Project duration:  10/2022- 09/2025

Trees have the ability to capture carbon. Stress and disease lead to less growth, and consequently less carbon is stored. Therefore, trees need to be vital to sequester carbon long-term. The water supply is one of the central factors for the vitality of the trees. To investigate the water status of individual trees and tree sites, soil and soil water conditions are studied using non-destructive geophysical methods such as ground-penetrating radar and geoelectrical methods. Stable water isotope analysis from the tree and the tree pits provide information on the depth from which trees take up water via their roots.

Urban tree vitality is regularly assessed and the data is collected in the tree cadaster. The tree cadasters of the cities of Brunswick and Brandenburg an der Havel are used for the development of an automated detection method of damaged trees. This will be based on Sentinel-2 data (for calculating vegetation indices and a subpixel analysis) and LiDAR data (single tree detection and derivation of structural features). Publicly available data characterizing tree sites will be combined in a machine learning approach to create a quality and risk assessment of the tree sites. The fusion of both methods should allow conclusions about the relationship between site conditions, and current and future tree vitality. The remote sensing tree vitality classification will be validated at selected tree sites. To do so, the biomass and growth rate of the trees are estimated with high-resolution terrestrial laser scanning. The vitality is determined through visual assessments of the crown architecture, crown expansion and plant damage.

While the observation of the biomass and growth rates allow statements about chronic stress for the trees, the project also investigates early or temporary stress symptoms on the trees. These stress symptoms are assessed through the measurements of the chlorophyll fluorescence and chlorophyll content. Detecting stress symptoms early could help green space agencies in their management decisions and thus assist to secure tree vitality. A decision matrix will be developed to illustrate the development processes of multifunctional, resilient urban tree plantation. This decision tool should support cities and municipalities to estimate the status quo of the urban tree's contribution to carbon sequestration, and maximize the climate benefits of urban green.

The CliMax project is funded by the German Climate Action Program 2022. The project aims to make a scientific contribution to climate reporting and impact assessments.