The CliMax project, which came to an end in September 2025, spent three years investigating how to maximise carbon sequestration in urban trees, focusing in particular on tree vitality and water supply. Two articles have now been published on this topic.
With the participation of the Departments of Landscape Ecology, Theoretical Ecohydrology and Environmental Geochemistry (Isodrones research group), the authors led by Johannes Hoppenbrock have examined in detail in the Journal of Applied Geophysics the potential of the geophysical method ‘Electrical Resistivity Tomography’ for investigating soil water dynamics. What is exciting about this method is that it allows researchers to determine where the soil is becoming drier or wetter without the need for the labour-intensive installation of sensors. Whilst sensors provide only point-specific information, Electrical Resistivity Tomography can visualise a two-dimensional cross-section. This allows a deep view into the root zone, and the method has the potential to better characterise tree sites for future plantings.
In a further article involving the Departments of Landscape Ecology, Climatology and Theoretical Ecohydrology, led by the author Vera Hörmann, published in Frontiers in Sustainable Cities: Urban Greening, a carbon footprint analysis was carried out for trees, quantifying how much CO₂ equivalent is released during production in the tree nursery, during planting in the city and through maintenance over the tree’s lifetime, and how much CO₂ the trees sequester through growth in their biomass. Depending on the tree species, it takes between 4 and 15 years for a tree to absorb more CO₂ from the atmosphere than was previously released during nursery production, transport and planting. Short distances between tree nurseries and planting sites, low irrigation requirements using tankers, and good growing conditions form the basis for high CO₂ sequestration. If the oak processionary moth has to be controlled, this significantly worsens the balance, which is particularly important given the many headlines on this topic in recent weeks.