Urban green spaces as hotspots for biodiversity

Subproject 1

PI-Leader of Subproject: Prof. Dr. Wolfgang W. Weisser

Affiliated Post-Doc and PhD Student: PD Dr. Sebastian T. Meyer & M.Sc. Xia Yao

Densification puts pressure on the remaining natural areas within cities, such that fragments of natural habitat shrink, then disappear, and connections between remnant green spaces are lost. Urban biodiversity can be high, yet it is only in the past years that the factors promoting urban biodiversity are beginning to be unravelled. While species richness in cities is positively related to the amount and size of urban green space available, the importance of particular elements of urban green infrastructure for the occurrence of certain species is only beginning to be understood. A recent study published by the research group (Fairbairn et al. 2024, Urban biodiversity is affected by human-designed features of public squares, Nature Cities) showed that the details of how a place in a city is designed strongly influences the number and type of species that occur in this place.

In the project, the focus will be on the occurrence of insects in the city. We will advance of our understanding of how particular elements of the urban green infrastructure, for example the occurrence of trees, the presence of bushes underneath trees, but also the built form, are important for the presence of particular species, but also entire insect communities. Insects will be sampled at different points in Munich, along various gradients. Sampling of insects will be done using a variety of methods including Malaise traps, but also sweep-netting and other techniques. Species will be identified either using conventional methods or using barcoding molecular and classic methods. Advanced statistical methods will be used to link the occurrence of species to the composition of urban green infrastructures. Where necessary and possible, experiments will be conducted to understand how the occurrence insect species can be increased in the city. The results of the project will provide novel insights into how the urban form can be modified in order to increase wildlife in cities.

Profile background for PhD candidate in Second Cohort

1. A master’s degree in Biology, Ecology or a related field

2. Interest in insects and their ecology

3. Knowledge in one or more of the following areas: statistical analysis of community data, ecological field work, insect identification, urban ecology

4. Ability to work in a team, high motivation, interest in interdisciplinary work

5. Excellent oral and written expression skills in English; German language skills are an advantage.

Link to Homepage of Research group: Terrestrial Ecology Research Group (tum.de)

Link to SP Description of First Cohort: Subproject 1: Biodiversity - Research Training Groups (tum.de)

Subproject 8

PI-Leader of Subproject: Prof. Dr. Richard Peters

Affiliated Post-Doc and PhD Student: Dr. Torben Hilmers and Martin Honold

Description: 

As climate change accelerates, trees in urban environments are increasingly exposed to atmospheric drought due to the rising vapor pressure deficit (VPD). This environmental shift forces trees to close their stomata in an attempt to conserve water and avoid lethal embolisms. In urban areas, this stress is further intensified by the urban heat island effect and increased salinity, which makes it crucial to understand species-specific stress thresholds.

The halting of transpiration as a result of stomatal closure not only impacts the health of urban trees but also diminishes their ability to provide critical ecosystem services, such as microclimatic temperature regulation. Cities, therefore, need to determine when targeted irrigation is required to sustain tree health and ensure the continuation of these ecosystem services.

This project seeks to develop near-real-time monitoring methods for transpiration rates to assess drought stress in urban trees and identify irrigation needs. The following key research questions will guide the project:

1. How is water use regulated in urban trees during drought periods?

2. Which ecophysiological measurements can provide near-real-time insights into the drought stress experienced by specific tree species?

3. Can we develop a predictive model to identify periods when irrigation will support both transpiration and tree growth?

Intended Methods:

In this project, you will collect data from multiple tree species across the city of Munich. Utilizing state-of-the-art automated sap flow sensors, specifically the heat-ratio method, you will accurately quantify transpiration at sub-hourly resolutions. This data, combined with local meteorological information, will enable precise identification of periods when stomatal closure occurs, signalling the onset of drought stress.

A unique aspect of this project is the use of novel dendrometer sensors, which are capable of recording both drought stress and growth signals. In addition, weekly branch sampling will be conducted to measure leaf water potential—a critical indicator of drought stress—and assess the risks of lethal embolisms in the trees. This comprehensive dataset will allow for the precise determination of drought stress periods across species.

Finally, these ecophysiological measurements will support the development and application of a mechanistic model capable of continuously simulating drought stress in urban trees. This model will help inform irrigation strategies tailored to different species, ensuring the maintenance of valuable ecosystem services provided by these urban trees.

Profile background for PhD candidate in Second Cohort: 

1. Background in urban ecology and environmental science: A foundational understanding of urban ecosystems, plant physiology, and climate change. 

2. Experience in field data collection: The ability to collect accurate and representative data on vegetation, environmental conditions, and thermal properties.

3. Proficiency in programming languages (e.g., Python, R) is beneficial for data analysis, visualization, and model integration.

4. An interest in electronics and mechanistic modelling.

Link to Chair Homepage: Peters_Richard (tum.de) 

About us

The new Chair of Tree Growth and Wood Physiology focuses on studying tree growth and their responses to climate change, from individual trees to entire forest stands. Our research aims to understand the mechanisms that govern tree and forest stand growth, as well as wood physiological processes, which are essential for explaining forest resilience to changing environmental conditions and their role in the global carbon budget. To advance this field, our research group employs a unique combination of innovative sensor technologies at the tree level with sub-hourly resolution, along with forest inventory data, tree ring analysis, and quantitative wood anatomy. Our findings will provide crucial insights for science-based forest management decisions and conservation actions, aimed at enhancing forest ecosystem resilience to climate change.

Link to SP Description of First Cohort: Subproject 8: Urban Trees - Research Training Groups (tum.de)

Subproject 9 (Universität Augsburg)

PI-Leader of Subproject: Prof. Dr. Claudia Traidl-Hoffmann (Universität Augsburg)

Affiliated Post-Doc and PhD Student: Dr. Maria Pilar P. García and Caroline Holzmann

Description: 

Urban green areas provide vital services that help control adverse conditions for life in cities. However, some tree species can cause asthma or allergic sensitization in the population. In addition, global warming is affecting the timing and intensity of flowering of many tree species in temperate climates, which will have effects on respiratory allergies and, indirectly, on the global economy.

In this changing scenario, monitoring flowering trends of allergenic plants is crucial for public health, but in situ phenological and pollen production databases are scarce. This study aims to develop: I) a model of the thermal requirements and climate conditions of common trees in urban areas of Central Europe using aerobiological data, pollen production and phenology information, II) a model that shows the interaction among different pollutants in the cities, pollen and fungal spores, and III) to make future projections under various climate change scenarios to predict and address future potential health risks associated with changing environmental conditions.

A field campaign will be conducted to collect data on the geographic, biological and phenological characteristics of several urban green areas, with the possibility of urban laboratories along an urbanization gradient. In the laboratory, pollen production of several individual will be determined. Airborne pollen concentration data will be also sampled.

LiDAR data for each urban area will also be used from public GIS databases. Digital surface model (DSM) and a digital elevation model (DEM) from these files could be obtain and measure UGI structural parameters such as building shape and height, tree height, street width and number of traffic lanes, etc. The analyses will be performed in GIS software (ArcGIS or QGIS) or in a statistical programming language (R or Python). The obtained UGI parameters will be combined with the biological parameters collected in the fieldwork to estimate allergenicity. Geospatial interpolation methods or machine learning-based approaches will then be used to interpolate the estimated allergenicity index to other areas within the city that were not sampled. This analysis will be performed in statistical programming software (R or Python).

The outcomes of this research would allow a better assessment of allergenic potential in cities but are also closely related to the other PhD projects of the RTG, especially those focusing on the study of tree mortality, crown calculations and urban microclimate. 

 Profile background for PhD candidate in Second Cohort

1. Completed university degree (Diploma/M.Sc.) in geography, forestry, landscape ecology, biology or related disciplines

2. Knowledge of data analysis, statistical methods and GIS in connection with biological and/or climate data

3. Laboratory skills are an additional advantage

4. Ability to work both in a team and independently

5. Very good communication skills in German and English are required

6. High motivation to contribute own skills and expand own knowledge to develop innovative approaches to clinically relevant research questions

Link to Chair Homepage: Environmental Medicine (uni-augsburg.de)

Link to SP Description of First Cohort: Subproject 9: Health and Disease - Research Training Groups (tum.de)

Subproject 11

PI-Leader of Subproject: Prof. Dr. Monika Egerer

Affiliated Post-Doc and PhD Student: Alex Zink

Description

The soil-based ecosystem functions of Sustainable Urban Drainage Systems (SUDS) depend on the soil structure and architecture controlled by the formation and structure of soil aggregates, as well as the plant species composition and the resulting soil-root interactions. A diverse plant community of SUDS can include wetland edge vegetation, such as wildflowers, sedges, rushes, ferns, shrubs and small trees. Below-ground, the plant-root systems influence infiltration through soil channeling to increase soil permeability that enhances stormwater filtering. Above-ground, these plantings can support urban insect habitat as well as complex insect-plant interactions that underly ecosystem functions, such as pollination, pest control and decomposition. Some wetland plant species may both be key for facilitating water storage but also may be, for example, insect pollinator-friendly through the provision of quality nectar and pollen, though this may be reduced by the uptake of stormwater contaminants. 

This PhD research project will combine experimental and empirical approaches to inform the design and planning of multifunctional SUDS that support below- and above-ground ecosystem functions with both knowledge of soil-plant interactions as well as insect-plant interactions. It will study SUDS of various soil and plant combinations and how they affect below- and above-ground functions in different environmental contexts (e.g., along an urbanization gradient under different climatic conditions). Combining prior experiments that focused on soil structure, high carbon amendments (HCAs) and carbon storage in the laboratory, the PhD student should transfer the results into a semi-technical scale with real and synthetic stormwater runoff from buildings in vegetated infiltration swales implemented in outdoor plots at TUM Garching.

The objectives of the PhD are to (1) investigate the role of different soil compositions and wetland plant communities on soil-root interactions to improve soil structure for water infiltration, and (2) assess the ability of wetland plant communities to attract insects and increase insect abundance and functional group richness. Furthermore, they will (3) analyze the potential of SUDS to dually improve infiltration and insect habitat to inform the implementation of systems in different city contexts. Finally, they will (4) examine the status quo of SUDS in Munich from an ecological perspective and propose where experimental SUDS could be implemented within the City of Munich. The doctoral researcher will collaborate with vegetation scientists, engineers, soil scientists, ecotoxicologists and microbiologists.

Profile background for PhD candidate in Second Cohort: 

1. Excellent diploma or master’s degree in related field

2. Motivation to elucidate complex biophysical and ecological processes that underly mechanisms driving multifunctionality in SUDS 

3. Excellent skills in laboratory and field experiments

4. Excellent knowledge of soil science; knowledge of insect biology preferred

5. Enthusiasm for and competence in ecological field work

6. Experience with environmental data and quantitative data analysis

7. Experience modelling and relevant languages (R, etc.) 

8. Pronounced scientific and writing skills are a benefit

9. Interest in supervising and working with other students during your PhD

10. Excellent knowledge of English, knowledge of German is preferred 

Link to Chair Homepage: Home - Urban Productive Ecosystems (tum.de)

Link to SP Description of First Cohort: Subproject 11: Soil Functionality - Research Training Groups (tum.de)

Subproject 13

PI-Leader of Subproject: Prof. Dr. Johannes Kollmann

Affiliated Post-Doc and PhD Student: Dr. Markus Bauer and NN

Description:

Sustainable Urban Drainage Systems (SUDS) are effective elements of urban green infrastructure (UGI) within the overall strategy of sponge cities. They deliver multiple ecosystem services, including mitigation of flooding and drought, improved microclimate, reduced pollution, carbon capture, support of pollinators and pest antagonists, and recreational values.

Many technical and ecological aspects of SUDS are well understood, while there are knowledge gaps with respect to ecologically informed design and planning of such UGIs. Planning must evaluate and integrate the multiple functions of SUDS, and this challenge has been rarely addressed so far. Moreover, planning must acknowledge that the ecological value of SUDS is controlled by local and landscape factors, since the significance the individual functions may vary depending on the immediate neighborhood, the urban landscape and the placement within the urban–rural gradient. 

Profile background for PhD candidate in Second Cohort: 

1. Interest in urban plant biodiversity and its driving factors. 

2. Expertise in experimental design and statistical analysis of field data. 

3. Knowledge in GIS and R

4. Willingness to collaborate with soil scientists, ecotoxicologists, microbiologists and urban planners is beneficial. 

5. Experience in publishing in international journals and interest in presenting at conferences are appreciated.

Link to Chair Homepage: Home - Chair of Restoration Ecology (tum.de)

Link to SP Description of First Cohort: Subproject 13: Plant Systems - Research Training Groups (tum.de)