental sites in Munich), quantified and modeled depending on tree size/age, environmental conditions, competition, and facilitation. The resulting regression models may be implemented in a spatially explicit model for urban trees. Mortality will be analyzed and modeled species-specific by logistic regressions based on urban tree records of selected cities including Munich. The tree–tree interactions will be studied at mature trees in the city of Munich and also in pot experiments with common tree species and species assemblages. Further, we will develop a spatially explicit model for sustainable management of urban trees, analogously to the concept of sustainable forestry developed by von Carlowitz. The main drivers of the model will be species-specific tree diameter growth functions and mortality rates. By auxiliary relations, ESS such as biomass, carbon stock, or cooling can be estimated. A given state of an urban tree stock can be assessed by a set of sustainability indicators regarding its distance from a target stock. As old and tall trees provide large portions and unique aspects to ESS and as they were somehow under-represented by urban tree research so far, we will pay attention to them by our empirical and model work. The empirical and the modeling part of this project will cover the following indicators at the individual tree level but also (by modeling and up-scaling) at the quarter level: Indicators for human well-being (in cooperation with SP9 and SP12), climate smartness in terms of mitigation and adaptation (SP2, SP5, and SP6), water regulation (SP10 and SP13), pollution reduction (SP7 and SP9), and habitat and biodiversity provision (SP1).